Question:
I had a quick look on the guitar amp group but decided to post there. Thought this a more appropriate site. I just watched an amp I fancied go through the roof (finacially) on ebay. Here's the schematic http://www.blueguitar.org/new/schem/sundown/sndn_a50.gif. Not sure why I liked it, think it was the two channels and a govenor, gov on the diag' that drops the sound levels whilst keeping the tube distortion. I do have a vague grasp of such things as 400V not harming but 30mA can kill. ex electronics. All I know about valves is they get hot. If I price up the project and go for it can anyone mentor me? Or is the info on that diagram too lacking? If you live in England I could stretch to a bottle or two of malt. Ah yes England, need to adapt to readily available valves etc. Any imput ?
Answer:
The gov merely shunts across the grids (drive) to the P-P output stage. Not sure that this will have the desired effect, especially if that gov pot can be turned all the way to a short - which it apparently can... but yes, if you reduce the drive to the final tube, then you can turn up the gain to the input or along the way and achieve clipping (distortion). No magic here. You can use this little bit on any schematic that has capacitively coupled drive to the grids. My advice, is pick a schematic of an amp that you already know you like the sound of. (Is this one of the amps that Clapton uses? Sundown??) The second bit of advice, is don't even consider trying this sort of thing if you have no experience building electronics - not until you know something more. Too complex, and requires all sorts of specialized parts, tools and test gear. Third bit, the parts will cost you more than you expect, AND, it won't sound like you expect - the sound will be all over the map depending on parts chosen and tubes and minor deviations in values. Fourth bit, try to buy an amp from some bloke who has smoked it beyond repair, and repair it. At least that way you'll get a large part of the thing, especially the chassis already there - hopefully all you'll need to do is to replace one or both transformers, some tubes, and maybe a cap and/or resistor or two. After that you can mod it until it looks like the amp you're interested in now if you should like. Fifth bit, learn how power amps and preamp circuits work a little bit and dork with some simple stuff in isolation to build your experience before tackling a large and complex project. Both hi-fi (of any type and size) tube gear and guitar tube gear (even 5 watt practice amps) are extremely similar in design - good places to learn with inexpensive stuff. Like an old tube console with a record player in it, for example. Makes a nifty guitar practice amp, and electronics practice test bed.
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