Larrchild

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #60 on: February 26, 2006, 11:53:13 PM »


This was sooo close to a 5 *fingers close*. But alas, it took me a year to find non-bevelled jewells, lol ..Gave me respect for the searching part of DIY.

The engraving and ink inlay here  is actually much harder than the silkscreen of the 1176 I gave a 5 to.  It just passed the "5 feet away " test better=)


chrissugar

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #61 on: February 27, 2006, 10:23:06 AM »
Many thanks frank for the Epcos info. :thumb:

chrissugar
Christian Mike Sugar
        CMS-LAB

Xopek

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #62 on: February 27, 2006, 04:46:01 PM »
Thanks huge, Frank!
Pair questions, as always  :wink: :
1. The core with a backlash or without?
2. Winding is made a coil to a coil, or is simple, how it is necessary (in Russian it is said as "v naval" ) ?

 :guinness:
I only observe... Because I speak only in Russian :)

TomWaterman

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #63 on: February 27, 2006, 08:23:13 PM »
Thanks for all your info Frank - your studio is going to look badass with all these EQPs and 1176s.

Are we building everything in fives now-whats next?
-Tom

khstudio

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #64 on: March 10, 2006, 03:49:48 AM »
Frank,
I am gathering parts for this project but need some help.

Make-up Gain:
Are you saying from the makeup gain pot to the output stage can be a 5532? I'm I'm not good enough at this stuff yet to adapt the circuit... could you or anyone help me with a drawing? I'm assuming that whole section is the discrete amp your reffering to & that can all go?

Power Supply:
I could also use a little help setting up the power supply. I think I could do it but I don't want to screw it up. Could I build a similar supply like the GSSL but only the 15v section? Since there is only a few amps in this thing I thought I'd build 2 in 1 box with 1 supply... should be plenty of current.

If there are any links to Topics, PCB files or additional info about THIS version I could really use them.

Thank you for your help.
I thought this would be a great EQ on a budget, using parts I have laying around.

Kevin
KHStudio

PS. You site is a KILLER resource... thank again. :thumb:
Kevin ~ KHStudio

clintrubber

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #65 on: March 10, 2006, 06:40:14 AM »
Quote from: "khstudio"

I thought this would be a great EQ on a budget, using parts I have laying around.

I doubt if going for solid state gainmakeup really makes much difference in price. When I look at the total cost & effort I think using the tube i.s.o. discrete solid state or an opamp is just a detail. You need a 2HE of course, but still, the Gustav-PCB doesn't cost much, the tube can be a cheap PCC88 etc. I used plastic conductive pots, IIRIC these were the biggest cost. You could skip the iron.
So while at it I'd say go for the G-version, tube & all. The picture might be different for your situation, but for me here the tube-stage doesn't influence total cost.

khstudio

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #66 on: March 10, 2006, 07:21:29 AM »
Good point. The one concern I have is SPACE... my studio racks are FULL. Not much room left. 2 LA-2A's just about ate it all up... for just 2 channels :mad:  oh well.

I'd like to squeeze the Pultec into a 1 space unit.
Kevin ~ KHStudio

Greg

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #67 on: March 10, 2006, 08:24:54 AM »
Quote from: "khstudio"
my studio racks are FULL.

hmmm... well then DIY a new rack then !!!  :green:  :grin:  muahah
Greg Stein
New Orleans, LA

clintrubber

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #68 on: March 10, 2006, 08:32:19 AM »
Quote from: "khstudio"
Good point. The one concern I have is SPACE... my studio racks are FULL. Not much room left. 2 LA-2A's just about ate it all up... for just 2 channels :mad:  oh well.

I'd like to squeeze the Pultec into a 1 space unit.

It'd be easy to 'tilt' the tube 90 degrees, I bet with a simple adapter board you could still use the G-Pultec-PCB. Or go PtP.

nrgrecording

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #69 on: March 10, 2006, 10:05:01 AM »
Hello.

There is no make up gain pot in the pultec. At least I don't have a  general make up gain pot. The pultecs I did are with a ba382 gain stage... but it seems that the gain stage doesn't make it better sounding or so. There is a 5532 at the output. You can easily change the resistor values so that the opamp does the needed gain. The pultec circuit can be found on Steffens website. For a power supply you can use keith's ssl psu or so...

When using the opamp for make up you don't need the 24V for the neve gain stage. My idea is to make an eurocard pcb with the filter so you'll have the original pultec frequencies... and some additional frequencies. Than maybe a small pcb with in and output buffer amps (output= + gain) with psu. There is a thread where PRR did a small drawing if you don't want to use the ba382 amp. The problem is the inductor. I haven't seen that much pultecs around, I think the inductor is the only reason. But its not that hard to do. Steffen has some nice infos for this also on his site. another Idea would be to use the farnell indcuctors and put some together to get the exact values... but we'll need much for this.
With a passive filter you could use every make up gain/output amp you like... for example Jakobs nice SRPP stage. As clintrubber says... something like a 90° board will work fine for 1HE. But Kevin... i bet this is not your last diy project eh?   :wink:  You need some new racks!  :green:

Frank.
Frank Röllen. www.energyrecording.de [FORUM · DIY WEBSITE · STUDIO]°°°° www.frontpanels.de [Engraved Frontpanels]°°°°


clintrubber

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #70 on: March 10, 2006, 10:54:39 AM »
Inductors, inductors...  
.... since there are no tubes in the intended versions anymore
I don't see why you couldn't replace the inductors with gyrator-based simulated coils  :twisted:  :twisted:

nrgrecording

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #71 on: March 10, 2006, 01:00:35 PM »
Hey clintrubber... you should make a [gyra(f]a)tor and hear how it works!  :wink:
Does anyone know in wich professional audio product  a gyrator is used? Maybe its useful for 31band eqs or something like that? Wasn't there a pultec type eq available for the ssl? Could be possible that they'd used opamps maybe?

I think there is one thing what a gyrator can't do... The inductor reacts different from the simulated gyrator circuit. I don't know if it makes big effects with low voltages but... when using a door opener and the inductor don't have a diode wired parallel and the circuit is turned off... the magnetic field changes and there is a kind of inductive bang. Its strong enough to destroy my previously installed acess control systems.  :green: I'd seen defective 1N4004s because of the evil inductors.  :wink:

Haven't tried such a gyrator... iam afraid because nobody else does. Maybe there is a reason for this.
Frank Röllen. www.energyrecording.de [FORUM · DIY WEBSITE · STUDIO]°°°° www.frontpanels.de [Engraved Frontpanels]°°°°

clintrubber

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #72 on: March 10, 2006, 01:15:41 PM »
Gyrator-based filters are around a lot, but the best examples don't come to mind right now. So some rambling:

Those API active EQs, they had 'real' coils, right ?

The Ampeg SVT bass-preamp has this tapped coil for it's active midrange control, but I'm not sure how it'd sound had they been using 'emulation'. It sure is a seeling point of those amps though, up to the point where they've put glossy pics of that inductor in the leaflets. It's vintage, must be good  :wink:

The SWR bass-amps (hey, they're labelled 'professional') use opamps & C realizing 'fake-coils'.

FWIW, those Boss distortion pedals use fake-coils a lot to shape freq-response.

It'd sure be interesting to do a comparison between (1) 'real' coil, (2) one transistor gyrator+C, (3) opamp gyrator+C, ...  uhh, and how about a tube realizing a gyrator  :grin:

... and how then about coils+gyrator for realizing fake-caps ? (patent applied for)
Might be an interesating but totally uneconomical approach to bring some saturating possibilities to previously coil-less filter circuits....

enough !


Quote
I think there is one thing what a gyrator can't do... The inductor reacts different from the simulated gyrator circuit. I don't know if it makes big effects with low voltages but...

It could of course be made to do so, but that's then the same story as non-tube stuff emulating tubes etc etc

Quote
Haven't tried such a gyrator... iam afraid because nobody else does. Maybe there is a reason for this.

Not unlikely they don't sound 'as pleasing', but note there might be a commercial aspect of it, as in people wanting real old tasting stuff, as mentioned already above @ SVT.
This is fun, and actually the other way around since most stories about gyrators start with the benefits of getting rid of coils.
And while lots of circuits use them, maybe some circuits simply don't use them because of unfamiliarity of the designer with this stuff.

have a good weekend all,

  Peter

CJ

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #73 on: March 10, 2006, 03:00:45 PM »
the inductor only shapes the upper half of the bell curve, so any effects from using different inductors will be divided by 2.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

khstudio

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #74 on: March 10, 2006, 04:25:45 PM »
Hey I made a mistake... I WAS refering to the 24v section.
And yes I need more racks... just like any man would :green:



Has anyone used the Sowter inductor for the Pultec?
Kevin ~ KHStudio

tv

some finished Pultec EQP1A - 'pimp my pultec'
« Reply #75 on: March 16, 2006, 03:17:38 PM »
Has anybody thought of modding the neve stage to work with mosfets like bs170 etc. yet? imo the input 120k, the 68k base resistor and 18k nfb resistor could be increased 10x (or 100x ..), collector resistors of first bc547 somewhat lowered - others recalculated for bias. Should the 1nf cap which goes from base to emiiter of first bc547 be omitted or recalculated if resistors I mentioned are increased? The internal sg cap of bs170 should be around 24-40pf.

This should give a different character to the solidstate gain unit.

On the second thought, the inductor is the only large component of the *eq core* circuit - could it be possible to mod it and throw in something like (one bjt, 2 caps, 3 resistor) boss-pedal gyrators - they're all over various boss pedals. This should minimise the circuit a lot - if possible.
If you sprinkle when you tinkle, please be neat and wipe the seat.


 

Related Topics

  Subject / Started by Replies Last post
15 Replies
4190 Views
Last post June 19, 2007, 06:55:34 PM
by CJ
4 Replies
5215 Views
Last post September 04, 2008, 12:54:43 PM
by electrochronic
5 Replies
3181 Views
Last post August 13, 2009, 03:50:03 AM
by Hamburg58
7 Replies
2425 Views
Last post July 21, 2009, 07:32:57 AM
by ioaudio