I don't doubt that's no problem but that's something that could be improved easily and since looking at it, I thought I should mention it. The amp enclosure with the chinese dual VU-meters looks very nice, sleek and minimalistic, elegant, I really love that. The amp on top looks nice too, blue fans but not hugely wild RGB, but if you'd like to use it without a case, I'd also mount a heat sink with cooling fins to the front, that would surely look nice.
That enclosure - it's not amp, it's a PSU with VU meters (not Chinese, they are from old Bang Oluffsen), and with speaker protection.
I use this PSU for (almost) all my amps, another example below. That's slightly different enclosure (newer) with VUs from old Technics amp.
I use this PSU for (almost) all my amps, another example below. That's slightly different enclosure (newer) with VUs from old Technics amp.
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Here is zipped Sprint Layout PCB file. It has 2 PCBS - one for original Circlophone, and one for the new one.
Feel free to use it whichever way you want.
Feel free to use it whichever way you want.
It seems you already build some amps with opamp input. Is it a Circlophone at left?
Please don't be offended by what I wrote. They (very likely) copied the B&O VU meters but I haven't seen the B&O original.
Both are very nice. And I love the fact you've used the heat-pipe CPU coolers for an amp. Not only is that a very cool and unusual look, that's great use of resources and a very effective and efficient way to cool an amp!
No, on the left is Alpha Nirvana and Beta Nirvana
See my threads for more op-amp based amps, especially this one. Over 15 op-amp based amps have been built.
Interesting, I would like to hear how your Circlophone performs sonicaly comparing other ones you have built so far?
Here is some discussion on the subject (several posts)
https://www.diyaudio.com/community/threads/alpha-nirvana-39w-8ohm-class-a-amp.344540/post-6665458
To me all amps of similar class/quality, sound the same.
Now what is the definition of "the same"??
Here is my experience: If I switch from amp A to amp B, it doesn't sound the same.
I feel differences. Then I switch to amp C. Also feel differences. Then switch to A again - feel difference.
I can't tell which sound is ''better' or 'worse'. Just different.
I can tell which one I like better. The problem is that one day I like amp A better, the other day amp B.
All in all, if I repeat these tests many times in different order, different amps, blind or not,
there is clearly NO PATTERN of which amp I prefer.
So this question doesn't dig deep enough into the problem:
"It remains an intriguing question: why do sound amplifiers different, even when their
specifications are similar?"
Conclusion: in 'short term' testing amps of similar class sound different.
For a long run, they all sound the same.
I think this is caused not by amps, but rather by human's hearing system being not perfect,
and craving for a change.
I have over 20 amps right now on my rack and shelves. I rotate them every couple weeks.
They all have very decent parameters, and yet, I can't point one that I would call "the best".
The truth is I can't really tell class A over B amp, quasi vs complementary, etc...
That's of course assuming that they are all "good"amps in general. Not some junk.
I definitely can tell that my Pioneer SX-1000 from 1970 sounds not good 🙂
But all the new ones are, unfortunately, all the same.
As for Circlophone, one thing that puts it apart from others, is total silence in the speaker, when no input signal present.
I think Circlo is the quietest from all my amps (almost all of them using the same PSU).
https://www.diyaudio.com/community/threads/alpha-nirvana-39w-8ohm-class-a-amp.344540/post-6665458
To me all amps of similar class/quality, sound the same.
Now what is the definition of "the same"??
Here is my experience: If I switch from amp A to amp B, it doesn't sound the same.
I feel differences. Then I switch to amp C. Also feel differences. Then switch to A again - feel difference.
I can't tell which sound is ''better' or 'worse'. Just different.
I can tell which one I like better. The problem is that one day I like amp A better, the other day amp B.
All in all, if I repeat these tests many times in different order, different amps, blind or not,
there is clearly NO PATTERN of which amp I prefer.
So this question doesn't dig deep enough into the problem:
"It remains an intriguing question: why do sound amplifiers different, even when their
specifications are similar?"
Conclusion: in 'short term' testing amps of similar class sound different.
For a long run, they all sound the same.
I think this is caused not by amps, but rather by human's hearing system being not perfect,
and craving for a change.
I have over 20 amps right now on my rack and shelves. I rotate them every couple weeks.
They all have very decent parameters, and yet, I can't point one that I would call "the best".
The truth is I can't really tell class A over B amp, quasi vs complementary, etc...
That's of course assuming that they are all "good"amps in general. Not some junk.
I definitely can tell that my Pioneer SX-1000 from 1970 sounds not good 🙂
But all the new ones are, unfortunately, all the same.
As for Circlophone, one thing that puts it apart from others, is total silence in the speaker, when no input signal present.
I think Circlo is the quietest from all my amps (almost all of them using the same PSU).
I have also tested few discrete amplifiers in past but I feel Circlophone is the only amplifier which is dead silent with out input signal and also a very stable amplifier in terms of its parameters.
It perfectly mimic the old advertisement slogan of a motor cycle company's in India "Fill it, Shut it, Forget it".
One of the significant things is that there is no complementary parts... fully symmetrical from start to end. You can build and excellent amplifier from salvaged parts from electronics like computer PSU's. This was the first reason that I decided to build this amp.
I have tried different mosfet's in the MOSFET version and found no change in sound quality. Its sound quality is very much similar to the single supply Philips 40W amplifier of 70's quite similar to vaccum tube amplifier.
The best part of this amplifier is its stability. With CCS, the parameters almost remains same even with variation in supply voltage.
Some one can try to house the entire circuit in a modular form with SMD components some thing like STK modules manufactured by Sanyo japan leaving only out put transistors to be mounted externally.
After trying Circlophone I have not tried any other amplifier circuit.
I again thank Mr Elvee for the wonderful schematic.
While waiting for a PCB to arrive, I was trying to simulate op-amp based circlophone with cheap output devices, namely QTIP3055.
Rails at 25V, and final results are outstanding - same performance as with bigger MJL transistors (Thd, FFT, perfect squares).
Changes to the schematic were minimal: Zener resistors, and compensations caps: C4, C12, C2.
I guess that's because QTIP3055s are not really that much different than MJLs.
Bigger challenge would be try it with faster outputs, but I guess there is no need.
Even with slow 3055 outputs, the amp is still very fast (estimated Slew Rate at 78 V/us)...
Even if in reality it might be 50V/us, it's still more than enough.
Rails at 25V, and final results are outstanding - same performance as with bigger MJL transistors (Thd, FFT, perfect squares).
Changes to the schematic were minimal: Zener resistors, and compensations caps: C4, C12, C2.
I guess that's because QTIP3055s are not really that much different than MJLs.
Bigger challenge would be try it with faster outputs, but I guess there is no need.
Even with slow 3055 outputs, the amp is still very fast (estimated Slew Rate at 78 V/us)...
Even if in reality it might be 50V/us, it's still more than enough.
Attachments
See post #2476
https://www.diyaudio.com/community/threads/my-little-cheap-circlophone-c.189599/post-7730561
After it's built with LT1056, I'll test TL071 (should work for sure), and with other typical suspects (LT1056, LF356, TLE2071, TLE2081, LT1357, OPA134, LT1360)
I strongly suspect, that with current schematic/compensations AS IS, only LT1056, TL071 and TLE2071 will work without changing anything.
Any chance for testing some opamp models that I linked at post#2474 ? Especially Jellybean types like NE5534. It would be very interesting to see a super slew rate opamp in sim such as LM6171 at the link.
I think the best would be to sim it first.
If I had BJT op-amps in my stash, I would try them, but I don't have any. I was always using JFET opamps.
As for "super slew rate opamps" in audio amps, from my experience (trying E.g. LT1360 with 800v/us or LT1357) in my previous amps,
it's almost impossible (at least for me) to make them stable.
Not worth the trouble. <joke>20V/us should be enough for everybody 🙂 </joke>
The fastest amp I built was 140V/us, and it barely made it to be stable/usable.
So I would say 100V/us AND very stable - is as good as it gets for me.
If I had BJT op-amps in my stash, I would try them, but I don't have any. I was always using JFET opamps.
As for "super slew rate opamps" in audio amps, from my experience (trying E.g. LT1360 with 800v/us or LT1357) in my previous amps,
it's almost impossible (at least for me) to make them stable.
Not worth the trouble. <joke>20V/us should be enough for everybody 🙂 </joke>
The fastest amp I built was 140V/us, and it barely made it to be stable/usable.
So I would say 100V/us AND very stable - is as good as it gets for me.
Terra, here is ASC file with NE5532 op-amp, ready to be run.
The feedback caps need to be adjusted, if you have time - play with. All models are included, just click 'RUN' 🙂
The feedback caps need to be adjusted, if you have time - play with. All models are included, just click 'RUN' 🙂
Got the PCBs today, and will start populate them, but I'm afraid that real testing will happen in October, as I'm leaving for 2 weeks vacations...