One useful modification to add to an amp is to add 330k resistors in parallel to ground with all your can filter capacitors. By adding these the voltage automatically drains from the filter capacitors in minutes, and theoretically this reduces the need to drain the capacitors before working on the amp. These resistors have to be added to the amp anyway if you install Power Scaling, so if you plan on installing that at some point you can get it out of the way now and have a safer amp to boot.
<– here’s how to wire the resistors
However; don’t rely on the resistors to do their job – although it makes the amp much less likely to retain voltage, it’s still advised that you continue to drain the caps too with alligator clips just as an extra precautionary measure. If you’ve ever been shocked by an amp with residual voltage, you’ll agree that it’s worth spending the 30 seconds to do it.
I’d advise using metal film resistors for this job, rated for at least 2 watts. If you can get 5 watt resistors, that’s even better.
Copyright © Richard Baines 2006