Re: Re: BS
Thanks Andy, these figures are quite close to the 'official' ones!
Cheers, Edmond.
andy_c said:
Thanks Andy, these figures are quite close to the 'official' ones!
Cheers, Edmond.
estuart said:
Yes, its got everything to do with $$$ 🙂. I remember looking up the price of the simulator you're using, and I if I remember correctly it was something like $4500 U.S.? That's big bucks! 🙂
Re: BS
Oh, c'mon. That was the funniest thing I've read in ages. I want some of what Lineup is smoking.
Cheers,
Glen
PS
Bob looks like he needs to go on a diet.
estuart said:lineup, pleaseand
Oh, c'mon. That was the funniest thing I've read in ages. I want some of what Lineup is smoking.
Cheers,
Glen
PS
Bob looks like he needs to go on a diet.
Re: Re: BS
Hi Glen,
This is one of the more accurate things you've posted on this board in months 🙂.
Cheers,
Bob
G.Kleinschmidt said:
Hi Glen,
This is one of the more accurate things you've posted on this board in months 🙂.
Cheers,
Bob
Re: Re: Re: BS
G'day Bob.
I apologise for my cheekiness. However, I’m generally available to debate any inaccuracies allegedly contained in my posts.
Cheers,
Glen
Bob Cordell said:
G'day Bob.
I apologise for my cheekiness. However, I’m generally available to debate any inaccuracies allegedly contained in my posts.
Cheers,
Glen
Bob i'm realy enjoying the PDF on the Mosfet power amp with error correction on your site. Wish it had more drawings and footnotes, realy strugled through the first bit, but it gets easier here from halfway... still got a bit to go...
I realy love the sound of Mosfet amps. The output is non-linear, just like our hearing, lol.
I realy love the sound of Mosfet amps. The output is non-linear, just like our hearing, lol.
Hi John,
Effectively yes, I dabbled a few months ago and could get nowhere with it and gave up.
I downloaded Tina, SIMetrix & Switcher CAD (LTspice).
Effectively yes, I dabbled a few months ago and could get nowhere with it and gave up.
I downloaded Tina, SIMetrix & Switcher CAD (LTspice).
Just curious,
anyone simulated or built the Cordell FET amp, then substituted for the MOSFETs with bipolars and measured and/or listened?
anyone simulated or built the Cordell FET amp, then substituted for the MOSFETs with bipolars and measured and/or listened?
Off topic posts and noise moved. 
We have a rule regarding religion and politics.
http://www.diyaudio.com/forums/announcement.php?s=&announcementid=4&forumid=4
/Hugo - don't make him do this again while drinking his morning coffee.
We have a rule regarding religion and politics.
http://www.diyaudio.com/forums/announcement.php?s=&announcementid=4&forumid=4
/Hugo - don't make him do this again while drinking his morning coffee.
I repeat my Request
🙂
hey 🙂
I am still waiting for something constructive produced by this topic.
Something useful,
anything to, at least,
start working from for average diyAudio members
The conditions to make a good BJT/MOSFET are here:
.... some of the sharpest and finest audio-brains ever lived in the States
and a few above average from Europe/Japan/India, too.
What you say, comrades?
Regards lineup 🙂
...................................................
I repeat this my request.
Reason:
As bob hasnt even go a chance to reply,
before our dear censor did his over kill ?? job
... you can moderate postings or you can cut & kill off posts
... kill off, may even kill off a topic
why post,
when we can not exchange discussion?
we can not argue no more?
isnt this the whole point of an audio board or any other forum?
I am not afraid of The Gun Firing of Words.
A fair and Square Battle 😎
.. there are other kinds of bombs I do not like
At least, me lineup,
Will use Noble Art of SelfDefence.
I hope I can. I am No coward..
.. anyone afraid of other opinions & some good argumenting
should Not Join www.diyAudio.com
🙂
hey 🙂
I am still waiting for something constructive produced by this topic.
Something useful,
anything to, at least,
start working from for average diyAudio members
The conditions to make a good BJT/MOSFET are here:
.... some of the sharpest and finest audio-brains ever lived in the States
and a few above average from Europe/Japan/India, too.
What you say, comrades?
Regards lineup 🙂
...................................................
I repeat this my request.
Reason:
As bob hasnt even go a chance to reply,
before our dear censor did his over kill ?? job
... you can moderate postings or you can cut & kill off posts
... kill off, may even kill off a topic
why post,
when we can not exchange discussion?
we can not argue no more?
isnt this the whole point of an audio board or any other forum?
I am not afraid of The Gun Firing of Words.
A fair and Square Battle 😎
.. there are other kinds of bombs I do not like
At least, me lineup,
Will use Noble Art of SelfDefence.
I hope I can. I am No coward..
.. anyone afraid of other opinions & some good argumenting
should Not Join www.diyAudio.com
myhrrhleine said:
Hi Myhrrhleine,
Generally, it's not a good idea to replace the MOSFETs by BJTs in a design which is optimized for MOSFETs (and, of course vise versa).
Nevertheless, I did a quick simulation with BJTs and, not surprisingly, results were less favorable. Adding also two medium power BJT drivers however, did lower the THD somewhat.
Cheers, Edmond.
Re: I repeat my Request
Hi Lineup,
I apologize for not getting back to you.
The Class-A amplifier that I described briefly was just for puposes of illustration at the time, and was not meant to cover a complete design. Indeed, it was only focused on an aspect of the output stage.
At the time, the point was to illustrate that, although MOSFETs have a much smaller gm than bipolars at a given operating current, when a group of them is operated at a high total operating current typical of a Class A design, that gm disadvantage becomes largely irrelevent.
I must admit that I personally have never designed a Class-A amplifier, so I would certainly not be the best person to start such a project here.
Best,
Bob
lineup said:
Hi Lineup,
I apologize for not getting back to you.
The Class-A amplifier that I described briefly was just for puposes of illustration at the time, and was not meant to cover a complete design. Indeed, it was only focused on an aspect of the output stage.
At the time, the point was to illustrate that, although MOSFETs have a much smaller gm than bipolars at a given operating current, when a group of them is operated at a high total operating current typical of a Class A design, that gm disadvantage becomes largely irrelevent.
I must admit that I personally have never designed a Class-A amplifier, so I would certainly not be the best person to start such a project here.
Best,
Bob
Re: Re: I repeat my Request
Clearly you are as qualified as anyone else, however I appreciate
that it is a bigger challenge to get such performance from a
higher efficiency Class AB stage.
😎
Bob Cordell said:
Clearly you are as qualified as anyone else, however I appreciate
that it is a bigger challenge to get such performance from a
higher efficiency Class AB stage.
😎
estuart said:
Thanks for the info 🙂
Yes, it is not a good idea to substitute one for the other, but it does help with comparisons of the two technologies.
But I'm suggesting in this case a comparison of identical input, driver, and special error correction circuit.
Granted, an appropriate bias adjustment, compensation change, etc. would be in order.
But what I'm curious about is whether the quality of the amp comes from the MOSFETs, or the quality of circuit design, input, Vas, darlington drivers, error correction ckt, etc.
Mr. Cordell designed a very impressive amp!
There is a great deal to be said for the amp, FET output being only one.
myhrrhleine said:
Thanks for your kind words about my amp. You raise some very interesting questions.
My gut feeling is that the EC architecture of my amplifier could be made to work well with high-ft RET bipolars as long as the driver transistors could be operated at a bit higher standing current, deliver the base current needed, and dissipate the consequent power. This might mean having to add another EF stage in the chain, but I'm not sure; I suspect it could be done without resort to that, but its a big maybe.
More importantly, some additional voltage drop from the EC outputs to the BJT output transistor bases would be needed to create the amount of dc operating voltage headroom that currently exists with the vertical MOSFETs whose turn-on voltage is on the order of 3.5 to 4 volts (indeed, this might also be the case if one attempted to substitute lateral MOSFETs as well).
I always thought that vertical MOSFETs and EC were a match made in heaven, since the EC circuit really wants the speed provided by the MOSFETs, while the MOSFETs really want the error correction to mitigate the effects of their smaller transconductance and transconductance droop.
But that doesn't mean that EC can't be used to great advantage with bipolars, for sure. Indeed, the bipolars do not really have a problem with transconductance droop, but rather with gm doubling if they are biased above the Class-AB optimum (or if we use larger emitter resistors for better bias stability). The EC can do a very good job of mitigating the gm doubling, so we would be free to run the bipolars a bit hotter and perhaps in a more thermally-stable situation.
Cheers,
Bob
dimitri said:
Hi Dimitri,
Some old wives are more equal, but W.M. Leach is a little bit less equal.
Cheers, Edmomd.
estuart said:
This topic has been discussed before. While there was not a clear resolution, it appears that Leach and Self have a different definition of Class AB that may have lead to the dispute. It seems that what Self defines as optimum class B, Leach and many others on his side of the pond refer to as Class AB. Therefore, Leach may be correct that gm doubling does not occur in optimum B.