Least expensive output transformer option for ST-35?

for the DIY ST35, the Dynakit and every other PP EL84

Least expensive output transformer option for ST-35?

Postby nineno » Wed Nov 14, 2012 8:44 am

Hello DIY Tubers -
The cold weather is finally approaching here in the Midwest and it's time to turn my attention from outdoor projects to indoor projects.

I have a couple of DIY Tube projects that have been idling on the back burner for awhile. First up is a ST-35 that I started a couple of years ago. I acquired the board for free and my original ST-35 (made 9.5 years ago in college!) is working so well that there's been no need for a second one.

The populated ST-35 board has accumulated enough dust and it's time to finish it.
I know exactly how good an ST-35 with the 'spec' components sounds, but I thought I'd take a different approach with this build. The iron and tubes make up a huge percentage of the total amplifier cost, so I'd like to find output transformers that provide reasonable performance - let's say +/- 3dB response between 120Hz to 15kHz with appropriate power handling - for as modest a price as possible.

Ultimately, I plan to use this back-up amplifier with a pair of Akai Jet Stream SW-30 speakers that I was given recently. Clearly, the 40-something year old speakers aren't a mark of sonic excellence, but they don't sound too bad, either. I'm trying to match the performance of this ST-35 to bookshelf speakers like the Jet Streams.

The Triode Dynaco repros are great and I wouldn't hesitate to buy them for a top-flight build. I've also used and enjoyed Edcors and my original ST-35 uses Hammond 1650s that I am very, very happy with.

In general, these transformers run north of $75, each.

What's out there for half that amount?

My first stop was Hammond - and it looks like the 125E transformer could work. Wired to work with an 8 Ohm speaker the resulting primary impedance is 8200. I don't know what the center tap is wired at, but presumably it's between 20% and 40%.
Does anybody have any thoughts on how well these would or would not work?
Mouser sells them for about $46, each.

How about other options?

I'd also be interested in hearing about the lowest cost power transformer - but I recognize that there are more concrete limitations on power transformers because they handle a fairly consistent amount of power and there isn't a trade-off curve for cost vs. fidelity like there is on output transformers.

Thanks for your input guys - I'll look forward to hearing about what's out there -
Drew
nineno
 
Posts: 117
Joined: Sat Aug 02, 2003 10:59 pm

Postby TerrySmith » Wed Nov 14, 2012 9:10 am

Edcor GXPP15-8-8k outputs, $37.01 each.

Antek AS-1T300 toroid power trans. $34.50. I really like these, they run cool, no noise, and dirt cheap!

Triad C24X choke, $8.xx from Mouser. WARNING, made in China! (evil)
T. Smith
User avatar
TerrySmith
KT88
 
Posts: 973
Joined: Sat Jan 31, 2004 12:51 pm
Location: Maryville TN

Postby Shannon Parks » Wed Nov 14, 2012 9:51 am

http://www.edcorusa.com/p/593/xpwr005_120

This is basically an easy sub for the PA774.

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3764
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington

Postby Ty_Bower » Wed Nov 14, 2012 10:01 am

Go for the XPWR005 as Shannon indicates, plus the MS-8K-23 outputs.

http://www.diytube.com/phpBB2/viewtopic.php?t=4597
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
User avatar
Ty_Bower
KT88
 
Posts: 1494
Joined: Wed Mar 21, 2007 2:50 pm
Location: Newark, DE

Postby nineno » Fri Nov 16, 2012 8:15 am

Great information guys, thanks.

- Drew
nineno
 
Posts: 117
Joined: Sat Aug 02, 2003 10:59 pm

Postby Geek » Fri Nov 16, 2012 8:52 pm

TerrySmith wrote:Triad C24X choke, $8.xx from Mouser. WARNING, made in China! (evil)


So are the Hammonds nowadays :/
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia


Return to stereo 35

Who is online

Users browsing this forum: No registered users and 5 guests