Measure drop across R11 and derive mA (the one in RC filter feeding the buffer). The DC on source must be near 10.5V because is set by the previous stage. Give me DC on all points around the buffer. That way I will derive some conclusions of how your V really bias there as well. Also let me know the drop across 100R R17. I wanna see what really happens with the IDSS of those V in circuit.
Salas
I just checked my cabling, and I remarked I had a phase problem. I connected one of the output RCA's center pin to ground...
Now, EVERY hum is gone.
Franz
I just checked my cabling, and I remarked I had a phase problem. I connected one of the output RCA's center pin to ground...
Now, EVERY hum is gone.
Franz
Tomorrow, Salas!
Here at home, I have just a silly Voltcraft DVM, wich showed me recently 5VDC on a 3.3VDC point.
The support people from minidsp.com could not sleep well this weekend...
Tomorrow in the workshop I will use my Fluke wich is giving correct readings.
BTW: I am now very convinced, after the first comparison test with my musicserver.
THIS is what I like from vinyl. This small FET's are really better tubes 🙄
Franz
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Nice Franz. I hope that we did not have any wrong IDSS data initially so we are about right for gain, but we will converge using circuit data. See about the 11.5V & 10.5V bias points with the Fluke again. Happy about the hum too. See you. Listen to some more records by then!
Salas
I think, for perfect simulation of this FET's one should trace the relevant curves, and not only rely on static IDDS. But I will help to refine your model with my circuit by try and error 🙂
I am wondering, why all this FET's are sold as ONE type, separating with GR, BL and V versions.
It would be much more adequate, if the would have built a whole family of devices whith different names to separate them.
I remember a speach at one of the ETF's (was it John Broskie?) about simulation software and tube circuits. The problem is the same, I think. Good and adequate models for the active parts are needed.
Franz
I think, for perfect simulation of this FET's one should trace the relevant curves, and not only rely on static IDDS. But I will help to refine your model with my circuit by try and error 🙂
I am wondering, why all this FET's are sold as ONE type, separating with GR, BL and V versions.
It would be much more adequate, if the would have built a whole family of devices whith different names to separate them.
I remember a speach at one of the ETF's (was it John Broskie?) about simulation software and tube circuits. The problem is the same, I think. Good and adequate models for the active parts are needed.
Franz
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Unfortunately the available models are rough. I had managed to bring the BL very near by measuring data from actual prototypes. So all those builds with BL worked almost dead on for gain. With your V type its first time we try and there may very well be differences especially in Vgs(OFF). I don't have V, so we have to see it together.
Its sui generis with FETs that the channels give a whole range of transcoductance and pinch off, even with small manufacturing tolerances, so the Japanese just grade them in families GReen BLue and Violet. The Europeans A,B,C, (BF245A,B,C) the Americans up a number like 2N5457,8,9 J309, J310 etc.
You did not tell me, is the max volume you can reach as it is, enough for loud listening without hiss? Hum you killed.
Its sui generis with FETs that the channels give a whole range of transcoductance and pinch off, even with small manufacturing tolerances, so the Japanese just grade them in families GReen BLue and Violet. The Europeans A,B,C, (BF245A,B,C) the Americans up a number like 2N5457,8,9 J309, J310 etc.
You did not tell me, is the max volume you can reach as it is, enough for loud listening without hiss? Hum you killed.
Yes, but some more level would be apreciated, just to be at the same level as other line devices.
Franz
Hmmm, lets find out the real parameters in circuit first, and the real gain, I don't want it to go over 300mV RMS with average records, because second stage ups THD fast after that, and we don't wanna lose quality for the sake of matching a CDP exactly. If we are off gain target there will be margin to push it.
... here a picture of my creative LED selection
You can also see the bent legs of the BC550C, due to pcb layout error...
Franz
An externally hosted image should be here but it was not working when we last tested it.
You can also see the bent legs of the BC550C, due to pcb layout error...
Franz
In the meantime my little RIAA pre got an enclosure:
Salas fiddled out the best circuit for my choosen V-grade of the 2SK170 (15mA IDSS):
I am now really convinced about this phono preamplifier. Compared to my musicserver solution, what is always my reference, I prefer now the phono chain.
It is simply the best phono pre I ever had. Fantastic together with the Denon DL103R.
Soon, I want to build the shunt regulated psu with remote sense. Interesting topic!
Thanks Salas
Franz
/Edit
Here the schematics how I implemented it, including R12/C11 (should I remove C11 with the remote sense psu? Or replace by a lower value foil cap?):
An externally hosted image should be here but it was not working when we last tested it.
Salas fiddled out the best circuit for my choosen V-grade of the 2SK170 (15mA IDSS):
An externally hosted image should be here but it was not working when we last tested it.
I am now really convinced about this phono preamplifier. Compared to my musicserver solution, what is always my reference, I prefer now the phono chain.
It is simply the best phono pre I ever had. Fantastic together with the Denon DL103R.
Soon, I want to build the shunt regulated psu with remote sense. Interesting topic!
Thanks Salas
Franz
/Edit
Here the schematics how I implemented it, including R12/C11 (should I remove C11 with the remote sense psu? Or replace by a lower value foil cap?):
An externally hosted image should be here but it was not working when we last tested it.
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You are welcome. Happy listening. They were 15mA range indeed after all. Make your V1.2 shunt reg first, and you will decide about C11 subjectively. I am rather leaning towards you will delete it after listening with and without. If you do delete it, don't put a small film cap there. Just blank. But wait until you listen to it with its reg first. Its another story than now with 317.
P.S. I would like a family picture with TT near. Hey gear, say cheese!😀
P.S. I would like a family picture with TT near. Hey gear, say cheese!😀
Indeed, it is amazing:
60dB gain with no trannies, only two simple gain stages without global feedback. And a simple line driver. All pure Class-A.
60dB is an impressive amplification factor of one thousand!
No hiss, no hum, no nothing. No opamps,
Just music!
Franz
60dB gain with no trannies, only two simple gain stages without global feedback. And a simple line driver. All pure Class-A.
60dB is an impressive amplification factor of one thousand!
No hiss, no hum, no nothing. No opamps,
Just music!
Franz
Salas
Foto for you:
Franz
Foto for you:
An externally hosted image should be here but it was not working when we last tested it.
Franz
As you can see on the foto: a squeezebox, driven by a good quality smps. Attached with spdif the gigaworks DAC (analogue output stage: Lundahl trannies followed by a JC-2).
Yes, the line level is much too high with the JC-2, that could be the reason, that I was unsatisfied with the 60dB of the phono pre in the first try.
Franz
/Edit
Ahh, and all music on a NAS diskserver, WAV or FLAC.
Hey thanks for the pic! Real speakers I see also.😉 Good you got it no hiss no hum, because those horns would have shown. What is their sens?
Salas
As you may know: good speakers are always big 🙂
Low WAF, but I dont share my apartement with a "W"...
About revealing hum: I have an active 350W professional JBL subwoofer supporting the ACR Live 425 horns.
I think, the sensitivity of my speakers is about 100dB for the horns (Fostex D400/T925). I drive it with a 10W TA2024 t-amp.
This is not true for the four FW250 midrange speakers wich I have to drive with a 100W TK2050 t-amp.
The tube amps are not used any longer, at least not at time.
Franz
P.S.
Imho, every speaker with a sensitivity below, lets say 96dB, is wrong. Just look at pro speakers! Only exception: ESL's
As you may know: good speakers are always big 🙂
Low WAF, but I dont share my apartement with a "W"...
About revealing hum: I have an active 350W professional JBL subwoofer supporting the ACR Live 425 horns.
I think, the sensitivity of my speakers is about 100dB for the horns (Fostex D400/T925). I drive it with a 10W TA2024 t-amp.
This is not true for the four FW250 midrange speakers wich I have to drive with a 100W TK2050 t-amp.
The tube amps are not used any longer, at least not at time.
An externally hosted image should be here but it was not working when we last tested it.
Franz
P.S.
Imho, every speaker with a sensitivity below, lets say 96dB, is wrong. Just look at pro speakers! Only exception: ESL's
Looking forward to test the V1.2 remote sense psu.
Actually, I am euphoric listening to different records.
Vivaldi, four seasons: hey, the violins never had this real true wooden sound before! I can also hear the colophonium striving over the strings.
Then some german 80ies:, Spliff Radio Show: great!
Precise, dynamic, hard. No fatigue!
After this, Johann Strauss, die Fledermaus. A famous recording from Deutsche Grammophon.
Great stage. Big dynamics. Very silent parts. True natural voices!
Franz
Actually, I am euphoric listening to different records.
Vivaldi, four seasons: hey, the violins never had this real true wooden sound before! I can also hear the colophonium striving over the strings.
Then some german 80ies:, Spliff Radio Show: great!
Precise, dynamic, hard. No fatigue!
After this, Johann Strauss, die Fledermaus. A famous recording from Deutsche Grammophon.
Great stage. Big dynamics. Very silent parts. True natural voices!
Franz
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