Re: What could be done better...
I'm on your ignore list? So you are commenting on something you haven't even read? That's really smart.
Nevertheless I'm pretty sure you will sneakily look at my comments anyhow, just as you did in the past.
At 150mA we are still dealing with the weak inversion. In this region Id=f(Vgs) is NOT parabolic, rather logarithmic. Your math is wrong and as an expert on modeling, you should know better. Besides, you admitted that at Id=5A, a Vgs delta of 10mV results in Id delta of only 1%, see:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128809&perpage=25&pagenumber=6
At 150mA I get an Id delta of 9.5mA or 6.3%. These figures are based on real measurements and in accordance with the data sheet.
Clearly, there is something wrong with your measurements/observations/conclusions or whatever. Without C34 it's impossible that tf=tr, as the gate charging current is limited by the CCS (10mA), while the discharge current is determined by drive capabilities of the (diamond) emitter followers, at least 100mA, but probably more.
Anyhow, for HF signals C34 acts like a short between the two emitters of the driver stage and in terms of tr and tf, your diamond thing behaves exactly in the same manner as a normal driver stage (as used by anybody else).
The only difference consists of a bias shift if the OPS is abused by applying an unrealistic signal like a large sine of say 200kHz. C34 in your circuit will be discharged, resulting in under-bias, while in case of a normal driver, the cap will be charged, resulting in over-bias. Under normal conditions or even with a square wave of 20kHz or so, this phenomenon will not occur (provided that C34 is not much large than ~100nF).
syn08 said:
I'm on your ignore list? So you are commenting on something you haven't even read? That's really smart.
Nevertheless I'm pretty sure you will sneakily look at my comments anyhow, just as you did in the past.
At 150mA we are still dealing with the weak inversion. In this region Id=f(Vgs) is NOT parabolic, rather logarithmic. Your math is wrong and as an expert on modeling, you should know better. Besides, you admitted that at Id=5A, a Vgs delta of 10mV results in Id delta of only 1%, see:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128809&perpage=25&pagenumber=6
At 150mA I get an Id delta of 9.5mA or 6.3%. These figures are based on real measurements and in accordance with the data sheet.
Clearly, there is something wrong with your measurements/observations/conclusions or whatever. Without C34 it's impossible that tf=tr, as the gate charging current is limited by the CCS (10mA), while the discharge current is determined by drive capabilities of the (diamond) emitter followers, at least 100mA, but probably more.
Anyhow, for HF signals C34 acts like a short between the two emitters of the driver stage and in terms of tr and tf, your diamond thing behaves exactly in the same manner as a normal driver stage (as used by anybody else).
The only difference consists of a bias shift if the OPS is abused by applying an unrealistic signal like a large sine of say 200kHz. C34 in your circuit will be discharged, resulting in under-bias, while in case of a normal driver, the cap will be charged, resulting in over-bias. Under normal conditions or even with a square wave of 20kHz or so, this phenomenon will not occur (provided that C34 is not much large than ~100nF).
TMC
Hi Andy,
After some thoughts I think that we are on cross purposes. What I mean is that the gain inside the compensation (Miller) loop must be increased. See also my previous comment on this topic:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1160022&highlight=#post1160022
With more gain only inside the inner loop (along C2/C12), the ULG of the outer loop (along R52) will hardly be affected.
As for non-dominant poles, TMC will push them a little bit further. So, no need to lower the ULG.
Cheers,
Edmond.
Edmond Stuart said:
andy_c said:
Hi Andy,
After some thoughts I think that we are on cross purposes. What I mean is that the gain inside the compensation (Miller) loop must be increased. See also my previous comment on this topic:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1160022&highlight=#post1160022
With more gain only inside the inner loop (along C2/C12), the ULG of the outer loop (along R52) will hardly be affected.
As for non-dominant poles, TMC will push them a little bit further. So, no need to lower the ULG.
Cheers,
Edmond.
Bonsai said:
Bonsai,
I promise this is my last message on this topic; in fact, I am seriously considering moving away from this virtual place. It's gone well beyond having fun and any kind of DIY spirit.
I cannot have warm feelings for anybody that insulted, in public and in private, my education, credentials, past and present jobs, DIY work, the country and even the continent I am living in. Perhaps I should not respond to any of these attacks (I know I'm not an angel myself) and understand from the very beginning that this is a war that can't be won; I cannot compete with someone that has all the time in the world, has an overinflated ego and is enjoying his own frustrations. Also, to me, an intelligent person ought to be doubtfull; somebody that believes only in his POW and refuses to look from other perspectives (the HEC debate is a very good example, there are others as well) is, to me, anything but.
As you mentioned the PGP... I was trying to avoid opening that file but perhaps a few things have to be told. Edmond's contribution to the PGP amp was designing and simulating the front end. Everything else, including the website content and deployment, is my work, on my time and dime (and well over a regular DIYer budget) and I guess anybody looking on the website could estimate the effort. Any common sense would tell that Edmond should mention this on his website, or at least acknowledge this in public.
Anyways, this week we are launching a new satellite and I'll be busy as hell. Then I'll leave for a month of vacation in Europe and be back sometimes in the second half of october. I'll keep an eye around...
Mr Popa,
looks like you could use the break, thanks for sharing so much info plus the occasional intelligent wit.
Enjoy the holiday and don't get mugged by euro trash.
looks like you could use the break, thanks for sharing so much info plus the occasional intelligent wit.
Enjoy the holiday and don't get mugged by euro trash.
Re: What could be done better...
In the mean time I've discovered a few:
1. The TPC resistors R54/R56 should be tied to ground instead of to the supply rails.
2. R15 (in the front-end with op-amps) should also be connected to ground instead of the non-inverting input of U6. What's even more striking is that this part of the schematic is blindly copied* from the Alexander amp (without giving him the credits btw). In the original amp this connection has a clear function: DC coupling of the input signal. In YAP however, DC is blocked by C10, so it's pointless to leave it connected to the non-inverting input. Even even worse, the output offset voltage is increased by an amount equal to the voltage drop across R11, i.e. 10k x 6uA = 60mV.
Of course there are more flaws, but enough for today.
(* except for the gain setting, Haksford cascodes and (TMC?) frequency compensation)
syn08 said:
In the mean time I've discovered a few:
1. The TPC resistors R54/R56 should be tied to ground instead of to the supply rails.
2. R15 (in the front-end with op-amps) should also be connected to ground instead of the non-inverting input of U6. What's even more striking is that this part of the schematic is blindly copied* from the Alexander amp (without giving him the credits btw). In the original amp this connection has a clear function: DC coupling of the input signal. In YAP however, DC is blocked by C10, so it's pointless to leave it connected to the non-inverting input. Even even worse, the output offset voltage is increased by an amount equal to the voltage drop across R11, i.e. 10k x 6uA = 60mV.
Of course there are more flaws, but enough for today.
(* except for the gain setting, Haksford cascodes and (TMC?) frequency compensation)
syn08 said:
Exactly!
That's right, but for quite another reason.
I have told that to many others.
History distortion.
Agreed, I will do that ( edit: has been done, see: http://home.tiscali.nl/data.odyssey/PGP.html ).
What about acknowledging me for the NFB-OPS and Alexander for the front-end?
Meet you in Amsterdam. 🙂
Re: Re: What could be done better...
Remember that this design is under US patent but it's rather easy to get permission of using it. I have such a permission.Edmond Stuart said:
Hi Per-Anders,
I know it is also patented.
I had a quick look at your phono amp. Looks nice and good specs too.
Cheers,
Edmond.
I know it is also patented.
I had a quick look at your phono amp. Looks nice and good specs too.
Cheers,
Edmond.
Plot
The whole YAP closed loop frequency and phase responses. Market is at the 3dB point.
The measured 3dB bandwidth at full power (200W into 4ohm) is 537KHz and the phase shift at the 3dB point is 41 degrees. In the audio band, the phase shift is very small. Unfortunately, the resistive power load that I am using is not made out of anti-inductive resistors (as much as I was able to look after, such resistors are very expensive), so probably the phase measurement is a little off.
The bump, both in amplitude and phase at around 300KHz, is a little strange and needs more analysis. Could it be related to the Zoebel and/or the output inductor? Food for thought for when I'll be back...
The whole YAP closed loop frequency and phase responses. Market is at the 3dB point.
The measured 3dB bandwidth at full power (200W into 4ohm) is 537KHz and the phase shift at the 3dB point is 41 degrees. In the audio band, the phase shift is very small. Unfortunately, the resistive power load that I am using is not made out of anti-inductive resistors (as much as I was able to look after, such resistors are very expensive), so probably the phase measurement is a little off.
The bump, both in amplitude and phase at around 300KHz, is a little strange and needs more analysis. Could it be related to the Zoebel and/or the output inductor? Food for thought for when I'll be back...
Attachments
anti-inductive load resistor
how bad
because the figures, test data you will get
will not match your anti-inductive 8 Ohm speakers
well, not much you can do now, syn08
with your all screwed up test results
( i did not even bother look at your attachment .. sorry )
Linie
how bad
because the figures, test data you will get
will not match your anti-inductive 8 Ohm speakers
well, not much you can do now, syn08
with your all screwed up test results
( i did not even bother look at your attachment .. sorry )
Linie
lineup said:anti-inductive load resistor
how bad
because the figures, test data you will get
will not match your anti-inductive 8 Ohm speakers
well, not much you can do now, syn08
with your all screwed up test results
( i did not even bother look at your attachment .. sorry )
Linie
You think such measurements should be done in a reactive speaker load? If so, which speaker model would you suggest to use?
I thought he was just joking.
It might be interesting to see what the impedance of the load resistor is at that frequency. Maybe there is some kind of resonance that interacts with the output inductor-resistor combo. I'm assuming this is not at the feedback point, but at the other side of the output inductor?
It might be interesting to see what the impedance of the load resistor is at that frequency. Maybe there is some kind of resonance that interacts with the output inductor-resistor combo. I'm assuming this is not at the feedback point, but at the other side of the output inductor?
andy_c said:
Yes it's at the output, after Zoebel and coil. I think it's a resonance between the output coil and the Zoebel cap, strongly dampened (the bump is around 1dB) but I have to confirm this.
The 3dB corner is set by the input filter.
Re: Plot
Syn08,
Just on the mechanics of the graphs, if I may: I guess this is done with your new HP network analyzer. Does it have an interface to a PC to get the graph, or do you use a separate program to import the graph from HPIB/GPIB? (I use 7470.exe for my 3577A).
Jan Didden
syn08 said:
Syn08,
Just on the mechanics of the graphs, if I may: I guess this is done with your new HP network analyzer. Does it have an interface to a PC to get the graph, or do you use a separate program to import the graph from HPIB/GPIB? (I use 7470.exe for my 3577A).
Jan Didden
Re: Re: Plot
It has the feature to capture a screenshot and save it on an internal disk (RAM drive or floppy) in TIFF format (about 180k/screenshot). Move the floppy to the PC and copy the file then convert to whatever format fits you.
It also has the option to download the data or screenshots via FTP. Unfortunately the network interface is AUI and 10BaseT only, you would need a AUI to RJ45 adapter ($20 on EBay, $60 brand new, mine is on order).
Of course, everything is available over HPIB as well.
janneman said:
It has the feature to capture a screenshot and save it on an internal disk (RAM drive or floppy) in TIFF format (about 180k/screenshot). Move the floppy to the PC and copy the file then convert to whatever format fits you.
It also has the option to download the data or screenshots via FTP. Unfortunately the network interface is AUI and 10BaseT only, you would need a AUI to RJ45 adapter ($20 on EBay, $60 brand new, mine is on order).
Of course, everything is available over HPIB as well.
Neat!
You *may* be interested in 7470.exe; it waits for you to press 'plot' on the test set (in listen mode), then reads in the data via the GPIB and draws the plot. See attached example.
Jan Didden
Edit: The is a problem to upload files. I'll try later.
You *may* be interested in 7470.exe; it waits for you to press 'plot' on the test set (in listen mode), then reads in the data via the GPIB and draws the plot. See attached example.
Jan Didden
Edit: The is a problem to upload files. I'll try later.
An externally hosted image should be here but it was not working when we last tested it.
janneman said:
I tried that... I am using a National Instruments GPIB ENET interface (to be able to control the instruments remotely, from upstairs, over TCP/IP, and that's because ultra sensitive measurements don't like humans around). For whatever reason, 7470.exe was never able to retrieve plots from my 3562A spectrum analyzer, and I tried any configuration that I was able to figure out. That's why I'm instead taking photos as screenshots 🙁
For the 3577, and probably also for the 3562, the trick is to configure 7470.exe to 'listen only' and the test set to 'talk only' Then press 'w' to let 7470 wait for data, and press 'plot' on the test set. But I guess it's getting to OT now.....
Jan Didden
Jan Didden
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