Volume control gets too loud too quick - mods?

[bazzle592]

I have a NAD L40 that I've overhauled. I love it to death - it's such a charming little thing. CD player, tuner, preamp, and amplifier all in one classy little package the size of a standard CD deck. It's no slouch either, its sound quality is what sold me on British amplification as a whole.

It has one major annoyance though - the volume control just seems poorly implemented. It has some low-volume channel imbalance, which I would be able live with, but the volume control gets way too loud way too quickly, making it so I can never really make it out of the imbalanced portion. 9:00 is more than enough volume for me most of the time; 2/3rds of the range is unusable! And it's only a 40W RMS amplifier, it's not like it would be able to pull off THX levels of dynamic range anyways.

Is there a known mod I could do surrounding the potentiometer to get more usable range out of it? I'm thinking I can put some resistors in there somewhere, I just don't know the best angle to attack it from. Any input is appreciated!

Thanks!

 

[gadget73]

does this happen to have pre-out / main in jumpers ?

 

[bazzle592]

does this happen to have pre-out / main in jumpers ?

It does not use that setup unfortunately. It has pre-out jacks for use with an external amp, they aren't used to loop back into its internal amp though.

 

[Okke 70s]

Just a resistor in series with the volume pot will do (one for each channel). Of course you would lose the top of the volume range, but in practice that is probably unusable anyway.

Another option is to replace the volume pot. You could try to find out whether the current pot runs up faster then a normal logarithmic pot should. Considerable imbalance between left and right would indicate some wear.

 

[gadget73]

Was thinking if it had the jumpers, sticking an attenuator in place of the jumper would be a nice clean solution

Is this a motorized volume pot? Looking at the schematic and it seems to be telling me that. The mistracking is probably the pot, but motorized ones are not quite as straightforward or cheap to replace unless the pot can be split from the motor easily.

anyway, resistance between the "top" (non-grounded, and not the wiper) of the pot and wherever it comes from would make it less touchy. I can't tell by the scans, but its possible that J604 and J605 happen to be a convenient spot you could do that. You'd have to trace it out for sure. Failing that, it appears that R626 and R627 sit between the sources and the top of the volume control (R628). Those are 1k by the schematic, if you make it say 10k it should make the volume control a lot less touchy.

NAD L40 Service Manual download, schematics, eeprom, repair info for electronics experts (elektrotanya.com)


per that, its an A or audio taper, which should be correct.

 

[bazzle592]

Just a resistor in series with the volume pot will do (one for each channel). Of course you would lose the top of the volume range, but in practice that is probably unusable anyway.

This was my initial thought as well - I was afraid it might make a big dead zone at the start of the range though. Of course with this pot that may be a good thing...

Is this a motorized volume pot? Looking at the schematic and it seems to be telling me that. The mistracking is probably the pot, but motorized ones are not quite as straightforward or cheap to replace unless the pot can be split from the motor easily.

It is a motorized pot. It's an interesting design through - it looks to be a fairly normal-looking pot strapped to a big gear box. Might look into pulling that apart in the future and see if I can get a fresh pot installed. This unit definitely had massive amounts of hours put on it by the previous owner, so it's probably a little worse for wear.

anyway, resistance between the "top" (non-grounded, and not the wiper) of the pot and wherever it comes from would make it less touchy. I can't tell by the scans, but its possible that J604 and J605 happen to be a convenient spot you could do that. You'd have to trace it out for sure. Failing that, it appears that R626 and R627 sit between the sources and the top of the volume control (R628). Those are 1k by the schematic, if you make it say 10k it should make the volume control a lot less touchy.

Good call - i'll take at these later today.

 

[Okke 70s]

I was afraid it might make a big dead zone at the start of the range though.

If you balance it out, it probably won't be that much. A bit of trail and error.. Using a potmeter to determine the required resistance might save you some time. If the design permits you could even set the volume knob on the pot, so to point to "0" right where it starts making sound.

It is a motorized pot

Ah, that makes replacement a bit more problematic. A lot more, probably.

Good call

Gadget knows best

 

[bazzle592]

its possible that J604 and J605 happen to be a convenient spot you could do that. You'd have to trace it out for sure. Failing that, it appears that R626 and R627 sit between the sources and the top of the volume control (R628). Those are 1k by the schematic, if you make it say 10k it should make the volume control a lot less touchy.

J604 and J605 just ended up being some motor stuff, but I swapped out R626 and R627 for some 15k 1% resistors and that was definitely the solution! 9:00 is now a very reasonable listening level, and I have a lot more usable range to work with. I'd imagine this isn't too hard of a mod to duplicate to other pieces of equipment with this problem as well - now I know what to look for!

Thanks for taking a look!

 

[gadget73]

no problem. I'm not a big fan of the excessively touchy volume control. I guess its marketing, "look how loud it is, and its only 1/4 of the way up!". For me who listens at relatively low levels it means I'm trying to find the happy spot within a very small amount of travel.

 

[rudolfo]

Any suggestion on a motorized remote volume potentiometer to replace this? Its a custom made amp and I have plenty of space. Thanks...