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Old 11th November 2017, 03:31 AM   #5421
Lazy Cat is offline Lazy Cat  Slovenia
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Quote:
Originally Posted by QES View Post
I think that I can release the schematic (pretty conventional actually), but I will get permission anyway ...
Agree, no need to bother, pretty conventional, so trivial one can clearly read SCH from PCB. Amps should not be motor drivers only, so W, A, MHz, ... are basics and have pretty little in common with sound quality. Great work though.
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Old 11th November 2017, 08:04 AM   #5422
suzyj is offline suzyj  Australia
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Originally Posted by QES View Post
I should have mentioned in the original post that this was the 1khz measurement. The 10khz isn't much worse at about 0.0012%.
Way cool. The 10KHz result is indicative of plenty of bandwidth and fast slew rate. Looks beautiful, too.
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Old 11th November 2017, 08:47 AM   #5423
traderbam is offline traderbam  Europe
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Novel use of a bulldog clip?
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Old 11th November 2017, 02:21 PM   #5424
QES is offline QES  United States
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Indeed that is a binder (bulldog) clip on the input and current mirror transistors which simply helps to keep them close to the same temperature. The output DC of this amp rarely goes beyond +/-1 mV and I have never had one worse than +/-2 mV. The transistors are not matched beyond simply taking them from the same strip. I just cut them off in pairs and the Vbe matches close enough. For some critical (non audio) applications I have sorted from there, but not for production units.
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Old 11th November 2017, 03:02 PM   #5425
QES is offline QES  United States
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Thanks SuzyJ, I think it's cool too It has a pretty symmetrical 40V/mS slew rate and has no trouble being perfectly flat and effectively distortionless well into the ultrasound.

Although this amplifier is primarily used for PA and Hi Fi applicaions, I have techniques that put tube/valve style distortion into it for guitar applications. I have other designs that do this in my production guitar amps. Audio circuits are no doubt a source of infinite fun.
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Old 12th November 2017, 07:52 AM   #5426
stumpamp is offline stumpamp  Luxembourg
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Quote:
Originally Posted by Lazy Cat View Post
so trivial one can clearly read SCH from PCB.
Unfortunately, I can't There are 2 driver transistors on the left and only one on the right Some loose transistors spread around the PCB with the routes being below. How is thermal runaway considered, only the output transistors seem connected to the heatsink Anyhow this thing took 4 years to build as I see, with the use of pro equipment. I'd be very happy for a schematic (even w/o values if you want to keep those) or a similar reference. Thanks.
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Old 12th November 2017, 05:29 PM   #5427
sajti is offline sajti  Hungary
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Originally Posted by stumpamp View Post
How is thermal runaway considered, only the output transistors seem connected to the heatsink
CFP output. The thermal compensation is on the left driver.

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Old 12th November 2017, 07:29 PM   #5428
QES is offline QES  United States
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Default XPA-150 schematic

Yes it is a CFP output. In my experience building audio amps I have never actually seen thermal runaway in practice. The thermal compensation is primarily for maintaining accurate bias to minimize crossover distortion.
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Old 13th November 2017, 07:33 AM   #5429
borys is offline borys  Ireland
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My lastest idea to ''end of the story'' amplifier is very close
In the nature bird is flying, fish is swimming, vacuum tube is amplifying voltage and BJT's are amplifying current.

So why not to let it stay this way ? In my opinion perfect combo.
Some 40-60hours more of work, slowly but forward

Regards
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File Type: jpg prototyp2.jpg (202.2 KB, 724 views)
File Type: jpg ptototyp1.jpg (208.3 KB, 653 views)
File Type: jpg preamp1.jpg (99.2 KB, 630 views)
File Type: jpg tpsu1.jpg (170.1 KB, 622 views)
File Type: jpg tpsu6.jpg (122.0 KB, 312 views)
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Old 15th November 2017, 05:42 PM   #5430
thimios is online now thimios  Greece
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Quote:
Originally Posted by borys View Post
My lastest idea to ''end of the story'' amplifier is very close
In the nature bird is flying, fish is swimming, vacuum tube is amplifying voltage and BJT's are amplifying current.

So why not to let it stay this way ? In my opinion perfect combo.
Some 40-60hours more of work, slowly but forward

Regards
Nice Peter!!!
Is power amplifier the i=AMP100?
I see an input stage together,what is the role of tubes,is it a buffer?

Last edited by thimios; 15th November 2017 at 05:44 PM.
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