Studio Reference Amplifier

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#2,302
r_merola said:
Olaf
Thank you about your answer. I could not see the picture.

I suppose there is big differences in your input devices. Can you match pairs?
I suppose it will resolve your problem.

I attached B285 file. It is a commercial product from 80's with this topology. Good sounding in my personal opinion. Also attached my version of SR60

SDS/Ronaldo
Click to expand...

Nice THD, is there DC offset on your SR60 simulation? Thank you for your contribution on this prototype.
Regards
 
#2,304
Hi Mile, thank you for your attention. I'm sure I have some error in it or I've mistaken the transistors. But I'll find it.
Here is a foto. The quality of the pcb is not so good - my printer is defective and I had to take another one ... Hard times 😉

regards Olaf
 

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#2,309
SR60

Well, here we are. After eliminating the error with the air wire the amplifier plays - and not bad. The offset is stable at 10mV. All components were very warm, so I went back from +-50V to + -40V. I think it also sounds better so. A very balanced and warm sound, completely unstrained. Maybe the heights could have a bit more transparency at the top. But this is completely subjective and I have not heard enough.
I would say the time to try the little amp is a good time!
The next days I will rework the layout (more distance between the transistors on the heat sink, a small heat sink for the 2SC4793 in the middle, a bit of cosmetics) and then build the second channel and upload the files.

Thanks to dobrivoje for finding the mismatch and to Mile for a new excellent amplifier.

regards Olaf 🙂
 

Attachments

  • PCB_SR60.jpg
    PCB_SR60.jpg
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  • SR60_ok_01.jpg
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#2,310
olafk said:
Well, here we are. After eliminating the error with the air wire the amplifier plays - and not bad. The offset is stable at 10mV. All components were very warm, so I went back from +-50V to + -40V. I think it also sounds better so. A very balanced and warm sound, completely unstrained. Maybe the heights could have a bit more transparency at the top. But this is completely subjective and I have not heard enough.
I would say the time to try the little amp is a good time!
The next days I will rework the layout (more distance between the transistors on the heat sink, a small heat sink for the 2SC4793 in the middle, a bit of cosmetics) and then build the second channel and upload the files.

Thanks to dobrivoje for finding the mismatch and to Mile for a new excellent amplifier.

regards Olaf 🙂
Click to expand...

Thank you for building SR60.
Regards
 
#2,313
apexaudio said:
You can tweek compensation in simulation to get it stable...
Click to expand...

I made the simulation and I did made a few mistakes on my own but mister Mile point out what I did wrong and after I fix my mistakes it works really well, 🙂 I add other stuff like base stoppers and coil and extras as usual, I adjusted to about 20mV single emitter resistor bias adj and a supply of 50V and it has really low THD according to the software results. I did the simulation as a normal use example simulation like you are using only 5W @1KHz sine wave to 8Ω load and THD is 0.001% sometimes 0.000% maximum power with 50V supply can reach about 100W "not going crazy" I mean not need to add more pair of power transistors I will build just as it is no changes 🙂

I'm getting old why I did not see that I made a wrong connection ? I need new glasses 😛

Regards
Juan
 

Attachments

  • SR60.pdf
    SR60.pdf
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  • APEX SR60 100W.JPG
    APEX SR60 100W.JPG
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Last edited:
#2,314
vargasmongo3435 said:
I made the simulation and I did made a few mistakes on my own but mister Mile point out what I did wrong and after I fix my mistakes it works really well, 🙂 I add other stuff like base stoppers and coil and extras as usual, I adjusted to about 20mV single emitter resistor bias adj and a supply of 50V and it has really low THD according to the software results. I did the simulation as a normal use example simulation like you are using only 5W @1KHz sine wave to 8Ω load and THD is 0.001% sometimes 0.000% maximum power with 50V supply can reach about 100W "not going crazy" I mean not need to add more pair of power transistors I will build just as it is no changes 🙂

I'm getting old why I did not see that I made a wrong connection ? I need new glasses 😛

Regards
Juan
Click to expand...

Virtual Zero Distortion Amplifier 🙂
 
#2,315
SR60 Part II

Hi, here is Part 2 of the SR60. Works from the first moment. Very nice sound.

Changes:
- Required heat sink
- Zobel
- Space for 10uF MKP input
- some corrections

The amplifier is definitely a recommendation.
Layout will be uploaded next day (on another PC).

regards Olaf
 

Attachments

  • PCB_SR60_P2_01.jpg
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  • SR60_P2_02.jpg
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  • SR60_P2_01.jpg
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  • SR60_P1+P2.jpg
    SR60_P1+P2.jpg
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#2,318
prasi said:
Hi Olaf,
nice work. are you getting those Wima's at a discount?, I see them in your all builds... they are super premium here on Farnell/RS Components. For my Slewmaster build, i had to import them from Canada from a nice gentleman.
reg
Prasi
Click to expand...
Hi, all the Wimas come from a German distributor (www.reichelt.de), where I buy the most components. They are not very expensive and the shop also ship internationally. But I do not know the shipping costs to India, but they are listed on the webpage (also in English).

regards Olaf
 
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