• 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.

ECL82 power supply question

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The negative feedback applied to the input stage of the Wave 8 means that you'll pick up a little headroom there. i.e. It might take a full volt before the input stage clips. But it probably doesn't matter as I expect the output stage will clip before that.

Having said that, my advice is to not worry about it. Just build the amp the way it's designed and see what happens. You'll need to have some kind of volume control before it anyway (a variable voltage divider!) It might turn out that you can only turn it up to 12 o'clock before it starts to distort. So what?

-- Dave
 
Shoog and Dave,

Thanks for your help, even if your advice is contradictory ;)

As I am trying to gain experience and confidence, I think I will take the advice to build as-is (or close too). I have taken your comments on board Shoog, and I suspect, now that I have been well and truly bitten by the bug, I will re-visit this build and experiment and modify! I have a bunch of 6P15P, 6P14P and 6P3C tubes waiting for experimentation. After this build is the GingerTube "Baby Huey", which I think uses a long tailed pair with constant current source. If that is successful, I think I might try then to come up with a design of my own - with the kind stewardship of you guys I am hoping.

Once again, thanks guys!

Chris
 
Having used the wave-8 in the past I can't say that I recall running into a clipping problem when it was in use. Not saying that it won't just that I was blissfully unaware of any issues at the time. Maybe efficient speakers and apartment living made me keep the input into the amp quite low. Fixing this input issue could make this design even better.

Thanks for the info and ideas to all in this thread. I think I may bring out the waves for some "adjustments".
 
Thanks for the comments Folhaseca. The Wave-8s you have, are they home built? In any case, any chance of a photo of under the hood on these? I think that my biggest hurdle is going to be coming up with an efficient layout of the components around the tubes.

Cheers,

Chris
 
Thanks for the help finalising the design guys. I have completed the amp!

I built the Wave 8 design almost stock. As the small output transformers have ultralinear taps and I don't require high volume levels, I wired the design ultralinear instead of pentode. Also, noticed that the load resistor on the concertina was 33K and the cathode was 39K. Using these values gave different gain from the two signals from the concertina. I hooked one channel of the scope up to each output of the concertina and then summed the output. If the two signals are equal and opposite phase, then the scope should show a nice flat trace. It didn't. Replacing the cathode resistor with a 33K gave about 1/3 the distortion, so that is what is in there now.

Also, worked straight up when I tried it before hooking up the feedback with just about zero hum. Pretty happy about that, grounding efforts must be paying off. Murphy's law stated that the phase would be wrong for the negative feedback, so had to rewire the outputs from the tubes to the output transformers.

Overall, pretty happy with the result. Accomplished my aim of building a hum-free point to point, push pull amp for my office. Next project is a "Baby Huey" and my son now wants an amp and speakers for his computer...
 

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Hosted photo on image shack for better resolution...

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


One thing I have noticed is that the chassis is getting VERY hot. Suspect it is due to using R C network in power supply rather than L C. Will have to get the drill out for some ventilation holes!
 
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