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Old 20th May 2003, 09:59 PM   #21
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Default the views express here are solely that of the auther and in no way reflect....

Quote:
Not that many people here understand OTL amps which is probably why you mainly depend on me and quite likely SY... Sorry if I left someone out.
Well my dad actually, and so far the only thing I've asked him is what he thinks about the DC/AC thing for the screen resistors. And what he thinks of the extra inductance. And both of those questions were asked since my last post.

I'm kinda surprised that SY hasn't expressed horror that anyone would think that my opinions are actually his from behind the scenes.

As for you, so far, all I've learned from you is, well, I'm sure I'll think of something.

No, I've relied on my own ability to read, and to figure out something from concepts. Sorry, I'm nobody's puppet.

Actually those resistors are on the cathodes for fault protection, and they have the added benefit of equalizing the current through the tubes during high power operation. However, if we assume for a moment that they are only for measurement, and in that case we're just trying to balance the tubes, what effect would a little stray ultrasonic oscillation have on the measurements? Regardless of the intended purpose, if you don't want any stray inductance on the screen, you most certainly don't want it on the cathode do you?

Quote:
just keep in mind that there's is nothing
mysterious about OTLs other than you always have an innate imbalance between the anode and cathode followers...
Ah yes, and now the moment we've all been waiting for...Ladies and gents, the patent.

So you end up with degenerative feedback in the upper tubes caused by the upper tube being in phase with and referenced to the output while the lower tubes are referenced to ground. So somehow you need to compensate for this lost voltage on the upper tubes. Futterman had a pretty good idea, so good in fact Bruce said in his GA article it was in essence 'perfect'. Drive the tubes with a phase splitter with the cathode referenced to the output. Not bad. But (there's always a 'but' somewhere) B.R. later discovered that this configuraton ends up causing unequal forward voltage gain throughout the whole system because you're adding correction to the lower tubes as well, and they don't need it.(I'm still working on how that happens, but I will figure it out) What you can see on a scope, is that a negative DC offset appears, proportional to the output. This in turn pulls the woofer back, and limits cone motion, reducing bass. (By how much I haven't the foggiest, but I'd love to know) So, why not just correct for the upper tubes and leave the lower ones alone. How? Add a buffer stage and just have the upper buffer bootstrapped to the output (using the 3 zeners that don't have anything to do with the patent) providing Futterman style correction and the lower one untouched for symmetry. Ta da! Not a bad way to tie your shoes huh? But if you don't like those noisy zeners you could do the same thing with a low noise series pass regulator.

Quote:
Seems you're vulnerable to the easy way out kind of explanations for most of that makes sense to me...and I do involve in comparitive listening...
How much of that 'comparitive listening' is double blind? Everyone is vulnerable to the easy way out, hey I'm not the one proposing a global ban on WW resistors in output stages because of what they might do. I'm trying to find out if they have a real impact on the circuit. I am however, very vulnerable to common sense arguments in the face of lunacy.

Quote:
As a matter of fact I use tri-wire....what about it?
It's just that I had some Cardas Biwire cables for sale but I guess not huh?

I've got lot's to learn yet,

Chris
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Old 20th May 2003, 10:22 PM   #22
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I'm beyond mere human emotions like "horror."

Some inductance in resistors is not always a bad thing- sometimes, it can even help bandwidth. It's a trick to be done with caution and eyes wide open, however. Really, what you need to do is see how much inductance you're talking about and how the inductive reactance compares with the resistance. And consider where the part is being used in the circuit.

Have you tried to actually measure the inductances in question?
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Old 20th May 2003, 11:03 PM   #23
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Default RE:TUBE FAILURE.

Hi,

Quote:
Well my dad actually, and so far the only thing I've asked him is what he thinks about the DC/AC thing for the screen resistors. And what he thinks of the extra inductance. And both of those questions were asked since my last post.
If it were me I'd ask my dad all I had in mind...
Now, for the record I'll restate it once more: those inductive wirewounds are not going to prevent the amp from working one way or the other.
Ideally though they should not be inductive, certainly not in that position.

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I'm kinda surprised that SY hasn't expressed horror that anyone would think that my opinions are actually his from behind the scenes.
Why would I have thought that?

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As for you, so far, all I've learned from you is, well, I'm sure I'll think of something.
You will, eventually.
I'm glad you're not my kid though...

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Actually those resistors are on the cathodes for fault protection, and they have the added benefit of equalizing the current through the tubes during high power operation.
Which is what I told you anyway.

Quote:
However, if we assume for a moment that they are only for measurement, and in that case we're just trying to balance the tubes, what effect would a little stray ultrasonic oscillation have on the measurements? Regardless of the intended purpose, if you don't want any stray inductance on the screen, you most certainly don't want it on the cathode do you?
You seem to be jumping from grid to cathode...the cathode resistors are not just for measurement. And you're correct in assuming I try to avoid stray inductance...anywhere...amongst other things.
You don't mind a little oscillation?
Phew, since when is that O.K.?


Quote:
Ah yes, and now the moment we've all been waiting for...Ladies and gents, the patent.
Patent? If any than it should Julius Futterman's.
You rely on reading for yourself? Please do us all a favour and learn how to read.
Come'on...

Quote:
B.R. later discovered that this configuraton ends up causing unequal forward voltage gain throughout the whole system because you're adding correction to the lower tubes as well, and they don't need it.(I'm still working on how that happens, but I will figure it out)
B.R.? No way, he did discover that...even J.F. knew that already or his amps wouldn't have worked...he only solved that problem in a different way.
And there are other ways of solving it too...

But fine, you do understand what the patent is about and I notice you learn fast.
Good on you...

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It's just that I had some Cardas Biwire cables for sale but I guess not huh?
Nothing against them but I already designed a successful range of cables.
Thanks for offering though.

Cheers,
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Old 21st May 2003, 12:56 AM   #24
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Default and a liar to boot

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B.R.? No way, he did discover that...even J.F. knew that already or his amps wouldn't have worked...he only solved that problem in a different way. And there are other ways of solving it too...
He most certainly did, he just didn't discover it first.

Actually, as I see it, the Futterman design creates the forward voltage gain imbalance. The B.R. design eliminates the degenerative feedback problem without creating the voltage gain problem in the first place.

Quote:
Nothing against them but I already designed a successful range of cables.
Cool, how did they fair against the competition when you took them into the anechoic chamber?

Hey SY, now we're talking, I'm not sure if you meant me or Frank, but I have a co-worker checking out a 150 ohm WW I had in my tool box on an inductance meter he has burried in his basement. While you're here, care to weigh in on the DC/AC thing?

Chris,
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Old 22nd May 2003, 12:44 AM   #25
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Default LIARS?

Hi,

Quote:
Actually, as I see it, the Futterman design creates the forward voltage gain imbalance.
Hell no, the problem is there from the word go.Futterman didn't 'create it and BR didn't eleminate it.

BTW, on this forum people don't call other people liars, not for any reason...I see such action as a last resort and a sure sign of a lack of education.

This is the best audioforum I know of and I want to keep it that way, if you want help or a simple explanation than just ask.
I'm beyond kindergarten but I realise 99% of the plebs isn't, so beware.

All the best,
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Old 22nd May 2003, 12:20 PM   #26
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Default Huh?

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BTW, on this forum people don't call other people liars, not for any reason...I see such action as a last resort and a sure sign of a lack of education.
Your joking right? You called me a liar!

Quote:
If it were me I'd ask my dad all I had in mind...
Holy cow, that reference in the subject line was meant to be a coy reference to what you have called me so far,

1 Wise guy
2 undeducated (several times)
3 stupid
4 dishonest (the reference that I was getting a stream of info from SY or someone else)
5 Niave (things are much more complicated than my feeble little brain can comprehend)
6 Iliterate
The level of condesention you have shown through this entire thread has been very tough to ignore. I'm not completely above name calling myself I did say you were arrogant. I try like hell to ignore that stuff because it just detracts from the core of the discussion, but for the love of god, how can you come here and give me a lecture on name calliing? And I'm not the only one, every time anyone asks you to back up something you say, your usual response is a personal attack and not answer the question.

I have learned a ton of stuff because of this discussion, lots because of you, but nothing from you. The closest you ever came to explaining anything was the back EMF comment. And I'm not sure that back EMF qualifies as an explanation, as those resistors are intended to reduce the fault current in the event a tube arcs over. I'm not sure how that equates to back EMF, but I'm willing to learn.

So, now, I was going to put my idea out there on how the forward voltage gain happens, in the Futterman and not the B.R, and yes in hindsight it happens in other non-futterman OTL's. I was thinking it over in the car Tue night, and I realized I had been looking at 3 designs and not 2. I still maintain that the B.R. patent compensates for the degenerative feedback without creating the forward voltage gain imbalance, but it's your turn to refute that with a real explanation. I don't mind being wrong, I like being right, but I learn alot more when I'm proven wrong. So here's your chance, instead of me putting my explanation out there for you to say 'no, sorry that's wrong.' Why don't we switch rolls for once. And while you're at it, why don't you explain how the intent of the patent could be accomplished without those zeners (or a 3 terminal regulator)

Chris
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Old 22nd May 2003, 10:02 PM   #27
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Default RE:Failure.

Hi,

Christopher,

Read AR as many times as you deem necessary...if it doesn't help you understand OTL designs it would at least help your reading capabilities.

And before you go into a wild accusation fute again, read and read carefully and you will realise that all of this is of your own doing.
Yes, I can prove that easily...

Cheers,
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Old 23rd May 2003, 01:47 PM   #28
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Default Fute? Is that a word? maybe I am illiterate.

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You're being stubborn or downright stupid?
:stupid, stubborn
Quote:
Go educate yourself before jumping to conclusions. Learn how to read replies, it may help.
:Illiterate, uneducated
Quote:
I'm glad you're not my kid though...
:the pinacle of condescension
Quote:
Really a novice to all things electronic or what?
:uneducated
Quote:
Seems you're vulnerable to the easy way out kind of explanations
:lazy, naive, and even a little simple
Quote:
Not that many people here understand OTL amps which is probably why you mainly depend on me and quite likely SY...Sorry if I left someone out.
: you really outdid yourself with this one, you managed to accuse me of dishonesty and tell me I was too stupid to be carrying this discussion without outside help. One of your best I must say.
Quote:
Please do us all a favour and learn how to read.
:Illiterate (again)
Quote:
if it doesn't help you understand OTL designs it would at least help your reading capabilities.
:Illiterate (recurring theme now)
Quote:
P.S. And I always had the impression Canadians were open minded, hospitable people...
:closed minded, inhospitable
Quote:
If it were me I'd ask my dad all I had in mind...
:and a liar to boot

Wild accusation fute? Hardly.

I haven't shown you alot of respect I'll admit, and perhaps I should have shown a little more. I'll try harder. But I want to make something clear. I have no time for qualifications and experience as a justification for why anyone should be taken as an expert. There are far too many false experts out there based on the above and all they are capable of is disseminating bad information. To be an expert, you have to really know a topic. Any professional will look like an expert to a layman. It's their peers they have to prove themselves to to be a real expert. In this case, like it or not, you are not dealing with a layman. Neither am I an expert. I deal with my world through analysis, that's the way I am. I have to troubleshoot and repair systems on virtually all of the various types of airliners flying today. I can't possibly know everthing about every system so when something isn't simple, I have to read, figure out how the system works, and then, based on that, figure out what could cause the anomally. I am very good at this. Eight months ago I was struggling to understand how a phase splitter worked. I know very little about tube circuitry so when I think I've got something figured out, I may have missed something obvious. Eventually that won't be true, but that takes time.

The time has come to for you prove you're an expert Frank. I think I have figured out the forward voltage gain imbalance mechanism, and I don't think it occurs in the B.R. patent design. If that is not the case, and you can explain it, then I learn something more about this circuit I did not know, and you prove to me, and all who are following this thread that you are, in the realm of the OTL amplifier, an expert.

Sorry if this offends you, that is not my intention.

Chris
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Old 23rd May 2003, 10:34 PM   #29
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Default FEELING BETTER?

Hi,

So after you summed up whatever it was you insist on misreading, how can I help you?

Quote:
The time has come to for you prove you're an expert Frank. I think I have figured out the forward voltage gain imbalance mechanism, and I don't think it occurs in the B.R. patent design. If that is not the case, and you can explain it, then I learn something more about this circuit I did not know, and you prove to me, and all who are following this thread that you are, in the realm of the OTL amplifier, an expert.
Yes, Chris, and I'll be the last to say I'm the expert here but...

The imbalance originates from the outputstage topology used, all the patents in the world aren't going to change that and as stated before I know of more elegant ways to deal with it.

Does the BR design deal with it? Yes it does but not by changing the outputstage but by adding a bufferstage referenced to the FB loop.
Clever enough, but there are different ways as I stated in previous posts.

So, if you ask me if the zener diodes are part of the patent : I'd say no, there only there because that stage is in the NFB loop and the B+ of that stage is shared with the previous one.

Quote:
The time has come to for you prove you're an expert Frank. I think I have figured out the forward voltage gain imbalance mechanism, and I don't think it occurs in the B.R. patent design. If that is not the case, and you can explain it, then I learn something more about this circuit I did not know, and you prove to me, and all who are following this thread that you are, in the realm of the OTL amplifier, an expert.
I don't think I have to prove anything to anyone anymore, Chris...
The imbalance is present in the RB design as much as it is in my own, Futtermans' or anyone else using the same topology at the output...which is exactly why Mr.Rosenblitt patented his solution.

And, yes Julius Futterman didn't understand all of what was going on...
And..I hope Mr.BR says thank you to John Broskie as well, for it is he who understands 101% of how the current flows.

Am I an expert now?

No Chris, I don't even aspire to that status...I only try to help.

Cheers,
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Old 26th May 2003, 12:10 PM   #30
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Default yes, much better thankyou

Now we're talking, I can see a real and very useful discussion evolving for both of us, let's just forget about the history on this thread and discuss the circuit. I've been dying to get back to my computer since I read your post but this is my first chance since, and I don't have a lot of time, so I'll address the easy bit first, and try to get to the imbalance this afternoon if I can get the time.

The job of the zeners is to of course provide a reference for the upper buffer, but the plate voltage has to be referenced to the output for this thing to work properly. I tried to find a way to do that without either the zeners or some kind of regulator but you always end up referencing to ground. (well I do at least) also if it was just because it share's the B+ with the previous stage, then the lower buffer would require the same treatment wouldn't it?

I don't have time to layout a full analysis of the voltage imbalance but I'll at least put this out for now. I think we're talking about two different things here. Granted, as you said previously there are no complimentary pairs in tubes, you will always have this imbalance with the upper and lower tubes, I think that both the Futterman and the B.R. design's deal with that so well, you can say it doesn't exist. But there are new imbalances generated in the Futterman that are not present in the B.R. because the Futterman applies correction to the phase splitter which is common to the lower tubes as well, and they don't need it.

That's all for now, I'll try to get back later this afternoon.

Chris
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