[R-390] Better BA sound

[Perry Sandeen]

List,
There are several ways to get much better sound fro the "A" and SP 600.
If you D/L the sp 600 anthology from the Hammarlund site the is a mod by Chuck Rippel.
The "A" has few different chocies (it depends, as Bob would say) from audio chassis mods to full blown audio mod rebuilding.
The simplest chassis mod is by Chuck Felton, found in the Y2KR3.  It basically does some part changes
A more comles mod is the Kleronomous mod.  This isa very clever mod using compoent changes and a dual tetrode tube in the output in a P-P circuit.
The las choice is one that I started on but never completed.  It takes the thee chokes off of the audio module as well as the filter caps. The chokes are replaced with ones from Triode Eletronics that easily mount behind the power transformer.  Also the OEM caps are replaced by 390uF caps by the new chokes.
Basically, this allows to 6AQ5's to be intalled in place of the filter caps in a triode P-P circuit using a 8W Hammond transformer (150 cps to 15K cps) at 1 db points. 
There is more to it and I have an uncpleted article that can walk a competent tech through the whole process.
Please send me an ORIGIAL email if you want me to send the data for this. The two chokes and output transformer will set you back about $75.
Another experimental circuit uses one the National Semi LM series of audio chips.  Ther are cheap but one has to careful of how much current you pull from the 26 volt line
A SS audio output was listed on epay a while back. IIRC it waw $225.
Now last but not least is getting an audio output module from China.  Bang good is one supplier although it seems a whole bunch of sellers buy from the same factory. How good are they? Don't know but they are so cheap it's not much of a loss if it doesn't work. Caviot: derate power output rateings by 4.
Regards,
Perrier