SOHA II Review

[regal]

I decided to build a SoHA II while waiting on the Stacker II project to get out of grid lock.

The SohaII is a very interesting design with a few limitations. The tube current is very low, I can only get about 1.5 mA thru each section and the plate voltage is only about 40V.

That said this is a terrific sounding amp. I didn't like the recommended RCA 5693 tubes, they were too congested with distortion in complex passages. I switched to 8416's which sound very nice. In comparison to my Bijou this little SOHAII actually has clearer better defined mids, I was very surprised to hear more of the ambience of the recording in voicing and guitar. The Bijou beats it in power handling easily and the Bijou has a better grip on the lower octaves. I believe the Stacker II will combine the strengths of these two amps and we will be building a Zana Duex killer for under $400 buck. Can't wait.

[luvdunhill]

cool! I prefered the SOHA II to the Bijou when I compared the two. The SOHA II is an excellent ortho amplifier as well, as it has plenty of drive to it.

[dBel84]

The SOHA II can be modded to run 90V on the plates and iirc 5-7mA. Ferrari was the first to do this and it is in the HF thread. Actually, Alex mentions the 55V - 100V psu on his web site. I have mine set to 60V ( before this psu was designed ) and it runs the tubes at 2mA ..dB

[regal]

Someone on the head-fi thread has a 220V PS with 10 mA tube supply, but the details are sketchy, he had to use higher voltage rated transistors above the plate, also changes some resistors, but no one including the modder remembers the details. I can understand as I used to mod/design stuff on the fly and not keep, records. But this SOHA II with about 30V higher plate voltage and 5mA per tube section would be a giant killer.