Re: Re: Re: Slew rate etc
http://patft.uspto.gov/netacgi/nph-...1=AND&d=ptxt&s1=5097223&OS=5097223&RS=5097223
Interesting, I'm wonder if they have permission from Analog Devices because the design is proteced by a patent 5097223mikek said:
http://patft.uspto.gov/netacgi/nph-...1=AND&d=ptxt&s1=5097223&OS=5097223&RS=5097223
I'm not sure what MCP is but I refered to the link under and Fred is right, the opamp is feedbacked conventionally but the overall feedback is about current.
The Marantz amp is also very much current feedback and the design is by the schoolbook.
Mike, if you don't agree on this I'll stop this yes-no war here.
The Marantz amp is also very much current feedback and the design is by the schoolbook.
Mike, if you don't agree on this I'll stop this yes-no war here.
IMO the original statement was not very accurate. If your first stages are sluggish (as could be the case with some amps using op-amps there) then the transient performance could definitely profit from gain in the output stages, if these are really capable of high slew-rates (the Miller effect will come into action here). In this case the statement is definitely true.
OTOH why should one care about this with ordinary amps ? I see only two advantages for output stages with gain: Additional NFB can be applied around the output stage(s) and you may have slightly improved max output voltage for a given supply voltage.
Regards
Charles
OTOH why should one care about this with ordinary amps ? I see only two advantages for output stages with gain: Additional NFB can be applied around the output stage(s) and you may have slightly improved max output voltage for a given supply voltage.
Regards
Charles
Subjective Evaluation....
Ok Mike, in what terms is two pole compensation better than single pole ?.
Does it decrease load dependence of an amplifier ?.
You seem to be big on measured performance (and this is valid but only part of the equation), and very supportive of BLTs (these are NOT valid as typically implemented).
Does this two pole technique make for a better sounding amplifier with a range of speakers and speaker cables ?.
The Leach amplifier (a variant that I have heard) is spectacularly load independent, and does not get confused or fussy in the manner that many high feedback amplifiers do.
How does your design compare to other benchmark amplifiers ?.
Eric.
mikek said:I..merely said two-pole compesation is demonstrably superior to single pole...and all hell broke lose....
Ok Mike, in what terms is two pole compensation better than single pole ?.
Does it decrease load dependence of an amplifier ?.
You seem to be big on measured performance (and this is valid but only part of the equation), and very supportive of BLTs (these are NOT valid as typically implemented).
Does this two pole technique make for a better sounding amplifier with a range of speakers and speaker cables ?.
The Leach amplifier (a variant that I have heard) is spectacularly load independent, and does not get confused or fussy in the manner that many high feedback amplifiers do.
How does your design compare to other benchmark amplifiers ?.
Eric.
On Subject
Better psrr over wider frequency range....
Ok, commercially, better psrr means you get away with a lesser power supply, yeah ?.
Lower noise.....better Thd+N extended over wider frequency range...
Ok, commercially, these look good in spec sheets.
Lower so-called SID...
Is SID a big problem given typical programme sources ?.
Mike, I assume your better measured figures are of sinewaves into a resistive load - is this correct ?.
Do you have a sonic opinion of your amp into real loads ?.
What advantages or disadvantages ?.
Eric.
Better psrr over wider frequency range....
Ok, commercially, better psrr means you get away with a lesser power supply, yeah ?.
Lower noise.....better Thd+N extended over wider frequency range...
Ok, commercially, these look good in spec sheets.
Lower so-called SID...
Is SID a big problem given typical programme sources ?.
Mike, I assume your better measured figures are of sinewaves into a resistive load - is this correct ?.
Do you have a sonic opinion of your amp into real loads ?.
What advantages or disadvantages ?.
Eric.
There are many subjective design choices
in aircraft, cars etc..
I don't have any beef with a correctly conducted blind test. The only correctly conducted, useful, blind test would be to play a selection of pieces of music (half on system a and half on system b), then ask the subjects to rate the pieces of music. If, after lots of subjects, the pieces played on system a scored significantly better or worse than when played on system b, we can say system a is better or worse.
(Obviously the music selections would have be alternated between the systems for different subjects.)
in aircraft, cars etc..
I don't have any beef with a correctly conducted blind test. The only correctly conducted, useful, blind test would be to play a selection of pieces of music (half on system a and half on system b), then ask the subjects to rate the pieces of music. If, after lots of subjects, the pieces played on system a scored significantly better or worse than when played on system b, we can say system a is better or worse.
(Obviously the music selections would have be alternated between the systems for different subjects.)
A significant off-topic portion of this thread has been split off on its own.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=17164
dave
http://www.diyaudio.com/forums/showthread.php?s=&threadid=17164
dave
The case for higher slew...
A 100W amp. need only posses a maximum slew rate of just over 5V/us according to orthodox observations elsewhere in this thread.
However, a 900Mhz cellular 'phone signal need only peak at 0.89mV at the output to drive such a marginally designed amp. into hard slew limiting. Assuming a gain of 32dB, then peak input at 900MHz is just 22uV!!!
Indeed, if a ten to one margin for error were adopted to give a slew rate of 50V/us, then the RF signal just described need only peak at 0.22mV to switch the entire first stage tail current to one limb or other of the first stage diff. pair.
Thus, although 5V/us is sufficient for audio frequency program, it may be taken as axiomatic that such an amplifier will most certainly not be in the position to present a linear audio-frequency facsimile of the input stimulus in the presence of cellular RF interference.
Input RF filtration is therefore mandatory.....However, the crude, unbuffered single pole affair normally found on the vast majority of systems is unlikely to be of much use....., as over 90 dB of RF attenuation would be required.....
A 100W amp. need only posses a maximum slew rate of just over 5V/us according to orthodox observations elsewhere in this thread.
However, a 900Mhz cellular 'phone signal need only peak at 0.89mV at the output to drive such a marginally designed amp. into hard slew limiting. Assuming a gain of 32dB, then peak input at 900MHz is just 22uV!!!
Indeed, if a ten to one margin for error were adopted to give a slew rate of 50V/us, then the RF signal just described need only peak at 0.22mV to switch the entire first stage tail current to one limb or other of the first stage diff. pair.
Thus, although 5V/us is sufficient for audio frequency program, it may be taken as axiomatic that such an amplifier will most certainly not be in the position to present a linear audio-frequency facsimile of the input stimulus in the presence of cellular RF interference.
Input RF filtration is therefore mandatory.....However, the crude, unbuffered single pole affair normally found on the vast majority of systems is unlikely to be of much use....., as over 90 dB of RF attenuation would be required.....
Mark your calendars........
Something that makes sense.
Uh, just one problem..........well, two.
How many amps will respond to a 900 MHz stimulus, and in what manner, and how much will it take to cause it to act in a manner other than what is was designed to.
It depends on several things.
Even if you do make a really good filter, it may still be possible for RF to circumvent it due to parasitic coupling.
Let's not argue RF here, bub. We have enough other stuff to disagree about.
But you are on the right track for a change.
Jocko
Something that makes sense.
Uh, just one problem..........well, two.
How many amps will respond to a 900 MHz stimulus, and in what manner, and how much will it take to cause it to act in a manner other than what is was designed to.
It depends on several things.
Even if you do make a really good filter, it may still be possible for RF to circumvent it due to parasitic coupling.
Let's not argue RF here, bub. We have enough other stuff to disagree about.
But you are on the right track for a change.
Jocko
The case for higher slew........
Suffice it to say that less than 1mV ingress at 900MHz is guaranteed to give your amp. bad breath.......subject to caveats declared above...
This it would appear, puts 400V/uS described at the top of this thread into its proper perspective....
This problem may explain why lower powered amps. ,(sub 100W), have a reputation for 'better' sound quality than their high power relations......again...no mystery there.....a higher output voltage swing would require a commensurately higher slew to accomodate RF ingress......
Susceptability to RF is easily measured...designing it out entirely is of course another matter all together!!.....
So...high power, (>100W), design in mind? use output stage with gain, or stereo amps. in BTL,...the later may explain why high power BTL amps. such as Krell are successful. ....
Jocko Homo said:
Suffice it to say that less than 1mV ingress at 900MHz is guaranteed to give your amp. bad breath.......subject to caveats declared above...
This it would appear, puts 400V/uS described at the top of this thread into its proper perspective....
This problem may explain why lower powered amps. ,(sub 100W), have a reputation for 'better' sound quality than their high power relations......again...no mystery there.....a higher output voltage swing would require a commensurately higher slew to accomodate RF ingress......
Susceptability to RF is easily measured...designing it out entirely is of course another matter all together!!.....
So...high power, (>100W), design in mind? use output stage with gain, or stereo amps. in BTL,...the later may explain why high power BTL amps. such as Krell are successful. ....
Re: The case for higher slew...
Ahem...No.....apologies to folks....an audio amp. CANNOT have gain at 900MHz....
.....
However the basic idea is sound.....less than 1 mV (at 900MHz), swing at the output of the transimpedance stage will drive the amp. described above into slew limit.
mikek said:
Ahem...No.....apologies to folks....an audio amp. CANNOT have gain at 900MHz....
.....However the basic idea is sound.....less than 1 mV (at 900MHz), swing at the output of the transimpedance stage will drive the amp. described above into slew limit.
How to "design it out".......
You could start with JFETs in the input stage, which won't rectify RF the way bipolars will.........
So.....if your hypothetical amp with "gain in the output stage" and a slew rate of >400 V/uS is less susceptible to RF.......why the hell didn't you bring this out at the start of this thread???????
No........you ramble on, crying "rubbish" and "nonsense" at every reply. When asked to explain what the point of this thread was, you sidestep it.
I don't really think that you are intrerested in an intelligent exchange of ideas.......just to babble on, irritating all, and doing so in a condescending manner.
So......you want to talk RF suscepibilty, and why the type of amp you put forth is good in that respect, then say that. Drop the pompous posturing, and act like a regular bloke.
Unless that is beneath you somehow.
Cheers........
Jocko
You could start with JFETs in the input stage, which won't rectify RF the way bipolars will.........
So.....if your hypothetical amp with "gain in the output stage" and a slew rate of >400 V/uS is less susceptible to RF.......why the hell didn't you bring this out at the start of this thread???????
No........you ramble on, crying "rubbish" and "nonsense" at every reply. When asked to explain what the point of this thread was, you sidestep it.
I don't really think that you are intrerested in an intelligent exchange of ideas.......just to babble on, irritating all, and doing so in a condescending manner.
So......you want to talk RF suscepibilty, and why the type of amp you put forth is good in that respect, then say that. Drop the pompous posturing, and act like a regular bloke.
Unless that is beneath you somehow.
Cheers........
Jocko
Re: How to "design it out".......
No.....nothing to do with rectification....just good old diff. stage tail source running out of current to charge compensation cap.
If you knew this why didn't you bring it up??
...an output stage with gain will increase effective slew at the output of an amp. period.
I think you are quite....quite mad.....quick folks....bring in the men in white coats...and straight jackets.....
Jocko Homo said:
No.....nothing to do with rectification....just good old diff. stage tail source running out of current to charge compensation cap.
Jocko Homo said:
If you knew this why didn't you bring it up??
The original point of the thread was to point out a small technical detail that i am certain you were unaware of:Jocko Homo said:
...an output stage with gain will increase effective slew at the output of an amp. period.
Jocko Homo said:
I think you are quite....quite mad.....quick folks....bring in the men in white coats...and straight jackets.....
deep thoughts
Are you sure your first name is not Jack? Even as a relative newbie, I would expect that having additional gain would enhance the slew rate of a amp. But I could easily be wrong.
But perhaps a newbie question would be in line here - is there such a thing as "slow" gain, or the inverse "fast" gain? Or is gain neutral as to speed - meaning that it just tells us an amplification factor and has nothing to do with speed, rate of change, or velocity of sorts (however you choose to express it)?
Are you sure your first name is not Jack? Even as a relative newbie, I would expect that having additional gain would enhance the slew rate of a amp. But I could easily be wrong.
But perhaps a newbie question would be in line here - is there such a thing as "slow" gain, or the inverse "fast" gain? Or is gain neutral as to speed - meaning that it just tells us an amplification factor and has nothing to do with speed, rate of change, or velocity of sorts (however you choose to express it)?
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