EQP-1S5 500 series PULTEC ---- HELP/BUILD thread

[Studio Mollan]

Hi!
Does anyone know the output impedance and drive capability of this EQ? I plan to use it where it's driving a 600ohm fader in a vintage API desk.
/
Emil

 

[kante1603]

Hi Emil,


the build manual points to it as follows:


Our AA56 are made using the same laminations and winding structure,wire diameter,etc,as theTriad HS56’s used in the original Pultecs.
We made all necessary connections of the various taps internally to make wiring them easier.
In other words,the difference between the AA56 and the original HS56 is that ours can be wired only as 600Ohms on the primary and 600 or 250 on the secondary (the taps used in the solid state Pultec),while the original had taps for 600, 250, 150, and 62.5 on both primary and secondary.

Cheers,


Udo.

 

[Studio Mollan]

Hi Emil,


the build manual points to it as follows:


Our AA56 are made using the same laminations and winding structure,wire diameter,etc,as theTriad HS56’s used in the original Pultecs.
We made all necessary connections of the various taps internally to make wiring them easier.
In other words,the difference between the AA56 and the original HS56 is that ours can be wired only as 600Ohms on the primary and 600 or 250 on the secondary (the taps used in the solid state Pultec),while the original had taps for 600, 250, 150, and 62.5 on both primary and secondary.

Cheers,


Udo.

Alright thanks Udo,
A bit hairy then...
/
Emil

 

[Dr Gris]

Wanna try mine?

Cheers
//Magnus

 

[kante1603]

What about omitting/lifting the transformer and driving the fader directly from the DOA ?
From what I know a 2520 does it down to 75 Ohms or so.


Just an idea,


Best,


Udo.

 

[mitsos]

Hi!
Does anyone know the output impedance and drive capability of this EQ? I plan to use it where it's driving a 600ohm fader in a vintage API desk.
/
Emil

Hi Emil,
like the original EQP-1A, the EQP-1S5 has 600 ohm input and output.  I'm not 100% clear on what you plan on doing, but if the opamp you use in the EQ is a 2520 then *I think* it should be OK, as that's pretty much how the ACA amps in the  desks are hooked up. 
hope that helps!

 

[jdurango]

Was going to pull the trigger and order a pair of EQP1S's, but it appears the website is down and the order link is gone.  Are these still available? Thanks!

 

[mitsos]

Yes, we are still around! The website is being redone (again), and the white market thread should be up today.  I was in Shanghai and Niels was in Japan and we had stopped the recurring payments to gdiy a few months ago because we were getting double billed.  Anyway, I'm back home but Niels will be back at the end of next week, so you can place an order now if you like, but it will only ship once he gets back. 

Sorry for the confusion!

cheers!

 

[weiss]

finally i finished my pultec
But two things appear to be not working properly..

- Bandwith pot cuts the low end and makes signal more quiet when turned completely CCW
- When Bypass is deactivated, the signal is much more quiet..

Is this normal? Could it be the opamp?

I hope someone can help me  with this matter..

thanks
weiss

 

[kante1603]

finally i finished my pultec
But two things appear to be not working properly..

- Bandwith pot cuts the low end and makes signal more quiet when turned completely CCW
- When Bypass is deactivated, the signal is much more quiet..

Is this normal? Could it be the opamp?

I hope someone can help me  with this matter..

thanks
weiss

Hi Ansgar,


I guess you followed the troubleshooting guide in the manual,right?
What are the results?
Do you have a clean gain of about 17 dB with the jumpers attached?
Do you have a clean signal at the filter board output (the header) at a loss of about 21-22 dB?
Does the trim pot work at all?


Since you posted you have used a known as working DOA it could be that you have a faulty amp board.
There's something to read starting on page 7 reply #127ff.
Is it a rev2 board?
If so there might be traces missing,these are for ground connections.
In this case you might want to contact Niels or Dimitri,seems to be an easy fix.


Did I mention these eqs sound fantastic ;D


Merry christmas,


Udo.

 

[mitsos]

- Bandwith pot cuts the low end and makes signal more quiet when turned completely CCW
- When Bypass is deactivated, the signal is much more quiet..

Is this normal? Could it be the opamp?

As Udo said, it's best if you test the two circuit boards separately before connecting them, but you can still do the tests if you have them soldered together already.  Off the top of my head, two things to check would be
1. Make sure there is a cap (optional and usually not necessary unless your opamp has high DC offset) or a jumper in the cap marked C_DC near the trimpot.  You must have either one or the other for the makeup gain amp to work.
2. If #1 is OK, then:
2a) turn all boost/cut controls to 0 (CCW),
2b) send a steady sine wave in and observe the output either with a volt meter or in your DAW
2c)You should have no change in output when you toggle the EQ-in switch. 
If you have a change in level, adjust the makeup gain up or down using the trimpot until 2c is true.

Your bandwidth issue is strange, and points to something else, bad solder, etc, I am going to christmas dinner with the family, I'll try to post later! 

Good luck with it, try to follow the troubleshooting instructions and you'll get it!

 

[weiss]

Thanks guys, loudness problem solved!
and indeed, the eq sounds nice!!

i attached a sound sample to this post to show you what i mean with the bandwidth knob (rename txt to zip first):
- First part is the original sample
- Second is routed through the pultec, first all knobs on zero (bw in the mid position) and then moving bandwidth to the left (S) side (Low end is going completely away)

I may have missed something but where did you find a troubleshooting guide?

Merry Christmas!

 

[kante1603]

Eeehhhhmmmmmm.......did you read the build manual?
Last two pages entiteled "Troubleshooting".....


What was the loudness issue?


Udo.

 

[weiss]

Eeehhhhmmmmmm.......did you read the build manual?

Not really! Look for yourself..  maybe there are different versions? Btw how could i have built this without reading the guide?

What was the loudness issue?

volume when bypassed and active were different

 

[mitsos]

One down, one to go...

There are two build docs, the one you linked is for the first version, the one in the first post is for the second (current) version, the one with the full metal jacket.  The little troubleshooting guide is at the end of the second one:

https://dl.dropboxusercontent.com/u/16176593/Analog_Allstars_build_doc_FMJ.pdf

As for the BW pot, that's a new one.  The BW pot is wired as a variable resistor in series with the inductor and cap in the boost section..  There must be something wrong either in your high boost section or low cut section I think.  Do the individual frequencies seem to work in the high boost?  If you have a program to test frequency response (Fuzzmeasure is a very nice one for mac, and I think many windows people use RMAA, which I think is free, or used to be, I'm not sure. Fuzzmeasure costs like 30-50 but it's very worth it), it's nice to see exactly what's going on, but you can also use a plugin like waves PAZ audio analyzer works in real time and can be quicker, though I think has less resolution. 

Anyway, try to use something like this and see which functions work, it's especially interesting to know where you have a flat response (all knobs to zero should be flat 20-20K, the BW pot should have no effect, but from what I understood, in your audio file the high boost was kept at zero the whole time, only the BW pot was turned, right?)

good luck!

 

[kante1603]

o.k.,I got it now.
It's always a good idea to look for updates,it is all in the first post of this thread,dated of july.
It does(!) contain the before mentioned guide.
The newer revision has a full metal housing and molex connectors,all the rest seems to be the same.
Which one do you have?


About your loudness issue,I know how it behaved,you've written it before.But what was the solution?
This info might help other builders.


Best,


Udo.


Editouble post,excuse me Dimitri!

 

[weiss]

thanks for your replies!

Aah now i see.. i have the old revision and therefore the old guide! thanks, i missed that one.

To make things clear, only the BW pot is being used in the sample! All other knobs are on zero position.
you notice a little cut in the highs (which i assume is because of the sound going through the transformer and components) when deactivating the bypass. Then i move the knob slowly to the left side (CCW) and the lows disappear. All other knobs and frequency work as they should. I will do some test later today!

Udo: i just didn't turn the trim pot enough until a change took place. Didn't want to overturn the trim pot, but then i managed to match the volumes

 

[kante1603]

Udo: i just didn't turn the trim pot enough until a change took place. Didn't want to overturn the trim pot, but then i managed to match the volumes

Cool,thanks for the answer,that's important.
So you have the first rev boards same as mine.
I haven't heard this phenomenon before,maybe because I haven't had the knobs standing in the exact same configuration as yours before.What I can do is check it with mine,I have a pair,to compare if it happens on mine too.
It will take some days because I have them in a studio and not here at home.
Let's wait and see...or hope the problem gets solved.


Best,


Udo.

 

[mitsos]

- Bandwith pot cuts the low end and makes signal more quiet when turned completely CCW


thanks
weiss

Hi, have you been able to get anywhere with that?  It would help if you could run a frequency sweep and post the resulting graph(s) to see exactly what is going on.  Take a look at the following site, it has a list of various passive filters, and graphs of the response to expect, you might be able to figure out what is wrong with yours by comparing your frequency response graph to the ones on the page.  BTW, the link will take you to the low shelf cut section (scroll up and down to see more stuff), but take a look to see if you don't have a solder bridge to ground in the BW pot or at the inductor leads. 

good luck!

 

[porkyman]

having problem with my unit. just plunging it into lunchbox causes a crazy distortion noise. the lunchbox isnt even plugged in. theres no signal running through it, but its making my ad converter scream. tried other unit in the same slot and it was fine. tried switching out ops and no change. you cant see it in the pic but d1 and d2 are installed correctly, and c_dc is jumpered. i saw that revision 2 boards needed to be wired for ground. those posts were in 2013 so i figured the issue has been resolved.  is that the case or do i need to do it.

thanks