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Old 13th August 2011, 10:06 AM   #181
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Quote:
Originally Posted by MiiB View Post
I would much prefer two capacitor-banks one bank driving the output and one bank with diode separation driving the other stages...then PSU sag will only affect the output stage.. to me this clearly improves the amplifier...
I agree but please draw these diodes from the main rails and add DC smoothing caps for the input stage, than you will see that in this amp this is really not necessary, since we only have to supply DC current to one - zener potential and this can be done in the same manner like you mentioned, just with adding more capacitance in parallel to zener diodes.
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Old 13th August 2011, 12:48 PM   #182
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I have found this supplier to be dependable up to this point. I hope to have the transistors matched in one week for those who are interested. I will confirm authenticity and give numbers when finished. I also look forward to building this amp as well.
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Old 14th August 2011, 10:29 AM   #183
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Wink SSA complete BJT version

As we agreed with Nico that there should be three versions of SSA (Simple Symmetrical Amplifier), regarding output buffer, presented for listening tests:
- BJT driver/BJT output
- BJT driver/MOSFET output
- MOSFET driver/BJT output

Here is my sch proposal for the first one from the list. I intentionally left blanks for the values so we can have something to discuss about here. My only suggestion would be about the currents: input pair 2-5 mA, driver current 15-20 mA, output current 100-250 mA. Defining these currents will lead to proper resistor values, types of BJT's, etc. Any comments?
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Old 14th August 2011, 10:32 AM   #184
AndrewT is offline AndrewT  Scotland
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How should the 4 input devices be thermally coupled to gain best resistance to varying output with variations in ambient temperature and operational dissipations?

Thinking about Roender's amps, he used some diodes to provide some temperature compensation for the input stage. Can we gain similar performance advantages doing something similar?
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Old 14th August 2011, 10:41 AM   #185
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Input stage is in a perfect temperature balance regarding symmetry if the two input BJT's are in thermal contact - tested. Cascodes are non critical, drivers should be separated from the main heatsink - small, almost constant power dissipation, outputs are compensated with Vbe multiplier, so thermally looking everything is in order.

Last edited by Lazy Cat; 14th August 2011 at 10:43 AM.
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Old 14th August 2011, 11:22 AM   #186
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Wink Thermal Track BJT outputs

If someone has some NJL Thermal Track leftovers schematics is even simpler.
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Old 14th August 2011, 12:36 PM   #187
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Offset trimmer was missing, now output DC OK.
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Old 14th August 2011, 12:50 PM   #188
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I have completed the L-MOSFET with drivers. It sounds really good, clean, open and dynamic. It is stable and can operate into dubious loads. Again my compliment Lazy Cat it is a job well done.

Regards

Nico
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Old 14th August 2011, 01:02 PM   #189
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Smile SSA sound

Thanks. Yes, yes, ... the sound from this simple schematic is only what it matters. It is so neutral, transparent, dynamic, easy flowing, like there is nothing in between source and the speaker, wire with the gain. Enjoy Nico!
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Old 14th August 2011, 01:08 PM   #190
hoktuna is offline hoktuna  Sweden
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I`w got my rubber gloves on and acid is mixed
Just waiting for mr Gerber
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