Studio Reference Amplifier

[thimios]

My opinion..this is a small not suitable heatsink.
Fins are horizontal and few!
You need a large one with vertical fins.
Something like this.
You must mount transistors direct on heatsink not using angle corner brackets.
If you can't find a better heatsink, lower the bias current as Mile suggest.

 

[AndrewT]

your outputs are biased to ~17mV
The bias current is ~ 0.017/0r333 = 0.051A
The dissipation in each output is ~ 68Vdc * 0.051A =~3.5W
You have six devices requiring cooling for 20.8W
They should not be getting hot.
But your heatsink is nearly useless.

And the matching between devices is pretty poor. Min = 14mV and max = 20mV, that is +43% for the hottest devices.

 

[tommeeto]

the bias current 100ma but in 3x1ohm resistors the voltage (mV) aren't the same on Ground to Emitter Q14-20mV Q16- 16mV Q18-14mV Q15-20mV Q17-17mV Q19-15mV.

You measured voltage to GND. The sr-200 schematics shows that emitter resistors (.33ohm ones) are connected to amplifier output. So measure voltage drop on R33 resistors, between emitter and OUTPUT.

 

[alex mm]

SR 300 V1.0 PCB

Hi all ,
I promise, to layout a decent PCB for SR300, so I start six or seven hour ago and this is what came out...... Not tested . PCB it's diy friendly, one layer, can be built easy.
Best regards,
Alex

 

[apexaudio]

Hi all ,
I promise, to layout a decent PCB for SR300, so I start six or seven hour ago and this is what came out...... Not tested . PCB it's diy friendly, one layer, can be built easy.
Best regards,
Alex

Nice PCB, thank you.
Regards

 

[samratsarkar]

Excellent PCB layout. Thank you Mr. Alex and Mr. Mile Sir for sharing such wonderful designs for DIY.

I am planning to build SR-200 with three pairs of output. I wanted to know which PSU design to consider . With one pair of 2sc5200 or 2 pair of 2sc5200 for a 50-0-50 VAC , 700 VA power supply.

Please Help.

Regards,
Samrat

 

[thimios]

Hi all ,
I promise, to layout a decent PCB for SR300, so I start six or seven hour ago and this is what came out...... Not tested . PCB it's diy friendly, one layer, can be built easy.
Best regards,
Alex

Nice work doctor PCB

 

[samratsarkar]

Excellent PCB layout. Thank you Mr. Alex and Mr. Mile Sir for sharing such wonderful designs for DIY.

I am planning to build SR-200 with three pairs of output. I wanted to know which PSU design to consider . With one pair of 2sc5200 or 2 pair of 2sc5200 for a 50-0-50 VAC , 700 VA power supply.

Please Help.

Regards,
Samrat

Sir,
Kindly help me - Which PSU (with one pair of 2sc5200 or 2 pair of 2sc5200) is required for SR-200 having 3 pairs of outputs.I am having Power Supply 50-0-50 VAC , 700 VA

 

[saminnografix]

My opinion..this is a small not suitable heatsink.
Fins are horizontal and few!
You need a large one with vertical fins.
Something like this.
You must mount transistors direct on heatsink not using angle corner brackets.
If you can't find a better heatsink, lower the bias current as Mile suggest.

your outputs are biased to ~17mV
The bias current is ~ 0.017/0r333 = 0.051A
The dissipation in each output is ~ 68Vdc * 0.051A =~3.5W
You have six devices requiring cooling for 20.8W
They should not be getting hot.
But your heatsink is nearly useless.

And the matching between devices is pretty poor. Min = 14mV and max = 20mV, that is +43% for the hottest devices.

You measured voltage to GND. The sr-200 schematics shows that emitter resistors (.33ohm ones) are connected to amplifier output. So measure voltage drop on R33 resistors, between emitter and OUTPUT.

thank you for the assistance
i will try 20-30mA while finding good heatsink and change my OP devices.
since i have been using this circuit for 2weeks @3-5 hours a day with fan.
with excellent sound quality.

thank
regards

 

[rottalpha]

Hi all ,
I promise, to layout a decent PCB for SR300, so I start six or seven hour ago and this is what came out...... Not tested . PCB it's diy friendly, one layer, can be built easy.
Best regards,
Alex

Your skill never seizes to amaze me

 

[apexaudio]

Sir,
Kindly help me - Which PSU (with one pair of 2sc5200 or 2 pair of 2sc5200) is required for SR-200 having 3 pairs of outputs.I am having Power Supply 50-0-50 VAC , 700 VA

Use PSU10 with 2 output pair.

 

[samratsarkar]

Use PSU10 with 2 output pair.

Sir,
Thank you for the reply.

Which circuit to consider for PSU

My SR-200 has 3 pairs of output and I will use 3.2 version PCB designed by Mr.Alex.

 

[44250]

this is my attempt of SR300,based on alex-mm APEX A40 board (i like the way he designed output stage-transistors emiter-resistors and aded some electrolite capacitors to it)

 

[Rick G]

Alex mm,
do you have pdf files of SR300 layout. If so, please post.

 

[alex mm]

SR 300 V1.0 PDF FILES

Alex mm,
do you have pdf files of SR300 layout. If so, please post.

I have check again and find two errors .... corrected PDF file for tonner transfer attached.
Best regards,
Alex

 

[delange]

There are two strange traces on the SR300 PCB. See the attached picture (red circle). Is that supposed to be that way?

 

[Rick G]

Alex mm
THANK YOU

Rick

 

[Dacz]

hi delange, i think it is option for smd fet

 

[alex mm]

There are two strange traces on the SR300 PCB. See the attached picture (red circle). Is that supposed to be that way?

Yes it's correct , 2SK2145 it's placed on bottom side of PCB .

Rick as always , my plesaure ....

Regards,
Alex

 

[apexaudio]

SR50R idea