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General Discussions => Drawing Board => Topic started by: ruffrecords on April 08, 2011, 01:49:58 PM

Title: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 08, 2011, 01:49:58 PM
I have had an idea for a poor man's version of the Pultec EQP1-A. Low boost/cut  and hi cut just as the EQP1-A with the hi boost modified to not need an inductor (based on the Helios Type 69 EQ). So just four pots (no bandwidth control) and a couple of cheap Lorlin 2 pole 6 way switches will give us 6 lo and 6 hi frequencies (more than the EQP1-). I have done some sims of the circuit and it still produces the classic Pultec bump in the response so I think I will knock one up and see what it sounds like.  Schematic attached - and I have changed the pot values so that it has a nominal 10K input impedance so it can be driven by a normal 10K:10K bridging transformer. Insertion loss is about 21dB so plenty of options for gain make up.

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/poormanspultecscaled.jpg)
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 08, 2011, 02:21:44 PM
Hi Ian,



   are you reading my mind . . . . Fantastic stuff . . . .


    Brilliant. Thank you


    Kindest regards,



      ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruairioflaherty on April 08, 2011, 02:28:43 PM
Excellent Ian!  I have something related on the bench right now but it's all peaking filters and laden with inductors, in fact a parcel of 6 nice Sowters just arrived yesterday.  I think the passive idea has great merit but I'm not a fan of needing huge make up gain for my specific application - in the mastering chain.  With that my version has just 6dB insertion loss, the compromise of course being less range.

Your idea will work wonderfully.  Once you get a handle on cap values please post an update, I'm visiting a huge surplus place soon and I might pick up what's needed to knock up a few channels.

Thanks,
Ruairi


Title: Re: Poor Man's Pultec EQP1-A
Post by: zebra50 on April 08, 2011, 02:38:00 PM
Nice!

I'm a bit short on inductors right now  ;) , and this looks like a fun afternoon's project! Thanks for sharing.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruairioflaherty on April 08, 2011, 02:49:20 PM
Nice!

I'm a bit short on inductors right now  ;) , and this looks like a fun afternoon's project! Thanks for sharing.

 ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 08, 2011, 02:50:30 PM
Thanks some very encouraging replies. My only concern right now is that with maximum simultaneous top boost and cut the equaliser impedance drops continuously at very high frequencies which would probably be bad news for the driving source. So I think I might at a 4K7 in series with the hi boost wiper to make it into a shelving EQ just like the Helios which will limit to boost to about 15dB (low boost is limited to 14 to 15dB anyway). With a 750R in series with the hi cut wiper that also becomes a shelving type with about 15dB cut. Worst case EQ load then becomes about 5K4 which should be OK.

I'll do some more sims to check this out. What frequencies in addition to the normal EQP1-A ones do you think we should have?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 08, 2011, 02:58:40 PM
Hi Ian,


   sorry to be a pedant, but there are actually 7 freq in the hf boost on an EQP1a . . . .


    I would have to muck about, but I think going higher in the top end, say 22kHz or even 26kHz, and maybe come up to something like 150 or 200hz . . . even up to 300 or 400hz would be nice for guitars in conjunction with the lo cut . . . anything would be a bonus.

    bloomin marvelous . . .


   I built  the HF section of a Helios (10kHz) in a box once upon a time . . . . Lordy knows where it is now . . .


    ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 08, 2011, 05:35:13 PM
Hi Ian,


   sorry to be a pedant, but there are actually 7 freq in the hf boost on an EQP1a . . . .

No problem. There's quite a few EQP1-? models. As you say the 1A has seven hi boost frequencies but only 3 hi cut ones. The 1R has five frequencies for both hi boost and cut. The 1R goes 3K, 5K 8K 10K 12K so we could add one at say 20K or one at 16K and 20K and lose the 3K for example.


Quote
    I would have to muck about, but I think going higher in the top end, say 22kHz or even 26kHz, and maybe come up to something like 150 or 200hz . . . even up to 300 or 400hz would be nice for guitars in conjunction with the lo cut . . . anything would be a bonus.

The 1A does 20, 30, 60 and 100 at the low end and the 1R omits the 20 so we could for example do 30, 60, 100, 200, 300 and 400. I just need to check we don't end up with silly capacitance values.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 08, 2011, 05:38:15 PM
Hi,


   see what values are reasonable, Id say . . .


   Yay Ian . . ..


    ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 08, 2011, 05:50:24 PM
Hi,


   see what values are reasonable, Id say . . .

    ANdyP

I just checked out the Manley 'enhanced' Pultec. That has 20, 30, 60, 90, 120 on the lo, an amazing 11 frequencies for hi boost and 4K, 8K, 12K, 16K and 20K for cut. Since it is hard to get caps in odd values and its a pain to combine them in pairs instead, I think I'll continue in the spirit of this being a poor man's EQ by seeing what frequencies we get using standard values of capacitor.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: lassoharp on April 08, 2011, 09:01:41 PM
Quote
No problem. There's quite a few EQP1-? models. As you say the 1A has seven hi boost frequencies but only 3 hi cut ones. The 1R has five frequencies for both hi boost and cut. The 1R goes 3K, 5K 8K 10K 12K so we could add one at say 20K or one at 16K and 20K and lose the 3K for example.


Nice work Ian - look forward to trying this one out.  The 15db boost seems plenty on top and bottom.  I seldom find myself needing more than 11 or 12 o'clocks worth of low boost and 1 or 2 oclock on the high on the standard EQP1A.

I vote for at least adding the 16K.  I find that point most useful for adding presence without the 'chewiness' associated with the lower highs. 

Thanks for sharing.

Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 08, 2011, 09:25:03 PM
A few legacy EQs only give you +-12 for anything so I think we're on the right track. +1 on keeping to standard caps, us poor men can't be too picky.

+1 yay Ian, you're a good chap for doing the leg work here. If I could be more useful, I would...but I'm not, so no.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Ptownkid on April 08, 2011, 09:26:15 PM
I applaud this kind of thinking...I hate over complicated gear with way too many knobs...
Title: Re: Poor Man's Pultec EQP1-A
Post by: pucho812 on April 08, 2011, 10:19:49 PM
looking good. if you ask me, gotta have a 30K boost to add air. makes for perfect mp3
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 09, 2011, 06:29:11 AM
Good work Ian. I presume the valve section from the Gyraf pultec will still compliment this nicely?

Chris

PS +1 on adding a high 'air band'
Title: Re: Poor Man's Pultec EQP1-A
Post by: zayance on April 09, 2011, 06:43:14 AM
Nice Stuff! 8)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 09, 2011, 07:26:39 AM
Good work Ian. I presume the valve section from the Gyraf pultec will still compliment this nicely?

Probably not in its current form. Since I have raised the input impedance of the EQ so we can use a 10K:10K input transformer, this means the output impedance has also been raised from about 1K to about 5K. This means the gain make up input impedance also needs to be about five times higher to avoid loading the EQ. The Gyraf uses a 10K:10K+10K transformer connected directly to the grids of the input tubes. This means the reflected primary impedance will be nice and high which is good but the LF response depends on the primary inductance of this transformer. If, for example, this is high enough for the existing design to be -1dB at 10Hz then it means in this design the -1dB point will likely be at 50Hz which is not so good.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 09, 2011, 07:52:00 AM
Hi,


   does it need an interstage transformer . . .

  could you use 2520 like this . .
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 09, 2011, 07:53:05 AM





 or SRPP like this . . .
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 09, 2011, 07:54:14 AM



  that srpp is 27.5dB gain, so just about perfect with 2 to 1 output tranny . . . .
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on April 09, 2011, 08:21:57 AM
I'm working on making one tube stages work with 1U of 51x so that would make an awesome project. But I'll say no more :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 09, 2011, 09:21:02 AM
I did not mean to imply that you could not do gain make up without an interstage transformer I was just answering a specific query about the Gyraf tube gain make up stage which does use one. Of course there are plenty of ways of achieving the necessary gain make up. My personal preference would be a mu follower stage based on a 6CG7.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 09, 2011, 09:24:41 AM



   Thanks. understood. Ooh, this is exciting   . . .
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 09, 2011, 10:33:32 AM
OK, I have done a few more sims and worked out some initial capacitor values. Looks like it is going to be very hard to avoid the need to parallel up caps in a few cases e.g. 8nF = 4n7 + 3n3 and we might need to do 15nF = 10nF + 4n7 and 150nF = 100nF + 47nF but apart from that the values have so far turned out reasonably OK. For experimental purposes I have added 200Hz lo boost/cut frequency and a 30KHz hi boost/cut frequency.

The key to creating the Pultec 'bump' is that the boost and cut turnover frequencies are NOT identical for a given frequency shown on the switch. In fact they are an octave apart although by the time you reach the switch frequency the boost or cut is pretty much fully established ( you can see these turnover frequencies quite clearly on the curves published by Pultec).  If the turnover frequencies were identical then the boost and cut would simply cancel out. So, with the values in the circuit below, with max lo boost and cut together you get a 5dB dip at the following frequencies

Switch f    Dip f
20            50
30           100
60           240
100          350
200          750


Similarly with max hi boost and cut together you get a 5dB peak at the following frequencies:

Switch f    Peak f
5K            1K6
10K           3K5
20K           5K
30K           10K


(http://www.ianbell.ukfsn.org/pics/PMEQP1-A.png)


Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: danijel on April 09, 2011, 05:01:50 PM
Thank you very much! :)


Danijel
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 10, 2011, 06:32:31 AM
I have been doing some further sims and research concerning the Pultec 'bump'. It seems the little 5dB dip at the lo end is supposed to be followed by full boost at lower frequencies but the current circuit does not do this. I then realised that Pultc have the lo cut pot outside the main pot divider that the EQ is based on and has its own separate load to form its own separate pot divider for lo cut. This load could be returned to ground as you would expect but is in fact returned to the top of the lo boost pot (this is NOT immediately apparent from the way the EQP1-A circuit is normally drawn). The effect is to reduce the lo cut if the low boost is used at the same time and neatly produces the Pultec dip followed by full lo boost.

So I have redrawn the circuit to reflect this and called it the MKII. I also changed the way the hi cut/boost shelving is achieved by moving the series resistors to the wipers of the associated pots. This reduces the their interaction with the lo cut/boost pots. With the same resistor values as before you get the little 5dB upward bump reported earlier followed by a flat response. I wondered if it was possible to get the upwards bump followed by full cut (to mirror the lo bump and also be more like the peaking hi boost in the real EQP1-A) so I started by reducing the hi cut series resistor to zero which essentially gives infinite cut eventually but this destroyed the bump completely. After trying several different values I settled on 100 ohms as a good compromise and this is shown on the MKII schematic below. I'll run a couple of sims of the hi and lo bumps and post them so you can see what they  look like.

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png)

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 10, 2011, 10:54:47 AM
Here are the plots as promised. First one is 60Hz with full boost and full cut. This clearly shows the dip at about 800Hz followed by the regular boost. The second shows maximum hi boost and cut at 5 KHz which produces a nice peak at about 1.5 KHz then falls away. I found an article somewhere on the net that had the lo plot from a real Pultec that we could use for comparison but I can't find it right now.

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/60lobump.jpg)


(http://www.ianbell.ukfsn.org/pics/5Khibump.jpg)


Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 12:51:45 PM
very nice Ian


just in these days I am developing(near to be finished) an input and output board using DOA's for pulteq eq because some my friend wanted it , one for input as sbalancer and one in output as balancer in trasformerless or trasformer output mode. It's possible using a integrated opamp DIL8 instead of the DOA. The board has two servo DC stages and does not use electrolytic caps in the signal path. Just for who wants use DOA's in a pulteq eq and no trasformers.
 


Pier Paolo
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 10, 2011, 01:42:34 PM
very nice Ian


just in these days I am developing(near to be finished) an input and output board using DOA's for pulteq eq because some my friend wanted it

Hi Pier,

Forgive my ignorance but what is DOA?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 01:52:36 PM
very nice Ian


just in these days I am developing(near to be finished) an input and output board using DOA's for pulteq eq because some my friend wanted it

Hi Pier,

Forgive my ignorance but what is DOA?


Cheers

Ian

DOA is discrete op amp.  

I have designed this board for the classic pulteq eq but it is good also for your eq.
my board can be used with a lot of DOA's as my doa's , JE-990 , 2520 etc..  
actually I think that with the Poor Man's Pultec EQP1-A with my board it is possible to make a very cheap
Pulteq eq but with very high performances.

Pier Paolo
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 10, 2011, 03:01:04 PM
This is shaping up to be a great project. With DOA's, should be able to squeeze 2 into a 1U case. Keep up the good work  :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 10, 2011, 03:11:18 PM
DOA is discrete op amp.  

I have designed this board for the classic pulteq eq but it is good also for your eq.
my board can be used with a lot of DOA's as my doa's , JE-990 , 2520 etc..  
actually I think that with the Poor Man's Pultec EQP1-A with my board it is possible to make a very cheap
Pulteq eq but with very high performances.

Pier Paolo

Thanks Pier, I should have guessed DOA meant discrete op amp.

What is the input impedance of your DOA? As you know I have increased the impedance of this EQ to use a 10K:10K input transformer. This means the output should preferably loaded with not less than 470K.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 03:15:26 PM
I have a fet input doa, the APP2055.

cheers
Pier Paolo
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 03:18:25 PM
This is shaping up to be a great project. With DOA's, should be able to squeeze 2 into a 1U case. Keep up the good work  :)

thanks

the board enters in 1U case and it is just 170x100 mm so it's possible making a stereo eq.

Pier Paolo
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 10, 2011, 03:25:12 PM
are DIP8 footprints included on your board, or would it require an adapter PCB to use them?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 03:36:07 PM
the board can use or a IC opamp on input stage and a DOA in the output or two DOA's in these ones.
The input stage has both sockets 2520 style and DIP8.
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 10, 2011, 04:08:10 PM
Hi Pier,



   that sound very interesting to me . . . .wonderful . .


    Kindest regards,


     ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 10, 2011, 06:48:52 PM
this is the schematic

this is the scheamtic for the traditional pulteq eq , for the Ian's eq R14 = 1M and DOA2 is APP2055,  APP99F, FT992 ONLY.
the first DOA1 can be API2520 , JE990 and others.


EDIT: new schematic for one error in the previus
Title: Re: Poor Man's Pultec EQP1-A
Post by: Chris_V on April 11, 2011, 01:53:44 AM
this is the schematic

That's a lot of "gnd" for one design  ;)
BTW, there is still a mistake I think, the power supply of the upper left OPA604 differs from the others.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 11, 2011, 04:02:04 AM
this is the schematic

That's a lot of "gnd" for one design  ;)
BTW, there is still a mistake I think, the power supply of the upper left OPA604 differs from the others.

I think you will need to change the value of C250 as well if you want any HF response!

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 11, 2011, 06:24:09 AM
this is the schematic

That's a lot of "gnd" for one design  ;)
BTW, there is still a mistake I think, the power supply of the upper left OPA604 differs from the others.

I think you will need to change the value of C250 as well if you want any HF response!

Cheers

Ian

yes, C250 needs to be changed,

BTW it changes the HF response a lot using Poor Man's Pultec EQP1-A.

Using my fet opamps it could be 10pF to avoid to change the HF response in your design.


PS: this my schematic cames from a trasformerless 16 channels summing amp that I am designing , so I have changed some values and also forgotten to change some others..........  ::) , I'm reviewing it another time and finishing the PCB.


thank you Ian


cheers
Pier Paolo


Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 11, 2011, 06:38:35 AM
this is the schematic

That's a lot of "gnd" for one design  ;)
BTW, there is still a mistake I think, the power supply of the upper left OPA604 differs from the others.


I have separated the signal ground from the power gnd for lowest noise, this my schematic cames from a trasformerless 16 channels summing amp that I am designing , so it cames with the complex ground circuit needed for it , but BTW i prefer the separate grounds.

regarding the OPA604 it can work at +-24V power supply .
BTW the circuit is designed also for 2520, than can be used  many opamps can be used being the power rails at +-16V

However it's a good idea using some jumpers to use the same power supply voltages of the other IC opamps if needed, thank you  :D
Title: Re: Poor Man's Pultec EQP1-A
Post by: Kingston on April 11, 2011, 07:38:32 AM
regarding the OPA604 it can work at +-24V power supply.

I was wondering why such low 12V rails when many of your DOA's and OPA604 are happy with double that. But I wouldn't use OPA604 at all. LME49870 is a much better performing modern equivalent where you could still run 22V rails.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 11, 2011, 09:09:06 AM
regarding the OPA604 it can work at +-24V power supply.

I was wondering why such low 12V rails when many of your DOA's and OPA604 are happy with double that. But I wouldn't use OPA604 at all. LME49870 is a much better performing modern equivalent where you could still run 22V rails.



good question,

in my circuit is not required higher voltages for those
opamps that are used only as servo DC's,

on the contrary IC1 (as optional at the DOA1), that is used to sbalance the input signal, is connected directly to the main power supply voltages.

I have indicated the opa604 but the circuit is designed for many IC opamps, because as you have told , not all like the opa604.

I have added the regulators to use many IC opamps as possible, since that several opamps (as the TL071, for example) can not run at the same power supply voltage of the DOA's.  For the IC opamps that work at the same power supply voltage of the DOA's it's possible to bypass the regulators just with two wire bridges.

This circuit is designed for +-24V of power but also to operate at +-16V to permit to use the 2520 opamps and, since the 7815 and 7915 can not work with an input voltages of +-16V I have used the 7812 and 7912 regulators.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Kingston on April 11, 2011, 09:18:26 AM
I have added the regulators to use many IC opamps as possible

I didn't see that at first but makes sense now.

The inductor-less pultec circuit with these buffers would make a great small form factor project. four channels in 2U rack, or api 500 (or whatever variant) comes to mind.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 11, 2011, 09:28:21 AM
moreover, since the fet input is preferred for the inductor-less pulteq eq I am thinking to add a simple fet buffer, to use no fet input DOA's in the out stage, as , for example the 2520 or JE 990.
 
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 11, 2011, 04:00:29 PM
I have created a simple spreadsheet for calculating the capacitor values needed for the hi and lo cut and boost of the poor man's EQP1A. I have included a range of hi and lo frequencies but you can calculate your own simply by changing the values in the 'Switch f' column. The spreadsheet also gives an indication of where the lo dip and hi peak occurs when you use max boost and cut at any frequency.

The spreadsheet calculates capacitor values to 2 decimal places so you will have to work out the nearest available standard values or combinations thereof yourself. It is not necessary for the values to be exact for correct operation of the circuit.

http://www.ianbell.ukfsn.org/pics/capcalc.xls (http://www.ianbell.ukfsn.org/pics/capcalc.xls)

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: lassoharp on April 11, 2011, 04:20:40 PM
Excellent!  Thanks Ian!    8)
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 11, 2011, 05:40:24 PM
This is quickly becoming one of the most adaptable eq projects I've seen on here. Props to you, Ian!
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 11, 2011, 06:18:46 PM
the new schematic with the fet buffer added to use bipolar DOA's. 
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 12, 2011, 05:23:02 PM
is my schematic too complex or do you need a more simple one?
Title: Re: Poor Man's Pultec EQP1-A
Post by: MikeClev on April 12, 2011, 10:00:05 PM
Lets make some sense of what you've got on that pdf.

Top left: a balanced Line input using a DOA and with a servo. I assume the servo is there to eliminate the need for DC blocking electrolytic capacitors.

Top centre: 12v Power supply circuits for the servos, standard stuff.

Bottom right: a DOA circuit to provide gain to boost the post filter signal back up to line level.

Bottom left: A FET circuit to present a high impedance to the signal from the EQ network

Is the FET circuit meant to be used with the DOA gain circuit or to replace it? I would expect the first option.
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 12, 2011, 10:11:36 PM
Ian, what would be the effect of using 5K, 50K, 500K etc pots rather than the ones shown in your schematic... or maybe somebody can point me to a source for (cost effective) pots in the values needed. Mouser/digikey is coming up short.
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 12, 2011, 11:07:22 PM
This looks great, will somebody be drawing up a pcb so that we could home etch?  I'm thinking of making several and don't want to do a point to point...
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 13, 2011, 12:19:46 AM
I think you'd be spending the same amount of time etching and drilling than with just p2p...
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 13, 2011, 01:46:11 AM
Ian, what would be the effect of using 5K, 50K, 500K etc pots rather than the ones shown in your schematic... or maybe somebody can point me to a source for (cost effective) pots in the values needed. Mouser/digikey is coming up short.

nevermind, just found where to change the pot values in the spreadsheet to adjust my cap values.
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 13, 2011, 02:53:04 AM
Probably true but it makes it a lot neater and once made the PCBs are very easy to stuff.

M
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 13, 2011, 03:58:01 AM
ah, but Ian was kind enough to give us a spreadsheet that will calculate the caps for whatever frequencies you want, giving YOU the choice of what eq you want to build... that maybe be difficult to  implement on one standard PCB, unless we give space for 2,3 paralleled and/or series caps to make precise values.

BUT, i know what you mean, I like when everything is nice and tidy, looking like a well organized plate of jelley-beans. (that's just what polyprop caps remind me of)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 13, 2011, 04:41:01 AM
Lets make some sense of what you've got on that pdf.

Top left: a balanced Line input using a DOA and with a servo. I assume the servo is there to eliminate the need for DC blocking electrolytic capacitors.

Top centre: 12v Power supply circuits for the servos, standard stuff.

Bottom right: a DOA circuit to provide gain to boost the post filter signal back up to line level.

Bottom left: A FET circuit to present a high impedance to the signal from the EQ network

Is the FET circuit meant to be used with the DOA gain circuit or to replace it? I would expect the first option.

yes, they are, it's all correct

the FET circuit is to avoid the noise given by the bipolar input DOA's, so it is to used only with these ones , with the fet opamps as APP2055, FT992, JLM is not required
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 05:22:27 AM
Ian, what would be the effect of using 5K, 50K, 500K etc pots rather than the ones shown in your schematic... or maybe somebody can point me to a source for (cost effective) pots in the values needed. Mouser/digikey is coming up short.

nevermind, just found where to change the pot values in the spreadsheet to adjust my cap values.

I was thinking about making the pot values alterable because it occurred to me that some people might want to make a closer copy to the EQP1A and use the same pot values that it does. You just need to bear in mind that the ratio of the pots to each other must remain the same. I'll tweak the spreadsheet and reissue it.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 05:40:07 AM
This looks great, will somebody be drawing up a pcb so that we could home etch?  I'm thinking of making several and don't want to do a point to point...

I agree. I have built a version of the Pultec point to point and it was a royal PITA.  I am working on a layout right now (maybe we can do a group buy later if there's enough interest). In an attempt to keep this a poor man's project I have come up with an outline of one switch PCB that, by suitable component changes, can be used for both the hi and lo sections. I have excluded the pots as that gives lots of flexibility in their choice and mounting and its only a dozen wires to solder up. Here is a pic of the layout as it stands - the board is 2.1 inches wide and 1.4 inches high so it should fit in a 1U rack if required. I have tracked in two capacitors for each frequency for maximum tweakability.  The two resistors, R1 and R1 are only needed for the hi boost and cut and can be wire links or zero ohm resistors for the lo boost/cut. The terminals (pads really) T1 thru' T4 are the only external connections necessary. The only other component not on the PCB right now is the 56K resistor needed for the lo boost/cut. I am going to draw a version of the schematic using this PCB as building block so you can see how it would all wire together.

Cheers

Ian

(http://www.ianbell.ukfsn.org/pics/PMEQP1Apcb.png)
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 13, 2011, 06:24:41 AM
Fantastic!  Thanks Ian.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 13, 2011, 06:46:17 AM
very good Ian!


Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 07:04:35 AM
Here's a rough sketch of how the switch PCB would be wired up to the pots and the 56K resistor to make the poor man's EQP1A. As you can see, the 56K goes between T2 and T4 on the lo switch PCB and I think there is room for it on the PCB so I think I'll add it already connected to T4 and with a link to connect it to T2 if needed. That way the only external components will be the pots.

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/wiringsm.jpeg)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 07:28:55 AM
Here's the tweaked PCB including the 56K resistor (R3) and its link. I have checked with my favourite PCB supplier using his instant price calculator which tells me if we order 30 we can get them for about 3.50 GBP each. So a pair would be about 7 GBP and with post and paypal I reckon a pair could be delivered anywhere for less than 10GBP. I had to shuffle everything up a little to get that last track in and meet the design rules so the switch is now slightly off centre so I may make one further tweak to get it back dead centre as that makes it simpler from the construction point of view.

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/SWpcbV2.png)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on April 13, 2011, 08:56:19 AM
For £7 a pair + shipping I'd definitely be interested in 2 sets  :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: Joechris on April 13, 2011, 11:25:41 AM
Yeah, two sets here for shure  :)
j
Title: Re: Poor Man's Pultec EQP1-A
Post by: Joechris on April 13, 2011, 11:34:58 AM
Well I know that this is to be without inductors, but I see you have space for one of those small 5mm footprint inductors besides C1.
Could be a nice option for a bell boost on possision one. Just add a small link if not used. Mabye just a messy idea..
j
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 12:36:37 PM
Well I know that this is to be without inductors, but I see you have space for one of those small 5mm footprint inductors besides C1.
Could be a nice option for a bell boost on possision one. Just add a small link if not used. Mabye just a messy idea..
j

Yes, I think I could move C1 and C1A over a little and put in a 5mm space component in series with them and you could just short it out if not used.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 01:10:34 PM
OK, here's the V3 PCB with the switch centred and space for a 5mm pitch inductor L1 at the bottom left hand corner in series with C1 and C1A. I have also moved all the tracks to the solder side (this is designed as a double sided PCB because at the small quantities we want there is no price advantage in single sided and double sided I find much easier to solder). I just need to check the switch footprint is correct for the Lorlin 2 pole 6 way switch (its designed from an RVFM equivalent).

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/PMEQP1ApcbV3.png)
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 13, 2011, 01:25:58 PM
are you able to put a calculation for l1 on the spreadsheet?
Title: Re: Poor Man's Pultec EQP1-A
Post by: Albrebreton on April 13, 2011, 01:55:29 PM
Hi Ian, I am interested in 2 sets too (maibe 4)
Thank you.
Alberto
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 13, 2011, 02:18:59 PM
I'd be in for a stereo set please Ian. Good work.
C
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 13, 2011, 02:28:29 PM
Hi Ian, I am interested in 2 sets too

+1!

I just came along Igor's BA-283 output stage. Do you think it is suitable for this EQ?

Cheers,
Carsten
Title: Re: Poor Man's Pultec EQP1-A
Post by: Joechris on April 13, 2011, 04:05:21 PM
I think the second Neve stage has a input imp around 50k, I could be wrong...
I think it would be safer to use the standard pulteck resistors/pot values if you want to use Neve as makeup.
Or make a fet buffer to put infront of the Neve.
Or use a hamptone fetboy as makeup for even more mojo :-)

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 04:36:43 PM
are you able to put a calculation for l1 on the spreadsheet?

I have just been looking into this in some detail. One of the problems is that raising the impedance at which the EQ works (so we can use a 10K bridging transformer) means the value of inductance needed to provide a reasonable Q (small bandwidth) is correspondingly higher and the value of capacitance is correspondingly lower. For a modest Q of about 1.2 (which is roughly mid way between the sharp and broad setting on the Pultec) then the calculated values of inductance and capacitance are:

Resonant f    Inductance mH    Capacitance nF
3000                  530                  5.31
4000                  400                  3.98
5000                  320                  3.18
8000                  200                  1.99
10000                 160                  1.59
16000                 100                  0.99


At the high frequencies, the capacitance values are becoming impractically low and at the lower frequencies I suspect the values of inductance are greater than can be obtained in a 5mm pitch inductor. If we aim for a more modest Q of 0.6 we get a more reasonable set of values:

Resonant f    Inductance mH    Capacitance nF
3000                  270                 10.61
4000                  200                  7.96
5000                  160                  1.37
8000                  100                  3.98
10000                  80                  3.18
16000                  50                  1.99


There is little point in aiming for an even lower Q because you get a Q of 0.3 just using the normal hi boost and cut together.

So, right now I am not absolutely sure that the inclusion of an inductor actually offers much unless you want to have a 16KHz 'air' setting at position 1.

What do you think?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 13, 2011, 05:50:24 PM
Ian,

   I think you are a bloomin marvel . . . .


    ANdyP



 ps Thank you very much indeed . . .
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 13, 2011, 05:51:34 PM
Oh,


  and I am in for a stereo pair too please
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on April 13, 2011, 06:25:03 PM
a pair for me for sure. what's the width of the pcb? will it fit 51x front panel(1.5'')?
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 13, 2011, 07:00:32 PM
Count me in for 8.  Looking forward to this little beauty...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 13, 2011, 07:21:29 PM
a pair for me for sure. what's the width of the pcb? will it fit 51x front panel(1.5'')?

It is currently 2.1 inches wide and 1.5 inches high so it should fit in a 1U rack. Of course, there is no reason why you should not mount it the other way to make it 1.5 inches wide and 2.1 inches tall but I don't think you would get two of them plus four pots in the 3U height of a 51x module. For that it would probably be better to do a design for a  right angle mounting rotary switch. I think Lorlin do some but I have not tried them.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 13, 2011, 07:29:19 PM
May have to go greyhill...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 14, 2011, 05:10:06 AM
May have to go greyhill...

That would be the obvious, but expensive, choice.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 14, 2011, 05:55:18 AM
OK, here is the Version 4 PCB layout. I have checked the footprint for the switch against the Lorlin, Alpha and RVFM parts. They all have the switch contacts on a 22mm or 22.2mm diameter and my footprint has them on 22mm. The wipers are on either 7.7mm or an 8mm diameter and my footprint has them on just under 8mm diameter. Pin sizes are 1.1mm and recommend PCB hole sizes are 1.4mm and 1.5mm so I have gone for 1.5mm so there should be plenty of slack to accommodate slight differences between switch manufacturers. I printed the layout onto a sheet of paper and offered up an Alpha switch to it and pushed its pins through the paper and it fitted dead on so I am fairly confident the layout is correct. However, before I go ordering 100 GBPs worth of PCBs it would be nice to have a little insurance. Someone mentioned making their own PCB so I would be happy to provide the gerber files to anyone who wants to make their own in exchange for confirmations that the rotary switch fits OK.

Any takers?

Cheers

Ian


(http://www.ianbell.ukfsn.org/pics/PMEQP1ApcbV4.png)
Title: Re: Poor Man's Pultec EQP1-A
Post by: mrclunk on April 14, 2011, 05:57:21 AM
I think Lorlin do some but I have not tried them.

The Lorlin ones seem good quality but i couldn't get them anywhere in MBB (for pre's)but don't think that matters here?
Oh they are also stackable, so could build a stereo version easily.
I can send u one to play with if u like?
Title: Re: Poor Man's Pultec EQP1-A
Post by: Rob Flinn on April 14, 2011, 06:49:55 AM
The Lorlin ones seem good quality but i couldn't get them anywhere in MBB (for pre's)but don't think that matters here?
Paul, look in the RS catalogue ;)
Title: Re: Poor Man's Pultec EQP1-A
Post by: zebra50 on April 14, 2011, 08:11:49 AM
Cracking stuff!

I've been away for a couple of days and I come back to see this is nearly ready to go! Well done guys.

I'd love two sets.
Title: Re: Poor Man's Pultec EQP1-A
Post by: mrclunk on April 14, 2011, 08:17:13 AM
The Lorlin ones seem good quality but i couldn't get them anywhere in MBB (for pre's)but don't think that matters here?
Paul, look in the RS catalogue ;)
Not sure if i see em...
You talking about these wafers.
http://uk.rs-online.com/web/1742676.html
Think the part number means its shorting but i thought the same before ordering whole switches from farnel.
(The switches are half the price at farnel)
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 14, 2011, 09:30:35 AM
stackable for stereo would be so killer.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 14, 2011, 10:05:54 AM
I think Lorlin do some but I have not tried them.

The Lorlin ones seem good quality but i couldn't get them anywhere in MBB (for pre's)but don't think that matters here?

It shouldn't matter as there is no dc to worry about.

Quote
Oh they are also stackable, so could build a stereo version easily.
I can send u one to play with if u like?

That's a very generous offer. I'll PM you.

Cheers

Ian

[/quote]
Title: Re: Poor Man's Pultec EQP1-A
Post by: Rob Flinn on April 14, 2011, 01:15:05 PM
The Lorlin ones seem good quality but i couldn't get them anywhere in MBB (for pre's)but don't think that matters here?
Paul, look in the RS catalogue ;)
Not sure if i see em...
You talking about these wafers.
http://uk.rs-online.com/web/1742676.html
Think the part number means its shorting but i thought the same before ordering whole switches from farnel before.
(The switches are half the price at farnel)

Paul never search on line it just doesn't find things

Try these numbers for a metric shaft.  They're not pcb mount but work if you cut the eyelet off with a pair of snips !
320-714
320-720
320-736
320-742
or if you prefer an imperial shaft
327-664
327-664A
327-670
Title: Re: Poor Man's Pultec EQP1-A
Post by: mrclunk on April 14, 2011, 02:16:18 PM
ah no not those horrid things!
Sorry think we have our wires crossed, i was talking about this type
http://uk.farnell.com/lorlin/pt6434-bmh/switch-1pole-12-pos/dp/1123674
(rs do them also)

Ian, i started out down the post office and then realised the ones i have are 1pole 12pos not 2pole 6pos...
sorry.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Rob Flinn on April 14, 2011, 03:13:20 PM
ah no not those horrid things!
Sorry think we have our wires crossed, i was talking about this type
http://uk.farnell.com/lorlin/pt6434-bmh/switch-1pole-12-pos/dp/1123674
(rs do them also)

ah ! Ok it's just when you mentionmed Lorlin ......
Title: Re: Poor Man's Pultec EQP1-A
Post by: tomugli on April 14, 2011, 04:19:50 PM
definitely up for 2 pcb pairs, excellent project!
cheers, tom
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 14, 2011, 04:25:08 PM
OK, looks like we are good to go on the PCB. The list of people who have expressed an interest in a set (2 PCBs) at present is:

ej_whyte              2 sets
Joechris              2 sets
Albrebreton           2 sets
chrispbass            4 sets
culteousness1         2 sets
strangeandbouncy      2 sets
michalk               1 set
mylesgm               4 sets
zebra50               2 sets
tomugli               2 sets
Kamel                 4 sets
Audiohammer           2 sets
guze                  2 sets
Andreas Pfeiffer      2 sets
noulou                2 sets
mrclunk               2 sets
Holger                2 sets
Matthew Jacobs        4 sets
danijel               4 sets
Grooveteer            4 sets
kante1603             4 sets
0dbfs                 4 sets
3nity                 2 sets
Hank Dussen           2 sets
Citrus Hill          10 sets
baadc0de              4 sets
bovox                 2 sets
menigu                1 set
Michael Tibes         4 sets
Ptownkid              1 set
Davo                  1 set
tzman                 2 sets
MathisD               2 sets
benlindell            4 sets
gevermil              2 sets
hodad                 2 sets
peterc                2 sets
desol                 1 set



Total   101 sets = 202 boards!!!  OK that's it. I have now placed the order. Price will be 5 gbp a set (2 pcbs)

Cheers

Ian

Edit: added Kamel, Audiohammer and guze
Edit: added Andreas Pfeiffer, noulou. mrclunk, Holger, Matthew Jacobs and danijel
Edit: price reduction to 5 GBP per set
Edit: chrispbass +2 sets, added Grooveteer, kantel1603 and 0dbfs then 3nity and Hank Dussen
Edit: added Citrus Hill, baadc0de, bovox and menigu
Edit: added Michael Tibes, Ptownkid, Davo and tzman
Added: MathisD, benlindell and gevermil
Edit: added hodad, mrclunk+1set, peterc, desol
Title: Re: Poor Man's Pultec EQP1-A
Post by: Kamel on April 14, 2011, 04:53:23 PM
hi all,

I'm in for 4 sets

thanks
Title: Re: Poor Man's Pultec EQP1-A
Post by: AudioHammer on April 14, 2011, 05:04:36 PM
I'm in for 2 sets.

Thanks!
Title: Re: Poor Man's Pultec EQP1-A
Post by: guze on April 14, 2011, 06:37:42 PM
i'm in for 2 sets also. great project!!!
Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on April 15, 2011, 02:18:27 AM
2 sets for me please
Title: Re: Poor Man's Pultec EQP1-A
Post by: noulou on April 15, 2011, 04:05:12 AM
2 here please
Title: Re: Poor Man's Pultec EQP1-A
Post by: mrclunk on April 15, 2011, 04:31:25 AM
i'll have a set please.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Holger on April 15, 2011, 04:45:57 AM
2 here please...
Title: Re: Poor Man's Pultec EQP1-A
Post by: Matthew Jacobs on April 15, 2011, 04:59:31 AM
4 for me please...
Title: Re: Poor Man's Pultec EQP1-A
Post by: danijel on April 15, 2011, 05:07:58 AM
4 sets please...




Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 15, 2011, 06:34:20 AM
At this rate, we'll be getting these for free!  ;D

Think I'll have another stereo pair please Ian. (4 sets total)
cheers
C

Title: Re: Poor Man's Pultec EQP1-A
Post by: Grooveteer on April 15, 2011, 08:33:39 AM
I would like 4 sets as well  ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 15, 2011, 09:08:29 AM
4 sets please-thx ian!

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 15, 2011, 10:49:03 AM
I'm in for four channels.

What are you guys planning for makeup gain and transformers?

Thx,
jonathan
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 15, 2011, 11:27:53 AM
regarding the solid state I/O board I am near to finish it.

I have showed the schematic in these pages.
I am available for a group buy if there are enought people interested.

This input-out board is solid state only, it uses IC opamps and/or DOA's (APP opamps, 2520 clones, JE990, FT992, melcor, JLM.....)

cheers
Pier Paolo
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 15, 2011, 12:19:02 PM
There's a feeler for LL5402 iron group buy in the lab.

Maybe this is a sign...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 15, 2011, 12:24:40 PM
There's a feeler for LL5402 iron group buy in the lab.

Maybe this is a sign...

for the Poor Man's Pultec EQP1-A it needed an output stage with very high impedance input,

it's righ to ask to Igor if his project can run with the Poor Man's Pultec EQP1-A
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 15, 2011, 12:30:11 PM
regarding the solid state I/O board I am near to finish it.

I have showed the schematic in these pages.
I am available for a group buy if there are enought people interested.

This input-out board is solid state only, it uses IC opamps and/or DOA's (APP opamps, 2520 clones, JE990, FT992, melcor, JLM.....)

cheers
Pier Paolo

Sounds great Pier! Looking forward to adding a couple of these EQ's to the rack. Are you planning your board for self etch?

Best,
jonathan
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 15, 2011, 03:01:03 PM
What impedance does the output of these eq's need to see?
M
Title: Re: Poor Man's Pultec EQP1-A
Post by: 3nity on April 15, 2011, 03:09:41 PM
Im taking 2 sets please!
Jorge.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Hank Dussen on April 15, 2011, 03:35:18 PM
...and I'll take 2 as well...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 15, 2011, 05:01:47 PM
What impedance does the output of these eq's need to see?
M

Pretty high. 470K or greater would be fine. Ideal for a tube or FET input.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Citrus Hill on April 16, 2011, 12:13:21 AM
Hi Ian,
This looks like its going to be a great little project.  I'm in for 10 sets total if the order is still open.
Thanks,
Rob Mc.
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on April 16, 2011, 02:23:33 AM
Oh well, what the hell, if it's still open, 4 sets for me :) You can never have too many pultecs..
Title: Re: Poor Man's Pultec EQP1-A
Post by: bovox on April 16, 2011, 05:10:14 AM
Hey Ian, I´m also in for 2 sets please. Thanks for a great project.
Cheers Bo
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 07:26:01 AM
this the board quasi-finished
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 08:59:04 AM
Ian, i started out down the post office and then realised the ones i have are 1pole 12pos not 2pole 6pos...
sorry.

Hi Paul,

1 pole 12 way arrived in the post this morning. Many thanks. It looks to be of substantial construction - better than I had anticipated. Just one query, it is supposed to be 12 ways but  when I rotate the switch it appears to have only eleven positions.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 16, 2011, 09:03:27 AM
this the board quasi-finished

Interested...

I have 4 Triad hs56V's which I'm going to use. I think I'll keep one connected as output but will make the input one switch able.
This should all be possible with this board right?...maybe some fiddling around.

This should be great. Options to switch between an original solid state pultec topology and a modern opamp input variation and what not...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 09:10:40 AM
and this is the in-out board finished for pulteq eq (with inductor and inductorless).

it has trasformerless input only, usable with a IC opamps or a DOAs,
 
the ouptstage can use IC opamps or DOA's and can be used with or without trasformer  

you can use many IC opamps and DOA's in these stages as NE5534, OPA134, OPA602, OPA604, OPA606, OPA627.....and many others and APP opamps , API2520's , FT992, MM99, JE990, JLM and others.

if you want use a bipolar DOA (or IC opamp) on out stage you can use the fet buffer onboard to avoid the noise for the input noise current of the bipolar DOA's and IC opamps.


it's 173 x 102 mm

Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 16, 2011, 09:17:14 AM
Hi Radience,



   think you need a 10k - 10k input, not 600 - 600



   Kindest regards,



     ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: menigu on April 16, 2011, 09:18:49 AM
1 set for me please. Thank you very much for making these!

Best,

Max
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 16, 2011, 09:37:01 AM
Hi Radience,



   think you need a 10k - 10k input, not 600 - 600



   Kindest regards,



     ANdyP

Oops, sorry...I'm going to build the original Pultec.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 09:51:10 AM
this the board quasi-finished

Interested...

I have 4 Triad hs56V's which I'm going to use. I think I'll keep one connected as output but will make the input one switch able.
This should all be possible with this board right?...maybe some fiddling around.

This should be great. Options to switch between an original solid state pultec topology and a modern opamp input variation and what not...

yes, it's possible with an external switch using the tube section or the solid state section in a pultec eq as in a MM eq, using this board plus a tube board.

 
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 16, 2011, 10:01:14 AM
this the board quasi-finished

Interested...

I have 4 Triad hs56V's which I'm going to use. I think I'll keep one connected as output but will make the input one switch able.
This should all be possible with this board right?...maybe some fiddling around.

This should be great. Options to switch between an original solid state pultec topology and a modern opamp input variation and what not...

yes, it's possible with an external switch using the tube section or the solid state section in a pultec eq as in a MM eq.

 

I'm not going to use tubes. I'll switch between transformer or opamp input and maybe the same for output.
To have an original tube pultec I would have needed the notorious peerless 217 transformer which I don't.
I do have 4 triad HS56V's though...which, together with an API 2520 opamp, would be good for two original solid state pultecs, or a stereo version in my case....
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 10:08:51 AM

I'm not going to use tubes. I'll switch between transformer or opamp input and maybe the same for output.
To have an original tube pultec I would have needed the notorious peerless 217 transformer which I don't.
I do have 4 triad HS56V's though...which, together with an API 2520 opamp, would be good for two original solid state pultecs, or a stereo version in my case....


it's possible use an external switch on out to use or not the out trasformers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 10:43:46 AM
Hi Radience,

   think you need a 10k - 10k input, not 600 - 600

   Kindest regards,

     ANdyP

There's no reason you could not use a 600 - 600 input transformer with the poor man's EQP1A if you wanted. You just need to strap a 620 ohm resistor across the secondary instead of the current 12K.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 10:46:17 AM
Just a thought, would anyone be interested in a poor man's tube gain make up stage for the poor man's EQP1A if I can come up with one?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 16, 2011, 11:37:33 AM
Just a thought, would anyone be interested in a poor man's tube gain make up stage for the poor man's EQP1A if I can come up with one?

Great Ian! That's what I have been searching for!

I bet there will be 20++ sets ordered at least.
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 16, 2011, 11:40:47 AM
Absolutely!

Best regards,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: lassoharp on April 16, 2011, 11:50:18 AM
Quote
Just a thought, would anyone be interested in a poor man's tube gain make up stage for the poor man's EQP1A if I can come up with one?

Absolutely!


I already have a couple amps I'm planning on using but would like to see what you have in mind.  I like having about 10 or 15db beyond unity gain on the makeup amp so I've chose amps that will allow for that.

Nearly always sweeter with tubes.   :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 16, 2011, 01:04:50 PM



it's possible use an external switch on out to use or not the out trasformers

Good to know this!
Will your boards be available in the white market section?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 01:52:57 PM
I think yes, but first I would like a group buy if there are enough people that want them,
My target is a group buy for at least 50 PCB's, with 50 PCB's ordered I can make a very good price per board, but with 100 is much better. I think with a group buy for 50 pcs I could do 11 euros per board,  and  with a group buy for 100 pcs 9 euros per boardThe problem is that the dimensions are 173 x 102 mm and for these dimensions the prices can not to be cheaper, even if however the project is cheap.

The good thing is that several sound engineers prefer having the double section: solid state and tube section in the same chassis.

Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 16, 2011, 02:27:02 PM
BTW, I think that having a tube make up section (Ian's mu follower) and a germanium make up section (APP2050GE) together
 in a pulteq eq is good thing 8)
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 16, 2011, 03:21:46 PM
I think yes, but first I would like a group buy if there are enough people that want them,



Well, let me start of with saying I'm interested in two boards...
Thanks for doing this!
Title: Re: Poor Man's Pultec EQP1-A
Post by: zayance on April 16, 2011, 04:53:59 PM
Quote
However, before I go ordering 100 GBPs worth of PCBs it would be nice to have a little insurance. Someone mentioned making their own PCB so I would be happy to provide the gerber files to anyone who wants to make their own in exchange for confirmations that the rotary switch fits OK.

I'm a little late but Still need someone to test this out? Maybe i can help let me know.
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 16, 2011, 04:56:12 PM
Hi Radience,

   think you need a 10k - 10k input, not 600 - 600

   Kindest regards,

     ANdyP

There's no reason you could not use a 600 - 600 input transformer with the poor man's EQP1A if you wanted. You just need to strap a 620 ohm resistor across the secondary instead of the current 12K.

Cheers

Ian

Great!  I have a large selection of 600:600 transformers and only a few 10k:10K so this will be excellent.  What about using a non 1:1 transformer though?  I have quite a few 600:1200 tx that would be nice to use and though I could use them as output could I use them as input as well?  if so what should the strapping resistor be?


Just a thought, would anyone be interested in a poor man's tube gain make up stage for the poor man's EQP1A if I can come up with one?

Cheers

Ian

Um, now let me see... yes?

Thanks again for doing all the leg work on this project.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 16, 2011, 05:19:10 PM
OK, looks like we are good to go on the PCB. The list of people who have expressed an interest in a set (2 PCBs) at present is:

ej_whyte              2 sets
Joechris              2 sets
Albrebreton           2 sets
chrispbass            4 sets
culteousness1         2 sets
strangeandbouncy      2 sets
michalk               1 set
mylesgm               4 sets
zebra50               2 sets
tomugli               2 sets
Kamel                 4 sets
Audiohammer           2 sets
guze                  2 sets
Andreas Pfeiffer      2 sets
noulou                2 sets
mrclunk               1 set
Holger                2 sets
Matthew Jacobs        4 sets
danijel               4 sets
Grooveteer            4 sets
kante1603             4 sets
0dbfs                 4 sets
3nity                 2 sets
Hank Dussen           2 sets
Citrus Hill          10 sets
baadc0de              4 sets
bovox                 2 sets
menigu                1 set



Total   79 sets = 158 boards!!!  This is unbelievable! Let me know if there are any errors, corrections, additions or deletions and I'll aim to order 160+ PCBs next week which will definitely bring the price down to 5GBP a set plus shipping.

Cheers

Ian

Edit: added Kamel, Audiohammer and guze
Edit: added Andreas Pfeiffer, noulou. mrclunk, Holger, Matthew Jacobs and danijel
Edit: price reduction to 5 GBP per set
Edit: chrispbass +2 sets, added Grooveteer, kantel1603 and 0dbfs then 3nity and Hank Dussen
Edit: added Citrus Hill, baadc0de, bovox and menigu

Ian, would you like any money upfront seen as the quantity has increased somewhat? :)
C
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 05:37:24 PM
Quote
However, before I go ordering 100 GBPs worth of PCBs it would be nice to have a little insurance. Someone mentioned making their own PCB so I would be happy to provide the gerber files to anyone who wants to make their own in exchange for confirmations that the rotary switch fits OK.

I'm a little late but Still need someone to test this out? Maybe i can help let me know.

Sent you a PM.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 05:44:44 PM
Great!  I have a large selection of 600:600 transformers and only a few 10k:10K so this will be excellent.  What about using a non 1:1 transformer though?  I have quite a few 600:1200 tx that would be nice to use and though I could use them as output could I use them as input as well?  if so what should the strapping resistor be?

The input impedance of the EQ is about 50K ohms so all you need to do is add a resistor across the transformer secondary which, together with the EQ 50K is equal to the transformer secondary impedance. For small secondary impedances up to about 1200 ohms this essentially means using a resistor as close as you can sensibly get to the secondary impedance. So for a 1200 ohm secondary use a 1.2K resistor.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 16, 2011, 05:56:52 PM
Ian, would you like any money upfront seen as the quantity has increased somewhat? :)
C

Nice thought but this is a great community and I trust the people here. What I will do though is ask for payment as soon as I have placed the order. It is not until then that I get an invoice with the actual cost and I think we may well have another price reduction to come. I have to pay for the PCBs up front so getting payment soon after ordering will reduce my exposure. The other thing is I have yet to sort out the postage costs. At the moment it looks like a flat rate of 1.00GBP for UK, 1.50GBP for the EU and 2.00GBP for the rest of the world would be the most straightforward. Then there is the old problem of Paypal fees.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 16, 2011, 06:39:19 PM
Ian I think you should find out the cost per board and then add a nominal fee to cover the paypal fee.  The price per pcb is so low I don't mind adding a few extra dollars per set to cover the cost of paypal etc and there should of course be some return for yourself and the work you have put it into this.  You said the cost might be as low as 5gbp per board, why not charge 7gbp per board plus shipping?  thats still a great price.

Title: Re: Poor Man's Pultec EQP1-A
Post by: Kamel on April 17, 2011, 02:05:21 AM
+1

add paypal fees to the total price and why not shipping as Gustav do.

this project seems to be perfect for a tube console  ;)
Title: Re: Poor Man's Pultec EQP1-A
Post by: zayance on April 17, 2011, 05:23:14 AM
Quote
However, before I go ordering 100 GBPs worth of PCBs it would be nice to have a little insurance. Someone mentioned making their own PCB so I would be happy to provide the gerber files to anyone who wants to make their own in exchange for confirmations that the rotary switch fits OK.

I'm a little late but Still need someone to test this out? Maybe i can help let me know.

Sent you a PM.

Cheers



Ian

PM received

Sent you a MAIL   ;D

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 17, 2011, 07:00:53 AM
Ian I think you should find out the cost per board and then add a nominal fee to cover the paypal fee.  The price per pcb is so low I don't mind adding a few extra dollars per set to cover the cost of paypal etc and there should of course be some return for yourself and the work you have put it into this.  You said the cost might be as low as 5gbp per board, why not charge 7gbp per board plus shipping?  thats still a great price.

At the moment the price is 5gbp per SET of two boards so I guess that means it is already a great price  :) So if everyone is happy with that I'll leave it at that.

I think I have a handle on shipping and I discovered that if people select a 'gift' when paying by Paypal they pick up the charges themselves and I get the full amount.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 17, 2011, 07:02:35 AM
+1

add paypal fees to the total price and why not shipping as Gustav do.


What does Gustav do?

Quote
this project seems to be perfect for a tube console  ;)

Oh, yes! I plan to offer this in my custom tube consoles.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Michael Tibes on April 17, 2011, 07:50:02 AM
4 sets for me please if it's not too late...

Thanx,


Michael
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 17, 2011, 08:24:19 AM
4 sets for me please if it's not too late...

Thanx,


Michael

Just in time Michael. zayance is doing a test etch on Monday and if that is OK the order will go out Tuesday 19th April.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: radiance on April 17, 2011, 11:59:02 AM
I think yes, but first I would like a group buy if there are enough people that want them,
My target is a group buy for at least 50 PCB's, with 50 PCB's ordered I can make a very good price per board, but with 100 is much better. I think with a group buy for 50 pcs I could do 11 euros per board,  and  with a group buy for 100 pcs 9 euros per boardThe problem is that the dimensions are 173 x 102 mm and for these dimensions the prices can not to be cheaper, even if however the project is cheap.

The good thing is that several sound engineers prefer having the double section: solid state and tube section in the same chassis.



Maybe start a new thread for this...
Title: Re: Poor Man's Pultec EQP1-A
Post by: Ptownkid on April 17, 2011, 02:23:12 PM
another pair here if possible. Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 17, 2011, 02:51:33 PM
I think yes, but first I would like a group buy if there are enough people that want them,
My target is a group buy for at least 50 PCB's, with 50 PCB's ordered I can make a very good price per board, but with 100 is much better. I think with a group buy for 50 pcs I could do 11 euros per board,  and  with a group buy for 100 pcs 9 euros per boardThe problem is that the dimensions are 173 x 102 mm and for these dimensions the prices can not to be cheaper, even if however the project is cheap.

The good thing is that several sound engineers prefer having the double section: solid state and tube section in the same chassis.



Maybe start a new thread for this...

yes, I am going to start a group buy to another thread

Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on April 17, 2011, 03:03:31 PM
Wow, this developed quickly!

I'd like to get a pair if possible

cheers,
dave
Title: Re: Poor Man's Pultec EQP1-A
Post by: tzman on April 17, 2011, 05:59:28 PM
If I'm not too late: 2 sets for me, please!
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 17, 2011, 06:17:02 PM
If I'm not too late: 2 sets for me, please!

You are in along with Ptownkid and Davo.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: MatthisD on April 17, 2011, 06:58:27 PM
Can I put my name down for 2 sets please
Title: Re: Poor Man's Pultec EQP1-A
Post by: benlindell on April 17, 2011, 07:33:36 PM
I'd like to jump in and get 4 sets if it's still open.
Title: Re: Poor Man's Pultec EQP1-A
Post by: gevermil on April 17, 2011, 09:06:58 PM
cripes .... 2 here please if possible .
Title: Re: Poor Man's Pultec EQP1-A
Post by: hodad on April 17, 2011, 09:10:41 PM
I'm also in for 2 sets if it's not too late.

Thanks!
Tom
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 17, 2011, 09:12:47 PM
There maybe should be a black market thread for this group buy. Maybe then everyone will get a chance to see it and jump in.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 18, 2011, 04:08:48 AM
cripes .... 2 here please if possible .

You just squeezed in along with benlindell and Mathis D.

The total now stand at 190 boards so I am going to draw a line under this purchase right now and order 200 boards. If there is lots more interest I'll do a second group buy in the black market.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on April 18, 2011, 07:14:14 AM
Thanks Ian for doing this ... it's going to be quite an effort, I think, to ship 200 boards!
Title: Re: Poor Man's Pultec EQP1-A
Post by: mrclunk on April 18, 2011, 07:25:53 AM
hey Ian, any chance i could up my order to a pair instead of one.
may as-well do a stereo box init.
ta
paul
Title: Re: Poor Man's Pultec EQP1-A
Post by: peterc on April 18, 2011, 08:11:16 AM
Hi Ian

I'd also like 4 please.

Thx
Peter
Title: Re: Poor Man's Pultec EQP1-A
Post by: desol on April 18, 2011, 11:49:06 AM
I'll take a couple, if there's any left.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 18, 2011, 03:47:29 PM
I have now placed an order for 210 PCBs. zayance has today etched and drilled a PCB from the layout I provided and confirms that the Lorlin switch and other components fit OK.

http://img215.imageshack.us/img215/9360/p1030517y.jpg (http://img215.imageshack.us/img215/9360/p1030517y.jpg)
http://img98.imageshack.us/img98/9888/p1030519v.jpg (http://img98.imageshack.us/img98/9888/p1030519v.jpg)

I have decided to have a flat rate for shipping of 2gbp and if, when you pay by Paypal, you could select 'gift' I get the full amount and you pay the charges. Here's the list of buyers and the amounts to pay. The boards should be here in two weeks and it would be nice to have all the money in by then.

 Handle             Quantity        Price (gbp)
ej_whyte              2 sets            paid
Joechris              2 sets            paid
Albrebreton           2 sets            paid
chrispbass            4 sets            paid
culteousness1         2 sets            paid
strangeandbouncy      2 sets            paid
michalk               1 set             paid
mylesgm               4 sets            paid
zebra50               2 sets            paid
tomugli               2 sets            paid
Kamel                 4 sets            paid
Audiohammer           2 sets            paid
guze                  2 sets            paid
Andreas Pfeiffer      2 sets            paid
noulou                2 sets            paid
mrclunk               2 sets            paid
Holger                2 sets            paid
Matthew Jacobs        4 sets            paid
danijel               4 sets            paid
Grooveteer            4 sets            paid
kante1603             4 sets            paid
0dbfs                 4 sets            paid
3nity                 2 sets            paid
Hank Dussen           2 sets            paid
Citrus Hill          10 sets            paid
baadc0de              4 sets            paid
bovox                 2 sets            paid
menigu                1 set             paid
Michael Tibes         4 sets            paid
Ptownkid              2 sets            paid
Davo                  1 set             paid
tzman                 2 sets            paid
MathisD               2 sets            paid
benlindell            4 sets            paid
gevermil              2 sets            12
hodad                 2 sets            paid
peterc                2 sets            paid
desol                 2 sets            paid
creal                 2 sets            paid
   

I'll update this page as payments are made.

Cheers

Ian

Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 18, 2011, 03:57:49 PM
Wow! Moves quick around here sometimes. Good thing I wasn't napping :)

You might have already notated your paypal address but I don't remember seeing it in this thread.

Thanks Ian, This is awesome. So looking forward to it.

Best,
jonathan

Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on April 18, 2011, 04:12:21 PM
hi Ian

I'm also in for 2 sets if it's not too late.

Thx for this nice project

Cyril
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 18, 2011, 04:45:28 PM
Thank you very much Ian!

May I ask for the "How-to-pay"-procedure (your paypal adress,where to state the shipping adress (subject field))etc.

Thanks for all the work you´ve put in here!

Best regards from germany,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on April 18, 2011, 04:46:33 PM
Paid :) Looking forward to these
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 18, 2011, 05:05:33 PM
Thank you very much Ian!

May I ask for the "How-to-pay"-procedure (your paypal adress,where to state the shipping adress (subject field))etc.

Thanks for all the work you´ve put in here!

Best regards from germany,

Udo.

OK, a how to pay procedure would be a good idea!!!!

email for paypal is ianbellATukfsnDOTorg

Please put your forum name and full shipping address in a note attached to the payment. If you can select 'gift' in the paypal options you will pay the paypal charges rather than me.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 18, 2011, 05:06:07 PM
hey Ian, any chance i could up my order to a pair instead of one.
may as-well do a stereo box init.
ta
paul

Done.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on April 18, 2011, 05:25:40 PM
Paid, cheers for the project
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on April 18, 2011, 05:33:01 PM
Hi Ian,


   Paid. Thanks again.


   ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: Ptownkid on April 18, 2011, 06:19:03 PM
I wanted 2 sets...
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 18, 2011, 06:34:02 PM
I wanted 2 sets...

OK, page tweaked.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 18, 2011, 06:44:06 PM
Paid for four sets.

Thanks Ian!

-jb
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on April 18, 2011, 06:49:38 PM
Hi Ian
paypal'ed for 2 sets

Thanks
Cyril
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on April 18, 2011, 06:51:00 PM
just payed, thanks!
Title: Re: Poor Man's Pultec EQP1-A
Post by: 3nity on April 18, 2011, 09:45:33 PM
So the total has shipping included for 12GBP??
Paid anyways...

Thanks.
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 19, 2011, 03:07:24 AM
paid up.  Thanks again....

M
Title: Re: Poor Man's Pultec EQP1-A
Post by: Grooveteer on April 19, 2011, 03:45:10 AM
Paid.

Many thanks, Ian.

Cheers,

G
Title: Re: Poor Man's Pultec EQP1-A
Post by: zebra50 on April 19, 2011, 03:48:01 AM
Wonga'd!
 ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: Albrebreton on April 19, 2011, 03:49:51 AM
Hi Ian,

Paid. Thanks again.

Alberto.
Title: Re: Poor Man's Pultec EQP1-A
Post by: noulou on April 19, 2011, 04:29:21 AM
doon.  8)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 19, 2011, 05:06:02 AM
hi Ian

I'm also in for 2 sets if it's not too late.

Thx for this nice project

Cyril

Hi Cyril,

Strictly speaking you were after the deadline but I have received your payment! I ordered 10 extra PCBs and two people already said they wanted 2 sets not 2 PCBs so that has consumed 4 of them. Your 2 sets consumes another 4 PCBs leaving just a couple for me!!!

OK, you are in. I'll tweak the list to include you.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 19, 2011, 05:15:12 AM
So the total has shipping included for 12GBP??
Paid anyways...

Thanks.

You forget to send me your shipping details and real name.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: peterc on April 19, 2011, 06:02:26 AM
Paid. Thanks

Peter
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on April 19, 2011, 06:11:13 AM
Thanks you Ian
like we say in france
ouf c'etait moins une.
Best,

Cyril

hi Ian

I'm also in for 2 sets if it's not too late.

Thx for this nice project

Cyril

Hi Cyril,

Strictly speaking you were after the deadline but I have received your payment! I ordered 10 extra PCBs and two people already said they wanted 2 sets not 2 PCBs so that has consumed 4 of them. Your 2 sets consumes another 4 PCBs leaving just a couple for me!!!

OK, you are in. I'll tweak the list to include you.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: tzman on April 19, 2011, 07:11:43 AM
Paid for 2 sets!

Thanks!
Title: Re: Poor Man's Pultec EQP1-A
Post by: guze on April 19, 2011, 07:42:27 AM
paypaled
Title: Re: Poor Man's Pultec EQP1-A
Post by: menigu on April 19, 2011, 08:07:40 AM
money sent
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 19, 2011, 08:16:10 AM
Just paid Ian.
cheers
Chris
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 19, 2011, 10:49:16 AM
Paypal´ed for 4 sets,

thank you Ian!

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: bovox on April 19, 2011, 11:35:15 AM
Payed for 2 sets via paypal. Thanks!
Cheers Bo
Title: Re: Poor Man's Pultec EQP1-A
Post by: skal1 on April 19, 2011, 12:32:52 PM
Hi ian

if you do another run i will defo have a stereo set, will have to be end of may ,money tight.

cheers

skal1
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 19, 2011, 01:16:05 PM
Hi ian

if you do another run i will defo have a stereo set, will have to be end of may ,money tight.

cheers

skal1

Someone suggested that another run might be better in the black market then more people would see it. I plan to wait until the present run is delivered and people have had time to build them and listen to them before doing another run. So I guess that will not be much before the end of May anyway.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: desol on April 19, 2011, 01:30:03 PM
Paid.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Citrus Hill on April 19, 2011, 02:18:29 PM
Hi Ian,
I just paypal'd for the 10 sets.  Thanks!
Rob Mc.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on April 19, 2011, 02:40:40 PM
Hi Ian,

I wanted to grab two sets rather than one... am I too late?

Cheers,
Dave
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 19, 2011, 03:21:48 PM
yes...
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on April 19, 2011, 04:20:35 PM
gemini:  cheers, but the question was for Ian

I'm already in for one set (I thought one set was a stereo pair.)  If I could grab another that'd be great... if not, no worries

Thanks Ian!
Title: Re: Poor Man's Pultec EQP1-A
Post by: tomugli on April 19, 2011, 04:27:41 PM
payment sent.

cheers, tom ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 19, 2011, 04:31:39 PM
Paypal´ed for 4 sets,

thank you Ian!

Udo.

Hey Udo,

could you send the payment as a gift? It seems like my german paypal account hasn't got this option.

Greetings from Cologne,
Carsten
Title: Re: Poor Man's Pultec EQP1-A
Post by: tzman on April 19, 2011, 05:31:46 PM
Paypal´ed for 4 sets,

thank you Ian!

Udo.

Hey Udo,

could you send the payment as a gift? It seems like my german paypal account hasn't got this option.

Greetings from Cologne,
Carsten

I think you'll have to select the "Private" tab first...
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 19, 2011, 05:51:26 PM
gemini:  cheers, but the question was for Ian

I'm already in for one set (I thought one set was a stereo pair.)  If I could grab another that'd be great... if not, no worries

Thanks Ian!

link=topic=43859.msg549559#msg549559 date=1303203962]

Davo, sorry if I offended. I'm typing from my android, so my brief-ness must have come across as rude. I'm just trying to help Ian out since he did absolutely all the leg work on these PCBs as well as shipping them all out once they get here. But I'll make sure to let him do the talking next time. 

hi Ian

I'm also in for 2 sets if it's not too late.

Thx for this nice project

Cyril

Hi Cyril,

Strictly speaking you were after the deadline but I have received your payment! I ordered 10 extra PCBs and two people already said they wanted 2 sets not 2 PCBs so that has consumed 4 of them. Your 2 sets consumes another 4 PCBs leaving just a couple for me!!!

OK, you are in. I'll tweak the list to include you.

Cheers

Ian
[/quote]

Cheers, Gemini -minding my own business- 86
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 19, 2011, 05:55:48 PM
Hi Ian,

I wanted to grab two sets rather than one... am I too late?

Cheers,
Dave

I am rather afraid you are. I ordered a few extra but nearly all those have gone leaving just a couple for myself.

Sorry

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 19, 2011, 06:15:53 PM
This all happened very fast. Absolutely amazing to witness !

Cheers,
jb
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on April 19, 2011, 06:42:32 PM
Thanks Ian, I was afraid that would be the case... in any case thankyou for the great work!

Gemini:  I must admit, I took it as a bit rude... my humble apologies, and thanks for clearing that up. ;)

Cheers,
Dave
Title: Re: Poor Man's Pultec EQP1-A
Post by: benlindell on April 19, 2011, 11:18:48 PM
paid up.
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 20, 2011, 03:51:35 AM
Hey Udo,

could you send the payment as a gift? It seems like my german paypal account hasn't got this option.

Greetings from Cologne,
Carsten

Hi Carsten,

no,haven´t found it either-is it hidden somewhere or are there different options in different countries?Anybody?

@Ian:Sorry,we have got some problems with the "gift"-option-seems to be here in our german paypal-accounts.
If you can tell me how much the paypal fees are or how much money is missing i will send it to you immediately!
Excuse me/us for causing trouble!

Best,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on April 20, 2011, 04:07:55 AM
Udo,

On the first page of your paypal account (under "send money")  There's a couple of tabs that say "purchase" and "personal"... I don't know if I've
seen this before either...... anyway, hit the personal tab, and your gift option should be right in there.  It may very well be different with your paypal,
but this is where I found it.

And Ian, I just paid as well.

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: leadbreath on April 20, 2011, 04:11:03 AM
sh*t!! i cant believe ive just missed the boat on this one....  im gonna go off in a corner and sulk now. if anybody's got any boards to spare let me know please.

mick
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 20, 2011, 04:24:50 AM
Udo,

On the first page of your paypal account (under "send money")  There's a couple of tabs that say "purchase" and "personal"... I don't know if I've
seen this before either...... anyway, hit the personal tab, and your gift option should be right in there.  It may very well be different with your paypal,
but this is where I found it.

And Ian, I just paid as well.

Cheers

Thank you Davo,

but it´s too late because I have sent the money already-will wait for Ian´s reply and then pay the rest if possible!

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 20, 2011, 04:26:40 AM
Hi Carsten,

no,haven´t found it either-is it hidden somewhere or are there different options in different countries?Anybody?

@Ian:Sorry,we have got some problems with the "gift"-option-seems to be here in our german paypal-accounts.
If you can tell me how much the paypal fees are or how much money is missing i will send it to you immediately!
Excuse me/us for causing trouble!

Best,

Udo.

I just read that paypal changed their terms of use last november. Unfortunately the gift option is no longer available.

Maybe we german paypalers can send you a little extra to cover the fees, Ian?
Title: Re: Poor Man's Pultec EQP1-A
Post by: danijel on April 20, 2011, 05:07:29 AM
Just paid.

Cheers

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 20, 2011, 06:45:05 AM
Hi Carsten,

no,haven´t found it either-is it hidden somewhere or are there different options in different countries?Anybody?

@Ian:Sorry,we have got some problems with the "gift"-option-seems to be here in our german paypal-accounts.
If you can tell me how much the paypal fees are or how much money is missing i will send it to you immediately!
Excuse me/us for causing trouble!

Best,

Udo.

I just read that paypal changed their terms of use last november. Unfortunately the gift option is no longer available.

Maybe we german paypalers can send you a little extra to cover the fees, Ian?

Don't worry about it, it is only a small amount on transactions this size. If it really bothers you then add 0.50 gbp which should cover it in most cases.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 20, 2011, 11:55:03 AM
Don't worry about it, it is only a small amount on transactions this size. If it really bothers you then add 0.50 gbp which should cover it in most cases.

Cheers

Ian
Hi Ian,

some gbps sent for "us germans" :D
You are a generous man!

Cheers,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on April 20, 2011, 12:54:13 PM
Ian do you have a merchant account? because I believe you can only receive around 500 usd per month on a personal account...just thought I would throw than in there.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 20, 2011, 01:01:05 PM
Ian do you have a merchant account? because I believe you can only receive around 500 usd per month on a personal account...just thought I would throw than in there.

Good point. I need to check that out.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on April 20, 2011, 02:21:40 PM
Payment sent.

Cheers,
Carsten
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 20, 2011, 06:04:46 PM
Don't worry about it, it is only a small amount on transactions this size. If it really bothers you then add 0.50 gbp which should cover it in most cases.

Cheers

Ian
Hi Ian,

some gbps sent for "us germans" :D
You are a generous man!

Cheers,

Udo.

Thank you that was very kind indeed. I have always found the Germans to be a very courteous people.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Kamel on April 21, 2011, 01:54:23 AM
Hi Ian

paypal'ed for 4 set

May thanks for this offer

Kamel
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 21, 2011, 05:29:07 PM

Thank you that was very kind indeed. I have always found the Germans to be a very courteous people.

Cheers

Ian
You´re welcome Ian,but may I say that the germans have also their "black sheep"(hope this is the same in english?) as anywhere else :D :D :D

Best regards,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 21, 2011, 05:58:56 PM

Thank you that was very kind indeed. I have always found the Germans to be a very courteous people.

Cheers

Ian
You´re welcome Ian,but may I say that the germans have also their "black sheep"(hope this is the same in english?) as anywhere else :D :D :D

Best regards,

Udo.

Yes, we have black sheep too! When I was working we had many clients in Germany and we had a small office in Frankfurt. I had many pleasant business trips to Germany. One of my favourite memories is staying is a hotel in the Black Forest that was like an enormous log cabin. We had wild boar and asparagus soup followed by wild boar steaks - wonderful!

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on April 21, 2011, 06:10:27 PM
Isn't that what a German-black-sheep is (Wild-Boar) ??

Gruess Gott !!
-jb
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 21, 2011, 06:46:21 PM
Isn't that what a German-black-sheep is (Wild-Boar) ??

Gruess Gott !!
-jb

No-completely off topic now-but here´s a pic of a wild-boar.The males weigh up to 190kgs and it´s better not to meet them in the forrest ;)

Pfüa Gott,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: okgb on April 22, 2011, 07:27:40 AM
Didn't see this thread  [ now in the wrong section ? ]
but i'm in for a pair , what do i do ?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 22, 2011, 08:07:32 AM
Didn't see this thread  [ now in the wrong section ? ]
but i'm in for a pair , what do i do ?

Looks like there may be enough interest already for a second run. So, I'll start a new thread in the black market for a second group buy and see how many takers we get.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 23, 2011, 04:26:52 PM
The males weigh up to 190kgs and it´s better not to meet them in the forrest ;)


it is better to meet them inside a bread  :P
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on April 23, 2011, 04:40:19 PM

it is better to meet them inside a bread  :P

Yes,or in a soup or as roast or as steaks or..... :D
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on April 24, 2011, 07:54:40 AM
I think yes, but first I would like a group buy if there are enough people that want them,



Well, let me start of with saying I'm interested in two boards...
Thanks for doing this!
Hi Pier

If you make a group buy, i 'm in for 2 boards with 2  Germanium DOA
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 24, 2011, 09:26:36 AM
I am waiting the quotes form some PCB companies for the boards for best quality/price,

just there are 4 persons interested, if there are other persons interested, they are invited to let me know it, please.


regarding the APP2050 germanium several my customers bought them for Peterc eq and they sounded impressive.

 
Title: Re: Poor Man's Pultec EQP1-A
Post by: Matthew Jacobs on April 24, 2011, 10:12:08 AM
I am waiting the quotes form some PCB companies for the boards for best quality/price,

just there are 4 persons interested, if there are other persons interested, they are invited to let me know it, please.


regarding the APP2050 germanium several my customers bought them for Peterc eq and they sounded impressive.

 

I am interested in 4 sets for 2 stereo builds. We're do we express our interest? In your white market thread?
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on April 24, 2011, 10:22:30 AM
I'm interested in a stereo set Pier and would love to use your germanium 2050 in them.

M
Title: Re: Poor Man's Pultec EQP1-A
Post by: [silent:arts] on April 24, 2011, 10:48:14 AM
The males weigh up to 190kgs and it´s better not to meet them in the forrest ;)


it is better to meet them inside a bread  :P


while I grew up in the black forest: I have seen more in the berlin city than in my youth :o
http://www.youtube.com/watch?v=1AZxuZUeUW0
http://www.youtube.com/watch?v=1S0ZYM0mjh0
http://www.stadtentwicklung.berlin.de/forsten/wildtiere/de/wildschwein.shtml
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 25, 2011, 05:51:11 AM
just a note:

for the group buy on my IO board on Poor Man's Pultec EQP1-A and the traditional PULTEQ EQ see here, thanks.
http://www.groupdiy.com/index.php?topic=33576.360



Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on April 26, 2011, 03:39:29 AM
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on April 26, 2011, 06:37:35 AM
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

Check black market for Ian's poor mans pultec boards. Above for Pier's boards for make up gain.
Ian is also curently designing a valve make up gain board. Check in the 'drawing board'.
Title: Re: Poor Man's Pultec EQP1-A
Post by: jackies on April 26, 2011, 09:48:00 AM
Just wanted to say, looks like a great project, I wonder why nobody came up with this before?
Great work Ian, and thanks for sharing!
...Not to mention that this is yet another great project for strictly p2p club!  8)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ppa on April 26, 2011, 09:49:39 AM
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

regarding my IO board, it is 12 euros each one if bought in the group buy
one board is mono and also two layers (double face),

it is 173x105 mm



Title: Re: Poor Man's Pultec EQP1-A
Post by: Michael Tibes on April 26, 2011, 10:00:14 AM
Hi Ian,

I paid mine as well and made it 24 GBP to cover the transfer fees because of the missing 'gift' option here.
Thank you so much for this great project and your efforts in making the pcbs available!

Michael
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 26, 2011, 11:32:32 AM
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

Andreaas, I have you down for two sets of the EQ PCBs (that's four in total) for a total of 12gbp including shipping. See page 9 of this thread for the complete list.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on April 26, 2011, 11:49:04 AM
Thanks Ian. I Know.
My question was directed to Pier...he answered me already.
Title: Re: Poor Man's Pultec EQP1-A
Post by: MatthisD on April 27, 2011, 09:00:13 AM
Hi Ian, £12 sent from matdamcATyahooDOTcom, I forgot to mention my forum name in the message content.
cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 27, 2011, 09:27:57 AM
Hi Ian, £12 sent from matdamcATyahooDOTcom, I forgot to mention my forum name in the message content.
cheers


Thanks. PCBs should be here any day now.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on April 29, 2011, 08:46:00 AM
paypaled today for the two boards, thanks a lot for a nice project  :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on April 29, 2011, 02:03:55 PM
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.
I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Best,
Cyril

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 30, 2011, 12:46:53 PM
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.

The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

Quote
I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Basically you need to divide the pot values by 4.7, so the 4K7 becomes 1K, the 47K becomes 10K and the 470K becomes 100K just like the original Pultec.

Then you need to multiply all the capacitor values by 4.7

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on April 30, 2011, 01:34:30 PM
The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

I've been thinking about it for a while and I decided to go 2U in 500 format. Lot's of space on the front panel to put all the knobs and enough current to supply tube makeup stage. Hope to finish it soon :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 30, 2011, 01:49:04 PM
Here are a couple of design updates. I have redrawn the EQ schematic to show just the EQ alone and I have included the calculated values for a recommended set of frequencies for both the hi and lo boost/cut. I have also changed the value of the series resistor in the hi cut. The new value (430 ohms)  gives a broad bell response with simultaneous max cut and boost followed by a flat response. If you want the same bell followed by a cutting response use 100 ohms instead.

I have also attached tables of the calculated values for all the hi and lo boost/cut capacitances at the recommended frequencies plus a recommended combo of capacitors to get as close as practical to the stated frequency plus a 'cheapskate' capacitor (single) value where possible for those who want to reduce cost as much as possible.

Lastly I have drawn and EQ system schematic which shows the input and output transformers, the EQ, the gain make up amp and the EQ in/out switch so you know how it is all meant to go together.

Cheers

Ian

http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png (http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png)
http://www.ianbell.ukfsn.org/pics/CapValues.pdf (http://www.ianbell.ukfsn.org/pics/CapValues.pdf)
http://www.ianbell.ukfsn.org/pics/EQSystem.png (http://www.ianbell.ukfsn.org/pics/EQSystem.png)

Edit: corrected resistor value.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on April 30, 2011, 03:17:09 PM
Ian, you still have the lin/logs a bit messed up, if your going by what you said about the original pultec over in the make-up thread.

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 30, 2011, 03:25:42 PM
Ian, you still have the lin/logs a bit messed up, if your going by what you said about the original pultec over in the make-up thread.

Cheers

I think it is right, LOL. Both the hi pots are lin and both the log pots are log. That's what I said on the other thread too.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on April 30, 2011, 04:57:50 PM

Both the hi pots are lin and both the log pots are log.


The pic shows hi cut as log, and low cut as lin, unless I am mistaken somehow?

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on April 30, 2011, 06:34:16 PM

Both the hi pots are lin and both the log pots are log.


The pic shows hi cut as log, and low cut as lin, unless I am mistaken somehow?

Cheers

No, that's right, but that is the old schematic. The new one was referenced above:

http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png (http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png)

If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 01, 2011, 08:39:18 AM

If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian


Aah thanks, got it now, sorry for the confusion  :-[

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 01, 2011, 09:35:02 AM

If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian


Aah thanks, got it now, sorry for the confusion  :-[

Cheers

No problem, it is easily done.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on May 01, 2011, 03:00:07 PM
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.

The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

Quote
I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Basically you need to divide the pot values by 4.7, so the 4K7 becomes 1K, the 47K becomes 10K and the 470K becomes 100K just like the original Pultec.

Then you need to multiply all the capacitor values by 4.7

Cheers

Ian

Many thanks Ian for advices.
I will be little busy this week little, but i'll post the BOM for the 600ohm version and the front panel for the 500 format.

Best
Cyril
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 03, 2011, 07:03:17 AM
Just had an email to say the PCBs have been shipped and should reach me Wednesday 4th May.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on May 03, 2011, 07:46:15 AM
Excellent  ;D ;D ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: buschfsu on May 04, 2011, 10:08:18 AM
any chance of getting two boards?
thanks
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 04, 2011, 12:07:20 PM
any chance of getting two boards?
thanks

All the current order are spoken for I am afraid but there's a list in the Black Market for those who want to place an order for the second run. It's up to over 100 PCBs already so your best bet is to express your interest on that thread and I'll add your order to the rest.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 04, 2011, 12:12:22 PM
The 210 PCBs have arrived!! I have just soldered the switch into one of them to make sure it fits and the connections are correct and all is OK. So I shall start shipping tomorrow. Below is a copy of the list of purchasers and I will change paid to shipped as  I ship each one:

 Handle             Quantity        Price (gbp)
ej_whyte              2 sets            shipped
Joechris              2 sets            shipped
Albrebreton           2 sets            shipped
chrispbass            4 sets            shipped
culteousness1         2 sets            shipped
strangeandbouncy      2 sets            shipped
michalk               1 set             shipped
mylesgm               4 sets            shipped
zebra50               2 sets            shipped
tomugli               2 sets            shipped
Kamel                 4 sets            shipped
Audiohammer           2 sets            shipped
guze                  2 sets            shiooed
Andreas Pfeiffer      2 sets            shipped
noulou                2 sets            shipped
mrclunk               2 sets            shipped
Holger                2 sets            shipped
Matthew Jacobs        4 sets            shipped
danijel               4 sets            shipped
Grooveteer            4 sets            shipped
kante1603             4 sets            shipped
0dbfs                 4 sets            shipped
3nity                 2 sets            shipped
Hank Dussen           2 sets            shipped
Citrus Hill          10 sets            shipped
baadc0de              4 sets            shipped
bovox                 2 sets            shipped
menigu                1 set             shipped
Michael Tibes         4 sets            shipped
Ptownkid              2 sets            shipped
Davo                  1 set             shipped
tzman                 2 sets            shipped
MathisD               2 sets            shipped
benlindell            4 sets            shipped
hodad                 2 sets            shipped
peterc                2 sets            shipped
desol                 2 sets            shipped
creal                 2 sets            shipped
   


Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on May 04, 2011, 12:17:51 PM
HI Ian,




  delighted to hear this. I hope you have an army of elves to help pack em all up . . .



        Kindest regards,



            ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: tomugli on May 04, 2011, 01:20:30 PM
brilliant news!! thanks for such a great project.

cheers, tomugli
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on May 04, 2011, 02:04:48 PM
Very good new ;)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 06, 2011, 04:49:07 AM
My boards arrived this morning! Looking very nice :)

Like to say thanks to Ian for all the effort you put in, and all those envelopes you have to post :o

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 06, 2011, 08:32:26 AM
OK, I have shipped all the first round PCBs now except for guze and gevermil.

Edit: guze I have your shipping address now and your boards have been shipped.

gevermil has unfortunately had to drop out.

gevermil dropping out means I have two spare sets so Davo it is your lucky day because I have shipped you the 2 sets you wanted all along. It also means there is a set for me so I can build the circuit and check it out myself.

Enjoy!

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on May 06, 2011, 09:00:08 AM
Hi Ian,



   you bloomin marvel . . . I hope you used self-sealing envelopes, that glue really tastes disgusting after just a couple of envelopes . . .



   I think i speak for one and all, Thank You, and we are all very excited . .



     ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: e.oelberg on May 06, 2011, 03:31:55 PM
I bought this http://www.seeedstudio.com/depot/capacitance-meter-kit-p-268.html?cPath=174&zenid=3ea4b275130754b313b55dfeca9dcbf2 (http://www.seeedstudio.com/depot/capacitance-meter-kit-p-268.html?cPath=174&zenid=3ea4b275130754b313b55dfeca9dcbf2) and it is way more precise than my multimeter, if you want to go for a mastering eq, this might be helpful

nicholas
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 06, 2011, 03:36:26 PM
So, know that i have the boards  :) let me just clear up the jumpers/resistors.

Hi Switch:
R1 & R2 in
R3 Unconnected
Jumper L1 (assuming i don't want the inductor)

Low Switch:
Jumper R1 & R2
R3 = 56k
Jumper | near to R3
Jumper L1

Correct?

Also, here are my updated values for using stepped gain pots. I used 40dB as you suggested, and the graph curves seem much better.

Thanks again for the boards

Cheers,
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 06, 2011, 05:21:02 PM
So, know that i have the boards  :) let me just clear up the jumpers/resistors.

Hi Switch:
R1 & R2 in
R3 Unconnected
Jumper L1 (assuming i don't want the inductor)

Low Switch:
Jumper R1 & R2
R3 = 56k
Jumper | near to R3
Jumper L1

Correct?

Yes, that seems right to me.

Quote
Also, here are my updated values for using stepped gain pots. I used 40dB as you suggested, and the graph curves seem much better.

Yes, they look good to me, the resistance is about 10% at the half way point as expected.

Just a note about capacitors. The PCB is laid out for 5mm pitch capacitors and I have checked that WIMAs are available in this spacing at the values required and at suitable voltage ratings (50 to 100V). However, where two capacitors are required, if one is a high value (say 330nF) it may not be possible to fit both side by side. Fortunately, the PCB is double sided so you can one on the other side of the PCB. I would like to claim I thought of this when I designed the PCB but I have to admit it only occurred to me later.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 06, 2011, 05:29:53 PM
So, know that i have the boards  :) let me just clear up the jumpers/resistors.

Hi Switch:
R1 & R2 in
R3 Unconnected
Jumper L1 (assuming i don't want the inductor)

Low Switch:
Jumper R1 & R2
R3 = 56k
Jumper | near to R3
Jumper L1

Correct?

Yes, that seems right to me.

Quote
Also, here are my updated values for using stepped gain pots. I used 40dB as you suggested, and the graph curves seem much better.

Yes, they look good to me, the resistance is about 10% at the half way point as expected.

Just a note about capacitors. The PCB is laid out for 5mm pitch capacitors and I have checked that WIMAs are available in this spacing at the values required and at suitable voltage ratings (50 to 100V). However, where two capacitors are required, if one is a high value (say 330nF) it may not be possible to fit both side by side. Fortunately, the PCB is double sided so you can one on the other side of the PCB. I would like to claim I thought of this when I designed the PCB but I have to admit it only occurred to me later.

Cheers

Ian

Ok cool, thanks for the clarification.

I was just looking up all the caps on mouser, they have them all in stock except the 2.2nF and 330nF :/ Also, most of the caps are 63 or 100v, but with the smaller values they only had 630v in. I know its perfectly fine to have a higher value than required, and i thought the only disadvantage to larger voltage ratings was physical size, but i just wanted to check there wouldn't be any significant noise increase or any other disadvantage?

With 2 sets of caps for stereo, they come in at £23.65 by the way.

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 06, 2011, 06:10:25 PM

Ok cool, thanks for the clarification.

I was just looking up all the caps on mouser, they have them all in stock except the 2.2nF and 330nF :/ Also, most of the caps are 63 or 100v, but with the smaller values they only had 630v in. I know its perfectly fine to have a higher value than required, and i thought the only disadvantage to larger voltage ratings was physical size, but i just wanted to check there wouldn't be any significant noise increase or any other disadvantage?

With 2 sets of caps for stereo, they come in at £23.65 by the way.

There should be no noise issues with higher voltage caps.

You did not mention what tolerance and make of caps you were looking up on Mouser.

I tend to use Rapid, which has the 2n2 in a WIMA but also is lacking the 330nF


Cheers

Ian
Cheers
[/quote]
Title: Re: Poor Man's Pultec EQP1-A
Post by: strangeandbouncy on May 06, 2011, 06:14:50 PM



 . . . . HALE-FLUMPIN-LUIAH . . . .


  I gots dem in me hand . . .


     Thanks so much, Ian,


       ANdyP
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 07, 2011, 04:47:36 AM

There should be no noise issues with higher voltage caps.

You did not mention what tolerance and make of caps you were looking up on Mouser.

I tend to use Rapid, which has the 2n2 in a WIMA but also is lacking the 330nF


Cheers

Ian

WIMA MKS4, 5% when they had them, otherwise 10%, did they have them all in 5% at rapid?

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 07, 2011, 06:32:18 AM

WIMA MKS4, 5% when they had them, otherwise 10%, did they have them all in 5% at rapid?

Cheers

No, they only have the 10% at Rapid.

They have 5% by other manufacturers but not WIMA.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ej_whyte on May 07, 2011, 08:12:58 AM
MKS2 i meant sorry.

RS has the 330nF in, but something wierd is going on with their website, whenever i try to add them to my cart it says 1 item in cart, price £0.00, and the cart is empty when i view it :s

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: guze on May 07, 2011, 09:08:25 AM
Do i really need the IO board, or can i just connect ii passive to a preamp? (noobie question)
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on May 07, 2011, 09:23:39 AM

gevermil dropping out means I have two spare sets so Davo it is your lucky day because I have shipped you the 2 sets you wanted all along. It also means there is a set for me so I can build the circuit and check it out myself.


 ;D ;D  Thanks Ian!
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 07, 2011, 10:38:02 AM
Do i really need the IO board, or can i just connect ii passive to a preamp? (noobie question)

This is a passive EQ which means that with all the controls set to flat, the EQ has a loss, in this case of just over 20dB. It therefore needs to be followed by some amplification to get the level back to normal working levels. This amplification is called the gain make up amplifier. You can use any amplifier you like as a gain make up amplifier so long as it has an input impedance of not less than about 470K and enough gain to make up the EQ loss.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on May 07, 2011, 01:04:29 PM
Boards have arrived and they look great. Thank you Ian for the undertaking, you've done us all proud  :)

Chris
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 07, 2011, 05:24:03 PM
Do you think I should start a support thread in the lab?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrisPbass on May 07, 2011, 07:19:07 PM
Do you think I should start a support thread in the lab?

Cheers

Ian

Sounds like a good idea Ian , especially given the amount of boards in circulation and the fact that this project has really captured peoples attention.

Just set up the thread and post some 'blank' posts for the first few replys so you can always go in at the start and add crucial info etc before anyone starts posting.

Be nice to think that it can be all contained together from the start  ;D

cheers

Chris
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on May 08, 2011, 02:58:13 AM
Do you think I should start a support thread in the lab?

Cheers

Ian

Hello Ian,

yes,it would be wonderful to have all project-related information in just one place for such an amount of potential builders out there.

Thank you very much for all your efforts again,

best regards,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on May 09, 2011, 07:18:45 AM
Got the pcbs today, many thanks!
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on May 09, 2011, 10:26:03 AM
Boards have arrived this morning
 ;D ;D ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on May 09, 2011, 12:08:52 PM
So I have been thinking how to fit the PCBs to 1u lunchbox panel. Here's how it looks like. I think it will be possible if the lorins will be screwed to another pcb that will also host pots. Huh, maybe I'll manage to fit a tube gain stage as well :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on May 09, 2011, 12:40:55 PM
So are you going to use really long shafts and put the switches behind the pots?
Title: Re: Poor Man's Pultec EQP1-A
Post by: michal_k on May 09, 2011, 12:49:30 PM
yes, either that or I will just go for 2U, depending on complexity of the first solution. I don't have too much space in my rack thouh.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 09, 2011, 03:27:08 PM
yes, either that or I will just go for 2U, depending on complexity of the first solution. I don't have too much space in my rack thouh.

I have set up a poor Man's Pultec support thread in the lab with the intention of covering constructions issues so perhaps it might be an idea to move this discussion there?

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: kante1603 on May 11, 2011, 06:59:09 AM
Boards received yesterday-thank you very much Ian!

Best regards,

Udo.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Michael Tibes on May 11, 2011, 08:29:14 AM
The boards arrived here as well, thanx again for the effort!

Michael
Title: Re: Poor Man's Pultec EQP1-A
Post by: culteousness1 on May 11, 2011, 08:32:23 AM
Got mine today. Thanks again!
Title: Re: Poor Man's Pultec EQP1-A
Post by: ChrioN on May 11, 2011, 06:02:43 PM
So I have been thinking how to fit the PCBs to 1u lunchbox panel. Here's how it looks like. I think it will be possible if the lorins will be screwed to another pcb that will also host pots. Huh, maybe I'll manage to fit a tube gain stage as well :)


Thats the way to go!

Exactly like one of my own designs.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Davo on May 12, 2011, 07:34:08 AM
Got my boards today, thanks Ian!!
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 12, 2011, 11:46:31 AM
Got my boards today, thanks Ian!!

Hey, that's not bad. All the way to the West Coast in a few days.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: tomugli on May 12, 2011, 01:57:39 PM
got mine mate.thanks again
Title: Re: Poor Man's Pultec EQP1-A
Post by: buildafriend on May 13, 2011, 12:19:20 AM
what does the inductor usually run you?
Title: Re: Poor Man's Pultec EQP1-A
Post by: Andreas Pfeiffer on May 13, 2011, 10:27:48 AM
boards arrived today :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: bovox on May 13, 2011, 02:34:34 PM
Thanks again, the boards are very fine. Arrived yesterday.
Cheers Bo
Title: Re: Poor Man's Pultec EQP1-A
Post by: Matthew Jacobs on May 13, 2011, 07:11:53 PM
Well since everybody is saying it... I got mine too.....   ;D

Thanks Ian for sharing and all your had work
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 14, 2011, 07:22:41 AM
what does the inductor usually run you?

The inductor was put in as a bit of an after thought simply because there was space on the PCB for a small one and somebody asked if I would include it on the layout. It just allows a small inductor to be used at one frequency setting only. You don't need to fit it and you can just  short it out.

If you look half way down this page:

http://www.groupdiy.com/index.php?topic=43859.60

you will see what I said about possible inductor values.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: danijel on May 18, 2011, 02:29:04 AM
Got the boards, thank you!

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 18, 2011, 09:08:01 AM
Got the boards, thank you!



Excellent. I think that is just about everyone now.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: fazer on May 18, 2011, 09:41:34 AM
Hi Ian,

I requested 2 board sets on the second run you posted.   I haven't heard anything about that order or received a PM.   I'm ready to pay for them just not sure what and to who.   

Sorry if this post is in the wrong thread.

Michael
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 18, 2011, 12:39:17 PM
Hi Ian,

I requested 2 board sets on the second run you posted.   I haven't heard anything about that order or received a PM.   I'm ready to pay for them just not sure what and to who.   

Sorry if this post is in the wrong thread.

Michael

There's a thread for this in the Black Market. I placed the order today and asked for payment in that thread. You are on the list in that thread. Check it out here:

http://www.groupdiy.com/index.php?topic=44025.40 (http://www.groupdiy.com/index.php?topic=44025.40)

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: tzman on May 18, 2011, 05:17:24 PM
Got the boards, thank you!



Excellent. I think that is just about everyone now.

Cheers

Ian

Yeah, I got them too!
Title: Re: Poor Man's Pultec EQP1-A
Post by: Grooveteer on May 19, 2011, 11:48:46 AM
Received them today.

Thanks Ian!

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: Albrebreton on May 23, 2011, 08:08:11 AM
Hi Ian, Boards arrived today.
Thank you.
Title: Re: Poor Man's Pultec EQP1-A
Post by: Holger on May 24, 2011, 09:54:45 AM
I've assembled one channel today using the JLM Dingo as make up stage (with a JLM high voltage OpAmp) 
and two old Altec transformers. I like what I hear.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on May 25, 2011, 04:36:50 AM
I've assembled one channel today using the JLM Dingo as make up stage (with a JLM high voltage OpAmp) 
and two old Altec transformers. I like what I hear.

Well done! I think you must be the first person, apart from me, to get a channel working. Glad you like it.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on May 25, 2011, 08:51:21 AM
I've assembled one channel today using the JLM Dingo as make up stage (with a JLM high voltage OpAmp) 
and two old Altec transformers. I like what I hear.

Care to share your wiring configuration with the dingo?

M
Title: Re: Poor Man's Pultec EQP1-A
Post by: Holger on May 25, 2011, 09:18:55 AM
This picture was never intended to get published, so please excuse the crappy photo.
The reason I used the term 'assembled' earlier is obvious...  ;) I should have used the term 'tinkered'.
This is still in the experimentation phase.

I've built only one half (balancing part) of the Dingo. The input signal goes to the terminal strip to use the relay functionality. After that I've used the molex connector at the phase reverse jumper point to connect the input transformer.


(http://audiofor.tv/diy/dingo.jpg)
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on June 04, 2011, 08:03:41 AM
I botched together a 3U 4 channel front panel for this project today.. thought it looked kind of cool, so here it is :D (http://distopik.com/Poorman/3U%20PoorMan.png)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 04, 2011, 04:28:23 PM
I botched together a 3U 4 channel front panel for this project today.. thought it looked kind of cool, so here it is :D (http://distopik.com/Poorman/3U%20PoorMan.png)

Nice pic. Love the colour - it is my wife's favourite - she has it all over the kitchen.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Hank Dussen on June 21, 2011, 05:01:45 PM
How well does it work for frequencies above 16K?
Do these only work with an additional inductor?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 21, 2011, 06:43:04 PM
How well does it work for frequencies above 16K?
Do these only work with an additional inductor?

I expect it will work fine for hi boost/cut frequencies up to 30KHz without any inductor, as much as anything because the switch frequency is where the final shelving occurs but to reach this the circuit has to start boosting or cutting at a frequency much lower than this. The inductor was only added as an afterthought because someone asked for it and there was space for it on the PCB.

If you look at the capacitor calculator spreadsheet you will see I have included 20KHz and 30KHz frequencies. Note that the boost cap is becoming rather small (about 1500pF at 30KHz) so stray capacitances, especially in screened cables, may begin to affect the response. You are welcome to experiment with higher shelving frequencies but I would suggest 30KHz as a useful upper limit.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Hank Dussen on June 22, 2011, 03:03:26 AM
If you look at the capacitor calculator spreadsheet you will see I have included 20KHz and 30KHz frequencies. Note that the boost cap is becoming rather small (about 1500pF at 30KHz) so stray capacitances, especially in screened cables, may begin to affect the response.

Would it be better to use unshielded cables for the Hi boost then?
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on June 22, 2011, 04:13:21 AM
The inductor was only added as an afterthought because someone asked for it and there was space for it on the PCB.

Could the inductor be rerouted to the topmost frequency with some trace cutting?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 22, 2011, 10:54:38 AM
The inductor was only added as an afterthought because someone asked for it and there was space for it on the PCB.

Could the inductor be rerouted to the topmost frequency with some trace cutting?

I would think that should be possible. Alternatively you could just fit the caps in reverse order so the frequency increases as you turn anti-closckwise.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 22, 2011, 11:19:27 AM
If you look at the capacitor calculator spreadsheet you will see I have included 20KHz and 30KHz frequencies. Note that the boost cap is becoming rather small (about 1500pF at 30KHz) so stray capacitances, especially in screened cables, may begin to affect the response.

Would it be better to use unshielded cables for the Hi boost then?

A lot depends on your physical layout - how far the pots are from the PCB, how directly you route the connections, where you site the power supply and whether the whole thing is in a screened box or not.

If you mount the hi boost/cut pots right next to the hi switch PCB you can make very short direct connections form the PCB to the pots - there are only two such connections to each pot. The same argument holds true for the lo boost/cut PCB and pots. There should be no need to screen these connections.

The connection from the hi boost pot to the hi cut pot probably does not need to be screened if the two pots are on the same side of the switch PCB, but if they are on opposite sides then it might just be necessary to screen it. The connections from the hi cut pot to the lo boost and cut pots might be quite long depending on your layout and might well benefit from screening.

Where you definitely should use screening is from where the EQ output is taken (from the low cut pot) to the EQ in out switch and from that switch to the input of the gain make up amplifier but try to keep these screened cable lengths as short as possible to avoid introducing unnecessary stray capacitance. Connect the screen to ground only at the gain make up amp input, carry it across the EQ in/out switch and leave it unconnected at the EQ output.

The EQ output is relatively high impedance and hence can be susceptible to interference from external sources of from the local power supply transformer. That's why I recommend screening the output connection. I would also recommend keeping the PSU transformer as far away from these leads as you can and enclosing the entire EQ in a screened enclosure.

Cheer

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on June 22, 2011, 08:24:53 PM
Hi Ian, hi all

Here is work in progress
One channel tested and works,  i used a trim pot instead the 470k.
also, i experiment with the format 500
The amp is a vero/325 API
input xfrm 10K:10K LL1540 Lundahl
ouput xfrm 600R:600R ??? (from old UREI EQ)

Here is the picture and the front.
(http://www.twin-x.com/groupdiy/albums/userpics/normal_IMG_0485.JPG) (http://www.twin-x.com/groupdiy/albums/userpics/normal_Capture_d%E2%80%99e%CC%81cran_2011-06-23_a%CC%80_01_10_37.png)

Thanks Ian for this great projet ;)
This PM eq sound very nice.

Best,
Cyril
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 23, 2011, 04:54:27 AM
Hey Cyril,

Thanks for the pic. I like the way you have remoted the switches - is that a short length of ribbon cable??

Glad you like the sound.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on June 23, 2011, 05:19:59 AM
Hey Cyril,

Thanks for the pic. I like the way you have remoted the switches - is that a short length of ribbon cable??

Glad you like the sound.

Cheers

Ian

Yes, it's shord ribbon cable.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 23, 2011, 08:07:44 AM
I also noticed, Cyril, that you have only 5 lo frequencies and 4 hi frequencies marked on the front panel and also that the hi include 20K and 30K.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Holger on June 23, 2011, 08:43:34 AM
Cyril needs the EQ for his upcoming 'symphony for dogs and bats' (sorry, couldn't resist)  ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on June 23, 2011, 12:46:27 PM
I also noticed, Cyril, that you have only 5 lo frequencies and 4 hi frequencies marked on the front panel and also that the hi include 20K and 30K.

Cheers

Ian
thx you for advices.
i changed plan, i think i put the pair in à 19" 1 or 2U.
May be with the tube Amp
I'll post the new FP soon

@Holger

Yes, i use many compressors and eqs for my symphony.
It's just, i like my toys

Cheers
Title: Re: Poor Man's Pultec EQP1-A
Post by: pigsnoot on June 27, 2011, 10:18:45 PM
hello I got the boards! thanx a lot

Are there any replacements for the sowter ST3575?

I can only find them here
http://www.canford.co.uk/Products/23-155_SOWTER-ST3575F-TRANSFORMER-Analogue-audio-leads-line-bridging-10k10k (http://www.canford.co.uk/Products/23-155_SOWTER-ST3575F-TRANSFORMER-Analogue-audio-leads-line-bridging-10k10k)

sorry to bother y'all pro-builders!
grtz!
M
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on June 28, 2011, 05:12:59 AM
hello I got the boards! thanx a lot

Are there any replacements for the sowter ST3575?

Any 10K:10K bridging transformer will do. I am sure Jensen, Cinemag, Lundahl and others will have suitable transformers.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: creal on June 28, 2011, 06:51:56 AM
hello I got the boards! thanx a lot

Are there any replacements for the sowter ST3575?

I can only find them here
http://www.canford.co.uk/Products/23-155_SOWTER-ST3575F-TRANSFORMER-Analogue-audio-leads-line-bridging-10k10k (http://www.canford.co.uk/Products/23-155_SOWTER-ST3575F-TRANSFORMER-Analogue-audio-leads-line-bridging-10k10k)

sorry to bother y'all pro-builders!
grtz!
M
hello I got the boards! thanx a lot

Are there any replacements for the sowter ST3575?

Any 10K:10K bridging transformer will do. I am sure Jensen, Cinemag, Lundahl and others will have suitable transformers.

Cheers

Ian

I use a  10K:10K LL1540 Lundahl for the input and it works and sound well
Title: Re: Poor Man's Pultec EQP1-A
Post by: pigsnoot on July 13, 2011, 09:51:34 AM
Is the Bridging transformer really Necessary? If you're coming from a line level or really hot signal?

Another probably stupid question : This unit doesn't need any power source, so where does the 0v lead go to? is it just to show there's isn't any current needed, or does it effectively go somewhere?

Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 14, 2011, 10:14:31 AM
Is the Bridging transformer really Necessary? If you're coming from a line level or really hot signal?

No, it is not essential. You can run the EQ unbalanced at line level if you wish

Quote
Another probably stupid question : This unit doesn't need any power source, so where does the 0v lead go to? is it just to show there's isn't any current needed, or does it effectively go somewhere?

The EQ does not need a power source but it needs a gain make up amplifier after it to make up for its insertion loss and obviously the gain make up amplifier needs a power supply. The 0V of the EQ connects to the zero volts of the gain make up amplifier.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on July 14, 2011, 11:54:27 AM
I am interested in learning what I might need to change around or add to make the output of this low impedance like a microphone. 150 or 200 ohms... 40dB of overall attenuation would be fine. It would be awfully convenient to feed line level to these and patch into a mic-pre-amp for makeup similar to the passive-summing-mixers that are all the rage.

Looking at possible t-pad configs and how perhaps various output transformers may work with that. Also noted that previously in this thread we could possibly use different pot values and use the spreadsheet to re-calc the caps for the desired freq's...

Would be pretty flexible to be able to make this look like a normal bridging destination for the input and like microphone source for the output while remaining passive.

Maybe it's not feasible or the noise would be too much but I am playing with some calcs at the moment.

Any thoughts?

Best,
jonathan
Title: Re: Poor Man's Pultec EQP1-A
Post by: abechap024 on July 14, 2011, 12:00:31 PM
that would be sweet
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 14, 2011, 01:45:40 PM
I am interested in learning what I might need to change around or add to make the output of this low impedance like a microphone. 150 or 200 ohms... 40dB of overall attenuation would be fine. It would be awfully convenient to feed line level to these and patch into a mic-pre-amp for makeup similar to the passive-summing-mixers that are all the rage.

The poor man's EQP1A uses larger value pots than the original to get the input impedance up to around 10K bridging. The penalty for that is the output impedance is even higher and needs to be loaded with no less than around 470K. The EQ has an insertion loss of about 20dB so for a 40dB overall attenuation you can allow only a further 20dB for an pad - so you could use 420K and 47K for example but you still have an output impedance of over 40K.

You could possibly change the 56K resistor to 5.6K plus 51K and tap off across the 5.6K with a 10:1 transformer to give a mic level output of about -60dBu but that is about as good as it gets I am afraid.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 14, 2011, 01:56:21 PM
I don't know what the real output impedance is on this new higher Z version but how about a traffo?  I've before used something like a direct box transformer which took my eq source impedance of 10K or near and transformed down to 150 ohm.  I made up the gain with a mic pre which had typical 2K input Z so the eq was not loaded downwards very much.
Is there a place you can point me to for the higher impedance eq?  Maybe it's in this thread but I'm just not seeing it  :o

Merci

Never mind, I'm an idiot :-[ - the doc is on the first page.  I just assumed it was the usual pultec one when I looked the other day.

Will look again now ::)
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 14, 2011, 02:07:10 PM
Back again.

I don't see why you couldn't use a Direct box traffo on the out but I'll let the designer answer for himself  8)

Jean
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 14, 2011, 05:48:12 PM
Back again.

I don't see why you couldn't use a Direct box traffo on the out but I'll let the designer answer for himself  8)

Jean

It depends what impedance load the trafo presents to the output of the equaliser. The output impedance of the EQ is about 56K so the load it works into needs to be considerably bigger than this or the EQ response will be affected. I recommend a load of no less than 470K. If a Direct Box trafo can provide this load then it will work OK.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 14, 2011, 06:39:14 PM
The output impedance of the EQ is about 56K

I don't know if this is the right topographie yes?
(http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png)

If I thevenize in my head I see a different output impedance:
With a signal source connected there is the source output Z in series with the 47K Hi-Boost Pot.  These two are in parallel with the 4K7 Hi-Cut pot and the 56K output resistor.  So 4K something total output impedance.
The Low boost and cut pots do not change the output Z, they just define the amount of Lo boost and cut but we could just put caps in by themselves for 6dB per octave simple filters or short them out. 
I do notice that you use the 56K to work your lo cut into so that bit is important but doesn't define the overall Z.
So, a typical DI traffo might present a load of 200K - if you adjust your 56K up a bit to accomodate for the parallel 200K then it should be OK.
Maybe I miss something here so please let me know  :)
Thanks Ian,

Jean


Edits:  I see your earlier schematic didn't rely on the 56K and used a topographie closer to pultec which would not need to account for the 200K in parallel.
I do also realise that what I propose for the parallel of 200K traffo and a slightly raised 56K is a bit loose for really spot on accurate low cut frequency but I still think you could make it work if you knew the traffo ratio, maybe loaded the output traffo a bit for more defined reflected Z? - And it would be cool if someone could use an existing mic pre for just the cost of a 30 Euro traffo   :D
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 06:33:51 AM
Hi,
I attached a screen capture drawing of what I meant above.  The changed/added resistor are in red.  The added 15K series R on the output is there to satisfy the transformer which is looking for a source of 20K for good response.  I used a Jensen traffo as model.
Assuming ideal pots and traffo, total loss is 43dB.

Jean
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 07:08:01 AM
Here's one attached with a very simple buffer so you can keep your original 470K load.  You could pull power for it from Mic Phantom supply.  It would not need much current to drive the transformer so adjust the Fet's source load R for a few mA by ohm's law:  Supply voltage minus the 4V torn on voltage of the Fet divided by 3 or 4 or ? mA. 

Jean
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 15, 2011, 11:51:25 AM
The load placed across the EQ output does affect the shape of the Lo boost/cut EQ curves and the maximum boost or cut that can be obtained. For example:

With full lo boost AND cut applied:

470K load gives a 5dB dip (the Pultec bump) and 14dB boost.
200K load gives a 6dB dip and a 12dB boost
100K load gives a 7dB dip and 10 dB boost
50K  load gives a 9dB dip and 7dB boost

Full Lo boost alone:

470K load gives  15.5dB boost
200K load gives  14.9dB boost
100K load gives  14.0dB boost
50K   load gives  12.5dB boost

Full Lo cut alone:

470K load gives 20dB cut
200K load gives 20.7dB cut
100Kload  gives 22dB cut
50K load gives 24.7dB cut

Changing the load from 470K to 50K makes only 0.5dB difference in the Hi and Lo Boost/Cut curves.

So I conclude that:

1. The load makes the greatest difference to the low frequency simultaneous boost/cut (bump)
2. The difference made by a 200K is quite small.
3. Most people could probably live with the curves produced with a 100K load.
4. 50K load messes up the lo bump and reduces the maximum boost by over 3dB

I think using a FET buffer powered by phantom supply is a very clever innovation.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 12:26:42 PM
The load placed across the EQ output does affect the shape of the Lo boost/cut EQ curves and the maximum boost or cut that can be obtained.

Thanks for doing that Ian :) 
Yes I thought that the low would be the one to be changed the most and with a typical 20K:150 ohm traffo presenting 200K to primary maybe not too much to care?

So I conclude that:

1. The load makes the greatest difference to the low frequency simultaneous boost/cut (bump)
2. The difference made by a 200K is quite small.

Yes.  And if we push it a bit by adding my build out from your EQ of 15K for 215K total load,  even a tiny, tiny bit  less small of a difference ;)


3. Most people could probably live with the curves produced with a 100K load.
4. 50K load messes up the lo bump and reduces the maximum boost by over 3dB

I think you are right that 100K is even fine for Rock 'N' Roll.  However, 200K is better myself but:

I think using a FET buffer powered by phantom supply is a very clever innovation.

Thank you Ian.  I would use this option myself as it costs so little and gives flexibility.  Maybe add a 'buffer out' switch to provide for sometimes not having phantom?   
I think using a C.C.S. on the source would be better than a resistor for a few reasons but I didn't flesh it out.  I wanted to quickly throw out an idea for people. 
I'll be glad to finish it and post it for anyone to use if you want?  Or someone else can chime in if they have better thoughts?

Thanks again Ian for taking the time to do plots for differing loads and good for you for doing the design in the first place :)

Jean.

Oops, Edit:  Ian, when you simulated, did you adjust upwards the original 56K so that total load for lo eq is the same as your 56K//470K = 50K? 
Maybe it only makes a very small difference?
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on July 15, 2011, 12:47:26 PM
Wow!
This EQ was already awesome. Looks like this can turn every mic-pre into a line-level EQ/channel-amp...
Keeping it PM with edcor's on the I/O and it can be completely passive with a 48V option with a single FET? That is completely outta control!
I wonder what 16 or 32 channels would sound like on a mix?
Ian, I haven't checked your WM thread but are you doing additional runs of these?

Cheers,
jb
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 15, 2011, 01:24:19 PM
Ian, I haven't checked your WM thread but are you doing additional runs of these?

Cheers,
jb

I did one extra run in the BM. If there is enough interest I am happy to do another run on the same basis as last time.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: MicDaddy on July 15, 2011, 04:05:12 PM
Quote
  "I am interested in learning what I might need to change around or add to make the output of this low impedance like a microphone. 150 or 200 ohms... 40dB of overall attenuation would be fine. It would be awfully convenient to feed line level to these and patch into a mic-pre-amp for makeup similar to the passive-summing-mixers that are all the rage." 

Quote
  "I don't see why you couldn't use a Direct box traffo on the out.." 

We are talking about the makeup gain, ok I'm following.  Using a stand alone preamp, after the PMEQP1-A for the makeup gain?

Would the chain look like:   mic--->Pre---->PMEQP1-A---->Pre(makeup?)--->interface etc etc...??

If this is correct, is there readily available (affordable, PM spirit  ;D ) transformers to achieve this?   And would we need to still have the output transformer, and then step down with a second transformer to mic level??

 I'm on board, I like where this is going.
Title: Re: Poor Man's Pultec EQP1-A
Post by: 0dbfs on July 15, 2011, 04:32:18 PM
Quote
Would the chain look like:   mic--->Pre---->PMEQP1-A---->Pre(makeup?)--->interface etc etc...??

Yes. Or this for mix/returns:

DAW/DA --->> Comprerssor101 --->> PMEQP1A --->> CoolMicPre-XYZ-MakeUpGain --->> Mixer

I'm thinking you could probably hit it pretty hard with level depending on the transformer spec's so that after 40dB of attenuation you don't need too as much makeup....

Cheers,
jb
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 15, 2011, 04:51:14 PM
DAW/DA --->> Comprerssor101 --->> PMEQP1A --->> CoolMicPre-XYZ-MakeUpGain --->> Mixer

I'm thinking you could probably hit it pretty hard with level depending on the transformer spec's so that after 40dB of attenuation you don't need too as much makeup....

Most DAWs seem to be set so +4dBu at the D/A output corresponds to -16dBFS which means 0dBFS corresponds to +20dBu. That means you can hit the EQ pretty hard, and as it is passive it can take it. So the EQ output is around 0dBu and you can afford to lose  another 30 to 40dB before it gets to the following gain make up mic pre.

Yes, looks like a good idea.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 05:16:40 PM
Here's a simple version of the FET buffer showing powering from 48V Phantom.  The ZVP3310A is available worlwide from Digikey/Mouser etc. and cost is less than a U.S. dollar.  There are exotic J-Fets from Toshiba etc. of course but they're hard to get and expensive  I think the Zetex 3310A is a fine choice for this job
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 05:24:22 PM
Here's a better (?) buffer using a constant current source load on the FET's source pin.  The current source will linearize the follower more and also seperates the buffer from any noise on the 48V line.  I think this is maybe worth trying but, up to you.
Like the FET, there are better PNP transistors to use instead of PN2907 but here also these are more than good enough for the job. 
AND, they are available from Digikey/Mouser for pennies/cents each so...
This follower has a bit more current through it than the simpler one, the ZVP3310A likes more current even though the transformer load doesn't need it. 
Maybe someone can try both and see?
Jean

Edit for changed values.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 15, 2011, 06:47:37 PM

Oops, Edit:  Ian, when you simulated, did you adjust upwards the original 56K so that total load for lo eq is the same as your 56K//470K = 50K? 
Maybe it only makes a very small difference?

All I did was keep the EQ the same and change the load. The 56K is key to producing the low frequency Pultec bump with simultaneous max Lo boost and cut. The extra load already makes the bump smaller so increasing the 56K would make it smaller still.

Cheers

ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 15, 2011, 06:58:56 PM
All I did was keep the EQ the same and change the load. The 56K is key to producing the low frequency Pultec bump with simultaneous max Lo boost and cut. The extra load already makes the bump smaller so increasing the 56K would make it smaller still.

Cheers

ian

OK sounds good.
Thanks Ian,

Jean
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 17, 2011, 11:48:22 PM

Most DAWs seem to be set so +4dBu at the D/A output corresponds to -16dBFS which means 0dBFS corresponds to +20dBu. That means you can hit the EQ pretty hard, and as it is passive it can take it. So the EQ output is around 0dBu and you can afford to lose  another 30 to 40dB before it gets to the following gain make up mic pre.

Sounds good to me.
I had assumed though the level out of the Eq was lower than 0dBu so, if you wanted to use a Fet buffer before a transformer, it would be better to bias up the gate a bit to allow for bigger signals.  You would need to cap couple from the Eq into it then of course to block the bias V from the Eq pots etc.
When I have more time later I'll post an update schematic showing what I mean. 
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 18, 2011, 01:23:18 PM
Hi Ian,
I posted here instead: http://www.groupdiy.com/index.php?topic=45054.0  so I wouldnt mess up your thread any more  :)

Jean.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on July 18, 2011, 01:58:59 PM
Hi Ian,
I posted here instead: http://www.groupdiy.com/index.php?topic=45054.0  so I wouldnt mess up your thread any more  :)

Jean.

Good idea. It is a topic worth discussing in its own right.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: Jean Clochet on July 18, 2011, 04:23:24 PM
It is a topic worth discussing in its own right.

Maybe so.  Just didn't want to0 mess with your thread too much!

I did have this idea:
Sometimes when I use a pultec, I have to use maximum boosts and cuts to push the freq. of operation outwards and leave the middle range unchanged.  But also, this sometimes gives too much boost, so what I do is blend in an uneq'ed amount of the same signal to fill it out and just leave the humps at the outer frequency ends. 
So I just figured that with the circuit I posted in the other thread you could add a 'blend in' for the uneq'ed signal and not upset anything.  I'll post this there when I have time

Jean.
Title: Re: Poor Man's Pultec EQP1-A
Post by: benlindell on October 06, 2011, 12:44:58 AM
What works better, shorting or non-shorting switches?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on October 06, 2011, 01:42:53 PM
What works better, shorting or non-shorting switches?

The problem with an EQ like this is that you are switching capacitors. It does not matter if you have shorting or non-shorting contacts, the capacitor still needs to get charged and so you can get clicks. Having said that, there should be no dc on these capacitors so there should be nothing to cause switching clicks. if you do get clicks, the type of contacts used will not help. The cure would be to wire 4.7Meg resistors across adjacent pairs of contacts so there is a dc path for all the caps to charge through but in the prototype I built I did not find this necessary.

So, in short you are probably OK using either.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 08, 2011, 05:00:33 AM
Not reading all 19 pages (sorry)..

What's the status of this project?
What's the cost of a unit?
Sound-examples?
Pictures?
Title: Re: Poor Man's Pultec EQP1-A
Post by: mylesgm on November 08, 2011, 05:18:55 AM
RTM. (sorry)
Title: Re: Poor Man's Pultec EQP1-A
Post by: baadc0de on November 08, 2011, 05:33:58 AM
Not reading all 19 pages (sorry)..
That's not the way you want to approach a tube project. I don't know how experienced you are, but statistically it's more probable that you haven't built much and in that case, please, read at least the whole thread and some of the others. These things can kill or at least zap you well.

What's the status of this project?
Two rounds of many many PCBs have been sold to my knowledge, which has probably made about 50+ people around the world very happy. I don't know if Ian has any left, but if there is interest, there could be a 3rd round?

What's the cost of a unit?
If you will browse around this forum, which you should if you are contemplating any project, this isn't how things are done around here. Project designers will create a PCB and possibly sell them along with some hard to find auxiliary components or some additional mechanic fasteners/brackets to offset development costs. Very rarely are there full kits offered and so what happens is that you select and order all the parts that go on and off the PCB, as well as the case that you want it in. Typically you will have to manage more than 5 different vendors selling different things. As with anything there is a range of prices available for any one kind of component, there are capacitors that cost 1 cent and capacitors that cost 100$ and both will fit into the project in the same hole and "do the same thing" but their subjective or objective quality may be different. So it's hard to say how much the project costs, it's better to ask, how much do you have / are willing to invest and see if you can get all the components for that kind of cash.

Sound-examples?
None that I know of. But it's a transformer isolated passive EQ with tube makeup stage. Can't go far wrong with that. With the right components I'm sure it sounds fabulous!

Pictures?
Even if there were any, all they're useful for is to get an idea of how you'd want to make the project, i.e. which case to use, how to drill it and position stuff, which knobs to use etc.. you have to use your own aesthetic.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 08, 2011, 10:49:42 AM
Not reading all 19 pages (sorry)..

What's the status of this project?
What's the cost of a unit?
Sound-examples?
Pictures?

Status: PCBs available for EQ and tube gain make up. Lot's of people have ordered PCB sets and built, it mostly into 1U rack boxes and mostly stereo units. Others have modified the EQ for their own purposes - for example one group member has built a bass guitar specific version.
Cost: A pair of EQ PCBs cost 7GBP and the optional tube gain make up PCB is 5GBP and  Paypal and shipping charges are 2GBP for Europe and 3GBP for the rest of the world. I still have some PCBs left.
Sound-examples: none as yet
Pictures: I have been sent one showing the EQ incorporated into a project but have been asked not to publish it.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 08, 2011, 12:24:08 PM
Thanks for you responses :)

Yes, I'm fairly new to DIY. Hallo.. :)

Yes, it didn't expect kits. Though 5 vendors sounds expensive (shipping to Norway).

Phrasing my questions a little different:
- What is typical cost per unit for the people here, building this project (singel channel)?
- What features does it have (like reading on the front-panel, the basic option)?
- Do I have to be very skilled to build it / get the right parts?

I'll soon build my first DIY, a Hamptone HJFP2, and is hoping to get some skills by that.

BTW: Do I always have to do these quizzes to post here? Almost had to ask on Gearslutz just to get the right answers
Title: Re: Poor Man's Pultec EQP1-A
Post by: gemini86 on November 08, 2011, 01:34:41 PM
Hi! Welcome! Trying to help you past this first speedbump. People around here generally don't care for laziness. Asking for all the answers in an open book test is right up there near the top of the list. When you're building something from parts and pieces,  yes,  shipping does add up. Some vendors try to supply parts kits but you gotta pay for the effort there as well. Good luck and please,  read!  You gain nothing by not researching.
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 08, 2011, 06:44:54 PM
Thanks for you responses :)

Yes, I'm fairly new to DIY. Hallo.. :)

Yes, it didn't expect kits. Though 5 vendors sounds expensive (shipping to Norway).

Phrasing my questions a little different:
- What is typical cost per unit for the people here, building this project (singel channel)?
- What features does it have (like reading on the front-panel, the basic option)?
- Do I have to be very skilled to build it / get the right parts?

I'll soon build my first DIY, a Hamptone HJFP2, and is hoping to get some skills by that.

BTW: Do I always have to do these quizzes to post here? Almost had to ask on Gearslutz just to get the right answers

Here is a link to earlier in the thread where there is a picture and a comment on the sound

http://www.groupdiy.com/index.php?topic=43859.msg560160#msg560160 (http://www.groupdiy.com/index.php?topic=43859.msg560160#msg560160)

Total cost depends on what you decide to build. The EQ PCB costs you know. To that you need to add the cost of the capacitors and the pots which should be less than 20GB. Then you need a gain make up amp, a power supply and a case to put it in. You may want to have input and output transformers or you may choose to leave them out to save cost.

I would estimate the cheapest using a simple box, power supply, op amp gain make up and no transformers would be a around 75GBP.

if you put it in a 1U rack case you could at 25GBP to that figure.

If you add input and output transformer you can add another 100GBP

So the real answer is it depends.

In terms of feaures it is a poor man's Pultec EQP1A -so it has a similar set of features but cost reduced. So it has the same hi and low boost and cut but only 6 freuwncies for each band. The hi response is shelving rather than peaking because the inductor has been removed to save cost.


DIYers from beginner to expert have built this project.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 09, 2011, 03:37:08 AM

Here is a link to earlier in the thread where there is a picture and a comment on the sound

http://www.groupdiy.com/index.php?topic=43859.msg560160#msg560160 (http://www.groupdiy.com/index.php?topic=43859.msg560160#msg560160)

Total cost depends on what you decide to build. The EQ PCB costs you know. To that you need to add the cost of the capacitors and the pots which should be less than 20GB. Then you need a gain make up amp, a power supply and a case to put it in. You may want to have input and output transformers or you may choose to leave them out to save cost.

I would estimate the cheapest using a simple box, power supply, op amp gain make up and no transformers would be a around 75GBP.

if you put it in a 1U rack case you could at 25GBP to that figure.

If you add input and output transformer you can add another 100GBP

So the real answer is it depends.

In terms of feaures it is a poor man's Pultec EQP1A -so it has a similar set of features but cost reduced. So it has the same hi and low boost and cut but only 6 freuwncies for each band. The hi response is shelving rather than peaking because the inductor has been removed to save cost.


DIYers from beginner to expert have built this project.

Cheers

Ian

Thanks a lot Ian!
That's the kind of info I was looking for :)

Seems very tempting.

The optional tube gain: how important do you think that is for functionality and sound?
And how much will it add in cost to the project? (ok 5GBP for the pcb)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 09, 2011, 04:59:21 AM
Thanks a lot Ian!
That's the kind of info I was looking for :)

Seems very tempting.

The optional tube gain: how important do you think that is for functionality and sound?
And how much will it add in cost to the project? (ok 5GBP for the pcb)

The tube gain make up is simply a matter of taste (and cost). If you look around this site or at my profile you will see that I specialise in custom tube consoles. I don't do semiconductors, so any preference I might express would obviously be biased.

For functionality you do need a gain make up stage to make up the loss in the passive EQ but it can be solid state or tube based.

The tube gain make up , as well as the PCB, needs a tube (less than 15GBP), a mains transformer (probably 25GBP) and the diodes and capacitors in the supply circuit (say about 15GBP). I also do a PSU PCB.

Cheers

Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 09, 2011, 08:26:11 AM
The tube gain make up is simply a matter of taste (and cost). If you look around this site or at my profile you will see that I specialise in custom tube consoles. I don't do semiconductors, so any preference I might express would obviously be biased.

For functionality you do need a gain make up stage to make up the loss in the passive EQ but it can be solid state or tube based.

The tube gain make up , as well as the PCB, needs a tube (less than 15GBP), a mains transformer (probably 25GBP) and the diodes and capacitors in the supply circuit (say about 15GBP). I also do a PSU PCB.

Cheers
Thanks!

Had a look at your site. Nice  :)

So, one more question about cost: To get the unit in the same ballpark as this http://www.recproaudio.com/diy_pro_audio/pultec_eqp1a.htm
( Sound wonderful I think)
How much would I need to add, getting better and more expensive components?
As you understand, I have little concept of what I would get for the budget-option mentioned above, compared to doing it all high-end.

Understanding the pultec eq: I was watching a video http://www.youtube.com/watch?v=uWbIAmLmdd8 and it seems like the fq on the unit are not really accurate. Like you dial in on 30hz and get something at 200hz. Is that right? Is this so for the high fq as well? Can someone enlighten me a little bit about this?

Thanks!
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 09, 2011, 08:30:40 AM
This might be the answer for my question:
http://www.gearslutz.com/board/6396212-post10.html
Is the Poor Man's Pultec EQP1-A replicating this behavior?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 09, 2011, 03:14:48 PM
Thanks!

Had a look at your site. Nice  :)

So, one more question about cost: To get the unit in the same ballpark as this http://www.recproaudio.com/diy_pro_audio/pultec_eqp1a.htm
( Sound wonderful I think)
How much would I need to add, getting better and more expensive components?
As you understand, I have little concept of what I would get for the budget-option mentioned above, compared to doing it all high-end.

The original EQP1A design you referred to above has a number of elements that were appropriate for the way equipment was used at that time.

First it was designed for use on a 600 ohm balanced circuit and its input transformer is 600:600. Today it is more common to use bridging inputs of 10K input impedance and the Poor Ma's EQP1A (PMEQP1A) uses a 10K:10K transformer for balanced inputs. Also today, some gear is operated unbalanced or electronically balanced and the PMEQP1A allows you to do this and save money. Neither of these changes affects the the way the EQ performs. Whether you use an input transformer or not, and if you do, which transformer you use, will inevitably affect the sound but not the way the EQ works.

Secondly, the original EQP1A it was designed to drive a 600 ohm output load at high power. This required using a push pull output and a phase splitter to drive it. In the original EQP1A both of these are achieved using transformers. Today we mostly drive 10K bridging inputs so the output power requirement is greatly reduced. We no longer need to use a push pull tube arrangement so we save the phase splitter transformer and some money. For the gain make up you can use a semiconductor amplifier or a tube based one. Both will have their own sounds but neither affects the way the EQ works. If you want a balanced output you can use a transformer with either a tube or semiconductor gain make up amp or use an electronically balanced semiconductor one. Again, these choices can affect the sound but not the way the EQ works.

Lastly, the PMEQP1A makes two compromises in the EQ to save cost. First we allow only 6 frequency selections because this allows us to use cheap 2 pole 6 way switches. Secondly, the hi boost EQ is modified to an RC shelving type instead of the resonant LC circuit in the original in order to save an expensive inductor. These are the only changes to the performance of the EQ.

So to answer your question, to get closer to the original does not necessarily make it  high end. That was the whole point of the PMEQP1A, to get as close as possible to the EQ peformance of the original at a fraction of the price. To build a replica of the original you are probably talking in the region of 1000GBP.

Quote
Understanding the pultec eq: I was watching a video http://www.youtube.com/watch?v=uWbIAmLmdd8 and it seems like the fq on the unit are not really accurate. Like you dial in on 30hz and get something at 200hz. Is that right? Is this so for the high fq as well? Can someone enlighten me a little bit about this?

Thanks!

Yes, this is a well known property of the original and creates what is known as the 'Pultec Bump'. It is not a question of the accuracy of the fq. There is no really accepted definition of fq for a shelving EQ although we have discussed that elsewhere on this forum. The fact of the matter is that to produce a curve that shelves at 30Hz you have to begin the boost at somewhere between 5 and 10 times that frequency. If you design so that the frequency at which boost starts is different to the one at which cut starts you can get interesting effects by boosting and cutting together. The original EQP1A went further by introducing a deliberate interaction between the lo boost and cut controls such that the cut becomes less effective as the boost is increased. This is what causes the Pultec bump and the PMEQP1A does exactly the same thing.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: rmaier on November 09, 2011, 11:23:38 PM

[/quote]
 I also do a PSU PCB.

Cheers
[/quote]

I had no idea you did a PSU PCB as well. I was under the impression everyone was perf-boarding their own and that you were only selling the EQ boards and tube makeup gain stage boards. Do you offer your PSU boards for sale, Ian?

Cheers,

Ralph
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 10, 2011, 02:48:03 AM
Thanks a lot Ian!
This looks like an affordable and nice build.

So, the choices are basically:
- Input transformer, or not
- Output-transformer, or not
- Tube-gain, or ss
? Right
What's the cost of a descent transformer?

Is it possible to do a stereo? 2 ch in 2 U rack?

Yes, accurate wasn't the right word, but the fq-labeling seems a little confusing when not knowing the unit :)

Hey: The forum-quizz dissappeared. Have I pased the intro-mark?  ;D
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 10, 2011, 04:57:19 AM

Quote
I also do a PSU PCB.

Cheers

I had no idea you did a PSU PCB as well. I was under the impression everyone was perf-boarding their own and that you were only selling the EQ boards and tube makeup gain stage boards. Do you offer your PSU boards for sale, Ian?

Cheers,

Ralph

Yes, I have a few left over from an earlier project of mine. They were not designed specifically for this project. I can let you have one for 8GBP plus the usual 3GB post and Payapl costs.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 10, 2011, 05:02:29 AM
So, the choices are basically:
- Input transformer, or not
- Output-transformer, or not
- Tube-gain, or ss
? Right

Correct

Quote
What's the cost of a descent transformer?

Good transformers start at around 40GBP and keep on going up and up  ;)

Quote
Is it possible to do a stereo? 2 ch in 2 U rack?

I deliberately made the EQ and tube gain make up PCBs slim enough to fit in a 1U case. I believe several people are building stereo EQs in 1U rack mounting cases.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 10, 2011, 07:05:45 AM

I deliberately made the EQ and tube gain make up PCBs slim enough to fit in a 1U case. I believe several people are building stereo EQs in 1U rack mounting cases.

Mmm.. Excellent :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: rmaier on November 10, 2011, 11:12:26 AM

Quote
I also do a PSU PCB.

Cheers

I had no idea you did a PSU PCB as well. I was under the impression everyone was perf-boarding their own and that you were only selling the EQ boards and tube makeup gain stage boards. Do you offer your PSU boards for sale, Ian?

Cheers,

Ralph

Yes, I have a few left over from an earlier project of mine. They were not designed specifically for this project. I can let you have one for 8GBP plus the usual 3GB post and Payapl costs.

Cheers

Ian

Excellent. Just Paypaled you. Thanks.
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 10, 2011, 11:15:59 AM
If I'd go for a cheap option, leaving the transformers and tube, would it be easy to later upgrade the unit with those parts?
Title: Re: Poor Man's Pultec EQP1-A
Post by: MrZpliff on November 10, 2011, 02:31:35 PM
If I'd go for a cheap option, leaving the transformers and tube, would it be easy to later upgrade the unit with those parts?

Yes, go for it  :)
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 10, 2011, 06:27:22 PM

I deliberately made the EQ and tube gain make up PCBs slim enough to fit in a 1U case. I believe several people are building stereo EQs in 1U rack mounting cases.

Mmm.. Excellent :)

Note, however, that the PSU PCB was designed for a different project and will not fit into a 1U case.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on November 10, 2011, 06:29:47 PM
If I'd go for a cheap option, leaving the transformers and tube, would it be easy to later upgrade the unit with those parts?

It would be easy to upgrade to input and output transformers. However, the mains transformer would have to be changed if you went from semiconductor gain make up to tube gain make up.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on November 11, 2011, 02:49:24 AM
Thanks Ian!
Think I'll wait a little and see how it goes with that mid-eq. Would be ideal to have it in.
Title: Re: Poor Man's Pultec EQP1-A
Post by: erikb1971 on November 17, 2011, 09:04:36 AM
For those interested: I started a feeler for the mid boards that Ian has designed to ad to the pm eqp1: http://www.groupdiy.com/index.php?topic=46575.msg584436#msg584436 (http://www.groupdiy.com/index.php?topic=46575.msg584436#msg584436)
When enough people register, Ian will be making dedicated boards!
Title: Re: Poor Man's Pultec EQP1-A
Post by: G-Sun on February 08, 2014, 05:42:42 AM
Has anyone compared the sound of the Poor Mans Pultec with the original/Rich Mans Pultec ?
Title: Re: Poor Man's Pultec EQP1-A
Post by: ruffrecords on February 08, 2014, 06:00:05 AM
Has anyone compared the sound of the Poor Mans Pultec with the original/Rich Mans Pultec ?

Good question but I don't know the answer. It is not a completely fair test because the poor man's does not have the inductive hi boost - it uses a simpler RC network to save money. The 3 band Pultec board I designed would be closer as this does have an inductor based hi boost. I know Pierre likes the 3 band Pultec but I don't know if has been able to compare it with the original.

Cheers

Ian
Title: Re: Poor Man's Pultec EQP1-A
Post by: anjing on February 12, 2014, 06:43:17 AM
Has anyone compared the sound of the Poor Mans Pultec with the original/Rich Mans Pultec ?

Good question but I don't know the answer. It is not a completely fair test because the poor man's does not have the inductive hi boost - it uses a simpler RC network to save money. The 3 band Pultec board I designed would be closer as this does have an inductor based hi boost. I know Pierre likes the 3 band Pultec but I don't know if has been able to compare it with the original.

Cheers

Ian

I never had the chance to touch an original pultec so i can't compare.
The eztubemixer card i used for the amplifiers is solid by itself...
so i don't know if it sounds the same, but it's certainly a high end eq!

Pierre


Title: Re: Poor Man's Pultec EQP1-A
Post by: ViciusbeatZ on August 04, 2016, 11:33:06 AM
Hello!
Anyone know a frontpanel for this project?
Thank you!