DIY Pultec EQP-1A Layout and Pics

[cayocosta]

Pultec EQP-1A

http://www.recproaudio.com/

 

[CJ]

Jeeez, that was fast!
No wonder we made it over here in a heartbeat!
Awesome work!
:guinness:

 

[MikoKensington]

VERY NICE! I have a boner. Haha!

 

[cayocosta]

For anyone interested, this is the original circuit laid out the best way I could think off.

I separated the amp section from the passive by way of two separate turret boards. The amp section is on the rear panel. This provided a nice way to route the heater wires in the upper corner of the rear of the chassis to keep things quiet as well as keeping the HT stuff away from the passive stuff.

One particularly neat thing is that the 6x4 runs off the same filament as the other tubes 6.3V, and the PT rectifier winding 5V goes to the lamp!

I ended up moving the interstage and input trannies to the left of the bottom turret board and the inductor to the right side. I think there are 3 grounds points: One at the OT lug. One at the input XLR, and one at the power tranny.

(I later trimmed the transformer wires.)

It works great and is very quiet. I ran a sweep on it and it's perfectly flat with the eq in and set flat. The eq curves look pretty accurate as well in all configurations, including gain.

 

[tommytones]

Wow! Very nice! This looks like one I might jump at very soon.... :wink:

 

[rafafredd]

Really great!

I may someday try this circuit...

It would be nice to know more about parts used on your clone.

What Transformers?

What Inductors?

What Rotary Swicthes?

 

[cayocosta]

Thanks Rafa.

This will run about $800 to build. Not bad considering a real one is $4000, and some clones are $1800.

There is a guy I tracked down that has NOS knobs - beautiful, brand new. And they're only like $5 each. He has more! Surplus sales wants $30 for used ones!

The PT is a Hammond 270-CAX, it specs out with the original exactly.

The input, interstage and outputs are from Sowter and the exchange rate is a killer. US$230 - I think. But they shipped to the US in like a week!

The inductor is from Cinemag with the specification of the metal can. I had to fabricate a bracket for that.

Switches are all Grayhill. 2x4 (low), 2x4(high atten) and 2x12(high) I think.

The chassis is Par-Metal and it's really nice. About $114 though.

Everything else is run of the mill. If you build this buy extra capacitors for the eq to dial in the frequencies as close as you can.

I think all the tranny wires in the layout are color coded to the Sowter's.

Send me a PM for more info.

 

[adrianh]

There was a person who sent me a PM on the old forum.
That had found I thought knobs made today just like the Pultec
knobs? Daka Knobs? Dec 03??????

 

[MikoKensington]

For those engaging in any turret construction, have a look.

http://smallbox.freeservers.com/catalog.html

I don't know what the prices are, though.

 

[adrianh]

The person was Elco;
I was wrong I think they were NOS knobs.
Daka-Ware knobs
They are still in business.
Have they destroyed the mold?
Someone please ask.

 

[cayocosta]

Adrianh,

There's a guy on Ebay named fixit-fox (US) that sells the Pultec NOS knobs 4 for $20. They're called "collins radio knobs." He doesn't have them for sale right now though. Send me a PM and I'll send you his email address and you can check with him for availability. But don't let-on what these are worth to us!

Miko, cool link for the turret boards, Newark sells the ones I used:

NEWARK INONE PART #: 35F1643 ; Standard Turret Terminal Board, 2.00 inch Width, 1.50 inch Row Space, Paper Base Electrical
QUANTITY: 3 @ $11.24 = $33.72

 

[Zee1usa]

Thanks for Sharing this Ron + web host!!

:grin:

 

[Plexibreath]

[quote author="cayocosta"]The chassis is Par-Metal and it's really nice. About $114 though.[/quote]
That looks real heavy duty, which series Par-Metal chassis is it?
Kelley

 

[Guest]

[quote author="adrianh"]There was a person who sent me a PM on the old forum.
That had found I thought knobs made today just like the Pultec
knobs? Daka Knobs? Dec 03??????[/quote]

That was me. These are original Daka-Ware knobs, in the same size used on the Pultec. The ones I have are the round ones, not the pointer ones. I have about 50 left.

I'll do a set of 5 for $20

Cheers,

elco
:shock:

 

[cayocosta]

Par-Metal 14-19053x. $116.00.

 

[Vetsen]

[quote author="cayocosta"]
The inductor is from Cinemag with the specification of the metal can. I had to fabricate a bracket for that.
[/quote]

How much for the Cinemag inductor?

Steven

 

[cayocosta]

I can't remember exactly, with the can somewhere from $40 - $50 including the shipping - I remember that was $15 of it.

 

[jrmintz]

Holy sh*t Ron! That is really gorgeous. That layout really makes the schematic comprehensible in three dimensions, which is usually hard for me. Thanks.

BTW, I just noticed - is there one too many zeros in the cap across pins 1 and 6 of the 12AX7? Is it 20pf or 200pf?

 

[cayocosta]

.00002 on the schematic.

 

[Learner]

[quote author="cayocosta"]Pultec EQP-1A

Thanks to CJ for hosting.

Layout:

http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/eqp-1a_layout5d.jpg

Pics:

http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/p_2.jpg
http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/p_3.jpg
http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/p_4.jpg
http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/p_5.jpg
http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/p_front.jpg
http://www.vacuumbrain.com/The_Lab/TA/Pultec/rons_eqp1a/pultec1.jpg[/quote]

WOW~ nice one Ron!!!!

Thanks for the GREAT work!!!! :thumb: