AudioBanter.com - View Single Post - NAD amp distorting heavily after running a bass guitar through it.

said:

Beginning a few months back it would sound fine and then all of a
sudden die and the sound would become horrible distorted. The time it
takes the amp to go from working fine to distortion box continually
shortens from 20 to 10 to 5 to 2 to 1 minutes. Now it doesn't work
for anytime at all.

So my question is this: Is there any fundamental reason why running a
bass guitar or mic through this amp would hurt it? Also, does anyone
have any idea what might be wrong with my amp.

Running any signal through an amp should be possible, including a bass
guitar or microphone.
Of course, a musical instrument is capable of generating huge dynamic
peak signals, so you'll have to use the volume control sensibly.
Also, playing loud and long isn't what the amplifier was designed for.
The heatsinks will have insufficient capacity to handle the generated
heat of the powerstage.

As to the problem, it is probably either temperature- or voltage
related.
My guess is a problem in the bias circuit, causing the power stage to
be cut off so there's a threshold to overcome before the signal gets
amplified.
Besides the obvious bad solder joints, check the bias transistor and
(in case it is there) the capacitor across the collector and emitter
of said transistor.

--
Sander de Waal
" SOA of a KT88? Sufficient. "