If the amplifier load impedance was flat and resistive (and then presumably inductive at higher frequencies) you wouldn't need an output inductor at all. The main point of the output inductor is to isolate the feedback network from capacitive loading, as capacitive loading reduces phase margin (interaction between load and amplifier output impedance). [This is of course ignoring any possible EMI/RFI issues which would be a secondary purpose of an output inductor].
With most real-world loads, the capacitive loading effect will actually be due to the parasitic capacitance of the speaker cable. If the output inductor isn't damped by a parallel resistance it will form a high-Q network with the loudspeaker cable.
Last edited:
Hi Bob,Your remarks about subjective comparisons and comments from different people is very interesting, even though it is not exactly a single or double-blind test. Is there any chance that you brought two different versions of the amplifiers to these people and they listened to both?
Maybe yours was very clean and neutral, and they were not used to listening to such an amplifier.
unfortunately, there were never two versions available. And as I know today, the amplifier was not exactly (
) neutral. But it impressed me, how high-end dealers in three different cities always provided very similar comments when hearing the amplifier.The differences between the versions were mostly things like ULGF/phase margin, snubber capacities at mains rectifiers, and things like that; I was obviously fighting EMI problems.
Having available good sources and speakers, it is incredible how good we hear. In this regard I was really assuaged, when I read Ovidiu's report on the PGP listening experience and the influence of some small compensation capacitor. It is exactly that 'miracle' that I continue to observe in all my hobby designs, even if they have 120dB NFB at 10kHz.
Cheers,
Matthias
Last edited:
Not sure any standard which wasn't absolute; eg pure Voltage Source would be useful. You only have to look at the IEC recommendation that headphones be designed to work correctly with 120R Zo and that H/P amps incorporate this 'standard'.
120R guarantees NO high quality headphones, past or present work well. Not only from max level point of view but response. So its ignored by both H/P and amp makers.
Us true speaker jocks just want amps to do what they say they'll do; ie provide a stiff voltage proportional to the signal and nothing else .. under ALL conditions. Even the 'damping factor' myth is an Amp marketing thing. Good speaker designers are well aware of how much difference this makes (I exclude the legions of pseudo speaker gurus.)
Actually there are many advantages to current, rather than voltage drive of speakers. Its just that designers have stuck to a voltage standard since the invention of Rice & Kellog's Moving Coil Speaker Notes on the Development of a New Type of Hornless Loudspeaker in 1937?. No one is quite sure how to do proper current drive speakers.
Conversely, their paper has many insights which the majority of Thiele/Small pseudo gurus have still to grasp. R&K also designed and built the first HiFi amp, with one giarnomous Watt of undistorted power, to drive their baby.
_________________
Bob, maybe a mention and brief survey of Current Drive or controlled Zo amps in the 2nd Ed. I don't think its worth too much effort until us evil speaker designers get our fingers out.
It might be worth mentioning in section 17.8 that some designers, like Bob Carver, believe the circa Ro=1 of valve amps is a big part of their sound.
Last edited:
The problem is that when one makes an unconditionally stable amplifier it can have a significant output impedance at treble. What would you say is a reasonable maximum output impedance an amp should have? Say the the amp impedance is a resistor in series with an inductor. What are the maximum amounts allowed?
A standard which satisfies speaker designers may not satisfy amp designers unless it provides a way to eliminate peaking from the response. The requirement to make an amp unconditionally stable can be costly in terms of performance if it's possible, when care is taken with the load impedance, to make a better amplifier that exhibits clean AC and step response and is stable into a controlled load. The cost of this, without a standard for the load, is that the amp may be unstable with certain loads.
The standard doesn't have to be an audio impedance. What is needed for stability is for RF impedance to be defined. It may be something as simple as putting a 120R+10n snubber across the speaker inputs and making sure the amp output is not shorted by a capacitor.
I know damping factor is overhyped, but it seemed related.
Hi Bob,
unfortunately, there were never two versions available. And as I know today, the amplifier was not exactly (
The differences between the versions were mostly things like ULGF/phase margin, snubber capacities at mains rectifiers, and things like that; I was obviously fighting EMI problems.
Having available good sources and speakers, it is incredible how good we hear. In this regard I was really assuaged, when I read Ovidiu's report on the PGP listening experience and the influence of some small compensation capacitor. It is exactly that 'miracle' that I continue to observe in all my hobby designs, even if they have 120dB NFB at 10kHz.
Cheers,
Matthias
Hi Matthias,
Thanks for the further clarification.
I've been somewhat off-line since I accidentally cut my underground Fios optical cable while edging a mulch bed on Sunday. They had only buried the cable 2.5 inches! So I've been without phone, Internet and TV service at home since Sunday. They claim they will be out to repair it tomorrow. Whatever happened to the good old phone company where they would be right out if your phone went dead?
Anyway, it is impressive to hear how keenly audible differences can sometimes be heard. Unfortunately, much subjective listening results are clouded by snake-oil and completely undisciplined arrangements, particularly with the usual reviewers. This casts an unfortunate shadow on subjective listening results, which remain very important.
In the high-end world, one of the biggest challenges is separating the snake-oil from the legitimate stuff.
Cheers,
Bob
Hi Bob,
thanks for your reply.
Cheers,
Matthias
thanks for your reply.
We are in accord. It is a really nice hobby to try to find out by sound (in both meanings) engineering, what's really going on.
Cheers,
Matthias
Ovidiu/syn08 said:
Hi Bob & Matthias,
Normally, I don't think one can hear the difference between 33pF and 47pF, unless more is going on. According to my sims, the right channel (with the smaller cap) was on the verge of instability. Most likely the 'faint harshness in the treble response' was due to ringing of the right channel.
Cheers,
E.
Us true speaker jocks just want amps to do what they say they'll do; ie provide a stiff voltage proportional to the signal and nothing else .. under ALL conditions. Even the 'damping factor' myth is an Amp marketing thing. Good speaker designers are well aware of how much difference this makes (I exclude the legions of pseudo speaker gurus.)
Actually there are many advantages to current, rather than voltage drive of speakers. Its just that designers have stuck to a voltage standard since the invention of Rice & Kellog's Moving Coil Speaker Notes on the Development of a New Type of Hornless Loudspeaker in 1937?. No one is quite sure how to do proper current drive speakers.
Conversely, their paper has many insights which the majority of Thiele/Small pseudo gurus have still to grasp. R&K also designed and built the first HiFi amp, with one giarnomous Watt of undistorted power, to drive their baby.
_________________
Bob, maybe a mention and brief survey of Current Drive or controlled Zo amps in the 2nd Ed. I don't think its worth too much effort until us evil speaker designers get our fingers out.
It might be worth mentioning in section 17.8 that some designers, like Bob Carver, believe the circa Ro=1 of valve amps is a big part of their sound.
Hi kgrlee,
Actually, I am somewhat of a DIY speaker jock, having designed several, both passive and active, which are described on my website (CordellAudio.com - Home). I also developed the EQSS (Equalized Quasi-Sealed System) system for better bass in a given size box. So I plead guilty to being somewhat of a speaker jock. I also admit to being a Thiele/Small believer
.Anyway, I've never bought into the use of current drive, at least for conventional louspeaker systems. Perhaps you can explain the advantages of current drive. Or are you advocating current drive of loudspeakers that are specifically designed to be current-driven?
I've been fascinated with the idea of controlled Z amplifiers since I think the Leak amps which had variable damping. Also interested in negative output impedance amplifiers for use in quasi-motional feedback arrangements that don't need an accelerometer (ElectroVoice did something like this back in about 1970). Might be worth a mention in the book - thanks for the suggestion. I plan to discuss a bit amplifiers for use in active loudspeakers, and maybe a bit on active loudspeakers themselves as examples of those amplifiers. That might be a place to mention variable Z. Each of my 3.5-way Athena louspeakers has four 125-watt vertical MOSFET amplifiers in it.
I tend to agree with Bob Carver that the ~1 ohm output Z of tube amps accounts for a good part of their sound difference, although that effect will vary considerably from speaker system to speaker system attached.
Note that on page 371, Section 17.8 "Optional Output Impedance" I do show a circuit for switching in an optional effective output resistance of 0.4 ohms without flowing the speaker current through a switch.
One of the questions I always like to raise is the following: With what kind of power amplifier did the loudspeaker designer voice his loudspeakers? If the speaker designer was a tube afficiando and used a tube amp, they are likely to sound rather different the 90% of the time they are hitched to a SS amp by the end user.
Cheers,
Bob
I had a very similar experience.Ovidiu/syn08 said:
A friend of mine with aspirations to being a High End manufacturer (I won't insult him by saying Golden Pinnae) once asked me to participate in listening tests on his new big supa amp. I wasn't happy and neither was his wife.
(BTW, nearly 20 yrs of doing Double Blind Listening Test to L&V standards bla bla standard have taught me NEVER to ignore your wife/girlfriend's opiniion even if they express no interest in sound. My statistics show, the 'woman in the street' is more perceptive than the 'man in the street' and both are better than the average High End reviewer (with notable but very few exceptions))
I was familiar with the circuit and added a VAS emitter resistor which cleared up the sound. Later when we put it on the bench, we found the amp had little parasitics on the guitar speaker (none on the pure capacitance) which the little resistor solved.
This 'on the spot fudge' earned me huge kudos
Ozzie Aboriginal Elders Thiele & Small not speak with forked tongue.I also admit to being a Thiele/Small believer
But both were academics and their evil T/S parameters are really aimed at someone who buys a couple of units and wants to dream up a box for them.
They focus on stuff which is misleading for anyone in the business of making loadsa good speakers.
We developed our own approach to Bass Design which was much more Production & QC orientated eg Garner & Jackson This is exactly equivalent to Thiele etc and Peter Fryer pointed out that the first accurate statement of the response of ported boxes was Novak (not in AES) though he didn't have Thiele's insights.
When we got fed up of making our own Factory Test Gear, we did a lot of work with Audiomatica. Many of my QC ideas are encapsulated in ClioQC. I tried very hard to get Mauro to do speaker parameters my way but he pointed out that trying to educate da unwashed masses was probably not to his advantage.
I wrote this in another forum when I emerged from the bush in 2005. Da WWW came to Cooktown at 28kB!
> For what it is worth, I think this is impossible. It seems to violate the cause and effect principle. How could the amplifier "know" what the speaker is up to? Short of sensing the actual motion of the drivers or the actual sound... this has to be sort of by guess and by golly, it seems to me.
It is entirely possible for an 'amplifier' to know what the speaker is doing.
It needs to sense the speaker current. An amp which twiddled its Output Z using both current & voltage feedback does this. Speakers act as accurate microphones (sense the actual sound) if operated into Low Z.
See "Loudspeakers as Microphones" - Peter Baxandall special lecture London AES (early 80s, late 70s?)
If operated into High Z, then the voltage at the terminals is a measure of cone velocity.
Both these mechanisms obey superposition & Thevenin so if you're clever, you can look at this while the amp is giving zillion volts and amps to the speaker. But non est tantum facile.
There are several tried & tested methods of using this 'controlled output Z' or 'current + voltage feedback' or 'actual sound & motion feedback' (different descriptions of the same thing) if you incorporate the amplifier design in the speaker. Some of these are in the zanier incarnations of my Powered Integrated Super Sub technology.
The simplest is the negative output R that Fons mentions.
More sophisticated but similar (??!) is ACE technology by Erik Stahl which was used by Audio Pro, Sweden for subs. Unfortunately, since he left, there isn't anyone there who understands it. Anyone have a contact for Erik? Or a clean copy of his original AES preprint?
These methods have the distortion reduction and dynamic overload protection features discussed in Mills & Hawksford. However, they are badly affected by heating of the voice coil.
David Birt (?) did an excellent IoA paper at Windermere where he arranged speaker and amp in a bridge so he could measure and compensate for heating on the fly. Anyone have an email for him?
These are the most elegant methods and they can be analysed from many viewpoints. Some of these viewpoints don't show up the distortion reduction advantages clearly.
I'm contemptous of methods which rely on extra transducers or extra windings (like Mills) or zillion point DSP EQ especially if they don't give ALL the advantages of the elegant methods.
A brute force zillion point approach possible today is measure accurately speaker Z (not that easy) and tailor the output of a High Z amp to suit. This would give some but not all the advantages of the above systems cos it wouldn't "know" what the speaker is up to.
Loudspeakers as High-Quality Microphones
Synthesis of Loudspeaker Mechanical Parameters by Electrical Means: A new Method for Controlling Low-Frequency Loudspeaker Behaviour
I think David Birt has a couple of patents on his bridge method
Dis beach bum only gets to read AES stuff through the generosity of the Benevolent Society for Deaf Loudspeaker Engineers in the Antipodes (BSDLEitA) but he finds it sad that there hasn't really been any advance on his Powered Integrated Super Stuff.
At the present SOA, we don't really know how to design moving coil speakers for current drive. We just fudge it. The best treatment is probably Distortion Reduction in Moving-Coil Loudspeaker Systems Using Current-Drive Technology
There has been no 'Ah Ha!' paper for current drive of moving coil like Rice & Kellog.
However, New Developments in Electrostatic Loudspeakers fulfills this function for current drive of Electrostatics .. but no present device takes advantage of this. The reciprocity stuff was actually via Peter Baxandall (who else?) I think there is a more detailed treatment in an out of print book.
So Yes. Any good current drive speaker/amp is likely to be a matched special.
Bob, this was a really important issue for me at one time.
I know of only 2 amps which are unconditionally stable with load without an output inductor. But neither was 1pp zillion THD or really that wonderful to listen to. We used them for lab/factory testing.
The amps we used for listening tests all had between 1u & 3u inductance with between 2R & 10R in parallel. This was probably the best compromise. IMHO, unconditional stability was paramount. Our Blind Listening Tests often included competitors speakers. I try not to design speakers with evil impedance at HF [*] but not everyone is as kind.
Should also point out that .. even if an amp doesn't have an output inductor, its output Z is probably still rising with frequency. ie inductive.
[*] In the midrange, my multi-way speakers have just as wonky an impedance as the next guy.
Last edited:
Hi Edmond,
thanks for the additional information. I agree, that not the capacitor value itself, but only its subtle consequences may change the perceived sound quality.
I assume that the (simulated) THD figures are not influenced by the (slight?) ringing, and that the ringing occured at high frequencies that cannot be heard directly (comparable to high-frequency power-supply ripple caused by the rectifiers).
If that is true: Where does the down-modulation of these high frequencies take place? Probably, the input stage is the majour suspicious, given the often "smoother" sound of FET input stages and the possible effect of a phase lead network in the global feedback network.
Have you encountered any other places where one should look for?
Cheers,
Matthias
Hi Matthias,
It's a pleasure.
That's right, real and simulated THD figures are not influenced, though simulated figures were not very accurate due to overly simplistic models of the lateral power fets. (btw, does anybody have reliable models of laterals, i.e. models that reliable predict THD?)
I don't know. Since the PGP amp is very complex, it could be anywhere. I didn't investigate (read: simulate) it, because it was too time consuming (due to convergence issues of the simulator).
One should check all loops under all possible conditions. That means also current limiting circuitry and if applicable also an active voltage clamp.
Cheers,
E.
It's a pleasure.
That's right, real and simulated THD figures are not influenced, though simulated figures were not very accurate due to overly simplistic models of the lateral power fets. (btw, does anybody have reliable models of laterals, i.e. models that reliable predict THD?)
I don't know. Since the PGP amp is very complex, it could be anywhere. I didn't investigate (read: simulate) it, because it was too time consuming (due to convergence issues of the simulator).
One should check all loops under all possible conditions. That means also current limiting circuitry and if applicable also an active voltage clamp.
Cheers,
E.
Ozzie Aboriginal Elders Thiele & Small not speak with forked tongue.
But both were academics and their evil T/S parameters are really aimed at someone who buys a couple of units and wants to dream up a box for them.
They focus on stuff which is misleading for anyone in the business of making loadsa good speakers.
We developed our own approach to Bass Design which was much more Production & QC orientated eg Garner & Jackson This is exactly equivalent to Thiele etc and Peter Fryer pointed out that the first accurate statement of the response of ported boxes was Novak (not in AES) though he didn't have Thiele's insights.
When we got fed up of making our own Factory Test Gear, we did a lot of work with Audiomatica. Many of my QC ideas are encapsulated in ClioQC. I tried very hard to get Mauro to do speaker parameters my way but he pointed out that trying to educate da unwashed masses was probably not to his advantage.
I wrote this in another forum when I emerged from the bush in 2005. Da WWW came to Cooktown at 28kB!
> For what it is worth, I think this is impossible. It seems to violate the cause and effect principle. How could the amplifier "know" what the speaker is up to? Short of sensing the actual motion of the drivers or the actual sound... this has to be sort of by guess and by golly, it seems to me.
It is entirely possible for an 'amplifier' to know what the speaker is doing.
It needs to sense the speaker current. An amp which twiddled its Output Z using both current & voltage feedback does this. Speakers act as accurate microphones (sense the actual sound) if operated into Low Z.
See "Loudspeakers as Microphones" - Peter Baxandall special lecture London AES (early 80s, late 70s?)
If operated into High Z, then the voltage at the terminals is a measure of cone velocity.
Both these mechanisms obey superposition & Thevenin so if you're clever, you can look at this while the amp is giving zillion volts and amps to the speaker. But non est tantum facile.
There are several tried & tested methods of using this 'controlled output Z' or 'current + voltage feedback' or 'actual sound & motion feedback' (different descriptions of the same thing) if you incorporate the amplifier design in the speaker. Some of these are in the zanier incarnations of my Powered Integrated Super Sub technology.
The simplest is the negative output R that Fons mentions.
More sophisticated but similar (??!) is ACE technology by Erik Stahl which was used by Audio Pro, Sweden for subs. Unfortunately, since he left, there isn't anyone there who understands it. Anyone have a contact for Erik? Or a clean copy of his original AES preprint?
These methods have the distortion reduction and dynamic overload protection features discussed in Mills & Hawksford. However, they are badly affected by heating of the voice coil.
David Birt (?) did an excellent IoA paper at Windermere where he arranged speaker and amp in a bridge so he could measure and compensate for heating on the fly. Anyone have an email for him?
These are the most elegant methods and they can be analysed from many viewpoints. Some of these viewpoints don't show up the distortion reduction advantages clearly.
I'm contemptous of methods which rely on extra transducers or extra windings (like Mills) or zillion point DSP EQ especially if they don't give ALL the advantages of the elegant methods.
A brute force zillion point approach possible today is measure accurately speaker Z (not that easy) and tailor the output of a High Z amp to suit. This would give some but not all the advantages of the above systems cos it wouldn't "know" what the speaker is up to.
Loudspeakers as High-Quality Microphones
Synthesis of Loudspeaker Mechanical Parameters by Electrical Means: A new Method for Controlling Low-Frequency Loudspeaker Behaviour
I think David Birt has a couple of patents on his bridge method
Dis beach bum only gets to read AES stuff through the generosity of the Benevolent Society for Deaf Loudspeaker Engineers in the Antipodes (BSDLEitA) but he finds it sad that there hasn't really been any advance on his Powered Integrated Super Stuff.
At the present SOA, we don't really know how to design moving coil speakers for current drive. We just fudge it. The best treatment is probably Distortion Reduction in Moving-Coil Loudspeaker Systems Using Current-Drive Technology
There has been no 'Ah Ha!' paper for current drive of moving coil like Rice & Kellog.
However, New Developments in Electrostatic Loudspeakers fulfills this function for current drive of Electrostatics .. but no present device takes advantage of this. The reciprocity stuff was actually via Peter Baxandall (who else?) I think there is a more detailed treatment in an out of print book.
So Yes. Any good current drive speaker/amp is likely to be a matched special.
Bob, this was a really important issue for me at one time.
I know of only 2 amps which are unconditionally stable with load without an output inductor. But neither was 1pp zillion THD or really that wonderful to listen to. We used them for lab/factory testing.
The amps we used for listening tests all had between 1u & 3u inductance with between 2R & 10R in parallel. This was probably the best compromise. IMHO, unconditional stability was paramount. Our Blind Listening Tests often included competitors speakers. I try not to design speakers with evil impedance at HF [*] but not everyone is as kind.
Should also point out that .. even if an amp doesn't have an output inductor, its output Z is probably still rising with frequency. ie inductive.
[*] In the midrange, my multi-way speakers have just as wonky an impedance as the next guy.
Hi kgrlee,
Thanks for providing all of these insights and historical notes.
One thing I used to think was good was to set the negative output impedance of the amplifier to just cancel the voice coil resistance (but not down to DC, of course). This effectively made the speaker act in a constant velocity way and caused it to roll off at 6dB/octave over the band of interest (usually just low frequencies), so it needed electronic EQ up front. This is an over-simplified version of non-transdicer dependent speaker control, and is one way to use sensed speaker current. Unfortunately, the devil is in the details, so, as you pointed out, this technique is, among other things, susceptible to voice coil resistance changes due to heating.
I completely agree that it is virtually foolish to build an amplifier without an inductor. I suspect that many well-intentioned high-end designs sound different because they are mis-behaving under some conditions of associated equipment and program material. Parasitic oscillation bursts may be one culprit.
Cheers,
Bob
I think it was kgrlee ? who gave a link to Loudspeaker Nonlinearities by Klippel http://www.klippel.de/fileadmin/kli...rature/Papers/Klippel_Nonlinearity_Poster.pdf If it was, Thanks, if not, Thanks to who did
I might be misunderstanding the data in the screenie ? but i don't mind being proved wrong to find out the facts. If you don't ask
It "appears" to me, to show that, out of All the possible causes of Distortion, Current is the least offender ! In which case to me, it "suggests" that Current Drive "might" actually be beneficial ?
Don't bite my head off, i'm Only throwing out an idea i had
*********
Only people who say Richard Small is an Ozzie He's actually American https://en.wikipedia.org/wiki/Thiele/Small
Funny thing though, when he was @ KEF i cheakily phoned up & asked to speak to him. Expecting to be sent away, to my Surprise the receptionist put me straight through to him ! I had about a 10 minute chat with him about speakers & T/S etc. As i wasn't a member of AES he Very kindly offered to send me his 3 papers on Vented etc matters. As promised these duly arrived a few days later Now this was before we all had PC's & nice software ! I spent weeks n weeks reading & re-reading it All, & eventually i was able to grasp enough to design vented boxes accurately Apart from the that, on noticing his accent wasn't Australian, i mentioned it, & i was sure he said he was English
You could add J.E. Benson to your list of distinguished audio Ozzies though
I might be misunderstanding the data in the screenie ? but i don't mind being proved wrong to find out the facts. If you don't ask
It "appears" to me, to show that, out of All the possible causes of Distortion, Current is the least offender ! In which case to me, it "suggests" that Current Drive "might" actually be beneficial ?
Don't bite my head off, i'm Only throwing out an idea i had
*********
Only people who say Richard Small is an Ozzie
He's actually American https://en.wikipedia.org/wiki/Thiele/Small Funny thing though, when he was @ KEF i cheakily phoned up & asked to speak to him. Expecting to be sent away, to my Surprise the receptionist put me straight through to him ! I had about a 10 minute chat with him about speakers & T/S etc. As i wasn't a member of AES he Very kindly offered to send me his 3 papers on Vented etc matters. As promised these duly arrived a few days later
Now this was before we all had PC's & nice software ! I spent weeks n weeks reading & re-reading it All, & eventually i was able to grasp enough to design vented boxes accurately Apart from the that, on noticing his accent wasn't Australian, i mentioned it, & i was sure he said he was English You could add J.E. Benson to your list of distinguished audio Ozzies though
Attachments
... again, no virtual news. I'll sell my soldering irons
.Thanks again and Cheers,
Matthias
I think it was kgrlee ? who gave a link to Loudspeaker Nonlinearities by Klippel http://www.klippel.de/fileadmin/kli...rature/Papers/Klippel_Nonlinearity_Poster.pdf If it was, Thanks, if not, Thanks to who did
I might be misunderstanding the data in the screenie ? but i don't mind being proved wrong to find out the facts. If you don't ask
It "appears" to me, to show that, out of All the possible causes of Distortion, Current is the least offender ! In which case to me, it "suggests" that Current Drive "might" actually be beneficial ?
Don't bite my head off, i'm Only throwing out an idea i had
*********
Only people who say Richard Small is an Ozzie
Funny thing though, when he was @ KEF i cheakily phoned up & asked to speak to him. Expecting to be sent away, to my Surprise the receptionist put me straight through to him ! I had about a 10 minute chat with him about speakers & T/S etc. As i wasn't a member of AES he Very kindly offered to send me his 3 papers on Vented etc matters. As promised these duly arrived a few days later
You could add J.E. Benson to your list of distinguished audio Ozzies though
Richard Small is a good AES friend of mine, and I think he is one of the finest, smartest gentlemen in the speaker business. He is also kind and humble.
Cheers,
Bob
@ Bob Cordell
Thanks for replying I hope kgrlee does too.
The next time you get an opportunity to speak with him, would you be kind enough to pass on my sincere Thanks to him for sending me those papers. After All these years i havn't forgotten, as it enabled me to correctly design speakers from then on
Regards
Thanks for replying
I hope kgrlee does too.The next time you get an opportunity to speak with him, would you be kind enough to pass on my sincere Thanks to him for sending me those papers. After All these years i havn't forgotten, as it enabled me to correctly design speakers from then on
Regards
... again, no virtual news. I'll sell my soldering irons
Thanks again and Cheers,
Matthias
I'm no Delphic Oracle, sorry.
Cheers,
E.
Hi Bob
Unless I'm mistaken was John Curl who brought this claim. I believe that JC is correct, because there loss of Slew Rate using output inductor. You should know that Ex: one amplifier with 50V/us can only have 25V/us with output inductor. The loss of Slew Rate (resolution) is audible because it has compression of analog audio.
Another issue, many amplifiers are stable in "born" but not with 2m cable (practically a pure inductor 2uH) with a capacitive load R//C.