• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Please recommend me an amplifier design.

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JayH3 said:
Any idea how this will compare to commercially available amplifiers?

I expect it'll far outperform anything solid state in the sub multi-kilobuck class. It should also be competitive with vacuum tube power amps costing 1.5x to 2.5x what you've paid. Shannon included some test and measurement data (freq. response & distortion) at the end of the assembly manual. Plus, you'll have the satisfaction of knowing this is something you've assembled yourself.

Pay attention to your grounding and signal wire routing. Be careful while soldering components to avoid overheating any sensitive parts (such as the LM334, or any poly caps you may have bought).

I've heard good things about Bob Pletka of Eurotubes. I believe he has a solid reputation. Which tubes did you select for the outputs? In the JJ lineup, I think you've got the choice of the EL34, E34L, and KT77.

What are you going to do for the chassis? Did you purchase a pre-cut and drilled chassis, or are you going to metalwork your own?
 
Ty_Bower said:

I've heard good things about Bob Pletka of Eurotubes. I believe he has a solid reputation. Which tubes did you select for the outputs? In the JJ lineup, I think you've got the choice of the EL34, E34L, and KT77.

What are you going to do for the chassis? Did you purchase a pre-cut and drilled chassis, or are you going to metalwork your own?

For tubes I went with the E34L's. I considered the KT77, but I think that would go better in my Marshall than a hifi stereo amp.

Im not going to crazy with the chassis. I got a basic hammond chassis that Ill probably paint black and put on some stained wood trim.

For capictors I just got cheap ones from Mouser to get the circuit running. Later on I think Ill get some Jenson paper in oil (copper). I have read some great things about these.
 
Hi JayH3,

I did exactly what you are contemplating. If you search under my name you can see the project (modified ST70) fro start to finish. I have also described along the way where I sourced all of the parts. Just look carefully because I followed up with a MK III and this was a more complex and expensive project than the ST70.

Triode electronics are great as are the guys at Radiodaze who can supply lots of extras like 600v cloth covered wire. The Dynaclone transformers (from triode) are great and they have the advantage that the wire colour coding is the same as the original so that you can refer to the circuit diagram without any undue confusion.

With respect to volume, I just put a duel gang100K pot on the input side of the circuit and it sounds great to me - I just plug the CD player in directly without the hassle of a preamp. I sometimes wonder whether the potential disadvantages of a simple pot outweigh the potential problems with a pre-amp (hum etc) - probably heretical thoughts but it is certainly a simple solution if nothing else. To be honest, if I was doing it again (which I will be), I would use a stepped attenuator (i.e a pot with lots of resistors) just to satisfy the purist in me!

Have fun and good luck, it is a really satisfying thing to do.

Cheers,

Rob
 
Ty_Bower said:
It's only been ten days or so... I'm guessing you haven't yet even received all the parts. Don't forget to drop us an update every now and again.



I received the last of the parts on Tuesday so I have been working on it for a couple hours a night after work since. I pretty much just have to wire the boards to the tube sockets and the inputs/outputs. I should have it done tonight. Im pretty excited to hear this thing.
 
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