My petulant exercise in amp layout may bear more fruit than I expect, as the layout is readily adaptable for other purposes. I've already spun off a version with mosfet input and lateral outputs. Before I proceed much further, I want to do some simulations to see if the compensation scheme I've chosen is actually sensible...
Amp ha been completed and it sings like crazy 
Everything worked even without test boards. No hum, dc offset 2mV and 10mV per channel.
Bias 40mA per transistor - runs cool.
no turn on/off thumps.
PSU - +- 45V 30 000Uf in each rail.
indicator diode foe each rail.
Transistors - ztx450,550,MJ340/350, mj11016/15.
0,5 ohm emitter resistors and base stopper divided-100R on PCB and 100 on transistor base pin.
I will measure later with scope and sound-card - now I am a little tired after amp hobby work
Everything worked even without test boards. No hum, dc offset 2mV and 10mV per channel.
Bias 40mA per transistor - runs cool.
no turn on/off thumps.
PSU - +- 45V 30 000Uf in each rail.
indicator diode foe each rail.
Transistors - ztx450,550,MJ340/350, mj11016/15.
0,5 ohm emitter resistors and base stopper divided-100R on PCB and 100 on transistor base pin.
I will measure later with scope and sound-card - now I am a little tired after amp hobby work
Attachments
Amp ha been completed and it sings like crazy
Everything worked even without test boards. No hum, dc offset 2mV and 10mV per channel.
Bias 40mA per transistor - runs cool.
no turn on/off thumps.
PSU - +- 45V 30 000Uf in each rail.
indicator diode foe each rail.
Transistors - ztx450,550,MJ340/350, mj11016/15.
0,5 ohm emitter resistors and base stopper divided-100R on PCB and 100 on transistor base pin.
I will measure later with scope and sound-card - now I am a little tired after amp hobby work
I love the front panel. How did you do it?
Yesterday I raised bias to 100mA per transistor - the massive heatsinks temperature after 5 h was reached 35C only (ambient - 22 C). bias is very stable as amplifier itself - i tested it with two way speakers and fullrange without crossover. Today i will measur amp preformance with scope and soundcard.
Since you have a push-pull output, 1W RMS of class A bias would amount to a total bias current of about 0.25 A, or 62.5 mA per output device. Since you're far in excess of that, you've got a lot more class A headroom (~2.5 W RMS). I'd leave the bias where it is if there are no other problems.
Here comes i time that i prove my self wrong and right at the same time
Wrong since a commercial that features more than one pair of darlingtons exist in the market actually just showed up in the shop today for repair .
Right because this amplifier was totally blown for the known reasons ( i expect ) but i will look into it and get back to you .
In between enjoy the schematic ....This is a commercial design existing in the market for a number of years and also features a patch of 150Pf in the upper side Only ! relatively low next to known other schematic . It could be also interesting to see how the amplifier will perform with and without the patch
Since i am way too busy and constructing the AB 100 will take some time I will grab the opportunity and measure and listen to this amplifier after repaired since i think its a look alike .
I will enjoy working with Tip 142-147 after 20 some years passed from the time i was blowing a few .
Wrong since a commercial that features more than one pair of darlingtons exist in the market actually just showed up in the shop today for repair .
Right because this amplifier was totally blown for the known reasons ( i expect ) but i will look into it and get back to you .
In between enjoy the schematic ....This is a commercial design existing in the market for a number of years and also features a patch of 150Pf in the upper side Only ! relatively low next to known other schematic . It could be also interesting to see how the amplifier will perform with and without the patch
Since i am way too busy and constructing the AB 100 will take some time I will grab the opportunity and measure and listen to this amplifier after repaired since i think its a look alike .
I will enjoy working with Tip 142-147 after 20 some years passed from the time i was blowing a few .
Attachments
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very fine ....
That is the second one lucky also to see that this one also does work without patches .
This is weird since this worth farther investigation
What other people did that their circuit required patches ?
how other designers manage without them ?
I think the repair of the amplifier i have on bench will reveal more secrets
Let see
That is the second one lucky also to see that this one also does work without patches .
This is weird since this worth farther investigation
What other people did that their circuit required patches ?
how other designers manage without them ?
I think the repair of the amplifier i have on bench will reveal more secrets
Let see
I found the Puccini schematic on the web - it uses a boosted opamp topology with the NE5534 and a single set of output Darlingtons. I did my own version using current mirrors that simulates pretty well, with an LF411 in the front end, as that was a model I had. If I actually built something like that, I might get all fancy-pants and use an OPA627 instead. All these designs benefit by loading in as much Class A bias as the traffic will bear, with considerations of heat and stability in mind.