As pointed by Janneman, high end audio market is no more
about hifi but about hype and fashion..
That may be true, but this thread is not about high end audio market; it's about a project to attempt to get the best performance without resorting to global feedback!
Do You considering to use tube VAS and short circuit output with triac for DC protect?
Regards
Regards
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I can clearly hear an amplifier...
With respect, you have provided an opinion, not fact. It proves nothing.
Oh well, never mind.
Mr. janneman I find your sarcasm disappointing.
I tried being serious, with similar results.
I would be thrilled if you, like me, were disappointed by that state of hi-end.
jd
That may be true, but this thread is not about high end audio market; it's about a project to attempt to get the best performance without resorting to global feedback!
If you defined 'best performance' we could have a more meaningfull discussion.
Let me help you:
If your definition is 'more accurate reproduction of music', you'r on a loosing streak.
If your definition is 'I like it', anything goes. Neg feedback, pos feedback, no feedback, you name it. There's no objective yardstick for 'I like it'. Ask 3 people and you get 4 opinions 😉
jd
“If controlled, repeated tests come out the same again and again - that's Nature saying you're right"
Or you are measuring the wrong thing. I can prove umbrella usage causes car accidents by repeated tests.
Everybody, could we please keep discussions for and against feedback now turning toward car accidents out of this thread ?
I would like to have this thread being technical about this specific design, where is decision about no feedback have been taken.
Soren
I would like to have this thread being technical about this specific design, where is decision about no feedback have been taken.
Soren
lol, thanks for the information eva 😀APV1121 is a photovoltaic gate driver. It transfers energy from the LED to the photodiode, a few microamperes are available to turn on the gate without any power supply, and turn off is active and powered with on-state gate charge. It can turn on and off the "relay" mosfet in a few miliseconds, like a relay.
http://pewa.panasonic.com/pcsd/product/pmos/pdf/mosfet.pdf
Get used to new funny parts. We are no longer in 1980s 😉
Makes vastly more sense now & i might even make use of that device myself if i can locate some 😉
Bests
Do You considering to use tube VAS and short circuit output with triac for DC protect?
Tube in input, yes, that would be pretty easy, just replace the LSK389 and two BSP88 with an ECC88, actually I have a schematic in my system where you can select between them....
Triac in output, I did consider it, but decided against it as I didn't like the consequences if there is a short in t.ex. a output transistor, as I don't want fuses in the power rail.
Soren
The Panasonic APV1121S (so8) and APV1122 (dip) are normally stocking parts at both Mouser, Digikey and Farnell....
Soren
Soren
Cheers Soren, thanks for the suggestions - Farnell will do nicely 😉The Panasonic APV1121S (so8) and APV1122 (dip) are normally stocking parts at both Mouser, Digikey and Farnell....
Soren
Bests, Mark.
I know how to achieve these three things with 40dB-60dB of global feedback. If you don't, you may be missing something 😉
Anyway, your approach to avoid global feedback instead of learning to use it properly is nice. Lazyness is very powerful.
Why such hate?
There are other reason not to want GNFB, which have nothing to do with stability.
Oh, I have finally found your thread (was waiting pointlessly for a pm)
That includes input/VAS?
Agreed.
Very nice choice. It was about time that someone made an electronic relay. I was going do make an electronic fuse in the PSU, à la JLH (and nothing else), but this works even safer.
300khz at -3dB?
And which is the highpass?
I'd like to know 1W and 10W THD20 into 8 Ohm. Can you do these measurements?
Good. The bigger version IMO can be adapted to run in class A at roughly 20W lowering the voltage rails.
Separate PSU, frontend and OPS would be nice, but probably too costful. At least keeping separate the PSU pcb?
1) Single power rails. It would be better having the driver part running on higher voltages than the outputs, but I would like to be able to use simple standard toroidal transformers. I have still tried to get as high output swing as possible, resulting in output voltage swinging to 4V-5V under the power rails when loaded.
That includes input/VAS?
2) jfet input. I believe in shortest path, and the only way to have that "single stage" high current folded cascode driver with high input impedance is if using a jfet differential input, and I have chosen the LSK389 dual part to avoid matching parts, and for the very low noise.
Agreed.
5) Mosfet output relay. The only way to fully protect expensive speakers is to be able to disconnect them. I hate mechanical relays, but now it's time to use mosfet relays, the parts are now good and inexpensive, and the special photovoltaic optoisolator make it simple.
Very nice choice. It was about time that someone made an electronic relay. I was going do make an electronic fuse in the PSU, à la JLH (and nothing else), but this works even safer.
6) Bandwidth limiting, I don't want a short wave transmitter so I believe in limiting bandwith to 300 Khz. I also don't trust what's it's being feed on the input so I like to have a DC blocking capacitor there.
300khz at -3dB?
And which is the highpass?
Some measurements on a breadboard prototype with just one pair of output transistors and into 4 ohms load:
1) THD <0.5% at full power and 10 Khz, quickly going down to <0.1% at lower power levels.
I'd like to know 1W and 10W THD20 into 8 Ohm. Can you do these measurements?
The schematic is designed for three versions, with output power up to 60W, 110W and 190W, using one, two or three sets out output transistors. I'm doing the 110W version first, if successful then the others will follow. The PCB is designed for directly mount on a heatsink, the 110W version to fit in a 2U case.
Good. The bigger version IMO can be adapted to run in class A at roughly 20W lowering the voltage rails.
I'm sending off gerbers for prototype PCB's now. When I'm done optimizing the design and if there are interest then I'm planning to start a small production and selling them a good prices....
Separate PSU, frontend and OPS would be nice, but probably too costful. At least keeping separate the PSU pcb?
Why such hate?
There are other reason not to want GNFB, which have nothing to do with stability.
Where is "such hate"?
Piercarlo
Telstar,
Yes, the output of the complete amplifier have been measured to swing to about 4.5V below the power rails, with load.
I have chosen the parts for -3 dB at 1.4 hz and 300 Khz.
I will post complete measurements once I have the real hardware, which should be in about 10 days, assuming planes with my parts can still land here....
My plans are to run them with high bias, but I also believe you can easily do more than 20W class A, I would say maybe one fourth of the class B specs.
I will personally do a three way active crossover system, planning to bias the amplifiers differently for each frequency range.
I want to make a really low cost and simple to use module, with everything on one PCB. You can always not mount the power supply parts if you want to have a separate power supply.
Soren
That includes input/VAS?
Yes, the output of the complete amplifier have been measured to swing to about 4.5V below the power rails, with load.
300khz at -3dB?
And which is the highpass?
I have chosen the parts for -3 dB at 1.4 hz and 300 Khz.
I'd like to know 1W and 10W THD20 into 8 Ohm. Can you do these measurements?
I will post complete measurements once I have the real hardware, which should be in about 10 days, assuming planes with my parts can still land here....
Good. The bigger version IMO can be adapted to run in class A at roughly 20W lowering the voltage rails.
My plans are to run them with high bias, but I also believe you can easily do more than 20W class A, I would say maybe one fourth of the class B specs.
I will personally do a three way active crossover system, planning to bias the amplifiers differently for each frequency range.
Separate PSU, frontend and OPS would be nice, but probably too costful. At least keeping separate the PSU pcb?
I want to make a really low cost and simple to use module, with everything on one PCB. You can always not mount the power supply parts if you want to have a separate power supply.
Soren
I'd like to know 1W and 10W THD20 into 8 Ohm. Can you do these measurements?
I will post complete measurements once I have the real hardware, which should be in about 10 days, assuming planes with my parts can still land here....
OK, waiting for those.
Yes, I can clearly hear an amplifier with numbers substantially worse than these, say THD not well below 1% and output impedance not well below 1 ohm, and in my experience most people can, it's easy. The result is quite random, may be pleasing or ugly depending on speaker impedance and freq. response.
Exactly what I have found in many test open listening, blind, and double blind. About 85% can hear this amount of error.
3) Unconditional stable no matter load
Beg to differ- I can make that thing oscillate in a heartbeat, no problem at all. Been there done that.
Real circuit measurements- very cool. Nothing personal but I really tire of specs quoted from simulations. I suppose if the music is simulated then the sim sounds good also, haha!
I like no global feedback for circuits driven by and driving know impedances especially at RF frequencies or for extremely low noise. Speakers are not even loads but in stereo pairs one speaker makes the other speaker produce a signal so a speaker is another source. This means the amp needs to be a little more robust than the one shown.
Lots of luck with it though. Will be curious to see the finals. Congratulations on the efforts!
planning to bias the amplifiers differently for each frequency range.
This is something I was thinking of for some time, great project.
All the best
Telstar,
I will personally do a three way active crossover system, planning to bias the amplifiers differently for each frequency range.
Soren
This is something I was thinking of for some time, great project.
All the best
This is something I was thinking of for some time, great project.
All the best
I'm doing the same but with completely different amplifiers for the various ways.
The hardest thing to do is the tweeter amp.
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