Servicing Amplifiers?

[Stoopalini]

I've noticed lately one of my amplifiers seem to have some strange issues going on. The audio seems to be scratchy when at low levels, but if I turn the receiver volume up very high, then back down, the audio cleans up.

The amp which seems to have the problem is a Mitsubishi DA-A110 which is running my mains(NHT Superones) and the issue typically pops up on either the right or the left speaker only.

I also have a Carver A-400x and an Adcom GFA-545, so wondering if it's worth getting all 3 of them calibrated professionally.

I have the service manuals for the amps, and looked into the service procedure for calibration, but I don't have the proper equipment to do it myself.

So, is it worth getting them calibrated, and if so, how can I locate a reputable company to do the calibration?

Thanks guys,
Thomas.

[wkhanna]

Give Tom a call at Vintage HiFi of Pittsbugh. He will be more than happy to give you advise, & is V familiar with the equipment you have.

Tell him Bill with the modified C-19 sent you.
Note the non-traditional shop hours at the bottom of the page I linked.

JMHO, 'freshening up' older amps can be a V worthwhile & economical option.

[Hdale85]

Certainly freshening up old amps can improve them a lot, things like capacitors and what not don't last for ever and can degrade over time, not to mention newer capacitors for audio have tighter tolerances and so on. They should also be able to check and adjust the bias and what not which can slowly get out of whack over time as well.

[JonMarsh]

Sounds like a contact issue in the volume control to me. That's assuming it uses a resistor based volume control.

[madmac]

Sounds like a contact issue in the volume control to me. That's assuming it uses a resistor based volume control.

Yep...agreed. I don't think it's a super big issue. Dirty parts on the inside. Unplug, pop the lid and spray the speaker terminals and volume control knob. Leave it alone and unplugged for the night however. Compressed air works well too but I think the volume will need both.

[Stoopalini]

Thanks for the replies guys.

These amps don't have volume controls/knobs, do you mean the gain pots? I did mess with the gain controls a bit in the past, maybe i just need to take some time and really clean them out.

When I 1st hooked the Mitsubishi up, I couldn't believe the sound these NHTs put out; especially listening to music! One of the best things I've done is get away from the receiver amps ...

Thomas.

[Lex]

perhaps what Dan and Jon meant was, it could still be on the pre-amp side volume, the amp just plays what is in the audio chain, and if pops are there, it plays them of course.