Just bought a '83 HK PM660

[almico]

Also note, the PM-660 runs very warm, even just idling. That's normal. She's a big, powerful amplifier and likes plenty of ventilation. Don't go stacking stuff on top.

It's phenomenally powerful into low impedances and also has a large transient capability. Consider its rating is a conservative 80wpc. It easily surpasses 120wpc continuous into 8R and nearly double that into 4R both channels driven. You will blow the fuses before you blow the amplifier.

Indeed. I've been leaving it on today to burn it in and get the caps up to speed. It's sounding better and better. I'm running through some Altec 604Cs which are 16R and it's putting out 105-110db @1M with he volume knob <5. It is cooking. It's 30* outside and I have a fire going all day to. Not sure which is keeping me warmer. Thanks for your help. Elvis thanks you too! He hasn't sounded this good in years.

 

[JCRC]

I have the same problem with the Main Direct switch. If depressed, one of the speakers down the DB. Suggestions? By now, I’m keeping it pressed. What is the “normal” (default) mode? I think, pressed.

 

[restorer-john]

I have the same problem with the Main Direct switch. If depressed, one of the speakers down the DB. Suggestions? By now, I’m keeping it pressed. What is the “normal” (default) mode? I think, pressed.

Main direct is -7dB less. It's meant to be like that. If one speaker drops out, the switch needs to be removed, dismantled and cleaned. HK switches from that era need a good cleaning every few decades.

It takes the active stages out and feeds the input direct to the volume pot and straight into the power stage.

 

[JCRC]

Main direct is -7dB less. It's meant to be like that. If one speaker drops out, the switch needs to be removed, dismantled and cleaned. HK switches from that era need a good cleaning every few decades.

It takes the active stages out and feeds the input direct to the volume pot and straight into the power stage.

Many thanks! Will do! I need to find a good technician for that were I live.

 

[DSJR]

Late to the party, but those HK amps - the ones that found their way to the UK, were very well liked and the 650 model had masses of current available for its output. Got to say that when I saw the amp it was initially compared to, I'd have blamed the OP being more used to a coloured 'creamy' sound rather than the HK being bad or 'wrong.' Glad it's coming together well now though, but a kind of warning that 'we' can get too used to a particular kind of presentation from our audio systems and if something else is substituted in, the 'sound' may well change and not be liked, at least to start with.