View Single Post
  #3   Report Post  
Old October 24th 04, 11:25 PM
The Eternal Squire
 
Posts: n/a
Default

- not enough decoupling on the 9v rail of the audio power amp (a
couple of hundred uF's as close as possible to the chip)


You mean short the power leads of the 386 with 220uf? Also, the
X100 amplifier is an AMD instrumentation amp, should I short those
with a cap as well?


- speaker leads running too close to the inputs to the x100 amp


The chain is in a single line, inputs on the left coming from
attenuated audio source, and about a foot to the right start the
leads to the speaker, thoseleads are only a few inches.

- try running the x100 board at less than 9v (anything from some
resistance and a decent electrolytic in the 9v line up to some
'proper' voltage regulation)


I had read an article today on solving motorboating in tube audio
chains, and the B+ in each of the chains have different voltages. The
final stage had +220 V, the stage just before that +200 V, the stage
before that had +180 V, and resistors were used as the voltage drops.
I do not understand how that solved motorboating.

I mean, what I would do is place an 8V regular between the battery
and my X100 stage, and run the final stage off the 9V battery itself.
But can you tell me why this should work?

- some kind of an earth loop ? - if the board are connected by coax
try lifting the braid at one end of the cable


You mean leave the coax floating at one end? Wouldn't that disable
common-mode signal rejection?

Hope these help ....?

Adrian
Suffolk UK