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Old 11th February 2019, 05:34 PM   #6081
apexaudio is offline apexaudio  Serbia
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Originally Posted by kct View Post
Hi apex,

Thanks for your complement. No, there is a servo in the circuit and works quite well, I might add. Initially I took the amp into operation without the servo. For simulation purpose, I also neglected to insert the servo to speed up the simulation since the old software version I have only uses one CPU core. Things take seemingly for ever... Even tho I had all components paired, there was still a nagging offset of about 70mV on the output. Once I installed the servo, it went below what I can measure. My DMM shows 0.0mV however I doubt my Fluke is that precise but I'd say with confidence the offset is less than 1mV.

Your work looks good to. The board material you used looks very familiar to me. Back than my work did not look as clean as yours, I must admit.
I suggest to use SU-V7 or SU-V9 schematic, circuit is similar but dual-fet current is 2mA work better and DC offset is better.
Regards
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Old 11th February 2019, 10:54 PM   #6082
kct is offline kct  Canada
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Originally Posted by apexaudio View Post
I suggest to use SU-V7 or SU-V9 schematic, circuit is similar but dual-fet current is 2mA work better and DC offset is better.
Regards

Alright, I have a look at it. I thought the SU series amps were all fully integrated amps.
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Old 12th February 2019, 08:07 AM   #6083
borys is offline borys  Ireland
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xrk971

Very nice cooling system for the amplifier.
Some day I must try some A-class myself, never build one so far.
Winter time there is about 5deg C in my office so I would really every aspect of Aclass would be highly recommended .

Mile
The A40 spider looks really cool on the board.


regards
Pit
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Old 12th February 2019, 08:59 AM   #6084
apexaudio is offline apexaudio  Serbia
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Originally Posted by borys View Post
xrk971

Very nice cooling system for the amplifier.
Some day I must try some A-class myself, never build one so far.
Winter time there is about 5deg C in my office so I would really every aspect of Aclass would be highly recommended .

Mile
The A40 spider looks really cool on the board.


regards
Pit
AA14 is simple class A amplifier it can give you idea for your class A amp.
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Old 12th February 2019, 04:36 PM   #6085
kct is offline kct  Canada
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Hi Apex,

Well, comparing the published specs. this is a bit of a head scratcher. The SE-A7 sports the better specs, yet uses the same OPS and drivers as the SU-V7. I am not sure, using the same components, how the specs in particular the dampening factor can be so vastly different. Either the transistors were much improved over time or the SU-V7 has poor output conductivity or layout deficiencies. Altho the circuits seem very very similar, if not identical, I am puzzled on the specs been so different. Well, I played a bit with the simulation, it appears increasing the current through the input FETs does not seem to help improve the amp performance, it seems to worsen. However, doubling the current through the intermediate stage improved THD significantly, effectively halfing THD figure at 20kHz ! I admit, I am not sure what you mean by better DC offset. How much better than less of a millivolt is this going to get ?
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Old 12th February 2019, 07:09 PM   #6086
apexaudio is offline apexaudio  Serbia
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Originally Posted by kct View Post
Hi Apex,

Well, comparing the published specs. this is a bit of a head scratcher. The SE-A7 sports the better specs, yet uses the same OPS and drivers as the SU-V7. I am not sure, using the same components, how the specs in particular the dampening factor can be so vastly different. Either the transistors were much improved over time or the SU-V7 has poor output conductivity or layout deficiencies. Altho the circuits seem very very similar, if not identical, I am puzzled on the specs been so different. Well, I played a bit with the simulation, it appears increasing the current through the input FETs does not seem to help improve the amp performance, it seems to worsen. However, doubling the current through the intermediate stage improved THD significantly, effectively halfing THD figure at 20kHz ! I admit, I am not sure what you mean by better DC offset. How much better than less of a millivolt is this going to get ?
SU-V7 and SU-V9 have tone control filters in feedback path, use same feedback as SE-A7... DC offset without servo will be better.
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Old 13th February 2019, 07:57 PM   #6087
ostripper is offline ostripper  United States
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Quote:
Originally Posted by apexaudio View Post
AA14 is simple class A amplifier it can give you idea for your class A amp.

That amp will clip with rounded corners and clamp saturations.
Will actually dissipate less when overloaded.
Nice.

OS
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Old 14th February 2019, 09:15 AM   #6088
apexaudio is offline apexaudio  Serbia
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Originally Posted by ostripper View Post
That amp will clip with rounded corners and clamp saturations.
Will actually dissipate less when overloaded.
Nice.

OS
Bias 1,2A heatsink around 55deg
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Old Yesterday, 04:36 AM   #6089
miro1360 is offline miro1360  Europe
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Originally Posted by kct View Post
The making of the SE-A7 Tribute.

Images are in no particular order.

I suggest people try this A7 amp. The sound is amazing
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