NAD amp distorting heavily after running a bass guitar through it.

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My NAD 214 stereo amp is dead or dying. Any signal I run through it is
extremely distorted and I have to turn up the volume to even hear that.


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.

I haven't been playing nice with it recently. I have run a microphone
and bass guitar through it. However, the amp had experienced the
problem I described above before this.

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.

Thank you!
-Jon

Ps here is my setup in case it's helpful.
NAD 214 Stereo Amp
NAD 512 CD player
Adcom preamp
KEF Q55 speakers
Monster XP cables

[Sander deWaal]

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. "

[Arny Krueger]

> wrote in message
ups.com

> I haven't been playing nice with it recently. I have run a microphone
> and bass guitar through it. However, the amp had experienced the
> problem I described above before this.

It's broken!

> So my question is this: Is there any fundamental reason why running a
> bass guitar or mic through this amp would hurt it?

No, no matter what someone may have told you or your guilt-wracked mind is
telling you.

One of the *loverly* things about electronic gear is that it can break for
no fault of your own. It can even break while it is not being used.

Basically, all the angst in the world isn't going to bring it back. You need
to fix it or throw it away or sell it as broken, or fix it yourself. Given
the questions you are asking, you lack the skills to effectively fix it. So
either find a qualified repair person or dispose of it some other way.

> Also, does anyone have any idea what might be wrong with my amp.

Whatever it is, it is affecting both channels, per what you are saying.
Since fuses aren't blowing, the problem might be in the low-level input
circuitry rather than the outputs.

I see that a NAD 216 is going (or to be exact not going - zero bids) for
about $500 for eBay, so there is a possibility that your NAD 214 might be
worth a fairly expensive repair.

[Sander deWaal]

"Arny Krueger" > said:

>Whatever it is, it is affecting both channels, per what you are saying.
>Since fuses aren't blowing, the problem might be in the low-level input
>circuitry rather than the outputs.

Haven't thought about that. Indeed would that probably rule out my
idea of a bias failure.
A power supply problem perhaps? I don't have a schematic of this amp
available right now.......

>I see that a NAD 216 is going (or to be exact not going - zero bids) for
>about $500 for eBay, so there is a possibility that your NAD 214 might be
>worth a fairly expensive repair.

Agreed.

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