Stancor A-3801 waiting for an Express to be built around it.

[premiumplus]

Hey guys,
I've been a long time member here but very rarely post. I'm a retired electrical engineer and longtime musician and bench tech for tube amps, so I do know which end of the soldering iron to hold!
I have been thinking about building an Express for several years. When I graduated from college, I had the good fortune to acquire a brand new in box Stancor A-3801. At the time, I didn't realize that it was the output transformer that KF used in his Express, and it came home to my lab and has been sitting for over 20 years. But I"m about ready to source parts and begin my build, so I am happy that I've got a good start on parts.
I have read up on a lot of the great info that's in the Trainwreck section of this website, and I've read KF's "Trainwreck Pages" a couple of times.
I have recently seen that there are a couple of versions of the A-3801 transformer...a black one (which is the one I've got), and a grey one. I have heard that the grey ones are superior, but can anyone tell me why, and what the difference is?
Also, I'm confident in my electronic skills, but I don't have the equipment or experience to build a cabinet for the amp. Does anyone build them, and what would the cost be?
Thanks!

[aaronz28]

hi,
I have a couple of each - and have installed them in the same amp to clarify this question... for a while, people stated that the grey ones sounded different -

in fact, the only difference I can tell is that the grey ones have plastic coated leads and the black ones have cloth.

of the 5 i've owned, 3 black, 2 grey - they all had subtle differences in the actual thickness of the iron, some had the A-3801 embossed into the cover, some did not - its not consistent at all.

As for sound - a grey NOS one I bought is very buzzy sounding -
my favorite is a black NOS one that i got for $50 on ebay.

Ken used the grey ones because they were available new from Stancor when he was building amps... when Stancor discontinued them, he had Pacific build clones without the 500k tap.

Some have claimed that the grey one sounds BETTER - i don't believe they do, i think they are all slightly different - in as much as any mass produced transformer would be.

Cheers.

Aaron

[didit]

I'd recommend you get a chassis & power transformer from RJ, and perhaps other components he's got on offer. There seem to be a few cabinet builders out there -- a posting in the "speakers and cabinet" section should land some helpful responses.

Best .. Ian

[premiumplus]

Thanks, guys...that's exactly what I was looking for.
I've got an old 100 watt Acoustic 164 tube amp chassis and iron in my shop that I'll have to measure to see if the power transformer would be useful in this build. It looks like I'm looking for 240 to 250 /0/ 240 to 250 vac at 300 mA, correct?
I'll check out the resources here...I'm sure I'll find what I need to know.
Great forum you have here, thanks for letting me share info with you all!
Dave

[Colossal]

Thanks, guys...that's exactly what I was looking for.
I've got an old 100 watt Acoustic 164 tube amp chassis and iron in my shop that I'll have to measure to see if the power transformer would be useful in this build. It looks like I'm looking for 240 to 250 /0/ 240 to 250 vac at 300 mA, correct?
I'll check out the resources here...I'm sure I'll find what I need to know.
Great forum you have here, thanks for letting me share info with you all!
Dave

Dave,

The correct AC secondary for an Express build is 300-0-300 at 300mA. Like all things with this amplifier, everything matters. If you need a source, check with RJGuitars.net (RJ is a respected member here) for the correct transformer.

[premiumplus]

Thank you, sir. I'll get it from him. I see he makes nice chassis too...

[donzoid]

Dave, you have come to "the" place for this build. +1 for RJ, and there are several cabinet builders here like ampmike, and Cbass who build just stellar looking stuff.

[premiumplus]

I think so! And I want to thank you all for the warm welcome. I've been into electric guitar for some 45 years and I've been in the hunt for great tone every since I heard Hendrix break out back in the mid sixties...There's so much to learn, I know from personal experience that there is ALWAYS more to discover, to try, to improve on. It's such a cool hobby...that and great stereo gear is my main interest and I'm so lucky to be able to have the time and resources in my retirement to be able to have fun with it all.
So thanks again for the great welcome, guys! It's most appreciated and I will do my best to add to the experience here, not just take away.
The cool thing about the internet is the vast amount of knowledge here. It's so great to be able to grab my laptop and in a few minutes find the answer to a question that 30 years ago would have taken literally days if not weeks to find. The voltages for the primary transformer in the Express is a perfect example, not to mention the schematics and the wealth of experience that other builders, techs, and engineers share freely.
I'll get off my soapbox and get back to lurking now...