My daughters pre-school has called upon parents to use their "gifts" and raise funds for the school. I had bought a chassis some time ago and decided to build a SOHA for the cause.
I am hoping to get **** shipped within USA.
This is "essentially" a standard SOHA. ie no boutique capacitors or resistors because I don't believe they make enough of a difference where it counts. The caps are upsized for the output section and run dual 15V rails. The power caps are also bypassed by film caps. The tube power supply is able to supply 40-60V to the plate and still allow enough headroom for the buffer to swing to it's rails ( were it capable. ) Thus CCS voltage is ~ 80V. The reason I chose to do this is because of the results from SOHA II which was originally run at 80V and then at 150V - essentially the higher the B+, the "better" the performance. I used a 18-0-18 VAC to generate the voltages - this was a compromise to allow a higher B+ ad keep the heater supply at a working temp.
The cathode coupling caps are also bypassed with film caps under the board.
I have set up the bias adjustment with small potentiometers on the side of the board to make this easy for anyone with little experience. You will still need a DMM to adjust the bias , there are small tabs for easy attachment of the probes.
The amp has been running near continuously for some time and has done so without any problems and is sounding very good indeed ( I forget just how good this amp performs. ) I have the OPA2107 in it at the moment along with anHP 5963, and will send it with OPA2134/2227 and 2 other 12au7 tubes for experimentation.
There is an inline fuse, a red led to indicate that the amp is plugged in and a green led to indicate the amp is on. It does not have an output relay. Here are a few pictures , PM me with any questions or if interested..dB
thanks , it's for a good cause
SOHA for a good cause
..dB
Linear Mode
