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bigdh31 14th August 2010 08:43 PM

A new simple se lives
I finished building it several months ago but I have been looking around for a variac to fire it up with the first time. Last night I got tired of waiting and turned it on. It worked and it sounds great.

I used Edcor power transformer XPWR035 and the CXSE25-8-5K audio transformers. I found Edcor to be a great company to deal with. I made a mistake in that I used a standard Hammond aluminum box and the Edcor transformers are so heavy they bend the top surface some.

Currently I am using a Sovtek 5AR4, a JJ gold pin 12at7 and Electo-Harmonix KT-88's.

I have not figured how to wire the CFB and ultalinear switchs with an inverted assembly yet so it is running with both right now. I get plenty of bass and it seems to have no trouble driving my Ohm Walsh 1000's. It has very nice midrange and imaging. So far I have listened to Vivaldi's Four Seasons, which sounded fantastic, and various jazz albums. They all have been enjoyable.

Thank you George for making this great amp design and circuit board available to hobbyist.

Ty_Bower 15th August 2010 12:47 PM

It sounds like a nice project. I'd love to see some photos.

A new build is less likely to benefit from being started on a variac. Presumably, all the power supply caps are new and there is no need to try to reform the electrolyte.

The Edcor transformers are a good bargain indeed. They perform well and are priced attractively. If the weight is causing the top of your chassis to droop, a piece of angle iron installed underneath might help reinforce things.

I made a sketch for wiring a CFB switch for my board, which is "under chassis" constructed. There are two versions - you only need one depending on the phase of your output transformers. Maybe it'll help:

onionskin 30th September 2011 12:40 AM

individual switches?
I am looking at some NKK switches and am wondering if I should get double pole or a pair of single pole for the CFB. Is there any danger of cross-talk between channels running both L and R through one switch?
Same issue for UL ,and thanks for the simple diagram Ty.

boywonder 2nd October 2011 04:47 PM

helps reduce white knuckles....

Originally Posted by Ty_Bower (
A new build is less likely to benefit from being started on a variac.

Apparently, you haven't seen any of my new builds......

Increasing that dial slowly helps keep the smoke in the components and helps lower my blood pressure......

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