Hi Esperado, are your comments only in relation to Lateral MOSFETs? I'm interested to know how what your thoughts are on the optimal VAS stage that can directly drive a pair of high power Vertical MOSFETs.
Using HEXFETs in High Fidelity Audio can answer most of your questions ?
The main issue with FETS is the voltage loss due to the voltage needed to bias the gate to the on condition. Some like to feed the OPS with ~ 5V less than the VAS.
Vertical or HEX need Vbe multiplier for thermal compensation. Lateral not.
About the VAS, the only question, on my point of view, is Cascoded or not. Each with his own advantages. I found Cascode to produce a little more 'nervous' sound (that i tend to prefer sometimes), due to the better HF isolation ? A little more difficult to make unconditionally stable, if you fight for extreme slew rates and bandwidth.
Now, the main question is, why not use laterals, witch are specifically designed for audio and linear ?
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Still4give, you are great audio builder with many different amps, if you are interested in VMOS output stage here is one you could build. http://www.diyaudio.com/forums/solid-state/243481-200w-mosfet-cfa-amp-49.html#post3776625 Some pages back there the PCB designed by Krisfr http://www.diyaudio.com/forums/solid-state/243481-200w-mosfet-cfa-amp-46.html#post3767322. If you are interested(this amp was never built) I could improve this amp a bit and see what is going on with the PCB.
BR Damir
Laterals
Mmm.. I realy like it laterals.http://www.diyaudio.com/forums/soli...lifier-i-have-ever-heard-246.html#post3975676
I think and Mr Lazy Cat loves laterals ... 200Khz
Nikos
Mmm.. I realy like it laterals.http://www.diyaudio.com/forums/soli...lifier-i-have-ever-heard-246.html#post3975676
I think and Mr Lazy Cat loves laterals ... 200Khz
Nikos
still4given, i had not followed the begining of this thread, and the various versions offered. The reason why is i had made all those experiments and comparizons (FETS vs BJT, VFA vs CFA etc.) during years to make my mind and get some kind of a personal 'religion'. It is just a matter of saving time, disgarding sub optimal solutions.
I am sure that you can try some lateral, just changing some resistances and caps values, using some straps to remove unnecessary parts, like VBE multiplier.
I'm mostly interested in this thread to read reports of the builders (like-you) and their listening experiences and see if they correlate with my experiences.
Nikosokey, i enjoy those Hitachi/Renesas too, since 1982 ;-)
My main 150W amp is that old and use a pair of 2SK135/2SJ50 for each channel.
And a VSSA when i want to play with multi amping and active filtering. Both CFA.
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Ηι Μr Esperado.
From the amplifiers I have made the best sound has my amplifier Vssa TO3 .(Sold)
My Goldmund clone 9.2 has all things that have the Vssa but also enough power. Maybe because use same TO3 EXICONS but different topology. Detailed, sweet sound that does not forgive bad records perhaps because they use the entrance JFET 2N5565 .
P3A amp also sound good and stable like rock with 2sc5359 and 2sa1987 output .
Regards Nikos
From the amplifiers I have made the best sound has my amplifier Vssa TO3 .(Sold)
My Goldmund clone 9.2 has all things that have the Vssa but also enough power. Maybe because use same TO3 EXICONS but different topology. Detailed, sweet sound that does not forgive bad records perhaps because they use the entrance JFET 2N5565 .
P3A amp also sound good and stable like rock with 2sc5359 and 2sa1987 output .
Regards Nikos
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Thanks for your reports, Nikos.
The Mimesis was a VFA, if i remember well ? With some clever details, like separated power supply for the Power FETs and cap multiplier filtering for the input/VAS rails at higher voltage ?
I don't know why, but never explored on my side Fets as input devices (more complicated) but i suspect it can have some advantages, like a good RFI protection. and isolation. Something to try on a CFA ?
I used a simple source follower at the input of my class "A" amp design (out of the global NFB loop by the way) exactly for good RFI protection and input isolation - very successfully - [HERE]
It's a great-sounding amplifier, first 20W - class "A", then up to 50W - "AB" (8 ohm)
Ok. Let's go.
1)Nad post#832,963,967,988,989,1005.
2)Spooky post#1247,1267,1292,1301.
3)Gnome v 1.3 post#1455,1476,1485,1500,1516,1531,1538,1567.
4)Symasui post#1642,1671,1672,1673.
5)CFA-X V1.2 post#1754,1756,1757,1784.
6)CFA-X V1.3 post#2976
7)Wolverine v 1-c post# 3543,3564,3637.
That's all.
PS If you are looking for original files please see post #1
Regards.
Thimios.
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thank you dear Thimios. hope these will help another builder that search for tested IPS.
Has anyone done a revised PCB layout for the 'CFA-X V1.3' rev of IPS?
And would be willing to share their Sprint Layout project file?
And would be willing to share their Sprint Layout project file?
I think Jason talked about doing that one earlier but he probably wanted for the design to settle. I think he's working on the Wolverine right now. Maybe he can be persuaded to do the CFA-XH BV MOD next. I have built that one but it takes quite a few mods to the board to get there. It doesn't sound any better but maybe it measures better, I don't know. Before OS left he posted his version but I couldn't get it to work. Hoping when he comes back we can work on it.
In my mind the most logical explanation is that Terry has reached the limit of his speakers distortion levels whereby any reduction in distortion in the electrical chain is being swamped out by the inherent distortion levels in the speakers themselves. The resolution of his speakers is not capable of showing the decreases at this point, he has reached the asymptotic point where any reduction in distortion is non detectable. We have to remember that we are looking at distortion levels of fractional values under .001% (approx) vs orders of magnitude higher such as 2 to 10% in a common domestic speaker system. There is just no way with this type of speaker to detect these ever decreasing levels of distortion. There is no reasonable reason for Terry to attempt any more distortion reduction in the electronic chain, he would be much better served to work on speaker distortion levels at this point.
Terry,
I am not trying to discount your preferences in loudspeakers, at the same time you have reached the limits of your audio chains resolution capabilities.
Terry,
I am not trying to discount your preferences in loudspeakers, at the same time you have reached the limits of your audio chains resolution capabilities.