Thanks guys and sorry for the late reply. I was at the countryside with my old mates from the school
beginning the 35th year festivities...see attached the menu.Thanks Symon. I have plenty of 5200/1943's and it would be easier to make the mod though I was reserving them for the Amnesis builds. The other option would be more elegant as it uses the free spots on the heat-sink.
A technical question: is it useful to compare FTs when using the BJT (or FET for that matter) in common-base configuration???
The plan is clear now. Thanks again to everyone.
Hi and welcome Tvi
Yes, of course and it was my inspiration for exploring the "cascoded common-collector" output in the first place.
I have posted here my version (or copy) of an Amnesis with that Sony output and prized it at possibly the best sounding (and easiest as in "less parts") option, several times, as the VFETs seem to "command" the final sound presentation.
Self biasing is a nice feature here.Guys, my attempts at recording and portraying the sound of my experimental amps with my phone have failed: the mic is worthless to capture anything of value...I wanted to represent dynamic constrasts and depth in the following, difficult piece:
YouTube
But it ended sounding too dry, hard and devoided of midrange through my Paradigm 3 test speakers. I will someday buy a good microphone but not in the near future. Youtube blocked my upload of a calmer Jazz piece
so I am trying to upload only old vynil rips or TV shows.Cheers,
M.
Attachments
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I am playing with the idea of a common-source output Amnesis, mixing the Sony and the Amnesis. Interestingly, this one could make a good phono/tape preamp with LTMD input.
The biasing is very tricky. My idea is trying later a Hagemann Vbe multilpier
instead.
I've been upgrading my Otari tape player. I may be posting some video here later...
Cheers,
M.
The biasing is very tricky. My idea is trying later a Hagemann Vbe multilpier
instead.
I've been upgrading my Otari tape player. I may be posting some video here later...
Cheers,
M.
Put a square wave on the input, and watch the current through R49.I am playing with the idea of a common-source output Amnesis, mixing the Sony and the Amnesis. Interestingly, this one could make a good phono/tape preamp with LTMD input.
The biasing is very tricky. My idea is trying later a Hagemann Vbe multilpier
instead.
I've been upgrading my Otari tape player. I may be posting some video here later...
Cheers,
M.
You will see an oscillating behaviour in the lower part of the square wave.
Increase R3 to 150 Ohm, problem solved.
With a Miller cap on Q15 you can increase stability, but it seems to be o.k. without.
Hans
Yes. Thank you. It could be optimized (I made some mistakes) but for a first take it works rather good and should make a nice little amp.
Yesterday I tried the phono input of the Sony, which has its own exclusive little VFET.
The switch selector is dirty though and hard to reach...
YouTube
Cheers,
M.
Hi Max,Yes. Thank you. It could be optimized (I made some mistakes) but for a first take it works rather good and should make a nice little amp.
Yesterday I tried the phono input of the Sony, which has its own exclusive little VFET.
The switch selector is dirty though and hard to reach...
YouTube
Cheers,
M.
Nice video and a very special PU Arm.
You do not only play records, but also the violin, right ?
Hans
Very badly.
I no longer practice. Too busy practising singing and electronics...I am a humble collector of old (18th C. -19th C) violins: I have a couple of lower countries' ones.
I have also discovered a technique by which I can improve ANY violin to a higher level one. I can convert a good violin into a concert violin.
An unpublished book was written.Edit: RESONANCE is the key to the Universe...contrary of what we seek forth here in amplifier land...
This is the Amnesis common-source corrected. R23 is reduced to 68R as in the original.
Cheers,
M.
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What for?
They are all dead by now...
But their knowledge (some of it) stayed with me.
I took six sabatic years away from DIYaudio learning all I could.
Here, some young artists that are benefiting from my meagre knowledge:
YouTube
YouTube
See attached an updated Amnesis with bootstrapped VFET output, for the brave. Lower ranking Sony 2SK60/2SJ18 VFETs should also work here.
Edit: in reallity, all of them should work but at higher Vgsoff, I believe.
Cheers,
M.
Attachments
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They may be all dead, but there’s a lot to see and hear, differences in sound between old and new violins, although made by exactly the same methods but nevertheless not as “full bodied” in their acoustical presentation.What for?
They are all dead by now...
But their knowledge (some of it) stayed with me.
I took six sabatic years away from DIYaudio learning all I could.
Here, some young artists that are benefiting from my meagre knowledge:
YouTube
YouTube
See attached an updated Amnesis with bootstrapped VFET output, for the brave. Lower ranking Sony 2SK60/2SJ18 VFETs should also work here.
Edit: in reallity, all of them should work but at higher Vgsoff, I believe.
Cheers,
M.
Interesting to hear that you found ways to upgrade the sound to concert level.
This one is also good:
YouTube
To be fair, the young lady's violin was almost perfect: I only had to improve D string's focus and attack...ballance between all strings is crucial and very difficult to achieve.
The young man's one was more demanding and is still unfinished work: I have to improve amplitude and power projection of the E string, but he is always studying so, still no chance.
The technique is very easy to understand, but difficult to master. One has to have several "to spare" violins...I am amazed that it is not common knowledge; the old Masters had only their hands and ears to accomplish it.
Maybe when I retire I will devote myself to this task.
Believe me, I can make this comparison chez moi any day. But know also that there "Masters of Tone" still in modern days...and then there is the problem of the varnish...
Cheers,
M.
YouTube
To be fair, the young lady's violin was almost perfect: I only had to improve D string's focus and attack...ballance between all strings is crucial and very difficult to achieve.
The young man's one was more demanding and is still unfinished work: I have to improve amplitude and power projection of the E string, but he is always studying so, still no chance.
The technique is very easy to understand, but difficult to master. One has to have several "to spare" violins...I am amazed that it is not common knowledge; the old Masters had only their hands and ears to accomplish it.
Maybe when I retire I will devote myself to this task.
Believe me, I can make this comparison chez moi any day. But know also that there "Masters of Tone" still in modern days...and then there is the problem of the varnish...
Cheers,
M.
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I love it when there remains a shade of romantic mystery around old craftmanship.
And even the old masters couldn’t make two violins sounding the same.
It’s like amplifiers, they all have the same low THD figures, seemingly far below perception level but they all sound differently.
And there are many violins sounding horrible. So there is a mère a boire for you once you have the time to invest, what a nice perspective !
Very well said.
The Masters of Tone were able to achieve a higher % of good ones.
Wood, even high quality, does not behave in a standard way.
Even more, the mass (and all derived effects) of the board varies linearly with the actual thickness of the board but the elasticity of the same, varies inverselly with the cube of the thickness!
(I hope I got it right. )You can see easilly now how the response, "power", "amplitude", richness and beauty of tone (proportion of harmonics) can be achieved.
You only need to know "where" to act...
Cheers,
M.
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Thanks, dear Hans, for renewing my interest in my violin adventure, which had decayed due to "combat fatigue" previously.
This weekend I treated one of my beloved, a beautyful violin made in Nicoló Gagliano style but which had no carrying power. Now it has a strong and deep G string and all other strings improved also. A little more on D string and it will be OK.
One of my best friends came home and delighted me with a private concert with Biber's Passacaglia (I should have recorded it) with a Rudolph Höss (Hoes) 1700 violin made in Steiner style (Steiner died in 1682) with gut strings and 432Hz tunning, which I lent to him. Very beautiful experience.
That violin has the record of signatures from repairers and now it also has my own luthier's one...
Cheers,
M.
This weekend I treated one of my beloved, a beautyful violin made in Nicoló Gagliano style but which had no carrying power. Now it has a strong and deep G string and all other strings improved also. A little more on D string and it will be OK.
One of my best friends came home and delighted me with a private concert with Biber's Passacaglia (I should have recorded it) with a Rudolph Höss (Hoes) 1700 violin made in Steiner style (Steiner died in 1682) with gut strings and 432Hz tunning, which I lent to him. Very beautiful experience.
That violin has the record of signatures from repairers
and now it also has my own luthier's one...Cheers,
M.
Attachments
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Wow, I’m impressed. What a treasure.Thanks, dear Hans, for renewing my interest in my violin adventure, which had decayed due to "combat fatigue" previously.
This weekend I treated one of my beloved, a beautyful violin made in Nicoló Gagliano style but which had no carrying power. Now it has a strong and deep G string and all other strings improved also. A little more on D string and it will be OK.
One of my best friends came home and delighted me with a private concert with Biber's Passacaglia (I should have recorded it) with a Rudolph Höss (Hoes) 1700 violin made in Steiner style (Steiner died in 1682) with gut strings and 432Hz tunning, which I lent to him. Very beautiful experience.
That violin has the record of signatures from repairers
Cheers,
M.
In the mean time I finished my layout and ordered a small batch of 10 of PCBs
- to check the PCB quality which is excellent
- to verify if the layout is correct
First I populated 2 PCBs of the QUAD version with JFET input stage.
I discovered two short cuts which were not easy to detect but easy to remove.
I performed some stress tests (sine wave, square wave) which were similar to my first prototype. The amp worked stable with a tendency to overshot / oscillation when coming near to clipping. Unfortunately I there was no real improvement with the new layout.
First listening tests were promising. The amp worked stable even with high output power and the sound quality was good from the beginning.
with different kind of music.
Everything was OK until I played
The Ultimate Demonstration Disc from Chesky
Transient Test track 25 Royal March (Strawinsky)
After 9-10 sec. there was some heavy transformer noise
and I switched of the power supply immediately.
Further investigations showed:
The behavior is reproducible with this track but occurs only at a certain volume level ( with and without any output load).
The current across each of the both emitter resistors 0.22R raised to1200mV which is more than 5A.
The scope showed a heavy HF oscillation modulated by the music signal which only can be stopped by switching off the power supply
(a very short moment is enough).
The same behavior occurs sometimes when switching on the power supply with a load connected (no output relay with switch-on delay).
I tried many measures against this oscillation without any success.
Btw this problem also occurs with my first prototype board.
This problem does not occur if
- the output MOSFETs are replaced by a wire
- the input transistors Q3/Q5 (BC557C) are replaced by a p-JFET
(e.g. 2SJ103) which limits the bandwidth of the input stage so that the
rise time increases to 2us even without any input filter.
I never watched that a real music signal can bring an amp into heavy oscillation while
a 20kHz square wave (with a moderate input filter) up to 3dB below clipping does not.
For the moment I use the version with output MOSFETs and JFETs at the input for further listening tests and improvement.
Next I will populate 2 boards with the AllBJT input versions and probably in a first step the Darlington output stage.
- to check the PCB quality which is excellent
- to verify if the layout is correct
First I populated 2 PCBs of the QUAD version with JFET input stage.
I discovered two short cuts which were not easy to detect but easy to remove.
I performed some stress tests (sine wave, square wave) which were similar to my first prototype. The amp worked stable with a tendency to overshot / oscillation when coming near to clipping. Unfortunately I there was no real improvement with the new layout.
First listening tests were promising. The amp worked stable even with high output power and the sound quality was good from the beginning.
with different kind of music.
Everything was OK until I played
The Ultimate Demonstration Disc from Chesky
Transient Test track 25 Royal March (Strawinsky)
After 9-10 sec. there was some heavy transformer noise
and I switched of the power supply immediately.
Further investigations showed:
The behavior is reproducible with this track but occurs only at a certain volume level ( with and without any output load).
The current across each of the both emitter resistors 0.22R raised to1200mV which is more than 5A.
The scope showed a heavy HF oscillation modulated by the music signal which only can be stopped by switching off the power supply
(a very short moment is enough).
The same behavior occurs sometimes when switching on the power supply with a load connected (no output relay with switch-on delay).
I tried many measures against this oscillation without any success.
Btw this problem also occurs with my first prototype board.
This problem does not occur if
- the output MOSFETs are replaced by a wire
- the input transistors Q3/Q5 (BC557C) are replaced by a p-JFET
(e.g. 2SJ103) which limits the bandwidth of the input stage so that the
rise time increases to 2us even without any input filter.
I never watched that a real music signal can bring an amp into heavy oscillation while
a 20kHz square wave (with a moderate input filter) up to 3dB below clipping does not.
For the moment I use the version with output MOSFETs and JFETs at the input for further listening tests and improvement.
Next I will populate 2 boards with the AllBJT input versions and probably in a first step the Darlington output stage.
Josi,
there are so many Amnesis variants, that I completely lost track.
If you could send the exact version that is causing you trouble, I can give it a try.
With a bit of luck I may find the cause.
Hans
Dear JOSI1,
Again, great work from your side!
I do use speaker protection circuits in all my DIY amps. AND NTC thermistor in series with power.
I never experienced that but I seldom listen loudly.
It is strange, as you mention, that square wave test doesnot reveal potential troubles. Did you use gate stopper resistors for the bootstrapped input JFET?
I saw that different versions need or can use different R values for the MOSFET gate stopper resistors: between 10 and 130R...which in its own lets see that the amp is a balancing act...
In the meantime, and thanks to Hans' clever remark (you see I evaluate all your advices) that the R in my "charge-transfer supply" was jeopardizing power roof (BTW, it was reduced from 2R2 to 1R in power circuits) I began to question it and ended trying chokes in many of my power supplies. For example, my beautiful TOKIN SK180 single ended amp (which has caps for speaker protection
) had a little hum (on the very sensitive Autograph clones and I am trying to see if this is due to a 20-30mV residual distorted sine on the PS line: previous to the mod, a 500mV sawtooth fed the power regulator. I built the biggest coil that would fit the tinny space that I had, with heavy gauge enamelled wire and iron core. Now the power regulator is presented with ony 200mV of gentlle sinewave and the residual is 5mV sine. I have not tested it yet on the big system as I am still enjoying the Sony there.Then, my ALLBJT input amp is still fed with the faulty cheap SMPS that produced that periodic oscilation and perhaps you remember that I described its sound as "dirty"...I've collected many PC-SMPS over time so I picked some toroids and made some HF coils by soldering the 3 wide wires in series. Instead of the recommended extra C, now I have extra CLC
The sound is much cleaner now, though I had not the time to test it yet with the scope. I find lesser difference between ALLBJT input and JFET input amps...A short clip, with an old LG DVD as source:
YouTube
I also modded my SD-card player n°1 (I am building now my fourth
SD-card player; that is why I am silent) with a faulty transfomer as a choke and I ended with 10mV sine prior to the high Q voltage regulators. Caps are much happier now with less stress.I hope to upload better clips latter.
Thank you guys for all the support and for believing.
Best wishes,
M.
PS: perhaps a current limiting circuit at the output, as Hans suggested, could help if the cure is not found...
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@Hans:
The attached .asc file is very close to my real amp.
Differences and modifications which did not solve the problem
are marked in red in the pdf-File.
Remarks:
Power Supply is +-32V
I do not use a coupling cap at the input since my audio source has a low DC offset <1mV
Changing the BC5xx transistors to your suggested 2Nxxxx types
does not solve the problem.
@Max
I use 330R gate stoppers for the JFETs and 150R gate stoppers for the MOSFETs.
What NTC thermistor (value, brand) did you use in series with power.
The attached .asc file is very close to my real amp.
Differences and modifications which did not solve the problem
are marked in red in the pdf-File.
Remarks:
Power Supply is +-32V
I do not use a coupling cap at the input since my audio source has a low DC offset <1mV
Changing the BC5xx transistors to your suggested 2Nxxxx types
does not solve the problem.
@Max
I use 330R gate stoppers for the JFETs and 150R gate stoppers for the MOSFETs.
What NTC thermistor (value, brand) did you use in series with power.