Hi,
It's commercial, so no schematic available. Measurements are in Stereophile.
Ciao T
It's commercial, so no schematic available. Measurements are in Stereophile.
Ciao T
Ingemar, I think Allen Wright did some non-complimentary phono circuits that were also 2SK170/valve hybrids and freely posted the schematics.
Scott,
I have done similar circuits, they are also in the public domain. They are good, but not that good, rather interesting however.
The particular design I referred to uses an input stage that was derived from a preamp designed for the AGATA Project (particle physics research gear), this is also in the public domain with a schematic, of course it was adjusted for audio use.
Anyway, the point was that a quad of 2SK170's can be as silent as the Vendetta measured by Stereophile. Actually, the Vendetta was one of the Units I considered to be benchmarks for low noise during the design phase and hence to be equalled or exceeded.
Ciao T
I have done similar circuits, they are also in the public domain. They are good, but not that good, rather interesting however.
The particular design I referred to uses an input stage that was derived from a preamp designed for the AGATA Project (particle physics research gear), this is also in the public domain with a schematic, of course it was adjusted for audio use.
Anyway, the point was that a quad of 2SK170's can be as silent as the Vendetta measured by Stereophile. Actually, the Vendetta was one of the Units I considered to be benchmarks for low noise during the design phase and hence to be equalled or exceeded.
Ciao T
Yup, it's not rocket science, BTW IFC is doing some of the best Stooges ever today, Prof. Bilbo's one shot tonic, Margaret Dumont harassment, it goes on and on.
John,
I don't have Audio's going back that far. Shame about that noisy servo.
But even so the SP measurement is pretty quiet.
In practice the unit I am talking about is way quiet enough for use with 0.1mV cartridges, which will be as low as anything you encounter this side of the Ortofon MC-2000 or a Kondo Io.
My stuff would do way better than the -79dBA (re 0.5mV) JA measured, except for hum pickup from the on-board mains transformers and chokes... And a slightly noisy tube made one channel 3dB noisier than the other.
Still better than the LP being played, even with 0.1mV Pickups.
Final noisefloor above a few 100Hz is -87dB equivalent re. -0.5mV
Ciao T
I don't have Audio's going back that far. Shame about that noisy servo.
But even so the SP measurement is pretty quiet.
In practice the unit I am talking about is way quiet enough for use with 0.1mV cartridges, which will be as low as anything you encounter this side of the Ortofon MC-2000 or a Kondo Io.
My stuff would do way better than the -79dBA (re 0.5mV) JA measured, except for hum pickup from the on-board mains transformers and chokes... And a slightly noisy tube made one channel 3dB noisier than the other.
Still better than the LP being played, even with 0.1mV Pickups.
Final noisefloor above a few 100Hz is -87dB equivalent re. -0.5mV
Ciao T
Joachim,
We do not cool it.
This seems a later version perhaps from the one I looked at, maybe not, your slide has little detail?
At the bottom line there are 4pcs 2SK170 in parallel in my design, with some unique twists that allow me a 42dB range of adjusting gain without significant noise penalty (unlike for example the common Microphone preamplifier chips) and low enough effective input capacitance for MM cartridges despite these 4pcs in parallel. The actual design methods are entierly conventional of course, just pure open loop.
I doubt too much of this design is of use for DIY anyway, it was arrived at to produce a certain set of parameters and features for a certain commercial nice.
A DIY'er can optimise things by far more for a single pickup, commercial products, especially in the high end of the high end must take "all comers", so the same performance is much easier to attain in a simpler DIY circuit.
Ciao T
We do not cool it.
This seems a later version perhaps from the one I looked at, maybe not, your slide has little detail?
At the bottom line there are 4pcs 2SK170 in parallel in my design, with some unique twists that allow me a 42dB range of adjusting gain without significant noise penalty (unlike for example the common Microphone preamplifier chips) and low enough effective input capacitance for MM cartridges despite these 4pcs in parallel. The actual design methods are entierly conventional of course, just pure open loop.
I doubt too much of this design is of use for DIY anyway, it was arrived at to produce a certain set of parameters and features for a certain commercial nice.
A DIY'er can optimise things by far more for a single pickup, commercial products, especially in the high end of the high end must take "all comers", so the same performance is much easier to attain in a simpler DIY circuit.
Ciao T
Indeed, the bloody things they smell AC mains fields if Tx is in same box even from the wiring. You can see the harmonic mains needles on my 61dB open loop DIY. But I can live with it at that level when still in small sized single box, I have a small rack. That is from 3XJfet front end & 2XBJT cascoded. (Graph=0.25mV input, 0dB=1VRMS).
Attachments
Hi,
Yes, the amount of shielding we build in is heroic, all AC wiring is twisted. My one is 72dB maximum gain... I learned things I NEVER wanted to about how magnetic fields behave in designing this one.
Next time, if I can, I put the mains transformer into another box, preferably a few meters or even kilometres away...
Ciao T
Yes, the amount of shielding we build in is heroic, all AC wiring is twisted. My one is 72dB maximum gain... I learned things I NEVER wanted to about how magnetic fields behave in designing this one.
Next time, if I can, I put the mains transformer into another box, preferably a few meters or even kilometres away...
Ciao T
A properly working Vendetta will have an equivalent noise resistance of 10 ohms or less from 400-80,000 Hz. Below 400Hz there will be some 1/f due to the added bass boost of the RIAA, thermal changes, and inherent 1/f noise of the devices. SOME Toshiba devices have excessive 1/f noise, and a few got into some of the older Vendetta Research preamps, so below 400 Hz will vary with a few units, but once I caught the problem, only preselected 2SK147's, that were Quan-Tech tested and sorted, were ever used, in the input stage. That gave me the extra, (reject) parts to use for the C mod of the Vendetta after a while.
The noisy servos were due to the National LF411 IC's that were not anywhere near their typical spec. AD711's worked OK.
The noisy servos were due to the National LF411 IC's that were not anywhere near their typical spec. AD711's worked OK.
Hi Salas,
Yes, cobblers kids and all...
Ciao T
PS, for the non-british, in the UK we often omit the punchline on common saying and the common saying referenced here is "Cobblers kids go barefoot"...
I got it butter like with 2 boxes builds for others, but for me, I don't mind drinking stinging nettle tea.
Yes, cobblers kids and all...
Ciao T
PS, for the non-british, in the UK we often omit the punchline on common saying and the common saying referenced here is "Cobblers kids go barefoot"...
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Dear John,
Oh yes, the joys of producing things and finding co mponents are not to spec and do not match what you prototyped with...
A good friend of mine was an architect. His prof at Uni told him: "Design it, consult on it, write academic papers on it, but for heavens sake, don't ever build anything..."
I do start to appreciate this remark...
Building stuff is hard work.
And work is the curse of the drinking (and music listening and shagging) class, to which I definitly should be a-counted...
Anyone needs a consultant?
Ciao T
Oh yes, the joys of producing things and finding co mponents are not to spec and do not match what you prototyped with...
A good friend of mine was an architect. His prof at Uni told him: "Design it, consult on it, write academic papers on it, but for heavens sake, don't ever build anything..."
I do start to appreciate this remark...
Building stuff is hard work.
And work is the curse of the drinking (and music listening and shagging) class, to which I definitly should be a-counted...
Anyone needs a consultant?
Ciao T
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