Cheap spud amp
I am looking for a small and cheap amp.
The 6BX7-GT tube is a nice dual triode.
The power dissipation is 12w (both triodes) and the amplification is 10. I think will be a good option in an spud amp.
The input transformer an Edcor WSM 600/10k can supply x 4 amplification.
The output transformer a toroidal (see Steve Bench web).
This idea will work?
Best regards Jaime
Seems like a viable approach, the important thing to remember is that the input transformer needs to be driven by a low impedance source, the lower the better for good performance.
A 6BX7's low mu, 10, will probably need a a bit of gain in your preamp to make it all work, even with the four times stepup.
If you cascade the two 6BX7 halves, then you should be okay. A dissimilar triode--6EM7, 6FD7, 6GF7--or triode pentode like a 6LR8 may work easier if your idea is just one tube per channel. These all have plenty of gain without a preamp.
If your idea of spud is one triode sectioin per side then a higher mu tube may work easier, like the 6C45, 5842, 8233, 7722. If your speakers are very efficient you may not need a preamp with these either.
I've never had good luck using torroids for output, but they do work. While I've no experience with Edcor's cheap single-end outputs, something like the XSE10-16-8K may not cost more then a torroid and a good blocking capacitor. But cheap usually means what you have at hand so your idea will work if that's what you have for parts.
Toroidals do work well, but getting the right ratios is tricky. Also you are stuck with the added complexity of a valve CCS or a SS CCS. If you are going to use a valve CCS then the spud idea is lost. Another cheap alternative is to use Microwave oven tranaformers as choke loads - big and heavy though.
All in all I think gapped EI's are a better bet for a spud amp.
Consider the highly respected ECL86, better than the ECL82.
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