Naim NAC 112 volume control

[Rob Boss]

Greetings--
I’ve made my way down the rabbit hole via Google searches, the Naim Forum and Acoustica, to ask you about a topic a few have dealt with before:
I have a Naim NAC 112 preamp. The volume started to go up and down randomly, and shortly after that, the remote control stopped working on the volume. The Google search revealed there is an IC chip related to volume balancing between all the inputs (phono could be raised, line inputs lowered, and they’d all be the same) that frequently malfunctioned and Naim discontinued that feature. Also mentioned on those message boards was the volume pot tended to fail in the 112, which also happened.

My questions:
1) Does anyone have or know where I can get a schematic diagram for the preamp?
2) What is this IC chip of which they speak?
3) Is the Alps Blue Beauty Motorized the suitable volume pot replacement, or is there a better choice?
4) Likewise, I'm inclined toward minor upgrades while the unit's under repair--but only minor.

Thank you very much for your time and your help.
Do have a lovely day,
Rob Boss
Portland, Oregon
USA

 

[MJS]

The volume control on the 112 was entirely under software control and used switched resistors. As far as I understand it the control circuitry failed and there was no desire by Naim to retro fit a suitable replacement after the original had gone obsolete. You could fit an alternative pot but you'd have no balance or remote volume control.

 

[DaveMc64]

This might be of some use/inspiration:
https://pinkfishmedia.net/forum/thr...-a-new-heart-transplant-avondale-821s.147869/

It does look like the original control for the volume was motorised so it might be possible to retain remote volume with a motorised pot allowing you to bypass the switched resistor circuitry.

The above linked post suggests there were some changes to the gain stage as well but it might also be possible to return that to Naim standard so you wouldn't need the 821 boards.

All in all though this is probably going to require quite a bit of DIY to get it back to operational.

 

[Beobloke]

That's an interesting tale and a neat modification!

To be fair, though, in the great scheme of electronics things, the original CMOS control chips aren't all that old, so even if they're "officially" obsolete, it probably wouldn't be too difficult to find some so that they can be replaced to retail all original functionality.

 

[Rob Boss]

This might be of some use/inspiration:
https://pinkfishmedia.net/forum/thr...-a-new-heart-transplant-avondale-821s.147869/

It does look like the original control for the volume was motorised so it might be possible to retain remote volume with a motorised pot allowing you to bypass the switched resistor circuitry.

The above linked post suggests there were some changes to the gain stage as well but it might also be possible to return that to Naim standard so you wouldn't need the 821 boards.

All in all though this is probably going to require quite a bit of DIY to get it back to operational.

Thanks Dave--Tracking down this volume pot was fairly easy, and the balance still works--as does volume, manually. It's the motor that's gone out, so that's sounding fairly easy to replace. Beo's point about the chips is encouraging, as well. The project's coming together. Thanks for the help!