Better than you spelling I hope..........
"IIC, Fred also claimed (and was very persistant) that Aleph X posted by Grey will not work and would oscillate. Yet number of amps have been built and no problems experienced either. So how good is his experise?" - PD
I think pinning all this on me and the validity of my expertise is smoke and mirrors. I didn't invent the zobel network, I didn't design it into the chip amp application note. I didn't design it into hundreds of amplifiers including some very successful designs by Nelson Pass.
My crime is that I know what the thing is in the circuit for. You have had respected designers like Demian Martin tell you what it is there for, and how to test for it's effect. I have made suggestions on how to implement it to work correctly and suggestions for quality parts to address sonic issues. You can rail on as long as you like, but amplifiers with good high frequency stability and phase margin; sound better, are more tolerant of various speaker and cable loads, and don't go all over the place in sound quality in differering RFI environments. Get Jocko to tell you about an amp I modded that sounded great at my house and smoked when I took it to our local hi end store located next to an airport.
All your stories about nobody having a problem are nice, other than the fact you yourself said the amp would not tolerate the Goertz speaker cable. Perhaps you can tell us exactly what capacitive and cable loads the amp will not tolerate. I really wonder where you are going with this other than helping your competition who build stable load tolerant chip amps. I and many others have found very stable amps designed to keep RF out of the circuit tend to sound better. Many believe that not including the output stage in the negative feedback loop sounds good due to increased stability and load tolerance. I am afraid we will have to agree to disagree, my points being based on engineering, listening experience, and countless examples of amplifier designs with output networks; and your points being based on ............. what was it again exactly? 😕
"IIC, Fred also claimed (and was very persistant) that Aleph X posted by Grey will not work and would oscillate. Yet number of amps have been built and no problems experienced either. So how good is his experise?" - PD
I think pinning all this on me and the validity of my expertise is smoke and mirrors. I didn't invent the zobel network, I didn't design it into the chip amp application note. I didn't design it into hundreds of amplifiers including some very successful designs by Nelson Pass.
My crime is that I know what the thing is in the circuit for. You have had respected designers like Demian Martin tell you what it is there for, and how to test for it's effect. I have made suggestions on how to implement it to work correctly and suggestions for quality parts to address sonic issues. You can rail on as long as you like, but amplifiers with good high frequency stability and phase margin; sound better, are more tolerant of various speaker and cable loads, and don't go all over the place in sound quality in differering RFI environments. Get Jocko to tell you about an amp I modded that sounded great at my house and smoked when I took it to our local hi end store located next to an airport.
All your stories about nobody having a problem are nice, other than the fact you yourself said the amp would not tolerate the Goertz speaker cable. Perhaps you can tell us exactly what capacitive and cable loads the amp will not tolerate. I really wonder where you are going with this other than helping your competition who build stable load tolerant chip amps. I and many others have found very stable amps designed to keep RF out of the circuit tend to sound better. Many believe that not including the output stage in the negative feedback loop sounds good due to increased stability and load tolerance. I am afraid we will have to agree to disagree, my points being based on engineering, listening experience, and countless examples of amplifier designs with output networks; and your points being based on ............. what was it again exactly? 😕
moe29 said:
The only reference that I had seen earlier to using a Zobel with the LM3875 was mhennessy's page:
http://www.mhennessy.f9.co.uk/gainclone/index.htm
but in the end, he wrote:
(referring to both the non-inverted and inverted circuits)
--
Brian
Are we reading the same sentence?
"Both circuits require a Zobel network across the output, but I haven't yet put this onto my prototype, and they are fine without them..."
Notice the operative words REQUIRED and YET...... I bet if a capacitive speaker cable caused him problems he might actually play with a zoble network long enough to see whats going on instead of just swapping the cables.
I know people are going to accuse me of pulling their leg,
but I honestly find Per-Anders chip amp design very interesting. The options of inverting, non-inverting, a jfet op amp buffered input, input RF filtering, servo, and an L-R output network as well as the zobel; give one enough configurations and parts options to make a fun circuit to fool around with. It would make a nice test bed for exploring the sonic effects of circuit topologies, parts quality, and RF filtering. As an experimenter's test bed for a simple amplifier block to try different things on, it looks like a great design. Since it seems to me that there seems to be a popular desire to investigate these things even in the chip amp crowd, he may have designed the chimp amp that people are the least likely to get board with in the near future and have the most fun exPERimenting with.
Who knew? 😕
"Both circuits require a Zobel network across the output, but I haven't yet put this onto my prototype, and they are fine without them..."
Notice the operative words REQUIRED and YET...... I bet if a capacitive speaker cable caused him problems he might actually play with a zoble network long enough to see whats going on instead of just swapping the cables.
I know people are going to accuse me of pulling their leg,
but I honestly find Per-Anders chip amp design very interesting. The options of inverting, non-inverting, a jfet op amp buffered input, input RF filtering, servo, and an L-R output network as well as the zobel; give one enough configurations and parts options to make a fun circuit to fool around with. It would make a nice test bed for exploring the sonic effects of circuit topologies, parts quality, and RF filtering. As an experimenter's test bed for a simple amplifier block to try different things on, it looks like a great design. Since it seems to me that there seems to be a popular desire to investigate these things even in the chip amp crowd, he may have designed the chimp amp that people are the least likely to get board with in the near future and have the most fun exPERimenting with.Who knew? 😕
Re: Better than you spelling I hope..........
Indeed, my spelling today is very bad. I went to sleep at 6am, as I had to put together some amps and preamp for this weekend's Stereophile Show in NYC. The amps are selling so well, that we have constantly shortage of complete units. None have Zobel network installed😉
We'll be exibiting in room 731.
I also mentioned that adding Zobel (to the amp that did not tolerate Goertz cables, in parallel with Monster Cables, for bi-amping) didn't solve the problem.
Fred Dieckmann said:
Indeed, my spelling today is very bad. I went to sleep at 6am, as I had to put together some amps and preamp for this weekend's Stereophile Show in NYC. The amps are selling so well, that we have constantly shortage of complete units. None have Zobel network installed😉
We'll be exibiting in room 731.
I also mentioned that adding Zobel (to the amp that did not tolerate Goertz cables, in parallel with Monster Cables, for bi-amping) didn't solve the problem.
Re: Are we reading the same sentence?
Don't mention that too often. He already started e-mailing me with complaints why I dismiss his design. I wonder is it because I'm not a mod anymore, or he was discussing his board with you?😉Fred Dieckmann said:
Thanks for the info Peter, I am really looking forward to ear
'Le Gainclon'. Is anyone else from NJ coming in?
Speaking of reliability issues Peter you do offer a warranty, doncha? The amp blows up with a pair of goertz cables? F' it! Send it back for repair FOC. 😉
Our group just received the third unit of a $200,000 piece of equipment, and this is from a swiss company mind you. The first one was never tested and was malfunctioning out of the box, the second one broke after a week of service.
At least the GC w/o zobel is doing its job. 😉
'Le Gainclon'. Is anyone else from NJ coming in?
Speaking of reliability issues Peter you do offer a warranty, doncha? The amp blows up with a pair of goertz cables? F' it! Send it back for repair FOC. 😉
Our group just received the third unit of a $200,000 piece of equipment, and this is from a swiss company mind you. The first one was never tested and was malfunctioning out of the box, the second one broke after a week of service.
At least the GC w/o zobel is doing its job. 😉
No I didn't, but neither it will be implemented when Zobel is installed at the amp end only (like Fred suggests). If you have to do it at speakers end, I don't see a problem in doing it at the amps end at the same time.
National also doesn't recommend installing Zobel at speakers end, so most of the "parts swappers" are probably not aware of that procedure.
National also doesn't recommend installing Zobel at speakers end, so most of the "parts swappers" are probably not aware of that procedure.
At present, we offer 10 years unlimited warranty. But who knows, if Zobel becomes an issue, we might change the warranty conditions😉
imho
Designing an amp with or without a zobel network is a matter that is up to the designer of the circuit. However, when a design is based on an application note from the component manufacturer I think that it is better to use the information given in the datasheet, rather the relying on a few individual amps that “work fine without the specified circuit present”
I have been brought up in the electronics world first as a repair technician and have just recently finished B.Sc.EE. One of my teachers said something that I’ll always remember…
“under no circumstances release a circuit that you don’t fully understand unless you are ready to suffer the consequences should something go wrong”.
Of cause this was about circuits that are supposed to be series produced for many years, and not a test circuit intended for personal use. I think that all this comes down to is seeing the difference between series production and one piece production.
I find it careless not to add a circuit specified by the component manufacturer and what’s worse it is very inconsiderate since I’m sure that the company who produces an amplifier that might oscillate does not want to pick up any bills for repairing a costumers speakers or other equipment that might suffer from an oscillating amp.
Zobel networks have been around for a long time, and with good reason. So use them, but be sure to use good quality components to make sure that the sonics of the amp stay un disturbed.
\Jens
Designing an amp with or without a zobel network is a matter that is up to the designer of the circuit. However, when a design is based on an application note from the component manufacturer I think that it is better to use the information given in the datasheet, rather the relying on a few individual amps that “work fine without the specified circuit present”
I have been brought up in the electronics world first as a repair technician and have just recently finished B.Sc.EE. One of my teachers said something that I’ll always remember…
“under no circumstances release a circuit that you don’t fully understand unless you are ready to suffer the consequences should something go wrong”.
Of cause this was about circuits that are supposed to be series produced for many years, and not a test circuit intended for personal use. I think that all this comes down to is seeing the difference between series production and one piece production.
I find it careless not to add a circuit specified by the component manufacturer and what’s worse it is very inconsiderate since I’m sure that the company who produces an amplifier that might oscillate does not want to pick up any bills for repairing a costumers speakers or other equipment that might suffer from an oscillating amp.
Zobel networks have been around for a long time, and with good reason. So use them, but be sure to use good quality components to make sure that the sonics of the amp stay un disturbed.
\Jens
I still believe that adding coupling caps would be more beneficial than Zobel. I fear much more extreme DC offsets, than slight chance of oscillations.
That his story and he sticking to it, sort of
'I also mentioned that adding Zobel (to the amp that did not tolerate Goertz cables, in parallel with Monster Cables, for bi-amping) didn't solve the problem."
Now there are more cables on the interface? ......... You realize that you can use two amps to bi-wire when the crossover for each driver is brought out to separate binding post and the amps aren't driving each other, right? Well, most amps anyway.
I honestly am happy that sales are good. I don't bemoan anyone making a buck through legitimate work. Stop wasting time here and get to work ... time is money. You should probably caution reviewers about bi-wiring. If anybody can find away to use a product with in the worst set up for its a reviewer. They really need baby-sitting most of the time...... I know, BTDT.
Too bad you are a fugitive from justice (or whatever the reason for your ban from the US) and can't come to the US for the show. I am sure it would be fun. The guys at Stereophile are very receptive to new products from lesser know designers. And don't worry about expensive advertising in the magazine. It really isn't necessary for a good review.
"I still believe that adding coupling caps would be more beneficial than Zobel."
And more problematic to sonics perhaps? There is a way to get by with a smaller higher quality feedback cap than the relative impedance values in the feedback network would lead one to reason. Lower value (not low ratio for gain change) feedback resistors in the feedback network lessen the influence the amp's non linea input capacitance on high frequency distortion but require a larger (and usually lesser quality) feedback cap to ground, for the same low frequency corner. Its boring engineering stuff and probably not worth discussing considering my credibility on amplifiers response at high frequencies though ..........
'I also mentioned that adding Zobel (to the amp that did not tolerate Goertz cables, in parallel with Monster Cables, for bi-amping) didn't solve the problem."
Now there are more cables on the interface? ......... You realize that you can use two amps to bi-wire when the crossover for each driver is brought out to separate binding post and the amps aren't driving each other, right? Well, most amps anyway.
I honestly am happy that sales are good. I don't bemoan anyone making a buck through legitimate work. Stop wasting time here and get to work ... time is money. You should probably caution reviewers about bi-wiring. If anybody can find away to use a product with in the worst set up for its a reviewer. They really need baby-sitting most of the time...... I know, BTDT.
Too bad you are a fugitive from justice (or whatever the reason for your ban from the US) and can't come to the US for the show. I am sure it would be fun. The guys at Stereophile are very receptive to new products from lesser know designers. And don't worry about expensive advertising in the magazine. It really isn't necessary for a good review.
"I still believe that adding coupling caps would be more beneficial than Zobel."
And more problematic to sonics perhaps? There is a way to get by with a smaller higher quality feedback cap than the relative impedance values in the feedback network would lead one to reason. Lower value (not low ratio for gain change) feedback resistors in the feedback network lessen the influence the amp's non linea input capacitance on high frequency distortion but require a larger (and usually lesser quality) feedback cap to ground, for the same low frequency corner. Its boring engineering stuff and probably not worth discussing considering my credibility on amplifiers response at high frequencies though ..........
The most common and IMO correct application of a Zobel is in conjunction with a damped output inductor.
The inductor isolates the amp from the output at higher frequencies while the Zobel makes the amp "see" something like a more or less ohmic (i.e. real) load up there. This is done because the amp prefers to see a real load in order to work correctly.
If one can guarantee a well defined load he can do without the Zobel. But one never knows what people will connect to an amp........
A Zobel at the other end of a cable can help if a highly capacitive cable is used. The Zobel will terminate the cable in order to "make it show it's characteristic impedance" at the amplifier end (approximately only of course).
This could be worth a try if nothing else helps.
Regards
Charles
The inductor isolates the amp from the output at higher frequencies while the Zobel makes the amp "see" something like a more or less ohmic (i.e. real) load up there. This is done because the amp prefers to see a real load in order to work correctly.
If one can guarantee a well defined load he can do without the Zobel. But one never knows what people will connect to an amp........
A Zobel at the other end of a cable can help if a highly capacitive cable is used. The Zobel will terminate the cable in order to "make it show it's characteristic impedance" at the amplifier end (approximately only of course).
This could be worth a try if nothing else helps.
Regards
Charles
Peter,
I have to agree with Fred and Jens
If the plan is to provide a product to the general public, you should CYA. Provide a switch that allows the user to switch the zobel in or out, but the circuit should be there (particularly with a 10 year warranty).
It's nice that in the audio industry you are not dealing with large liabilities. Do something like leaving a circuit out that is necessary for reliability just for the sake of a little added performance in other industries, and my may soon find yourself in court, or worse, jail. The reliability should come before performance in the development of a product.
I have to agree with Fred and Jens
If the plan is to provide a product to the general public, you should CYA. Provide a switch that allows the user to switch the zobel in or out, but the circuit should be there (particularly with a 10 year warranty).
It's nice that in the audio industry you are not dealing with large liabilities. Do something like leaving a circuit out that is necessary for reliability just for the sake of a little added performance in other industries, and my may soon find yourself in court, or worse, jail. The reliability should come before performance in the development of a product.
In other words
"This is done because the amp prefers to see a real load in order to work correctly."
Since the open loop falls with frequency. The application of feedback makes the output impedance look like an inductor. Since the inductance and cable capacitance are going to oscillate at some frequency with a high Q resonance that results in ringing or even amplifier oscillation if the resonant frequency is at a place where the amp has in sufficient phase margin. A zobel network's capacitor (being much larger than the expected load capacitance ) forces that resonant frequency where amp has adequate phase margin and the resistor damps the resonance so there is no ringing. This is very basic damped oscillator circuit and familiar to any second year engineering student. There are analogous equations describing mechanical systems in terms of mass compliance (stiffness for you poets), and damping (conversion of mechanical energy to heat). The shocks on your car do the last function and are analogous to the resistor in the Zobel network.
http://www.oz.net/~coilgun/mark2/rlcsim.htm
"This is done because the amp prefers to see a real load in order to work correctly."
Since the open loop falls with frequency. The application of feedback makes the output impedance look like an inductor. Since the inductance and cable capacitance are going to oscillate at some frequency with a high Q resonance that results in ringing or even amplifier oscillation if the resonant frequency is at a place where the amp has in sufficient phase margin. A zobel network's capacitor (being much larger than the expected load capacitance ) forces that resonant frequency where amp has adequate phase margin and the resistor damps the resonance so there is no ringing. This is very basic damped oscillator circuit and familiar to any second year engineering student. There are analogous equations describing mechanical systems in terms of mass compliance (stiffness for you poets), and damping (conversion of mechanical energy to heat). The shocks on your car do the last function and are analogous to the resistor in the Zobel network.
http://www.oz.net/~coilgun/mark2/rlcsim.htm
Those mysterious boxes
"A Zobel at the other end of a cable can help if a highly capacitive cable is used. The Zobel will terminate the cable in order to "make it show it's characteristic impedance" at the amplifier end (approximately only of course)."
Loudspeaker cables with such networks have been around for some years. If one wants to experiment with adding thier own network try a 0.01 to 0.047 uF polypro cap in series with 100 to 25 ohms. Start with the large value resistor value and work down. Short leads as usual and at the speaker end of the cable. 100 Volt axial cap and MK-132 resistors are said to work very well for such a network. Maybe just the thing for a finky Zoble-less amps..........
"A Zobel at the other end of a cable can help if a highly capacitive cable is used. The Zobel will terminate the cable in order to "make it show it's characteristic impedance" at the amplifier end (approximately only of course)."
Loudspeaker cables with such networks have been around for some years. If one wants to experiment with adding thier own network try a 0.01 to 0.047 uF polypro cap in series with 100 to 25 ohms. Start with the large value resistor value and work down. Short leads as usual and at the speaker end of the cable. 100 Volt axial cap and MK-132 resistors are said to work very well for such a network. Maybe just the thing for a finky Zoble-less amps..........
Re: Re: Better than you spelling I hope..........
Hi Peter
I'm looking forward to see the test of your gainclone in Stereophile...😉
Bests wishes!!
Peter Daniel said:
Hi Peter
I'm looking forward to see the test of your gainclone in Stereophile...😉
Bests wishes!!
Being at the show, doesn't get you a review. This show is like CES, but on a smaller scale. We don't advertise in Stereophile, so chances of getting review are not big😉
Show Success
This is getting off topic, but I can confirm that getting interest and press at a show is more about eye candy and outragessness than product values. One yeat I showed an over the top ($100K per pair) Plex and metal sculpture speaker and get lots of coverage but little sales activity. Next year with products that meet real needs and represent opportunity for dealers and customers, the press passes since its won't entertain readers.
Don't go tot he show expecting much from the press. Go to make contacts with dealers, distributors (both very thin on the ground at Stereophile shows) and potential customers which you will find in NY.
Good luck.
-Demian
This is getting off topic, but I can confirm that getting interest and press at a show is more about eye candy and outragessness than product values. One yeat I showed an over the top ($100K per pair) Plex and metal sculpture speaker and get lots of coverage but little sales activity. Next year with products that meet real needs and represent opportunity for dealers and customers, the press passes since its won't entertain readers.
Don't go tot he show expecting much from the press. Go to make contacts with dealers, distributors (both very thin on the ground at Stereophile shows) and potential customers which you will find in NY.
Good luck.
-Demian
I'd say that Peter has a good chance of exposure, then, as his equipment is visually more than eye candy and from others word, I think also sounds good.
Closer to on topic: I’m pretty sure you have already considered it, and I know others have mentioned it in passing, but I would triple think (again, I bet you have) about the fact that your future customers might not be quite as audiophile savvy as many of those on this forum. If a glitzy set of cables with high capacitance costs a guy his high-end drivers, I'd hate for you to get the brunt of that problem. Zobel or not, honestly makes no difference to me, as a) I can't afford your product b) I like to at least build my own stuff (with PCB's when I can!!) and am not likely to attempt an amp design of my own and finally c) I don't have multi-hundred dollar drivers, so the loss is not paralyzing if I screw up while playing hobby guy.
In the world of lawsuits, dumb buyers, exotic components and on the edge implementations, I would hate to see a problem arise from the combination! A guy riding a motorcycle doesn’t have insurance to help him out, he has it to make sure his wife is taken care of. Maybe a Zobel could be that insurance policy?
Hopefully the intense interchange as of late hasn't crippled the chip amp forum or your 'full time DIY' day job and things go well in NY.
Care to post a 'group picture' of what you're sending to the show. One amp at a time is nice, but a whole table could be almost obscene.
Sandy.
Closer to on topic: I’m pretty sure you have already considered it, and I know others have mentioned it in passing, but I would triple think (again, I bet you have) about the fact that your future customers might not be quite as audiophile savvy as many of those on this forum. If a glitzy set of cables with high capacitance costs a guy his high-end drivers, I'd hate for you to get the brunt of that problem. Zobel or not, honestly makes no difference to me, as a) I can't afford your product b) I like to at least build my own stuff (with PCB's when I can!!) and am not likely to attempt an amp design of my own and finally c) I don't have multi-hundred dollar drivers, so the loss is not paralyzing if I screw up while playing hobby guy.
In the world of lawsuits, dumb buyers, exotic components and on the edge implementations, I would hate to see a problem arise from the combination! A guy riding a motorcycle doesn’t have insurance to help him out, he has it to make sure his wife is taken care of. Maybe a Zobel could be that insurance policy?
Hopefully the intense interchange as of late hasn't crippled the chip amp forum or your 'full time DIY' day job and things go well in NY.
Care to post a 'group picture' of what you're sending to the show. One amp at a time is nice, but a whole table could be almost obscene.
Sandy.
- Status
- Not open for further replies.