Amplifier motherboard

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My new project. On motherboard PCB are PSU 0,+/-100V and 0,+/-15V; Soft-Start for X-former; DC and Anticlick speaker protect; Balanced/Bridge circuit and two Amplifier driver who can run all kind output stage Bipolar, Darlington, Mosfet with Complementary or Quasycomplementary circuit.
 

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This mini PA Amplifier use the same circuit with four BDW83D/BDW84D darlington outputs. Driver power suply is +/-50V up to +/-120V DC, and is have much stability than clasical circuit with single tansistor in VAS. Compenzations are R5,C3,C7.
 

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120w 8r

This amplifier module named Kelvin is made for testing driver circuit. There is no VI limiter just fast fuses. Work with +/-56V DC PS.
 

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Joined 2006
Hi Apex, can you give component values, Id like to simulate this one because of the unusual vas. You have compensated it in a different way I have seen such a vas stage done, the only manufacturer I know of that uses this setup is Yamaha in their subwoofer amps.

This type vas loves to oscilate in the Mhz range. Why dont you use driver for the output transistors.
 
R1-1k
R2,R11-22k
R4,R6,R7,R8,R16-560R
R5,R10,R14,R15,R17,R18,R19-220R
R9,R12,R13-100k
Emiter resistors-0R33 5W

C1-10uF/25V ELKO
C2-100pF KER
C3-1500pF KER
C4,C5,C11,C12-2,2uF/63V ELKO
C6-100uF/25V ELKO
C7-330pF KER
C9,C10-220pF KER
C8-100nF MKS

D1,D2,D3-1N4148

Q1,Q2,Q3-2N5401
Q4,Q5,Q7-BC547
Q6-BC557
Q8-MJE340
Q9-MJE350
Q10-BD139
Q11,Q12-BDW84D
Q13,Q14-BDW83D

I use 100nF KER beetwin input GND and power GND (not stufed on photo) if need to compensate HF oscilation, but not need in this case. Output transistor are darlingtons.
 
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This design is not so much about the shunt compensation although this vas might work using it, its a baxandall superpair setup, most linear stage Ive tried but problems with oscilation. There is a couple of threads dedicated to try stabilize this type vas.

I suppose that it works, since apexaudio has a functionnal unit..
Will try some sims of this Vas when i ve some time left, as i ve got
other things to sim currently...
 
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Hi Apex, sorry I dont know your real name, I didnt keep schematics was a while back but something similar to what you have except in compensation and output configuration, Ill try find the threads here where some of us were trying to stem this type vas, there is also a member who tried it in a super low distortion amp, -130db thd at full power 200 watts if I remember correctly but I dont think he came back with a built version, only simulation.
 
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In simulation its possible to get such figures but when measured Im pretty sure wont be as low, my current amp is also around -125db in simulation but not in real life. I must find the thread again, its a very high open loop gain amp using the same vas that apex is showing here.

The only circuit Ive built which correlates about right is a Jfet buffer which goes down that much, SYN08 s constructed amp is around 1 ppm THD20 so its possible to get very low THD figures with careful design.
 
SYN08 s constructed amp is around 1 ppm THD20 so its possible to get very low THD figures with careful design.


Yes, an original schematic, with fairly exceptionnal perfs.
The only critic i could make about it is a somewhat underdamping
in respect of the step response displayed with capacitive loads, even
there s a high value self at the output.
But this is little compared to the general behaviour which is first rate.
 
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