ST-35 from a Triode Electronics kit

[TomMcNally]

I built an ST-35 last night from the kit put together by Triode Electronics.
They include the board, all parts, their stainless steel chassis, transformers,
power cord, all hardware. Tubes are included or not, your choice.
It went together in about 3 hours and came right up sounding great.
It's nice to get it all in one box and just put it together !





Bigger pix and more amps at http://tmamps.com

[Ty_Bower]

It's nice to see the IEC connector on this kit. Little things like that mean a lot to me. Is three hours the record for building out a ST35? I assume that includes stuffing the board and dressing the wiring, too.

I like the chassis. The profile is relatively low, but wide and deep enough to spread everything out a bit. Nice looking amp!

[TomMcNally]

I don't know what the world record is .... I've built about 6 of them, and I think 45 minutes on the board and another hour and a half on the
pre-punched chassis was my record. What usually slows the
average person down is missing a part and not having it available
locally. With Triode's kit of parts, and Shannon's instruction book,
it's a pretty smooth build.

The IEC connector is definitely the way to go, as well as
standard 3/4" spaced binding posts. It makes it easy for
testing and auditioning when you build a lot of amps, or
switch them around. I like to burn in everything for about
24 hours, re-checking the bias if applicable now and then.

... tom

[Blackburn Audio]

Nice work as usual Tom, those kits are nice and its sure handy to get everything all in one bundle. Its also great for beginners since they don't have to worry about a part from mouser being backordered for 3 months and having to try and find a suitable replacement. Just out of curiosity did you have to omit the series resistors for the filaments to get the filament voltage up to spec, I remember prototyping one of these when I was working at Triode and I had to put in jumpers for the 0.025 ohm resistors to get the filament voltage up, I was only getting ~5.5VAC with the resistors installed.

That IEC connector was my little addition to the kit when they were getting ready to make the chassis's. I hate not having them since I like to switch amps quite often and being able to use one power cord for them all is just so handy, plus its a pain in the butt to crimp on those strain relief connectors. I also added one to their ST-70 chassis when they were getting the second run of those made, its a tight fit on that amp since there is really no good place to put the IEC jack. It sits real close to the PT on the inside of the amp but seems to work fine.


-Matt

[TomMcNally]

Hi Matt -

Sorry for the slow reply ... I didn't measure the filament voltages.
I probably should have though.

Those power transformers run pretty hot. I guess there is no
way to pack that much capacity in such a small package and
have it run cool.

... tom

[Blackburn Audio]

Yeah they do run really hot, you can barely touch them after they have been on for a couple of hours. I talked to the engineers at the transformer house about this problem and we came to the conclusion that there is nothing you can do to make them run cooler without making the core larger. We discussed using larger wire but were afraid we would run into problems with the transformers shorting out between windings which was a problem in the past as some people here are aware of. My solution to the problem was to make a new transformer with a larger core, add a 5V winding, bias tap, and to tap the HV winding for a second lower voltage output while we're at it so you can use them for a nice class A amp, call it the DIY774. My thinking was since most people are not using the PA774's in an original ST-35 or SCA-35 but rather in DIY projects why should everyone have to keep using the weaker undersized transformer for all applications just so there is still a drop in replacement for an original Dynaco. Make both transformers and let people decide which one they want. Triode never went forward with this idea but I suppose if enough people asked them about it they might consider making it sometime.

-Matt

[TerrySmith]

Just a bias tap would be nice! Yellow_Light_Colorz_PDT_06 Yellow_Light_Colorz_PDT_06 Yellow_Light_Colorz_PDT_06