Which Subamp? (P68,IRS2092,Thermaltrak)
 

I am currently cleaning up my audio chain. The front-amp's are 99% finished, the Sub-Sat filter is in a nice enclosure too and now I am thinking of cleaning up my Subamp. I have a 8 ohms subwoofer driver so for some power I need quite a lot of voltage.

I currently have a IRS2092 pcb with a psu of 2*70Vdc rails. I can of course reuse that pcb, but I want to look at other options too.
http://www.diyaudio.com/forums/class...0h-200w8r.html

I have interest in the ESP P68 amp, since I have some spare MJL21193/4's
300/500W Subwoofer Power Amplifier

Another option is going with Thermaltrak transistors since I have many of them. Maybe combining with a LME49810/1 or LME49830 is a good option.
Initial Series

Going cheap&easy is using the IRS2092 PCB I have
Going easy is ordering the PCB's for the Thermaltraks
Going "all the way" is designing a PCB layout and using the MJL21193/4 in a P68-like design or the Thermaltraks in combination with a LME49810/1

The options are there, but which one should I go for?

Hmmz, the "all the way" option is going fast. Maybe that's a sign.

About P68:
Does any of you have an idea on heat dissipation of +/-70dc on 8 ohms or bridged (+/-50vdc) onto 8 ohms in living room operations?
I am looking for a proper heatsink-method but don't know which to use.

I am still testing the P68. Harmonics are high. Is there a way of improving this. Maybe force the bias up or is this true class B?
Testing is currently done on a powersupply with lax +/- 35Vdc. Will incresin the supplyvoltage automatically increase the bias?

" Harmonics are high"

What about the woofer distortion?

The bias should not change much with a change in supply voltage, the optimum bias would be about 340mV on the bases of the outputs (class AB+B).

What I meant was, that it is high compared to for example a P3A or my previous amp. I was expecting lower 2nd and 3rd harmonics. I will make a proper measurement within a couple of days.

More open-loop gain will reduce 2nd harmonic, but so what?

Isn't everyones goal to make a proper amplifier, no matter if it is used to drive a subwoofer or expensive loudspeakers? Now I am not saying that the P68 is bad, but I noticed the hogh harmonics and started to wonder if it could be improved.

Sure, even harmonics can be reduced with more feedback. Using an active current source with the Vas and a Current-Mirror for the diff pair will raise the OLG quite a bit. Why not just stick a Ne5532 in front of it (as stock), it would be a lot simpler.

bridged +-50Vdc !!!!!
what kind of speaker are you planning to attach?