Studio Reference Amplifier

[thimios]

Thanks but is far away from me.

 

[Sunny22g]

Apex sr200 sound test

Sound apex sr200

 

[Gurpreet Turna]

Hello Mr. Miles, I have little problem with SR55 from last few days, when I plugged on SR55, bias and DC offset in high range and speakers produce little sound just like humming. After 15-30 minutes Bias and DC offset stable. Bias when amplifier start time 20-22mv and DC offset 200-300mv. After 15-30 minutes Bias 12mv(exactly I set on it) and DC offset between 0 - 5 milivolts , multimeter set on 200mv range. That both reading with short and open input. I use c2383/a1013 in place of bf420/bf421, Volts in BD139 Emitter to collector 2.30V.
Please solve my problem.

 

[Sunny22g]

Apex sr200 sound testing


apex sr200 - YouTube

 

[Vostro]

Theres something about the treble of the SR200 my "blameless" amp just can't reproduce.

One of my favourite amps

 

[Joel Wesseling]

View attachment 887170

Please tell me where you aquired the chassis?

 

[apexaudio]

SRA 28

 

[ross71]

l

last job,
please how to set the bias? thank you
and how to make inductance

 

[Sunny22g]

Hello sir

Hi very beautiful pcb .1st set u multimeter on 200 mili volt and check across emmiter resistor then tune trimpot on 5-10 mili volt according your heatsink . Leave set on after 30 minutes check again set on again.. 2nd type set u multimeter on 2 volt base to emmiter voltage max 570 mili volt.


And coil link Construction of a Zobel network for audio amplifier - YouTube. Here u see how make coil

 

[r_jik45]

Theres something about the treble of the SR200 my "blameless" amp just can't reproduce.

One of my favourite amps

SR200 build:
Found 2 layouts/silks saved on my drive,
- one has 3x 2SC5200 and 3x 2SA1943
- one has 6x 2SA1943 ???
Both transistors have the same package. Did not check the other components.
The first version looks like more genuine, the second might reveal a simple copy/paste error (?).

 

[kandimba]

This is the good one.
- one has 3x 2SC5200 and 3x 2SA1943

Regards

 

[ross71]

Hi very beautiful pcb .1st set u multimeter on 200 mili volt and check across emmiter resistor then tune trimpot on 5-10 mili volt according your heatsink . Leave set on after 30 minutes check again set on again.. 2nd type set u multimeter on 2 volt base to emmiter voltage max 570 mili volt.


And coil link Construction of a Zobel network for audio amplifier - YouTube. Here u see how make coil

thank you so much..

 

[Hicoco]

SR200

What is the best replacement for 2SC4793/2SA1837, Thanks

 

[prasi]

I think mje15035 and its complimentary would make it

 

[Hicoco]

Thanks prasi, i saw those but the Collector output capacitance is not documented (20pF for the 4793 and 30pF for the 1837) and the Transition frequency is 30Mhz (100Mhz for the 4793 and 70Mhz for the 1837)....not sure if that is ok

 

[rephil]

Hi Hicoco,


The 2SC4793/2SA1837 can be found at Profusion PLC (www.profusionplc.com) in England, and I know they are of good quality as I have used those often with good results, no problem at all.


Best regards


rephil

 

[Hicoco]

thanks..i will use those to try

 

[Hicoco]

SR200

My new Project......

 

[r_jik45]

Nice project and layout. What kind of 3 pins input is that?

 

[Vostro]

Ref can be ignored when not needed, only using IN/SGND. Im not sure what the function of the ref is. It seems like a substitute input that does not go through the input cap.