Great!  I have a LabSeries L5 combo and it is nice to hear that it is possible to make one by yourself. It is really well thought design and sounds awesome at any settings!

Thank you ToadMeister! I have an orange stripe Randall 120H. It is in good condition, but nice to have a schematic.  :dbtu:

Maybe there is a failed electrolytic capacitor at the power supply. Without capacitor regulation, DC ripple voltage makes the amp hum continuously. It should not cost a fortune to get fixed.

It depends how loud you play. I use a 9V battery and the battery life is rather long. Try it, you can chance the battery setup later if needed.

Maybe the switch in the power amp in jack is oxidized. Sometimes it helps to connect preamp out to poweramp in with a guitar cord. It bypasses the jack switch.

Nice to hear that phatt has built a transformer-coupled class A amp rather successfully. I must some day try to build such a design just for curiosity. It seems that they are not notoriously inefficient, but sound quality may leave something to be desired...

Quote from: dsmnoisemaker on January 20, 2009, 05:14:23 PM
interesting....no replies about them.. are they a tabu or something?

I don´t know why, but most solid state guitar amp manufacturers seem to use TDA chips instead. Maybe STK chips are more suitable to use in home hifi equipment. They may even perform better from sound quality standpoint, but TDA:s may be more ruggedly designed regarding low speaker impedances and such. Just maybe, i don´t know so much about STK:s... TDA:s are more familiar to me, because they are quite cheap.


But i have seen somewhere a guitar amp design using a STK chip, and  i see no reason why not to try and build a guitar amp using STK.

http://www.vintagehofner.co.uk/selmer/schematic/ssmerc.html

This is an interesting vintage design. If i understand correctly, the primary of the output transformer must stand 400 mA. I have no idea what the impedance ratio should be. Is it possible to somehow estimate it? And what should the power supply voltage be? I think 10-20 Volts is not enough as efficiency is poor in class A.

Sorry my english... but i´m quite interested about what type of output transformer was used at those SS Selmers.

Have you searched Gretsch Controfuzz schematic?

Hello!

Here in Europe that type of DIN (Deutsche Industry Norm) speaker connector was used through 60`s and 70`s. Here you can find them at junk store home stereos.

It is easiest to replace those speaker outlets with 1/4 jacks as teemuk said. Male DIN connector may be difficult to find, and standard jacks are much more convenient and technically reliable.