DIY Pultec EQP-1A w/original transformers due in 2 months

After several months of hunting, I've procured the original transformer lineup to put together my first DIY tube project, a Pultec EQP-1A program equalizer clone.



Notice that in addition to the original, I also picked up an S-217-D repro - the Sowter 9530A. My intent is to A/B these output transformers for the benefit of the group, all other things being equal. Considering what I paid for it, I hope the original is a lot better :grin:. Actually, my true hope is that the difference is minimal so that people will feel confident about moving forward with their Pultec clones using the Sowter. I'll post sound samples so we can try to get a sense of its contribution.

My front and rear panel are painted and out to FPE for machining and engraving. Once they're back I'll get to building.

Stay tuned!
Andy

That's awesome transformers lineup dude! Where did you get all those good stuff?

All the vintage stuff came from eBay. The Sowter I purchased here at Prodigy Professional. The inductor came from Cinemag direct.

Pat,

Thanks for the encouragement. I'm using new caps, and nothing quite so fancy as paper in oil, which I assume the original used in some places.

I'll certainly be in touch with you for a sound test against your original Pultecs - thanks for the offer. It'll be nice to have a set of comparisons up here, for what they're worth. I can only hope my clone produces samples that are within "subjective" territory of one of your originals.

Andy

That's unreal! I'm afraid to know what all that iron cost. I've done two EQP-1A clones, one with all Sowter and the other with Sowter and the HS56 input. The One with the Triad input sounds better to me. Better low end control. All those other original pieces were way to expensive for me to try out. I'll also be curious to know what you come up with. I'm totally jealous.

Steve

Don´t let CJ see this iron collection. He will send some terrorists, Mafia or whatever to your house.

Great score :thumb: I´m looking forward to hearing the files

:guinness:

Here's a site to track progress of the build:

http://www.floorbirds.com/crossenstreams/pultec/

great work so far :thumb:

Very nice work indeed!

Bummer that your paint came of a little during the engraving proces.
I once had the same problem. My panel was supossed to be powder coated and all but it turned out that they forgot to bake the panel (which makes the paint strong..) I have to say though that your panel still looks very good compared to what mine looked like.

I thought that you had a typo on the PSC-55 transformer, but, on closer inspection, I see that it is actually just that. What's the difference between the PSC-55 and the original PCC-55?

Click to expand...

I had the same question, and checked out the 1958 Chicago Transformer catalog. It shows the PSC/PCC series are identical physically and electrically, but have different mounting options. The PSC has solder terminals, and the PCC has colored leads.

Because a wiring sheet wasn't included with the transformer, I identified each terminal by process of elimination and measuring DCR. Only after I did that did I find this PCC/PSC series wiring sheet which confirmed my findings.

OK, two months was a bit unrealistic, but I managed to finish it up this past weekend.

Updated photos are here:
http://www.floorbirds.com/crossenstreams/pultec/

I'll get some sound samples up this week too. It sounds really nice playing some program material through it (Pet Sounds).

Thanks to everyone here who helped! What a great challenge and rewarding project.

Andy

Andy, where bouts in cHI tOWN?
i AM NOT GETTING ANY HITS ON PEOPLE fINDER FOR aCROSSEN/cHICAGO....A LIL HELP, PLEASE, OR IF ANYBODY
KNOWS ANDY'S ADDRESS, i AM WILLING TO DONATE MY LATEST CROP...
i DO NOT KNOW HOW THOSE 12 L lams got swapped out for 31DU.
really dont.

the A/B test:

my predictions:

1)input-no diff
2)innerstage-sowter better
3)output peerless better

That just friggin' rules! Can't wait to hear some clips.

Craig

Damn that looks great! Now your making me want to get around to building one this winter as well. I did manage to dig up the original knobs and switchcraft switch, one of the triads and vintage pilot light over the summer. Gonna have to start digging for transformers soon.

I'd love to hear yours. I don't have a original Pultec to compare it too, but I do have a Lang Peq-2 here.

See the below pic for the project I just completed today. I was able to get a couple of Cinema Engineering 4031 passive eq's which had no face plates, I got them fairly cheap about a year ago and finally got around to designing and having face plates made. I've been testing them using a V74 as make up gain, I have to say so far they sound great

http://i158.photobucket.com/albums/t117/twist2002/Cinemaeq002.jpg

Hey Twist, those are indeed cool sounding EQ's. I've always wondered (haven't put my head to it at all) what it would take to mod those so they have the later Langevin / Altec style bottom end with 40 and 100 Hz choices, as opposed to just the 100.

Andy, you know we're gonna hammer on you to compare the Sowter, try as you might to walk away. Figure out what easy method works; disconnect some wires and use those $2 test leads. Sure it's dangerous, whatever. That's how things progress! :razz:

Andy, you dont need to build the eq for camparison, just the line amp, know what i am gettin at?
Time is money, I got more money than time, what was the question?

You're right, I owe it to myself and the group to do this simple test. Sorry for attempting to wimp out. I won't get to it for a week or two, but hey, what's another week or two in the grand scheme of things.

If anyone has a Sowter 9330 interstage and/or 3603 input transformer they want to send me to test out, I'll try those out too. We could end up with a nice matrix of transformer combinations / sound clips.

I have an original filter caps set up from drpat
A pair of hs56vs and some other Nice 1:1 transformers .
Id gladly drive em over :thumb:
I live on foster

Sorry drpat , I should have said " collection of similar caps ".
Just moving slow on this .
Any inductors for sale ???
gary

Shhhhh!!! You'll wake up the vultures!