My 3 DUAL PULTECs - EQP-1a3 - Solid State

[maxwall]

Kevin

Fantastic work there. Thanks for sharing your experiences with this.

questions : many

1. Would you offer any vinyl panel services - just curious. Or can this be
found anywhere for front panel graphics.

2. looks like you used some polystyrenes in the filter section , are these preferred over polypro's or polyester orange drops or does the original
use polystyrenes.

3. Any difference in filter section in using a hand wound homebuilt torroid inductor as compared to say a production made one from a brand name maker. or is it just a cheaper way to get the real deal. By the way is the original inductor made the way you have yours done ?

4. Are the pots 2 watters, conductive plastic or carbon element ?

5. Is there a original eqp1a3 schematic available to post here for reference ?

6. how do you compare the Tamura version to the triad56 version
tone, body, frequency emphasis on overall sound ? What Yamaha
unit are those outputs from ? I have some outputs from a Pm1000
but there not as robust in size. wondering if the pm1000 outputs are
too small. I believe there 1:1's

thanks again :thumb:

 

[radiance]

[quote author="maxwall"]

5. dou you have a original eqp1a3 scematic to post here for reference ?
:[/quote]

There is no original eqp1a3 (solid state version) schematic.

That's what Dan Alexander told me.....

 

[maxwall]

Radiance,

the original exists, I have seen it with my own eyes, but I can't find it right know. was hoping someone had it within a minutes reach.

 

[bluezplaya]

This is on the first page of the thread. Don't know if that helps.

 

[maxwall]

Bluezplaya,

Yes I saw this already , but I was'nt sure if there were any mods here that departed from the original schematic.

Funny thing , whenever a pultec schematic is posted the filter block section is always left out - this is important to have as well.

Does any one have a the filter block details in schematic form ?

Also I don't see any pots in the schematic, could those be in the filter block section ?

The power block is just a off the shelf regulated bi-polar - easy

 

[khstudio]

[quote author="maxwall"]Kevin

Fantastic work there. Thanks for sharing your experiences with this.

questions : many

1. Would you offer any vinyl panel services - just curious. Or can this be
found anywhere for front panel graphics.[/quote]

I do have a few spare stickers for both versions I MAY sell off.

2. looks like you used some polystyrenes in the filter section , are these preferred over polypro's or polyester orange drops or does the original
use polystyrenes.

The original uses a MIX:
off the top of my head-
3,4 & 5k = Styrene
8, 10 = Paper
12 & 16 = Silver Mica

This is how I did my BLUE unit (which I tried to make as close as possible to original, EXCEPT the input section)

Black unit = all Styrene (maybe more "accurate" sounding)
RED = All Poly (maybe more "smooth" sounding)

They both sound good... just different.

3. Any difference in filter section in using a hand wound homebuilt torroid inductor as compared to say a production made one from a brand name maker. or is it just a cheaper way to get the real deal. By the way is the original inductor made the way you have yours done ?

Yes,
The Iron powder core ( I wound & used in my BLUE vers) is exactly like the original. Over 1300 turns each. I was lucky to get a pair of these. They're VERY hard to find & I couldn't begin to tell you where to find them.
They have a different sound compared to the Cinemags, which are CLEAN & Accurate! The Ferrite Toroidals I wound for my RED version are closer to the original... The toroidal cores seem to "Bloom" or spread more harmonics somehow, they add a "Grit" or flavor to the sound that the POT CORE's, like Cinemags, don't. But I DO like them BOTH!!! for different reasons.

I have some extra Ferrite Toroidal cores that I may wind & sell.

4. Are the pots 2 watters, conductive plastic or carbon element ?

Nope, Alpha's = CC

5. Is there a original eqp1a3 schematic available to post here for reference ?

The 1a3 filter section is the same as the tube versions except the output section which I posted.

6. how do you compare the Tamura version to the triad56 version
tone, body, frequency emphasis on overall sound ? What Yamaha
unit are those outputs from ? I have some outputs from a Pm1000
but there not as robust in size. wondering if the pm1000 outputs are
too small. I believe there 1:1's

Too hard to explain. Like I said before, I don't think you can go wrong with this circuit... just build it then listen. You'll never know until you here for yourself what the different parts do to the sound... they can ALL be cool.

 

[khstudio]

[quote author="bluezplaya"]Hey Kev, I have two Pultecs that I've built..one with a Telefunken diamond tube and iaudio's custom wound inductors. The other one needs some work to it. I't's not producing gain in the output stage. However, after checking out your builds I have now seriously considered changing the output to solid state by way of a green pre PSU (+/-15v) and a Melcor 1731. Would this work? I've already got the filter boards working (Gyraf) and using Edcor XS1100 ins and outs.

Thanks,
Adam[/quote]

I would try it... you can always drop in different DOA's.
If you build the make-up amp like posted - I'd change the 1.47k (fixed gain) resistor to a 5k trimmer so you can adjust for unity gain in bypass.

OR

Build a line amp, like the API 325.

If built correctly they'll all work.

There's a schematic around here for the M-tec (Manl*y version)
which uses a 100k on the output... this is what I did.(EDIT - WRONG, NO I Didn't use the 100k - I kept it stock & followed DRpats schematic for the filter section... there's a thread about this somewhere, I used a 10k)
I think it may have something to do with the SS output compared to the tube & removal of the "interstage TX"

 

[khstudio]

HS-56 Note (FOR THOSE THAT ARE USING HS-56 ON THE OUTPUT):!:

Look at the output amp I posted (from Pat).

The INPUT HS-56 on the SS Pultec is wired "Normal" = Primary IN, Sec to filter.

But on the OUTPUT, the HS-56 is Backwards!!!

& it also has a 1.8K LOAD!

 

[maxwall]

The 1a3 filter section is the same as the tube versions except the output section which I posted.

Where is the Pultec passive filter section posted ?

I know its the same as the EQP1A , but I have'nt seen it in schematic form
can this be put up here for reference, even a link would be fine.

How would one indentify an iron powder inductor core for using to make their own pultec authentic inductor. Are there any markings or identifiers on the core ? any possibility we can see a closeup pic of one ?


thanks.

 

[radiance]

[quote author="maxwall"]
.. a link would be fine.
.[/quote]

http://www.gyraf.dk/gy_pd/pultec/pultech.gif

 

[khstudio]

[quote author="radiance"][quote author="maxwall"]
.. a link would be fine.
.[/quote]

http://www.gyraf.dk/gy_pd/pultec/pultech.gif[/quote]

Not a Pultec!

The Gyraf schematic/version is actually from the TUBE TECH - Pultec.
It's close but...

 

[maxwall]

KHStudio, Radiance

thanks, this helps :thumb:

What are the physical dimensions of the original inductor core ?

its just a iron magnetic ring , yes ?

 

[khstudio]

http://www.groupdiy.com/index.php?topic=25482&postdays=0&postorder=asc&highlight=inductor&start=15
http://www.groupdiy.com/index.php?topic=26322

I asked Pat to comment here when he gets a chance. He's very busy.

I know he posted some info & possibly a schematic of his filter circuit but I can't find it or nor do I have time to look for it right now.

 

[radiance]

[quote author="khstudio"]
Not a Pultec!

The Gyraf schematic/version is actually from the TUBE TECH - Pultec.
It's close but...
:[/quote]

Are you sure ??? Gyraf has two schematics posted on his website.
One is for his DIY version and the other one (the one from which I posted the link) is a redrawn version.

Thanks to Chris Jenrick for sharing the "real" filter schematics for reference.

Either way, don't expect big differences between the two besides frequenties and different ways of implementing rotary switches.

See it as a couple of basic passive EQ parts patched together in a certain way. If at all, ther're limited ways of doing such a "patchwork" .....

 

[khstudio]

It says TUBE TECH right on it. :wink:

You are correct about different ways to get to the same point but there are a lot of elements that add up to the "Pultec Sound".
Also, I think the original questions was about a REAL Pultec schematic.

Like I said... all my units are set up a little different & I like them all for different reasons...
but after winding the original inductors & setting up the filters/caps to match, building the output amp like Pats SS Pultec with 2520's, 1uf CDE input caps & military sealed 150uf tantalum's on the output of the 2520 & HS-56 on the output with proper 1.8k loading - the EQ sounds VERY cool, I can't begin to describe it... it just adds weight to the low end & a completely different Hi Boost sound that the others (like the Cinemag vers) the Ferrite toroidal is much closer but still not the same.

EVERYTHING that I listed above changed the sound.
& note that MOST are in the "signal Path" (Amp section/Bypassed signal) as opposed to the "Filter section"

BTW... on the REAL Pultec, the 16k shares the same tap as the 8k.

I know Pat posted the Tap Values. I'll try to dig them up & post them if he doesn't.

I'll say it one more time... If your bypassed signal sounds good & your filter sections are built & work properly, you can't go wrong with ANY version... it doesn't have to be exactly like a Pultec to be a great "Passive" EQ. :green:

My RED unit with Yamaha DOA's, 470uf FC's instead of the Tants, 1uf SOLEN's instead of the CDE's, Tamura OT's & self wound Ferrite toroidals is KILLER too.

 

[khstudio]

BTW... Joe Malone from JLM posted a schematic he drew up from 3 different Tube Pultecs. It says "Hosef" or something on it & is ALSO a great reference.
It does differ from Pat's Pultec so it seems there were "some" variations.

But I was interested in the SS version & that Pat reversed from his original units.

 

[radiance]

[quote author="khstudio"]It says TUBE TECH right on it. :wink:
.[/quote]

did not see that

strange...Jakob never mentioned Tubetech other than on the schematic :?

 

[maxwall]

Well, I saw the 'Hosef' schematic too. But I have to take all the schematics lightly, until I see the original pultec one.

A real pultec passive filter schematic would help a lot. All the other passive inductor based filter sections I've seen are DIY versions that have some variance as kevin pointed out or what is not considered to be the original. I want to have the original to establish some kind of concrete baseline for my up coming builds. without it , it seems I'm not starting the project with any meaningful direction.


I have a local source here for vintage inductor cores that I think might have the cores I'm looking for in making an original inductor , but without knowing how to identify that core , I'll never know where to start. This makes it somewhat frustrating. Most electrical components have some kind of mark or stamp to that allow for indentification. So far I have no idea what to look for when trying to get the right core for this pultec inductor. If anyone has the info , can some clues or dimensions be given here. If I find these cores I could make them available for DIY members here on the forum.

I think I can source the inductor wire from a guitar pickup winder supply house. Just don't know the guage yet. maybe 40 or 44 , not sure. any clues ?

 

[khstudio]

No, do a search... Joe said he made that schematic from 3 REAL tube Pultecs.
Like I said, there are probably a couple different revisions.

 

[khstudio]

[quote author="khstudio"]No, do a search... Joe said he made that schematic from 3 REAL tube Pultecs.
Like I said, there are probably a couple different revisions.[/quote]

EDIT... I just found out they may not be as accurate as I thought, sorry.


In one of the links I posted, Pat gave the size & AL Value of the cores.

AL value = 876
Size = of a Quarter
Wire Gauge = 34 (if your core is close to 876 AL = (876uH - I think... 90% positive)

To find the AL value, you can wrap the cores 100x
it doesn't matter what gauge it is!!!
After wrapping, measure the inductance... this is your AL Value.

A little secret - if you wrap it 10x & you get aprox 12-16uH (I think), your VERY close. :wink:

After you get your AL value... there should plenty of info around that tells how to do the math for the number of turns for each tap.
I know the cores were Black... but I don't have or even remember if there was a # stamped on them.