Need help: I have 807s and the guts from a HK AA-100

[djn]

Hi All. So I have a parts Heathkit AA-100 and want to build a PP amp with the guts and the 4 807s tube, caps, and sockets I already have.

I focus on the art of gear as much as the sound, and in this case I don't have a lot of room for each channel so I would like to only use 2 807s and 1 other tube per side. Sorry I don't know the terminology.

I started this project years ago but life got in the way. Here is the basic structure of the chassis. It will be sided and all welded up in the next week or so. The layout is:

-on top of the armature will sit the PTX
-right bellow that pointed down will be the rec tube
-the OPTs will stick out the sides like ears
-the signal path will be in each leg of the base

The square base tubes are 2" square by about 8" usable so there is not a whole lot of room under there.

When I get it welded up and all the holes drilled and certain it is how I want it, I'll have it anodized....maybe gold.

 

[Eli Duttman]

The AA-100 is a 7591 amp. The O/P transformer primary impedance is correct for the 807 (a 6L6 family member), but the power handling capability is too little. You will have to wire the 807s to operate in triode mode.

SS rectify the B+ and CLC filter. The 7199 has gone the way of the dodo. However, you can use Heath's topology, with a member of the 6U8/6GH8/6BL8 bunch.

 

[djn]

Hi Eli. Sorry for my lack of knowledge. When you said "the power handling capability is too little" does that mean the 807 can't handle the amount of volts the PTX puts out?

Also, if I use SS rectification, will I get more volts out of the PTX?

Is the 807 part of the 6U8/6GH8/6BL8 bunch?

I am looking for a design that uses just one tube beside the output tubes. So, can you put a splitter and driver out of one two sided tube?

Finally, what does eLinear mean?

 

[JonSnell Electronic]

An 807 is a 6L6 and can be used like an EL34. Very versatile. I have just made and sold two amplifiers using 807 output, 6SN7 driver and 6SL7 pre/phase splitter for push pull output.

 

[llwhtt]

The output xfmrs from the AA100 are too small to handle the power that the 807s can produce unless wired for triode mode.

Craig

 

[djn]

If that's the case, maybe I should sell the aa100 and buy some proper iron.

 

[Eli Duttman]

If that's the case, maybe I should sell the aa100 and buy some proper iron.

I've heard worse ideas. 😉

Edcor's CXPP60-MS-6.6K should do the job, at "reasonable" cost. I'd roll the deep bass off below 30 Hz., just to be sure core saturation does not occur. Remember, the lowest note a "standard" double bass plays is 41 Hz.

You can pay Edcor a bit extra for some black end bells. OTOH, with care, you can refinish the stock blue end bells yourself. Disturbing the lamination stacks is a NO/NO.

 

[djn]

Thanks Eli. What would be good OTX? I've been painting custom Harleys for years and I would paint any transformer to match the amp style anyway.

This amp will be used to drive the Heils only so the low end should not be an issue.

 

[Eli Duttman]

The Edcor part I referenced is an O/P transformer. What is needed now is a power transformer. Would you entertain the notion of a toroid, as AnTek has some very cost effective models? Given your metalworking skills, covering a toroid, for cosmetic reasons, should be easy enough.

 

[rmyauck]

These should be an upgrade and not too much more $.

Transcendar Transformers - Push Pull Transformers

Or one of the their replacement vintage ones may be more suitable.