the views express here are solely that of the auther and in no way reflect....
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?
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.
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.
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
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?
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.
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.
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
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?
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?
RE:TUBE FAILURE.
Hi,
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.
Why would I have thought that?
You will, eventually.
I'm glad you're not my kid though...
Which is what I told you anyway.
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.?
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...
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...
Nothing against them but I already designed a successful range of cables.
Thanks for offering though.
Cheers,
Hi,
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.
Why would I have thought that?
You will, eventually.
I'm glad you're not my kid though...
Which is what I told you anyway.
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.?
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...
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...
Nothing against them but I already designed a successful range of cables.
Thanks for offering though.
Cheers,
and a liar to boot
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.
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,
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.
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,
LIARS?
Hi,
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,
Hi,
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,
Huh?
Your joking right? You called me a liar!
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
Your joking right? You called me a liar!
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
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,
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,
Fute? Is that a word? maybe I am illiterate.
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
:stupid, stubborn
:Illiterate, uneducated
:the pinacle of condescension
:uneducated
:lazy, naive, and even a little simple
: 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.
:Illiterate (again)
:Illiterate (recurring theme now)
:closed minded, inhospitable
: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
FEELING BETTER?
Hi,
So after you summed up whatever it was you insist on misreading, how can I help you?
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.
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,
Hi,
So after you summed up whatever it was you insist on misreading, how can I help you?
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.
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,
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
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
Hi,
Not necessarily since they operate differently.
If you look at the bottom buffer on the diagram you'll notice two fundamental differences:
The bottom one runs at full B+ and it has the cathode directly referenced to ground.
The top one however is far more complicated to figure out and the easiest way to understand (for me at least) is to look at the current flow as explained in the patent application.
I tell you upfront that I'm not quite sure what it is those zener do in that particular position...
I can only assume they're necessary because of the global NFB loop.
I get the feeling you are looking at the amps as a whole whereas I only meant to point to the fact that the outputstage, by it's very nature, is unbalanced.
Futtermans' solution to the problem is problematic although an amazingly simple idea at first sight.
B.R. solution is by far the better one since the bottom halve of the outputstage is not affected.
Cheers,
Not necessarily since they operate differently.
If you look at the bottom buffer on the diagram you'll notice two fundamental differences:
The bottom one runs at full B+ and it has the cathode directly referenced to ground.
The top one however is far more complicated to figure out and the easiest way to understand (for me at least) is to look at the current flow as explained in the patent application.
I tell you upfront that I'm not quite sure what it is those zener do in that particular position...
I can only assume they're necessary because of the global NFB loop.
I get the feeling you are looking at the amps as a whole whereas I only meant to point to the fact that the outputstage, by it's very nature, is unbalanced.
Futtermans' solution to the problem is problematic although an amazingly simple idea at first sight.
B.R. solution is by far the better one since the bottom halve of the outputstage is not affected.
Cheers,
Yes! Finally I think we are in total agreement.
Here's basically what I think is going on. The zener's provide a 450V envelope for the upper buffer to operate in. With the cathode referenced to the audio output, and the zener's tying the plate to the audio output as well, the setup provides a floating ground for the buffer. So as the audio output rises, all voltages associated with the upper buffer rise with it. Thus the output on the cathode with respect to ground is the input on the grid plus the audio output. The degenerative feedback is completely compensated for. The inspiration is Futterman, but the implementation is completely different. The Futterman concept relys on the fact that by tying the cathode to the output, the plate of the phase splitter goes up corresponding to the audio output, but the cathode is unaffected because it is a cathode follower and cannot give you more than .9 of it's input. The degenerative feedback is compensated for but by doing so a bunch of forward voltage gain get's eaten up by the cathode follower action of the phase splitter.
Whew! You have no idea how long it took me to get my head around this. And I'm still not sure I've got what's going on in the Futterman 100% right.
The nifty thing is, now you have two cathode followers driving the upper and lower tubes, with identical input and output impedances, everything is completely balanced. There's still one thing that's bugging me though. I think there is still a bit of voltage gain imbalance because the plate of the phase splitter is providing the DC bias for the upper buffer and it is not floating with the output. So in this respect, the B.R. design relys on the cathode follower action to compensate the way it does in the Futterman.
The only solution I can see for this is to provide separate bias' for the buffers and then AC couple it. Now, however you have added chances of instability, not to mention another capacitor in the signal path, and I don't know that the problem is all that bad anyway. Or for that matter if it even is a problem.
So that's my take, what do ya think?
Cheers,
Chris
CONGRATS.
Hi,
Very well...so my assumption of you being a smart person has paid off.
Sorry, couldn't resist.
We have been for a while already...guess my ego was standing in the way.
I think I'll have to print out some of the diagrams to study...and read the last couple of pages the A.R. book.
The actual effect of the NFB loop is notoriously hard to follow for we have to think in both D.C. and A.C. terms... not always simple.
Your're good, very good even.
When we look at it at the output (LS) yes....but there's a but.
Although B.R. attributes a snubber role in case of a fault for the shunt series R/C network at the output, this is actually only partly true.
It also performs the role of evening out the impedance of the L.S. as seen by the amp.
Not perfectly so, but stil better than nothing at all...
BTW. , once you have your ESLs you can leave this out or optimize for the xformer of the ELS if needed.
This is extremely important in view of the fact that hardly ( if any at all) speaker has a constant impedance with regard to frequency.
Usually measured as 8 Ohm at 1KHz for instance, this impedance will change with frequency.(Just stating the obvious.)
Do you see what that would do to our frequency response if we left that network out?
And how the global NFB would affected too?
It is a problem in theory, in practice however I feel the FB loop will act very fast to compensate for this...better than having an other cap in the signal path and create all kinds of other probs.
Now, if your interested in other ways of tackling this SEPP/OTL imbalance, I'm happy to go through it together with you...or for instance discuss the corners cut in the B.R. design etc.
Be my guest, but be forewarned that I believe in the influence of so called passive components, wires and a raft of other smaller details...such as PSUs.
Cheers and enjoy your amp,
Hi,
Very well...so my assumption of you being a smart person has paid off.
Sorry, couldn't resist.
We have been for a while already...guess my ego was standing in the way.
I think I'll have to print out some of the diagrams to study...and read the last couple of pages the A.R. book.
The actual effect of the NFB loop is notoriously hard to follow for we have to think in both D.C. and A.C. terms... not always simple.
Your're good, very good even.
When we look at it at the output (LS) yes....but there's a but.
Although B.R. attributes a snubber role in case of a fault for the shunt series R/C network at the output, this is actually only partly true.
It also performs the role of evening out the impedance of the L.S. as seen by the amp.
Not perfectly so, but stil better than nothing at all...
BTW. , once you have your ESLs you can leave this out or optimize for the xformer of the ELS if needed.
This is extremely important in view of the fact that hardly ( if any at all) speaker has a constant impedance with regard to frequency.
Usually measured as 8 Ohm at 1KHz for instance, this impedance will change with frequency.(Just stating the obvious.)
Do you see what that would do to our frequency response if we left that network out?
And how the global NFB would affected too?
It is a problem in theory, in practice however I feel the FB loop will act very fast to compensate for this...better than having an other cap in the signal path and create all kinds of other probs.
Now, if your interested in other ways of tackling this SEPP/OTL imbalance, I'm happy to go through it together with you...or for instance discuss the corners cut in the B.R. design etc.
Be my guest, but be forewarned that I believe in the influence of so called passive components, wires and a raft of other smaller details...such as PSUs.
Cheers and enjoy your amp,
I think he says that in the overview somewhere but I'd have to go back and check. I do remember him saying something about keeping the amp stable into high inductance loads. I've just started reading up on compensation and stablization so it will be a while before I could state anything for certain on how that affects anything in the amp let alone the global NFB, but I will. Right now I've relaxed my reading a bit, I almost blew out a cerebral cortex figuring out the Futterman vs Rozenblit deal.
As far as taking it out altogether if driving an ESL, I thought about that when you mentioned it way back, I may install a switch for dynamic/ESL, but that won't be for a while. My audio budget is a long way from ESL's right now.
Which reminds me, Positron (if that is in fact your real name[/quote], careful if your trying to figure out the amp by what's on those patent drawings. Figure 1 is prior art, and is neither the Futterman nor B.R. In the body of the text of the patent he uses it to explain his advantages over previous art. I'm not sure why he chose it and not the Futterman. Do you know who's design that one is Frank? I'd like to see a real schematic of it. Perhaps it's on the same page further up, I'll check later, I'm wondering if that was the way it was done prior to Futterman.
Right now, I have to go defend my honor on the DBLT thread.
Cheers
Chris
Hi Chris,
Since the sun was shining this afternoon I decided to give it a little well deserved rest, took the A.R. copies to the park an read it through.
I must say B.R. is even more down to earth than I'd imagined.
He seems to very well aware as to the where and how things matter most.
Not a criticism, just an observation.
Were it for my own use, I'd approach the idea differently, but that's just my personality talking.
That "Prior Art" mention in his patent application had me fooled for a while too.
Reading that, I commented to you " no not B.R. but Futterman has this patented, if you recall that unfortunate passage.
Really confusing, I wish they'd left that out or tagged it differently.
Anyway, in the book the whole idea is explained from A-Z in his blunt style ( reminds me of how I come across at times ) and I think you see the picture already so I don't feel any need to dwell on that.
More interestingly though, at least to yours truely, is that the idea can be easily adapted to non-OTL SEPP amps that are OPT coupled, especially when a PP OPT is used, but...I divert.
Yep, you could.
If you look at older OTL designs that were developped for 16 Ohm loads and so on you'd often encounter different compensation networks for different loads.
In my own system none is present, since every driver, bar my ribbon tweeter is impedance corrected right at the driver terminals.
By pure pot luck I pushed the WWW button on Positrons' post earlier today and found an old faithful from the days of TAA, SP and GA... more importantly it provides a link that actually shows you how these networks influence the speaker behaviour in a grapical view.
Ineresting stuff, thanks Positron.
I hope that answers your concern.
There's little honour to be found in that battlefield, I'm afraid.
Cheers,
Since the sun was shining this afternoon I decided to give it a little well deserved rest, took the A.R. copies to the park an read it through.
I must say B.R. is even more down to earth than I'd imagined.
He seems to very well aware as to the where and how things matter most.
Not a criticism, just an observation.
Were it for my own use, I'd approach the idea differently, but that's just my personality talking.
That "Prior Art" mention in his patent application had me fooled for a while too.
Reading that, I commented to you " no not B.R. but Futterman has this patented, if you recall that unfortunate passage.
Really confusing, I wish they'd left that out or tagged it differently.
Anyway, in the book the whole idea is explained from A-Z in his blunt style ( reminds me of how I come across at times
) and I think you see the picture already so I don't feel any need to dwell on that.More interestingly though, at least to yours truely, is that the idea can be easily adapted to non-OTL SEPP amps that are OPT coupled, especially when a PP OPT is used, but...I divert.
Yep, you could.
If you look at older OTL designs that were developped for 16 Ohm loads and so on you'd often encounter different compensation networks for different loads.
In my own system none is present, since every driver, bar my ribbon tweeter is impedance corrected right at the driver terminals.
By pure pot luck I pushed the WWW button on Positrons' post earlier today and found an old faithful from the days of TAA, SP and GA... more importantly it provides a link that actually shows you how these networks influence the speaker behaviour in a grapical view.
Ineresting stuff, thanks Positron.
I hope that answers your concern.
There's little honour to be found in that battlefield, I'm afraid.
Cheers,
WWW button?
You may have me confused with someone else, as I could't find any www on my posts. I think another should get the credit, not me.
I don't think I was functioning correctly earlier, as I have a schematic for one of Futterman's designs, I believe an OTL3.
Sometime, I shall have to look at it again.
Thanks Guys. Have a great week.
Steve
You may have me confused with someone else, as I could't find any www on my posts. I think another should get the credit, not me.
I don't think I was functioning correctly earlier, as I have a schematic for one of Futterman's designs, I believe an OTL3.
Sometime, I shall have to look at it again.
Thanks Guys. Have a great week.
Steve
Www.
Hi,
The button I meant is the one in your profile, visible to us in the left hand corner and in your case pointing to SASlabs.
Whether or not you have anything to do with that company is up to you, I don't care either way.
Sorry if I inadvertantly mistook identity...
P.S. Location seems to fit, hence my assumption.
Hi,
The button I meant is the one in your profile, visible to us in the left hand corner and in your case pointing to SASlabs.
Whether or not you have anything to do with that company is up to you, I don't care either way.
Sorry if I inadvertantly mistook identity...
P.S. Location seems to fit, hence my assumption.
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