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u/Taylor93UK

▲ 2 r/audiorepair

Heatsinking Class A/AB amps

In my workshop I currently have a few amps that I'm tinkering with or repairing and one thing that astounds me is the shear difference in heatsinking

NAD 310 - rated 20W/ch continous, sizeable heatsink

NAD C326BEE- 50W/ch continous, much bigger heatsink but still encapsulated in the case

Quad 306 - 50W/ch but the entire front is a substantial heatsinking

Arcam Alpha 6 - 50W/ch, tiny heatsinks which are almost comical compared to the others

I appreciate the arcams output drivers are FET and not BJT but I does make me question the claimed ratings when the heatsinks are smaller than the NAD 310 which is rated for less than half the continous power.

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u/Taylor93UK — 2 days ago
▲ 4 r/audiorepair

Recently picked up this NAD C326BEE from ebay, advertised as having a flashing red protection LED.

I've been having a play around with it and I'm having trouble setting the bias. Service manual says power up and wait 15mins, adjust trimmers for 3-3.5mV wait another 15min then re adjust.

By every time I adjust them, it obviously changes the power dissipation and therefore temperature and then the bias is out of adjustment. I've spent hours today going around and around waiting then adjusting. Feel like I'm over complicating it.

Annoyingly it behaved fine for several hours today, I switched it off when I went for dinner, switched it back on for it to immediately go into protection mode. After cycling a few times it started behaving for long enough to recheck the bias, heating up from stone cold again, after the first 15 mins, my previously adjusted bias (aimed for 3.25mV) was now out of spec! How can I trust the alignment if after allowing it to cool it doesn't show a repeatable bias voltage?

u/Taylor93UK — 25 days ago