Good old schematics

[roender]

Hello all

What do you think about this amplifier?
The performance it seems to be very good. Distorsion levels for second and third harmonics will be down into five-digit region at 1kHz and two-pole compensation pushes distorsion at 50kHz down to 0.0014% for second harmonics and 0.00052% for third harmonics.
Overal THD is approximately 0.0009%.
P = 80W rms, 8ohm

I don't know who is the designer of this hifi amp...

[ash_dac]

Doug Self ?

[bogdan_borko]

Slone I think.

BTW I never belived his thd figures...

[roender]

Originally posted by bogdan_borko
Slone I think.

BTW I never belived his thd figures...

O yes, my vote is for R Slone too.
Is there anybody who buid it?

[bogdan_borko]

I read some parts of his book and I`m NOT impressed at all... and somebody from the forum had trouble making one of his designs. Fairly complex for nothing, i think.

[Wavebourn]

Originally posted by roender
Hello all

What do you think about this amplifier?
The performance it seems to be very good. Distorsion levels for second and third harmonics will be down into five-digit region at 1kHz and two-pole compensation pushes distorsion at 50kHz down to 0.0014% for second harmonics and 0.00052% for third harmonics.
Overal THD is approximately 0.0009%.
P = 80W rms, 8ohm

I don't know who is the designer of this hifi amp...

Very professional design of a standard op-amp type, one of the best I've seen here. Built with low distortions in mind, also well protected against damage because of output overcurrent.

May sound perfect if you have a lot of headroom, when overdriven will ruin the sound.

[MikeB]

Okay, i checked the amp closely in sims...
THD values are impressive, BUT...

1khz 1w into 8ohm = 0.001% THD
1khz 50w into 8ohm = 0.0005% THD
10khz 1w into 8ohm = 0.0007% THD
10khz 50w into 8ohm = 0.001% THD
20khz 1w into 8ohm = 0.007% THD
20khz 10w into 8ohm = 0.016% THD
20khz 50w into 8ohm = 0.0095% THD

symasym:
1khz 1w into 8ohm = 0.0008% THD
20khz 1w into 8ohm = 0.001% THD
20khz 10w into 8ohm = 0.004% THD
20khz 50w into 8ohm = 0.011% THD

At 20khz this design fails in a way that is simply disgusting. Its very likely that this is the typical amp measuring exceptional, but sound like broken glass.
Attached is FFT-plot from sims for 20khz 10w into 8ohms, red is your showed design, green/yellow is symasym at same powerlevel. (I guess no comment is necessary)

I believe that an amp sounds like it weakest point, most standard designs completely fail at high frequencies.

Possibly that circuit might sound good if biased into ClassA. I guess this amp suffers from its CFP-output.

Mike

BTW, i never trust a circuit that reduces THD with increased power levels...

[mlloyd1]

it is a slone design.
probably a decent performer, certainly not the best there is.
others have built this design and been happy with it.
his distortion numbers are simulations, so beleive at your own risk.
the previously referred to problem was with a different design, not this one. that problem was when using current mirrors with a complementary symmetrical design, some voltages were undefined. i beleive it was stated that slone agreed with this assessment after questioned about it. more details can be found via the search function.

good luck and have fun!
mlloyd1

[powerbecker]

MikeB:
"At 20khz this design fails in a way that is simply disgusting. Its very likely that this is the typical amp measuring exceptional, but sound like broken glass."

Outrageous...especially the 9th harmonic with powerful 92 nW!
Mike, you must have good speakers and ears...
Heinz!

[roender]

Thank you very much, Michael. You are the best!