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Old 28th March 2013, 01:31 PM   #851
tinitus is offline tinitus  Europe
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Repeating "one transistor too much in the feedback path" is realy ridiculous.

true or not, you should stay to using technical wording, rather than abusing such non tech emotionally loaded words


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Old 28th March 2013, 01:36 PM   #852
dadod is offline dadod  Croatia
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Quote:
Originally Posted by tinitus View Post
Repeating "one transistor too much in the feedback path" is realy ridiculous.

true or not, you should stay to using technical wording, rather than abusing such non tech emotionally loaded words


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OK, "one transistor too much in the feedback path" it's not techicaly supported.
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Old 28th March 2013, 02:46 PM   #853
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Quote:
Originally Posted by dadod View Post
Ones I already answered to that in other thread. If you are so afraid of "one transistor to much" you can configurate VFA amp in inverting mode, that is, use inverting input as the amp input.
This always improve VFA amps, as the feedback does not suffer from the distortion of the additional active device in the feedback path: errors are subtracted in a passive way.
Quote:
Originally Posted by dadod View Post
Repeating "one transistor too much in the feedback path" is realy ridiculous. Good reason to use VFA amp in the inverting mode is not "one transistor to much" but less common mode distortion.
You already made the same mistaken analyze (last time in the non inverting configuration) in the same impolite way. The purpose of CFB is to reduce the number of poles involved in the servo loop. And to deal with the parasitic capacitance at the inverting input (A question of impedance, there).
We are several to have noticed that CFB amps sounded better than equivalent VFB ones, and it is "ridiculous" to try to convince us of the contrary: your words are light in front of our 'real life' experiences: All the amps i had preferred and chosen (blind) in my recording studios were CFA. Why ?
Just look how behave the bandwidth of a VFA when you change the gain ratio, then do the same with a CFA.
Just look at the point where correction inside the servo loop begin to increase with both of them: Around one octave higher with CFA.
Feel free to propose all the VFA amps of your own design in an other thread, we will compare if you are able to design such a good and simple amp as VSSA. And we will not go polluting your thread with some kind of CFA vs VFA lobbying, as you did... ad nausea.
On the contrary, we will thank-you for your efforts to share your work with the community, as we thanks L.C. for what is a masterpiece.
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Last edited by Esperado; 28th March 2013 at 03:10 PM.
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Old 28th March 2013, 04:12 PM   #854
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by Esperado View Post
This always improve VFA amps, as the feedback does not suffer from the distortion of the additional active device in the feedback path: errors are subtracted in a passive way.
You already made the same mistaken analyze (last time in the non inverting configuration) in the same impolite way. The purpose of CFB is to reduce the number of poles involved in the servo loop. And to deal with the parasitic capacitance at the inverting input (A question of impedance, there).
We are several to have noticed that CFB amps sounded better than equivalent VFB ones, and it is "ridiculous" to try to convince us of the contrary: your words are light in front of our 'real life' experiences: All the amps i had preferred and chosen (blind) in my recording studios were CFA. Why ?
Just look how behave the bandwidth of a VFA when you change the gain ratio, then do the same with a CFA.
Just look at the point where correction inside the servo loop begin to increase with both of them: Around one octave higher with CFA.
Feel free to propose all the VFA amps of your own design in an other thread, we will compare if you are able to design such a good and simple amp as VSSA. And we will not go polluting your thread with some kind of CFA vs VFA lobbying, as you did... ad nausea.
On the contrary, we will thank-you for your efforts to share your work with the community, as we thanks L.C. for what is a masterpiece.
The vssa is the closest you get to a beginner cfa AMP

It is stable because of the build up of the input pair.

This is not the case with the vsa.

Many "simple" cfa is not that simple or They are just not stable.
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Old 28th March 2013, 04:18 PM   #855
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Esperado View Post
This always improve VFA amps, as the feedback does not suffer from the distortion of the additional active device in the feedback path: errors are subtracted in a passive way.
You already made the same mistaken analyze (last time in the non inverting configuration) in the same impolite way. The purpose of CFB is to reduce the number of poles involved in the servo loop. And to deal with the parasitic capacitance at the inverting input (A question of impedance, there).
We are several to have noticed that CFB amps sounded better than equivalent VFB ones, and it is "ridiculous" to try to convince us of the contrary: your words are light in front of our 'real life' experiences: All the amps i had preferred and chosen (blind) in my recording studios were CFA. Why ?
Just look how behave the bandwidth of a VFA when you change the gain ratio, then do the same with a CFA.
Just look at the point where correction inside the servo loop begin to increase with both of them: Around one octave higher with CFA.
Feel free to propose all the VFA amps of your own design in an other thread, we will compare if you are able to design such a good and simple amp as VSSA. And we will not go polluting your thread with some kind of CFA vs VFA lobbying, as you did... ad nausea.
On the contrary, we will thank-you for your efforts to share your work with the community, as we thanks L.C. for what is a masterpiece.
You say pollution and this is not polite too, this forum is free and should not be privatized by any one. When lazycat called my simulation “your cartoons” is it this polite way to discus technical questions.
I never said that this amp is not good, it is quite good for such simple design, but to say it’s the best ever is a bit funny.
Lazy cat wrote “that's the fact not recognized by VFA lovers”. What facts, because him says that? And call some people VFA lovers is not polite either.
I like technical discussions and if someone says that my design is not what I thought it was, I will not be offended, on the contrary I’ll seek advices and suggestions. I like to learn new things(started to use spice two years ago) even at my age of 68.
Best wishes and hope more openness from CFA club.
Damir
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Old 28th March 2013, 04:44 PM   #856
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Quote:
Originally Posted by dadod View Post
I like to learn new things(started to use spice two years ago) even at my age of 68.
Than at this point please learn what LTP actually is. Please look to my "cartoon slides" from figure 1 to 3 and you'll noticed that LTP is simply emitter follower with additional buffer transistor in the feedback path. No new functionality added, the same subtraction principle preserved as before in figure 1. If that you cannot recognize from this simple 1 to 3 slides explanation, than it's just the phrase expression that you still want to learn something new, but not the real openness.
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Old 28th March 2013, 05:16 PM   #857
dadod is offline dadod  Croatia
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Originally Posted by Lazy Cat View Post
Than at this point please learn what LTP actually is. Please look to my "cartoon slides" from figure 1 to 3 and you'll noticed that LTP is simply emitter follower with additional buffer transistor in the feedback path. No new functionality added, the same subtraction principle preserved as before in figure 1. If that you cannot recognize from this simple 1 to 3 slides explanation, than it's just the phrase expression that you still want to learn something new, but not the real openness.
Arrogant answer as usual, and you should start to learn.
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Old 28th March 2013, 05:52 PM   #858
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Sorry to interrupt a technical debate; but it is a bit strange that an SMPS powered CF Amp should sound better than with a Linear Supply, given the amps relatively poor PSRR.

Perhaps, the Linear Supply tested needs to be a lot more stiffer and relatively free of ripple.

These findings are diagramatically opposite to what was reported in the Pass Labs forum with regard to Amp Camp Amp(ACA).
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Old 28th March 2013, 06:02 PM   #859
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Quote:
Originally Posted by dadod View Post
When lazycat called my simulation “your cartoons”...
A perfect (and funny) general definition of simulations on my point of view.
Spice simulators save time in calculations (good for lazy people like me), it helps to explore global things in a rough way without wasting solder, but, unless it will be equipped with a virtual listener, i t present the same image of the reality than a cartoon is for real life.
Quote:
Originally Posted by dadod View Post
...but to say it’s the best ever is a bit funny
Who said that ?
At this level of quality, an other amp can emulate better a given loudspeaker, or will compensate in a better way a given source. But one thing is for sure, the hundred of people witch had immediately subscribed to build one don't needed any simulation to be sure that such a high bandwidth, low distortion, low noise, stability, from a so simple and harmonious design implanted in such a little beautiful board is one of the rare best DIY amp they can buy.
Just looking at the schematic is enough to feel its extreme quality, and I am willing to bet that there will be nobody to prefer an another amplifier in direct comparison, once he has built this one.
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Old 28th March 2013, 06:18 PM   #860
shaan is online now shaan  India
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Erm, about what dadod said on inverting VFAs...

If we use the inverting input as the signal input then isn't the non inverting input playing as a buffer(cascode) again, now to the input signal rather than the feedback signal? If so, then there is still "one transistor too much" present in the circuit and all previous problems regarding phase/bandwidth remains.

edit: I may be wrong. Please be gentle.

Last edited by shaan; 28th March 2013 at 06:20 PM.
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