Channel Imbalance at low volumes

Amplifier at this age (30 years old?) all connectors, switches, selectors and pots should be cleaned by using DeOxit

This is due to the aging potentiometer that is used for the volume control.  The volume knob actually controls a two-channel variable potentiometer (one for left channel, one for right channel).  This unit is about 30 years old, so there are likely things that will fail on it or be worn out.  The "variable resistance" surface inside the "left" potentiometer is likely breaking down at the area where the volume is low and is actually showing a higher resistance than normal.  This is very similar to resistors wearing out -- the resistance value starts to rise greatly.  Pretty much the only thing you can do is have the potentiometer replaced.  If you did this, it would probably be worth it to have as much electrolytic capacitors replaced as possible (or as much as you are willing to pay for).  This will greatly increase the sound quality of the unit, as the caps are very old and dried out.

In some case, the output relay is the culprit

I had a Rega Brio with this problem and assumed it was the volume pot. Had a new pot put in and it didn't fix it. God knows what the problem was but, presumably, there are many things that can cause channel imbalance at low levels. Maybe get a decent technician to check it out.

It can be some resistor along the way (maybe on the input of a gain circuit).  With the volume down low, the imbalance ratio between left/right resistance could be far enough apart.   With the volume higher or wide open, it is not such a difference.

It can be dried out off brand capacitors, dirty relays, dirty pots, dirty switches, and so on.

the unit is from 1986, and was made in Taiwan with off brand capacitors.

It’s old and it’s tired.

It needs a cleaning, check out, new capacitors on many spots, a general check out by a competent technician.

Nobody gets to luck out on a unit that old. They all need service, even one in a hermetically sealed perfected environment since 1986. (stereo cabinet, out of the sun, no heat and a level room temp and humidity environment). Even that ’perfect’ unit would be in trouble, in some way, just from the heat of being operated the odd time and general environmental aging.

I've  had my hands inside probably 3-4-5 of that exact model, never mind the other many many dozens of times I've handled a NAD product at that level (service).

But it sounds so good at high volumes!

What should I expect to pay for a tune-up?

Thanks!

Impossible to say. Unless it is a full proper rebuild, which might cost $200+, then it's all going to be crutches of a sort (good crutches, bad crutches)....and the lifespan of the amp will be what the clock says when it finally fails.

This is the nature of audio electronics.  Like life, it's a series of blind and open trade-offs.

The most obvious things to clean/replace are the volume and balance pots, but don't forget any speaker switches or relays.

Over time they get corroded and can act like little diodes. I had this happen with a Yammaha P2050. Replaced with new and much better relays, and added sockets for next time, problem solved.

I agree with the Deoxit suggestion....also spray some in the volume/balance control (in the case)

There is no crackling whatsoever.  You still think cleaning is worth a try?

Everybody posting here is correct. The highest probability is the volume pot. I would clean it first and if that doesn't work replace it. If that doesn't work then you need to take it to a good technition
Alan

You may want to get an audiogram, to rule out a hearing imbalance. Recruitment occurs at higher volume levels.

You may want to get an audiogram, to rule out a hearing imbalance. Recruitment occurs at higher volume levels.

Or use headphones and see if the problem still exists

Only listen at higher volumes... problem solved.

Hello from Costa Rica. 
Your problem is the potentiometer of the volume control.   At low level, the left channel, due to its age, had became more resistive than the other channel.  You must change the pot, and that's it.  You can measure the resistance at any point, the left channel should be equal to the right channel or very close.  Usually the tracking balance is +-1.5dB between channels when it is correct for the type of integrated amplifier that you have. 
If you want to do an updated, you could use a step attenuator:


Happy listening!

No traditional pot meter is particularly accurate at low levels. Does it happen with all sources? I ask because there may be a mismatch between the output sensitivity of the source and the input sensitivity of the amplifier. Many modern sources like disc players or DACs have the nominal 2.0V output of the CD Red Book standard, but some have even more (to impress in the demo room - louder sounds better). At the same time traditional rca inputs are far more sensitive. This creates two problems. The first is that, depending on the amplifier topology (where is the volume control, before or after the input stage?) the input stage may be clipping from the high signal (with all the sonic issues that come with that). The second problem is that if you want to play at a comfortably low level, you have to turn the volume control down into the range where the pot meter is not very accurate, and you get channel imbalance. Do you get a pretty loud signal already very quickly, i.e. when you turn up the volume control perhaps only a quarter? If that is the case, you need to reduce the input signal. Inline attenuators are the simple solution.
This is not to say that the pot meter may not be failing as well. But even if it is no longer at its best, inline attenautors (or an attenuating cable) may still be a cheap fix (Partsexpress has attenuators from Harrison Labs).

@willemj it does indeed happen with all sources. The volume does gain VERY quickly, however the amp has a built in “low-level” button which brings the volume down by 4-5dbs so the knob can be turned up more. Would this be done by a built in attenuator? However the imbalance is still present at the same low audible levels. 

I tried lots of deoxit however it didn’t help. I couldn’t really get to the pot though so I was shooting a little blind - is there any source for a schematic or service manual?

In addition, I moved the amp to my kitchen which is a large room (~40’ long) so I’m listening at higher volumes more often and it’s noticeable less often. 😉

This is a classic symptom of a defective volume control. Get the control replaced.

I had the same problem with an NAD receiver, had it in the shop 2 or 3 times, but they never really solved the problem.  In my case, the left channel would be the same volume but only playing the system louder than I typically enjoyed.
Good luck!

Leemaze,
The fact that the volume gain goes up very quickly suggests that input sensitivity is too high, which is something you may want to addres in any case.
I am trying hard to think why the problem persists at the same sound level, but at a different part of mechanical rotation of the volume control when you push the low level button.

I agree that it's likely the volume pot.  I don't know if it's been mentioned, but many volume pots, even in expensive gear (such as my Shindo preamp), just do not adjust volume for both channels equally at the lowest volume settings.  They do fine at medium to high volumes, just not at the lowest volumes.  This is part of the reason people like to have their volume knob at 10-12 o'clock.  What I had to do, since the volume level was high even at the lowest volume setting, was add some 12 db attenuators between the preamp and my amp to allow me to use the preamp volume control between 9 and 12 o'clock.. Balance is fine at that setting, and the volume levels don't drive me out of the room.

Ah thank you! What my blank posts were supposed to ask is what Db level attentuator should I get?

Also, if the volume knob is always around 12 o’clock, does this make the amp work harder to potentially burn out faster? Is there any degradation of Sq?