Thank you, Jan. A colleague of mine has a video, with sine wave switched on and off and residual measured, to show how bias is settling to a final value.
That's indeed what the title suggests (Where TMC really shines), but that was not the primary objective of that design. An equally applicable title could be: "How to get rid of a CMCL" or "How to tame a push-pull VAS". Anyhow, the primary ojective was: how to make a symmetrical front-end simpler wihout sacrificing the performance.
First, which standard design with CMCL? 🙄 Second, please read my chapter "What we have gained" and you will understand that the SuperTIS will outperform any other front-end in (almost) every aspect.
Hmm.. good news 🙂 and bad news.🙁
That's right, the bandwidth is much higher (10x?), but it doesn't rely on positive FB (like HEC), instead, just ordinary (negative) FB. Actually, it's a kind of reverse CFA configuration (sorry for the misnomer): inverting input tied to the base and non-inverting input tied to the emmiter. On the other hand, frequency compensation is the same as in Bob Cordell's HEC amp (i.e. feed-through) opposed to shunt compensation (less optimal!) in the LT1166.
Sure. I hope in collaboration with Paul.
Understood.
Of course. I wouldn't expect anything else. 😀
Cheers, E.
Otherwise said, of theoretical interest only. That's my point.
Regarding the TMC vs. TPC, give me a Blameless with an optimized TMC compensation and I'll give you a TPC version with the same loop gain and phase margin, within a very few %. Or the other way around. The fact that TMC can, in particular topologies (different from a Blameless) perform better doesn't prove that "TMC is better", I'm sure there are topologies where "TPC is better". From somebody that claims it understands the feedback theory, I would expect to think in terms of maximum feedback, rather than searching for odd corner cases that ultimately do not prove anything.
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I agree Edmond, the 'thermal' way doesn't get that far. In my tests I went from heaksink-mounted TO-3 to 'air-mounted' TO-247 and the difference is very small - in each case you see the thermal delay from dissipation even to the diode on the ThermalTrak devices. Not sure I understand the exact mechanism though.
OTOH, with a few % transient shift in bias, should we worry anyway?
Jan
Absolutely true, but there are at least two more layers of complication: the bootstrapped power rails, and the error-correction output stage.
Please note that the Blameless configuration has three stages; it is the Lin that has two.
True enough, but I think this is already proven by the Blameless amplifier.
Again, anyone know what exactly happened to Halcro?
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Now that I've seen the updated circuit, I have to say wow, there are quite a few parts. More things to go wrong. It's always nice to have a ridiculously low amount of distortion, and a great theoretical phase margin, but... past a certain point, once the distortion is below 0.1%, reliability, ability to blow up elegantly without taking the speakers with them, and phase margin are what I look for in a power amp. Also how it performs when over driven.
A sound company I once worked for (McCune in SF) favored the old Hafler DH220 poweramps because of how elegantly they blew up. They never damaged the speakers, and very few parts got damaged. Reliability was perhaps their top priority. I've still got 3 of those in my home systems.
A sound company I once worked for (McCune in SF) favored the old Hafler DH220 poweramps because of how elegantly they blew up. They never damaged the speakers, and very few parts got damaged. Reliability was perhaps their top priority. I've still got 3 of those in my home systems.
I'd be interested to see that circuit.
Surely any amplifier with a decent DC-offset-protect system ought to be able to do this?
Huge amounts. One of the main reasons I'm in the business.
I've recently enjoyed live: CSN, Leonard Cohen, & The Eagles. But maybe I'm giving my age away here.
My mistake. I assumed the rather complex circuit 2-3 pages back was your latest. Apparently it isn't. Sorry.
Back in the early 70's I built a few SWTPC Universal Tiger poweramps, which I thought sounded great until one of them completely evaporated the entire voicecoil of a 4 inch test speaker when it blew up... I've been a bit paranoid ever since. I was testing a preamp that was probably oscillating at a supersonic frequency. In those days my lab consisted of a volt/ohm meter and a few tools. A rich friend had a scope and generator but I only occasionally had access to that.
Back in the early 70's I built a few SWTPC Universal Tiger poweramps, which I thought sounded great until one of them completely evaporated the entire voicecoil of a 4 inch test speaker when it blew up... I've been a bit paranoid ever since. I was testing a preamp that was probably oscillating at a supersonic frequency. In those days my lab consisted of a volt/ohm meter and a few tools. A rich friend had a scope and generator but I only occasionally had access to that.
Forr said:
Of course. I should have written "the same topology for two first stages as the Blameless".
Forr said:
DouglasSelf said:
My thinking was that the HEC output stage having low distortion, traces of non-linearities could emerge from the VAS.
If a single ended VAS was chosen for a design as sophisticated as the Halcro, it means that the linearity of such a stage is adequate and that we can't expect much from more complicated schemes here.
Since Edition 6, I am not sure I will ever try any VAS else than a single ended one.
.
That is awesome Doug, absolutely a requirement for building audio gear, perhaps an even better requirement than proficiency with a probe 🙂.
Forr, never write off anything until you build it, you may just be surprised. Some very legendary amplifiers measure bad but sound ethereal 🙂. There are levels of distortion in instruments that far exceed even a .1% threshold, I may be more of a subjectivist but I also actively play a multitude of instruments Drums, guitar, bass and am subjected to many more that I'm constantly around. At the end of the day I am interested in something that sounds real, acoustic guitars that contain the body, image and harmonics along with spatial cues . Drums that have a proper sounding/feeling leading edge with proper sense of weight on a good recording. That's what I found with CFA, sound so clean you can clearly pick out every nuance in proper relation IMHO to the music and effortless sound at even the loudest volume 🙂.
Colin
which para? - and where is this proved?
you have read the ~half of the last dozen of my posts in this thread which deal with 2-pole compensation and TMC with sims and analysis?
you have read the ~half of the last dozen of my posts in this thread which deal with 2-pole compensation and TMC with sims and analysis?
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The Halcro THD isnt that impressive as figures such as those were already achieved back in 1989. Anone here familiar with Technics SAE series amps. I may be wrong but I think the technics has better figures, Ill try post some figures later.
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