NAD 705 broken output stage?

[borges]

My NAD 705 is acting weirdly these days. One of the channels can be quiet or on low volume with noise in it. The problem stops if I turn the volume control up quite a lot and then down again.

What may be causing this problem? Do you have a 705 schematic that I could look at?

And when I take the amp apart, any good mods that would work in it?

Greetings,

Børge

[Nuuk]

And when I take the amp apart, any good mods that would work in it?

Yes, gut it and build an LM3875 based NIGC inside.

If the transformer voltage is OK (ie <27VAC) you can utilise it, but I would recommend replacing all other parts as I did with an old Arcam A60. Full story HERE.

[li_gangyi]

Maybe u wanna sell me the old output board and stuff...hehe...could use some for exprementing...NAD had some kinda soft-clip stuff built in right??

[aloneinkyoto]

Hi, I had the same problem with my 705....if you listen with headphones, the sound is fine? That was the case with mine at least which points out that the amp is working fine, just the speaker stage is dodgy...


...and in fact the problem lies with the relays that are used to switch the speakers on and off (sometimes if you use the buttons on the front to turn them on and off the sound can be restored to them)

I haven't sucessfully replaced the relays in mine (I will as soon as I get a bit of spare time) but as a stop-gap measure I removed the relays and put straight-wires through....the result being that both A and B channels work lovely, but there is a pop when you power on and off (this can be prevented by muting before you power off)

In short: it's probably your relays, nothing wrong with the amp :P

Have fun