Hotrod ST-35

[TerrySmith]

This is my latest project. It's the usual '35 that has been cut&jumpered to accept the 6GM5 output tube. The opt's are from a Heathkit AA-100 with new end covers I got from Ned at Tubezone, and the PT is a Hammond 272-HX. Rectifiers are 6DW4 damper tubes.

I wanted to use the new Soundtastick chassis, but all this would not fit so I ordered a Par-Metal 12x12x2 case.

BTW, the 6GM5 is a 9-pin version of the 7591 and 7868.

http://i147.photobucket.com/albums/r314 ... st35-2.jpg

http://i147.photobucket.com/albums/r314 ... st35-3.jpg

I'll try to replace these links as soon as I figure out how to use the image host.

[TomMcNally]

Very cool Terry ...

I have a dozen NOS 6GM5's and a set of AA-100 iron,
thinking about doing something someday soon.

... tom

[sorenj07]

those look really cool! i love the TV damper diodes being used as rectifiers...

anyway i took the liberty of re-hosting these at the Shack, for instant viewing :)

[TerrySmith]

Thanks for fixing my pictures Soren!

BTW, your 6SN7 linestage is what drives this amp!

[TomMcNally]

Terry - Are the transformer end bells on the Heathkit transformers the same size as the ST-70 or the ST-35 transformers ? I'm at work, so I can't look at mine. I have a set of Ned's cool looking nickel covers that I put on my ST-35, and a set for the ST-70 waiting in the box, so in any case, I have the easier to mount covers available in black or nickel.

Thanks

... tom

[TerrySmith]

Those covers are the same as the ST70. Actually, the AA100 trannies are thicker than the A470 (ST70) trannies.

I went this way so I wouldn't have to cut two gaping holes in the chassis for Z mounted trannies.

[sorenj07]

BTW, your 6SN7 linestage is what drives this amp!

wow, that's pretty cool! unfortunately mine died (I think the pot went, I had loud static/distortion sounds and stuff, when turning and even when not), and I'm about to put together a simple 12B4 linestage, but it's encouraging to see that it worked for someone else :).

[TomMcNally]

It's not that hard to cut the holes, I made this amp with AA-100 transformers on 1/8" aluminum ... I used the cutting wheel on my
Dremel tool, and they were so nice they didn't even need to be
filed - I was surprised.

[EWBrown]

Very nice, and original!


Hmmm, I also have a pair of AA-100 OPTs and a small collection of NOS 6GM5s (AES had them on sale last year), and a 350-0-350 VAC, 175 mA power trannie (that I recently bought from Shannon), all looking for gainful employment...

I would SWAG that with a higher B+, and plate current for the outputs, the power levels could 2X the power output of a stock ST35 Yellow_Light_Colorz_PDT_06

/ed B in NH

[erichayes]

Hi All,

Back in the days when the Mac 225 and 230 owners got a corner on the NOS 7591A market before JJ and EH came out with reasonably priced new versions, some Fisher and Sherwood guys were taking 6DZ7s (which are 2 6BQ5s in one bottle) and wiring the 7591 sockets to put both sections in parallel. The load impedance was a little off, but the 500C I modded for a guy still put out an honest 25 WPCBCD, which was as good as a stock 500C ever did.

[mesherm]

That's a nice looking amp you built Terry, I love those racing colors. Reminds me of a '65 GTO a friend of mine had once. Nice dual carb..uh..tube rectifiers too and fancy slotted side panels...all you need is a tach Yellow_Light_Colorz_PDT_16

[EWBrown]

I also have a pair of old "salvaged" OPTs from some (unknown) Fisher 7951-based amp, and its core has the same dimensions as an A-470 OPT, so I'll get a set of end bells from Uncle Ned, for those, too.

Their cores stacks are also a bit thicker than the Dynaco OPTs. Maybe the, same trannie as used in the AA-100 , just under a different name Yellow_Light_Colorz_PDT_02

/ed B in NH ?

[EWBrown]

I would imagine that quite a bit of PCB surgery was required, to accomodate the 6GM5s. Other than pins 4 and 5 for the heaters, none of the other connections have anything in common with EL84s.

IIRC, 6GM5s like to feed a 6600 ohm P-P load, and can go up to 50 mA plate current. (I don't have my handy-dandy RCA tube manual here at work).

[TerrySmith]

The muscle car look is exactly what I was shooting for. I would have made the striping a little more detailed, but I didn't have any 1/8" fine line tape.

As far as cut&jumpering the board, it's not as bad as you think. I'll take pictures if I ever pull the board out.

I've got a Super Sport fender emblem somewhere I might stick on the front! Yellow_Light_Colorz_PDT_01

[EWBrown]

I figured out a "cut and jump" method, just wanted to check that was how you did it. The other method is to use chassis mount sockets and hand wire them into the circuit. I still have a couple of unemployed Rev D boards looking for some gainful employment, maybe I'll try the 6GM5s out. The other is already set up for LM317 "autobias" and I'll go for a triode output for that one.

/ed B in NH