Yes
I write that earlier:
Then gradually increase I_bias so the voltage drop readings on R34 or R35 (0R33) are approx. 20...25mV/per 0R33
That is approx 23mV/0R33=>70mA BIAS OPS
Did you change R33 220R for 100R???
, with 100R you would have more Aclass Drivers bias (approx 12...15mA) => so you lower THD with more Drivers bias !
Congrat with your working amp!!!
I write that earlier:
Then gradually increase I_bias so the voltage drop readings on R34 or R35 (0R33) are approx. 20...25mV/per 0R33
That is approx 23mV/0R33=>70mA BIAS OPS
Did you change R33 220R for 100R???
, with 100R you would have more Aclass Drivers bias (approx 12...15mA) => so you lower THD with more Drivers bias !
Congrat with your working amp!!!
Thank you once again for your support Mr. Dragan100. You said it absolutely correctly that there is something wrong around R30, R31. I used 0R22 resistors for the emitter, the 23mV will be too much, around 100mA, I will reduce it to 13-15mV, I will get something around 60mA. I did not change the 220R resistors. Will it be reflected in the sound?
Hello everyone here on the forum. To sum it up. I adjusted the resistor R33 to about 110R, replaced the transistors with NJW0302/ NJW0281 (Mouser supplier), set the bias to 23mV. I'm enjoying it now, beautiful full sound! First of all, I want to thank Mr. Dragan100 for his support, for providing a lot of information on how to do what correctly.
I read with joy that you have managed to start the amplifier with additional small changes,
now your drivers are working with a slightly higher local Bias 10 ... 13mA => 1,3..1,4V/110R,
you set up OPS Bias to 23mV/0R22 => This is approximately 100mA
Did you control now the temperature of Main HeatSinks?
60°C is approximately that you can last with your fingers holding HeatSink approx for 5sec!
Or you can measure with ThermoCouple exactly temperature! DMM+ThermoCouple
Did you measure on resistors R26/28 100R Voltage drop => your VAS bias with 18V IPS Zeners?
now your drivers are working with a slightly higher local Bias 10 ... 13mA => 1,3..1,4V/110R,
you set up OPS Bias to 23mV/0R22 => This is approximately 100mA
Did you control now the temperature of Main HeatSinks?
60°C is approximately that you can last with your fingers holding HeatSink approx for 5sec!
Or you can measure with ThermoCouple exactly temperature! DMM+ThermoCouple
Did you measure on resistors R26/28 100R Voltage drop => your VAS bias with 18V IPS Zeners?
You rapport +/-18,2VDC on zeners in last schematics voltage measurements writing!
with +/-17,6VDC IPS Caskode polarization, {18,2 - Vbe} = 17,6V (Vbe = 0,6..0,8V)
and 1,33VDC voltage drop on resistors R26/28 100R. so this is 13,3mA VAS BIAS,
are Q10 and Q6 HOT??? ...more then 60°C+++
Uce*Ibias = cca 40...42VDC*13,3mA=> 0,5..0,6W thermal dissipation/per VAS TO92 BJT,
and they must be HOT BF420/421 in TO92 case, they definitely need little heatsinks,
or you use some compatible VAS BJTs there? ...TO128 case?
with +/-17,6VDC IPS Caskode polarization, {18,2 - Vbe} = 17,6V (Vbe = 0,6..0,8V)
and 1,33VDC voltage drop on resistors R26/28 100R. so this is 13,3mA VAS BIAS,
are Q10 and Q6 HOT??? ...more then 60°C+++
Uce*Ibias = cca 40...42VDC*13,3mA=> 0,5..0,6W thermal dissipation/per VAS TO92 BJT,
and they must be HOT BF420/421 in TO92 case, they definitely need little heatsinks,
or you use some compatible VAS BJTs there? ...TO128 case?
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Hi Dragan100, I'm sorry I'm writing now. I did a measurement after the jumper between the resistors, it behaved badly in general and after that everything calmed down. The measurements I wrote to you were before the dps repair. Now it seems to me that it behaves really correctly. I use BF420/ 421, I changed the resistor from 15K to 18K. The sound is delicious, beautiful, everything is quiet, nothing disturbs the sound is full of detail. I will have more time at the weekend.
PCB for Sanken ....and PSU ..
Tanks a lot for kind words , I'm glade to help you Apexaudio and viki_v2 . I have modified , an old PCB to fit Sanken output transistors .and PSU
Regards Alex .
Hi Alex,
If possible Please give me the Gerber files for the Sanken layout (SR200 V2.2)
