UTC A20 replacement for Triad HS56?

Hello,
I'm planning to build 2 PTP Pultec EQP-1A clones, as close as possible to the originals (but based on Cayocosta's layout). Some people say a UTC A20 or UTC A22 would be a good replacement for a Triad HS56. The difference is that a UTC is 500:500 and a Triad is 600:600. Is this not a problem? I know it will work, but will it work properly??? I mean, there should be some difference, no?

Also, anybody knows a UTC replacement for a Triad HS29? Or maybe Triad has a transformer like they have a HS66 that can replace the HS56?

Thanks a lot!

Bram

A-20 input should work

for the HS29:
Sowter makes a very close reproduction, otherwise you can try:
UTC
A-18
A-19
HA-105
O-4 ?
O-6 ?

But specifications say:
- HS29: primary impedance 20000/5000
- UTC both A-18 and A-19: primary impedance 15000
That's not the same right?

nope, but I don't think it matters that much. Just try it and it will probably work out fine.

sidenote: I'm wondering how it is used in the EQP as they don't use an interstage-transformer in the MEQ5 (different circuit of course). Probably more as a splitter than as impedance converter..?

bram9206 said:

But specifications say:
- HS29: primary impedance 20000/5000
- UTC both A-18 and A-19: primary impedance 15000
That's not the same right?

Click to expand...

Hi
I think Sowter is the better choice for HS29 replacement.
i used sowter xfrms for interstage and output of my EQP clones (Cayocosta's layout) and the sound is very FAT and WARM
http://www.groupdiy.com/index.php?topic=44657.msg559342#msg559342

Let me know if you need something about this project, maybe i can help you

Cheers
Cyril

I always liked the A-20 much more than the HS-56.  The HS-56 does this grainy milky cloudy thing.  500-600, same thing.

creal said:

Hi
I think Sowter is the better choice for HS29 replacement.
i used sowter xfrms for interstage and output of my EQP clones (Cayocosta's layout) and the sound is very FAT and WARM
http://www.groupdiy.com/index.php?topic=44657.msg559342#msg559342

Let me know if you need something about this project, maybe i can help you

Cheers
Cyril

Click to expand...

Hi Cyril,

Those clones of yours look realy nice! I will considere the Sowter replacement for the HS29 and I will get Triad HS56's anyway, as you can find them quit easily... Concerning your build: where did you get those nice faceplates and how much did you pay? Are they engraved? Still need to find the best faceplate, closest to the original Pultecs...

All my best,
Bram

bram9206 said:

Hi Cyril,

Those clones of yours look realy nice! I will considere the Sowter replacement for the HS29 and I will get Triad HS56's anyway, as you can find them quit easily... Concerning your build: where did you get those nice faceplates and how much did you pay? Are they engraved? Still need to find the best faceplate, closest to the original Pultecs...

All my best,
Bram

Click to expand...

Hi Bram,
The front panels and the knobs came from don-audio in the white market.
Yes, they are engraved and the blue is very close to the original units.
i don't know if you have make your choise for the inductors, for my clones i ask to ChrioN to do mine, it sound very well.
here the links
frontpanel and knobs
http://www.groupdiy.com/index.php?topic=38026.0
inductors
http://www.groupdiy.com/index.php?topic=43429.0

Don't hesitate to contact me, if you need help and support for your build.
I'll start a second pair now, just need to order some parts before start.
the only difference with the first pair will be the format of the rack 2U instead 3U and a silver face.

This EQ is a killer, the P2P version is the most closer as the real pultecs
Cheers,
Cyril

bram9206 said:

But specifications say:
- HS29: primary impedance 20000/5000
- UTC both A-18 and A-19: primary impedance 15000
That's not the same right?

Click to expand...

Look at the ratios.  The goal is to step up the signal to the grids of the make up amp while maintaining the best load for the passive section of the EQ to work into.  The original Pultec uses a resistor to terminate the secondary.  You can pick a different resistor to set the load the primary presents, so it's a very workable substitution. 

i did a side by side test on the hs 29 vs Sowter and found that the Sowter came out better by just a tad.
plus it is way cheaper and usually in stock.
and easier to mount, which is 90 percent of the hassle of getting a transformer onto your chassis.

For something else, anyone knows where to find a cheaper solution for those telever bypass switches? There is a very cheap and ugly Kippschalter switch that should work, but as it looks so cheap I'm looking for something else. I would like to find a switch that looks identical to the originals. Thanks!

Bram

for the bypass switch, you can use any 2 poles DPTD
http://www.banzaimusic.com/DPDT-on-on-Toggle-5A-125V-3A-250V.html

Sometime the switchcraft can be found on ebay but they are not cheap

And what switch did you use and where did you get it? Damn your Pultecs look so nice

Thanks

For my clone, i used the original switchcrafts.
i found them on evilbay

And do you think I can use 13033 lever switch too? What is a 'momentaraly' switch?

http://www.ebay.com/itm/Lever-Switch-Switchcraft-Moment-ON-ON-SPST-13033-/190590430857?pt=LH_DefaultDomain_0&hash=item2c60132e89#ht_1146wt_956

My best,
Bram

this switch is not suitable for the bypass.
'Momentary' is the not latching , it don't keep the contact on his state at release.

So 'Switchcraft Telever 16006' is exactly what I need? In that case I'm just going to check ebay every now and then. Hope I find those switches pretty soon...
Thanks again for the info!