Hi Hugh,
I'm not sure where the differences lie, other than in the models. LTspice gives essentially the same results as my copy of Intusoft. That, plus what I measured back when I could, does lead me to believe I was correct all along.
I'm sure there will be more debate on this. I am not willing to go into the evolution of my design until this is mostly settled. I don't expect what I presented here today to change all minds, but hopefully it will sway the ones on the fence.
Excuse me, I have no say in this
But I really dont understand this debate
I understand this amp has been built and sounds fine
How can you debate if it works or not
Either it works or it doesnt
No point in explaining it to me, because I wouldnt understand
Or have you just moved to questioning why the sims and theory doesnt work
Its a bit confusing
But a pitty if this is a fine amp that was lost in a stupid game
But Im afraid its not the first time
Do I need to say who loose the most
But I really dont understand this debate
I understand this amp has been built and sounds fine
How can you debate if it works or not
Either it works or it doesnt
No point in explaining it to me, because I wouldnt understand
Or have you just moved to questioning why the sims and theory doesnt work
Its a bit confusing
But a pitty if this is a fine amp that was lost in a stupid game
But Im afraid its not the first time
Do I need to say who loose the most
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Steve,
Based on my listening tests with very similar topology amps in Class AB and Class A, it may be that the switching or otherwise has little impact on the sound quality anyway. I actually find the Class A amps to sound slower, less dynamic. Most of the differences can be sheeted home to gm doubling at the crossover rather than the switching per se. I'm not too sure how you eliminate gm doubling without lapsing into Class A.
Sliding bias schemas seem to have their problems, too.
Tinitus,
The amp works fine. That's not the issue. It's whether the outputs turn off at all which is under discussion.
Hugh
Based on my listening tests with very similar topology amps in Class AB and Class A, it may be that the switching or otherwise has little impact on the sound quality anyway. I actually find the Class A amps to sound slower, less dynamic. Most of the differences can be sheeted home to gm doubling at the crossover rather than the switching per se. I'm not too sure how you eliminate gm doubling without lapsing into Class A.
Sliding bias schemas seem to have their problems, too.
Tinitus,
The amp works fine. That's not the issue. It's whether the outputs turn off at all which is under discussion.
Hugh
Interesting, but if it seems to be good to be true, maybe it's something else?
Not meant to criticize, but could you post the biasing volts and currents.
Is it biased in class A/B or maybe A?
stinius
tinitus;
Of course the amp works. I think the debate has been over whether the output transistors turn off or not. Many people have had trouble running a simulation on this circuit. I had problems with that myself at first. Some sim programs don't seem to like this circuit and don't give results.
Of course the amp works. I think the debate has been over whether the output transistors turn off or not. Many people have had trouble running a simulation on this circuit. I had problems with that myself at first. Some sim programs don't seem to like this circuit and don't give results.
In my sim program the outputs are biased at 202.77ma for a total output stage of 55W with 4 pair of outputs.
I am off fro the night now, not avoiding answering questions.
Steve,
Interesting concept.
We played with an amp 30 years ago that also didn't turn off - it was an adaption of the "Blomley" circuit pubished in a Wireless World magazine circa early 70's, and classes as a low standing current pure Class A.
I don't have the article any more, but still remember the concept. It used a fairly conventional front end that drove a pair of complimentary commonbase trasistors that acted as current directional switches - the output triples were biased on in very low AB1 (circa 10mA) and when a given common base tr was conducting, that output triple was powering the load, on the other half cycle, the reverse happened. But no visable crossover distortion, even in the residue of a distortion analyser.
Was the best sounding amplifier we ever had heard in the 70's, and still sounds great today.
Regards, Allen
Interesting concept.
We played with an amp 30 years ago that also didn't turn off - it was an adaption of the "Blomley" circuit pubished in a Wireless World magazine circa early 70's, and classes as a low standing current pure Class A.
I don't have the article any more, but still remember the concept. It used a fairly conventional front end that drove a pair of complimentary commonbase trasistors that acted as current directional switches - the output triples were biased on in very low AB1 (circa 10mA) and when a given common base tr was conducting, that output triple was powering the load, on the other half cycle, the reverse happened. But no visable crossover distortion, even in the residue of a distortion analyser.
Was the best sounding amplifier we ever had heard in the 70's, and still sounds great today.
Regards, Allen
Ah, sorry, stupid me, I understand
Its about output "biasing", whether theres switching or not
John Broskie is writing a lot about class-AC right now
Might that be related ?
Hugh, you mentioned your concerns with classA
Funny, the few supposedly classA amps I have built have always sounded better running with lower bias
But I always thought it was more related to "poor" design, or more correct a design not fit fore classA, rather than it was related to classA in general
That said, I always let my ears decide the best bias point
But seems to allign well with stable DC as well
Not sure how thats connected
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Not as far as I recall.
First, it was challanged that the outputs not switching off has any relevance for the crossover distortions. It does not.
Secondly, it was challanged that the Krill output stage will do anywhere significantly better (that is, to justify the extra complexity) compared to a EF triple (like the Locanthi), biased near the "Bernie Oliver" point.
Third, the posted performance (of 50ppm @ Ic=25mA, if memory serves) was challenged.
Syn08,
I think it WAS challenged if the outputs switched or not. That was the principle part of the challenge, in fact.
You say it does not matter. You may be right. Would you mind elucidating your reasons?
Any comparison with an EF triple would have required back to back testing. As I recall, no one had both amps and so the question was academic. Of itself, the question makes no factual statement, of course.
The distortion figure of 50ppm is certainly low, but wasn't it simply a simulation figure?
I think it WAS challenged if the outputs switched or not. That was the principle part of the challenge, in fact.
You say it does not matter. You may be right. Would you mind elucidating your reasons?
Any comparison with an EF triple would have required back to back testing. As I recall, no one had both amps and so the question was academic. Of itself, the question makes no factual statement, of course.
The distortion figure of 50ppm is certainly low, but wasn't it simply a simulation figure?
http://www.diyaudio.com/forums/solid-state/151295-krill-next-generation-4.html#post1946308, I couldn't put it better.
For the rest, at this point, we are talking simulations only. That's why Steve posted the models, to align as much as possible the results from various simulators.
I challenged the "no device turn-off" claim earlier in this thread, and posted a simulation that anyone with the free LTspice could run. It showed currents in the nominally "off" device on the order of microamps - leakage currents and leftovers of stored charge. I do agree though, that whether or not they do turn off is pretty much irrelevant to the distortion performance, just as Scott said. Steve's posted simulation results showed a small current in the nominally "off" transistor also, but it was larger than the currents in the simulation I posted, maybe a few mA?
When I asked Steve to post the simulation files, he did so after a time. But when I asked him for specifics, he stated it was for a circuit that was different from the one he posted simulation graphs from, and that the original one for which he posted graphs was no longer available. The simulation file he posted was a netlist, which requires a time-consuming process to get back to a schematic from which an equivalent LTspice simulation could be created. So I asked him to post a schematic annotated with node names to help expedite this, hoping to then have him re-run and post the simulation results for this second circuit to try to correlate results. He then posted schematics and a netlist for a third circuit, which was a complete amplifier, not just the output stage whose behavior was in question. Having the extra front end circuitry of course makes the translation from netlist to LTspice simulation files much more time-consuming, in addition to their behavior being completely irrelevant to the issue at hand. Also, the output stage of this schematic was different from the first two simulations Steve posted. Further, the schematics of this third circuit were chopped up into pieces in which the irrelevant part (the input stage) was intact, but some of the relevant parts (parts of the output stage) missing. Portions of the output stage of this schematic was just garbled nonsense that one would have to be literally blind to not notice a problem.
At that point, I realized that Steve could, and likely would, continue this cat and mouse game indefinitely. So I decided to not waste any further time on it.
First, I don't recall stating that the outputs not switching off has any relevance for the crossover distortions. I did claim that the outputs were conducting through out the entire cycle of the wave form.
Secondly, I don't think using six parts in the bias circuit makes the output stage extra complex as opposed to 8 as in the D. Self amp. I did not claim the Krill did better than many other designs. I simply mentioned what I had measured on some of the amps I built.
Third, yes it was challenged. Since I never posted a schematic of that amp and never claimed it to be biased at 25ma, that challenge, as well as the conclusions drawn, is based on incomplete or incorrect information.
I,m not sure where that link was supposed to point.
Yes, that is why I posted my models and the schematic of the output stage.
I don't recall saying the original one was no longer available. "Threw every thing out" was simply a figure of speech.
You have had the information for 28 days now. I didn't realize I was playing a cat and mouse game. Would you care to address this question?
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Jeez, it's on again......
More recriminations, more bile...... why not forget about it. Build the amp, listen to it, measure it, objectively report the results, refrain from absurd technical one upmanship.
In a world racked by poverty, war and disease it's not that important.
Still think it's a clever system, Steve, doffs me cap.
More recriminations, more bile...... why not forget about it. Build the amp, listen to it, measure it, objectively report the results, refrain from absurd technical one upmanship.
In a world racked by poverty, war and disease it's not that important.
Still think it's a clever system, Steve, doffs me cap.
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