Looks cool. Very nice...The populated V2.
Assembling was easier than I expected, and the assembled board looked also somewhat better than expected.
FET legs bent at 5mm from case and that's it. The VAS trannies are standing instead of lying because I like them that way (and because I have only metal washers now.)
Anyways, nice huh?
And here are some traces of the V2. All done into 10R load with +/-35V PS, zobel disconnected. VAS bias ~5mA. Offset is very responsive of trimmer control and stays once set.
Pic 1 - 1KHz response
Pic 2 - 1KHz moderate clipping
Pic 3 - 1KHz heavy clipping
Pic 4 - 16KHz square response
Pic 5 - 16KHz 80nS rise time input squarewave measured at 25VPP output. (as in V1.1)
Somewhat surprisingly, the V2 looks faster than V1.1 with about 70V/uS SR with the same PS, input RF shunt and Cdom values though the VAS bias is half, gate resistors and total capacitive load at VAS output is double
. I desoldered the film caps from the rails but that didn't make it go slow. My bet is that the MJEs are playing the role better than the BDs.
Coming later - distortion performance.
Stay tuned
Pic 1 - 1KHz response
Pic 2 - 1KHz moderate clipping
Pic 3 - 1KHz heavy clipping
Pic 4 - 16KHz square response
Pic 5 - 16KHz 80nS rise time input squarewave measured at 25VPP output. (as in V1.1)
Somewhat surprisingly, the V2 looks faster than V1.1 with about 70V/uS SR with the same PS, input RF shunt and Cdom values though the VAS bias is half, gate resistors and total capacitive load at VAS output is double
. I desoldered the film caps from the rails but that didn't make it go slow. My bet is that the MJEs are playing the role better than the BDs.Coming later - distortion performance.
Stay tuned
Attachments
Nice!!And here are some traces of the V2. All done into 10R load with +/-35V PS, zobel disconnected. VAS bias ~5mA. Offset is very responsive of trimmer control and stays once set.
Pic 1 - 1KHz response
Pic 2 - 1KHz moderate clipping
Pic 3 - 1KHz heavy clipping
Pic 4 - 16KHz square response
Pic 5 - 16KHz 80nS rise time input squarewave measured at 25VPP output. (as in V1.1)
Somewhat surprisingly, the V2 looks faster than V1.1 with about 70V/uS SR with the same PS, input RF shunt and Cdom values though the VAS bias is half, gate resistors and total capacitive load at VAS output is double
Coming later - distortion performance.
Stay tuned
Waiting for V2 PDF
Forgot to mention some additional details.
With a single diode to bias the 4 MOSFETs, the quiescent current through MOSFETs is 60mA total or roughly 30mA per device. I say roughly because the MOSFETs are not matched.
I wonder what effect the above will have on the 1KHz distortion spectrum.
Hi ljufa.
Running this amp in class-A will bring no audible benefit. My experience with LatFETs and high bias is that they sound no different from ~200mA onward, at least in this amplifier.
An SE implementation is different, and changing of bias has a huge effect on THD, both measurable and audible. That said, the typical HEXFETs like IRFP240 sound better than 2SK1058 at 1.5A bias in an SE amp.
Running this amp in class-A will bring no audible benefit. My experience with LatFETs and high bias is that they sound no different from ~200mA onward, at least in this amplifier.
An SE implementation is different, and changing of bias has a huge effect on THD, both measurable and audible. That said, the typical HEXFETs like IRFP240 sound better than 2SK1058 at 1.5A bias in an SE amp.
Hi,
Thanks a bunch for the reply,Thank you for considering my request ! Will have to try and get the board myself then,hmmmm........
Yesterday I went to the local market but unfortunately none of them had the mosfets in stock,they've asked for a day or two.So will check again and even then if not available will either ask you or look for a substitute.
If I have to use alternatives what are the best options ?? I have a bunch of IRFP460 with me,Will something like that work ?? Or even a better sounding options then 2SK1058 & 2SJ1620??
Ok,what are the other Amps you've compared to V1 ??? Like I said I just finished AX-14 and would love to see how this fares with that ?
Regards.
Thanks a bunch for the reply,Thank you for considering my request ! Will have to try and get the board myself then,hmmmm........
Yesterday I went to the local market but unfortunately none of them had the mosfets in stock,they've asked for a day or two.So will check again and even then if not available will either ask you or look for a substitute.
If I have to use alternatives what are the best options ?? I have a bunch of IRFP460 with me,Will something like that work ?? Or even a better sounding options then 2SK1058 & 2SJ1620??
Ok,what are the other Amps you've compared to V1 ??? Like I said I just finished AX-14 and would love to see how this fares with that ?
Regards.
Feel free.
IMO devices don't sound, the topology does. You can have the K1058/J162 pair sound both great and awful depending on how they are driven.
If you absolutely can't get these mosfets then try to see if you can get BUZ901P/BUZ905P pair or ECX10N20/ECX10P20 pair (expensive). These should work without problem.
I sold all my previous amplifiers coz PeeCeeBee sounded better than each one of them (in my system, to my ears (danger: extremely subjective opinion(don't trust other people's ears))).
I won't name any, coz all the best amplifiers sound exactly the same while driving the same speakers.
The truth is that i haven't listened all my amplifiers in comparison.
Today I took care doing this.
I listen the PeeCeeBee (old vers.) in comparison with VSSA pmi vers.
A record player ,a phono preamplifier(Elektor Supa,bc550c,560c),an Elektor line preamp.(ne5534) and the VSSA or PeeCeeBee.
It is the first time that i listen the difference.
Shaan's PeeCeeBee is the winner, i'm absolutely sure for this.
Now i listen what already was measured here.
http://www.diyaudio.com/forums/solid-state/270418-vssa-pmi-version-vs-peeceebee-shaan-version.html
Today I took care doing this.
I listen the PeeCeeBee (old vers.) in comparison with VSSA pmi vers.
A record player ,a phono preamplifier(Elektor Supa,bc550c,560c),an Elektor line preamp.(ne5534) and the VSSA or PeeCeeBee.
It is the first time that i listen the difference.
Shaan's PeeCeeBee is the winner, i'm absolutely sure for this.
Now i listen what already was measured here.
http://www.diyaudio.com/forums/solid-state/270418-vssa-pmi-version-vs-peeceebee-shaan-version.html
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Hi Terry,can you listen on your PeeCeeBee in comparision with PMI VSSA.
This will be interesting..
Hi Thimios,
I have done this many times. They are both in my stack of amps that are used in my A/B setup. The only difference that I hear is that the PMI version has slightly more noise when there is no input. Could just be a wiring issue. The peeceebee is Jason's layout for TO3's. That one is dead quiet. Both have Mr evil cap multipliers.
I have done this many times. They are both in my stack of amps that are used in my A/B setup. The only difference that I hear is that the PMI version has slightly more noise when there is no input. Could just be a wiring issue. The peeceebee is Jason's layout for TO3's. That one is dead quiet. Both have Mr evil cap multipliers.
Hi Thimios ,
thanks for the feedback, how peeceebee compares with other best amplifiers you have made or heard , just out of curiosity as i have do not have that privilege , and looking forward to terrys opinion too as he done most best amp here and reading all his posting he is subjectively very objective
thanks for the feedback, how peeceebee compares with other best amplifiers you have made or heard , just out of curiosity as i have do not have that privilege , and looking forward to terrys opinion too as he done most best amp here and reading all his posting he is subjectively very objective
Hi,
Well although it's very true in general but I beg to differ, I have heard the same Amp with two different transistors and they both sounded different. I absolutely have no intention to stir a controversy here or get into an argument of any sort,These are purely my observation based on several Amps that I have repaired and have had a chance to analyse.
Thanks will look and revert back.Not looking at expensive as I do have some plans to make a stereo and a multi-channel Amp (so with so many devices to buy it has to be affordable).
Ok great, Cause currently Am looking for a reference class Amp to test and tune my speakers (DIY speakers and cables are my specialty).
I myself have heard all the Amps that one can imagine,Right from a battery powered Amp (Touted as the holy grail ) to a gain clone to a My Ref ultimate with Blackgates and what not (Assembled many of them for my friends), So can say with certain clarity that to me each sounded differently and was noway same or similar (with everything being exactly same and only the change being the Amp),But yes indeed its very subjective but do like to know irrespective of that !
Btw can you please PM the price for the boards,I so far have to got that info.
Regards.
Well although it's very true in general but I beg to differ, I have heard the same Amp with two different transistors and they both sounded different. I absolutely have no intention to stir a controversy here or get into an argument of any sort,These are purely my observation based on several Amps that I have repaired and have had a chance to analyse.
Thanks will look and revert back.Not looking at expensive as I do have some plans to make a stereo and a multi-channel Amp (so with so many devices to buy it has to be affordable).
Ok great, Cause currently Am looking for a reference class Amp to test and tune my speakers (DIY speakers and cables are my specialty).
I myself have heard all the Amps that one can imagine,Right from a battery powered Amp (Touted as the holy grail ) to a gain clone to a My Ref ultimate with Blackgates and what not (Assembled many of them for my friends), So can say with certain clarity that to me each sounded differently and was noway same or similar (with everything being exactly same and only the change being the Amp),But yes indeed its very subjective but do like to know irrespective of that !
Btw can you please PM the price for the boards,I so far have to got that info.
Regards.
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Build one of these. A-B Box For Amplifier Comparisons
Once you have used it you may/likely will be singing a totally different tune.
Hi friends.
Today I measured the real world output impedance of the V2 amplifier board. Below are the traced value of the positive peak of a 1khz sine into 9.91ohm resistor load, mesured at amp output terminal.
Unloaded voltage = 4.97V
Loaded voltage = 4.96V
So ouput impedance Zo = 9.91(4.97-4.96)/4.96 = 0.01997ohm or ~0.02ohm
So with an 8ohm load we get a damping factor of 400 (if it really matters)
Cheers
shaan
Today I measured the real world output impedance of the V2 amplifier board. Below are the traced value of the positive peak of a 1khz sine into 9.91ohm resistor load, mesured at amp output terminal.
Unloaded voltage = 4.97V
Loaded voltage = 4.96V
So ouput impedance Zo = 9.91(4.97-4.96)/4.96 = 0.01997ohm or ~0.02ohm
So with an 8ohm load we get a damping factor of 400 (if it really matters)
Cheers
shaan
Here are the V2 1KHz distortion measurements done into 10R resistive load. VAS bias is 4mA and total OP stage bias 60mA.
Pic 1 - 3VPP
Pic 2 - 10VPP
Pic 3 - 30VPP
Pic 4 - Audio range frequency response
A bit of surprise, THD is less than the V1.1 at lower power levels. I don't match the FETs, only the input and VAS. Again, it seems the MJE trannies are better than the BDs when THD is considered. But the noise grass is higher with the MJEs, though the amplifier under test is DEAD silent at the speaker.
And about the FR curve, the attenuation in the lower and higher octaves are the artifacts of the soundcard's internal FR limitations. As can be seen, the response is flat.
Cheers!
shaan
Pic 1 - 3VPP
Pic 2 - 10VPP
Pic 3 - 30VPP
Pic 4 - Audio range frequency response
A bit of surprise, THD is less than the V1.1 at lower power levels. I don't match the FETs, only the input and VAS. Again, it seems the MJE trannies are better than the BDs when THD is considered. But the noise grass is higher with the MJEs, though the amplifier under test is DEAD silent at the speaker.
And about the FR curve, the attenuation in the lower and higher octaves are the artifacts of the soundcard's internal FR limitations. As can be seen, the response is flat.
Cheers!
shaan
