Has anyone heard of the "Mr.Grove" phonostage?
It works with a JAN6922 dual triode with not specified current sources each
has passive RIAA network and is not suitable for moving coil without step up transformer
it is said to have superb sound but the S/N is only 70 dB
i think that could be redesigned with jfets to avoid tubes who makes this JAN6922 tube today for which market? That tube is out of production since 1970 or even 1960 !
Tubes are just over and out. But anyway many users of this phonostage Mr.Grove claim it is simply the best
It works with a JAN6922 dual triode with not specified current sources each
has passive RIAA network and is not suitable for moving coil without step up transformer
it is said to have superb sound but the S/N is only 70 dB
i think that could be redesigned with jfets to avoid tubes who makes this JAN6922 tube today for which market? That tube is out of production since 1970 or even 1960 !
Tubes are just over and out. But anyway many users of this phonostage Mr.Grove claim it is simply the best
6922/E88CC are still in production, just not with the "JAN" designation.
People make claims about all kinds of things.
jeff
ok for diy or for Eniac mainframes?
there is no market for this kind of tubes
Are you talking about Frank's tube phono stage or something else?
Apparently you haven't heard a good recently designed tube phono stage.
There are at least two and probably more companies that manufacture 6DJ8/6922/ECC88 tube currently.
There are lots of tube phono stage designs here by SY, Salas, Frank DeGrove, Koifarm, and myself. One RCA variant that Eli touts over in the tube forums. Many others over the years I haven't mentioned.
Since you clearly don't like tubes I don't understand why you would take a design that was intended for tube application and convert it to semiconductors, there are semiconductor designs that are already thought through and that you can run with. Check this out:
http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa.html
http://www.diyaudio.com/forums/group-buys/241736-gb-salas-folded-simplistic-phono-pcb.html
Deliberately provocative tube bashing and posting wildly inaccurate information/assertions isn't going to make you a lot of friends around here, and it's not necessary.
Apparently you haven't heard a good recently designed tube phono stage.
There are at least two and probably more companies that manufacture 6DJ8/6922/ECC88 tube currently.
There are lots of tube phono stage designs here by SY, Salas, Frank DeGrove, Koifarm, and myself. One RCA variant that Eli touts over in the tube forums. Many others over the years I haven't mentioned.
Since you clearly don't like tubes I don't understand why you would take a design that was intended for tube application and convert it to semiconductors, there are semiconductor designs that are already thought through and that you can run with. Check this out:
http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa.html
http://www.diyaudio.com/forums/group-buys/241736-gb-salas-folded-simplistic-phono-pcb.html
Deliberately provocative tube bashing and posting wildly inaccurate information/assertions isn't going to make you a lot of friends around here, and it's not necessary.
This is the schematic of said Mr.Grove tube RIAA. The capacitors of the passive RIAA network C3 C4 need to be rated at at least 250 volts better higher and should be 1% .
Thus they have to be selected by capacitance meas rather cumbersome as there are no 330nf capacitors 250 Volts 1% available. C5 C6 R9 are not a subsonice filter - thus no IEC. Further no XLR output- but that is standard.
The current sources are specified at 1 mA but no type is given, could be selected njFets.
The RIAA network is described to have low values of resistors R7 R8 and consequently high capacitance C3 C4 but reason not given.
What could exactly be the advantage of this tube over jfets?
A disadvantage first: a fet RIAA amp can be operated on rechargeable battery a bunch of NiMH for ex. the tube cannot.
Certainly a triode is more linear than a Fet we know plate current= v grid/cathode ^3/2
but what about noise? Crucial in semiconductors is 1/f noise. In this respect jFets can outperform otherwise low noise pnp bipolars. But noise of tubes? Don't know besides it is certainly "statistical" but which statistic?
Thus they have to be selected by capacitance meas rather cumbersome as there are no 330nf capacitors 250 Volts 1% available. C5 C6 R9 are not a subsonice filter - thus no IEC. Further no XLR output- but that is standard.
The current sources are specified at 1 mA but no type is given, could be selected njFets.
The RIAA network is described to have low values of resistors R7 R8 and consequently high capacitance C3 C4 but reason not given.
What could exactly be the advantage of this tube over jfets?
A disadvantage first: a fet RIAA amp can be operated on rechargeable battery a bunch of NiMH for ex. the tube cannot.
Certainly a triode is more linear than a Fet we know plate current= v grid/cathode ^3/2
but what about noise? Crucial in semiconductors is 1/f noise. In this respect jFets can outperform otherwise low noise pnp bipolars. But noise of tubes? Don't know besides it is certainly "statistical" but which statistic?
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You are actually asking some pretty good questions, unfortunately I don't have a lot of time to go into detail, but this design is not great on a number of levels.
SNR is not a problem with a well designed tube phono stage - snrs greater than the best cartridges (which are low 80dBs range).
Another book to consider is Morgan Jones' "Valve Amplifiers 4th Edition" which is entertaining and useful for those with some electronics foundation to fall back on.
Widely available on the web are articles by Norman Crowhurst who was both knowledgeable and most active during the tube era. Engaging to read as well.
- The johnson noise of the cathode resistors will be amplified and will result in pretty significant noise over the audio band.
- The RIAA network throws away some gain that is still to be had.
- This design is probably not reflective of the designer's current thinking on these issues. To be fair I have designed very similar circuits with similar problems because I took a similar approach.
- There are a variety of tube noise mechanisms, but 1/F noise is probably the biggest meaningful contributor, but there are others.
SNR is not a problem with a well designed tube phono stage - snrs greater than the best cartridges (which are low 80dBs range).
Another book to consider is Morgan Jones' "Valve Amplifiers 4th Edition" which is entertaining and useful for those with some electronics foundation to fall back on.
Widely available on the web are articles by Norman Crowhurst who was both knowledgeable and most active during the tube era. Engaging to read as well.
On a different subject - selection of precision caps I purchase 2% and 5% and select to 1% or 2% respectively. For odd values or where trims are needed I add capacitance in parallel, again selected.
You can actually get very close and since polystyrene and polypropylene are relatively stable over time, temperature and voltage you can get close, and long term stability seems good in my somewhat limited experience.
Selection is also required for solid state designs operating at low voltages due to tolerance issues with the parts and a desire for tight conformance to RIAA.
I always aim for +/-0.1dB conformance to RIAA over 20Hz - 20kHz.
I think the IEC eq curve is a total waste of time, deal with rumble in the turntable rather than compromise the bass response of vinyl playback. I have similar feeling about the "Neumann pole" in the HF response, not part of the RIAA standard and was intended to cancel rising HF response far outside of the audio band with a specific line of cutters. (This is somewhat controversial amongst a certain crowd of audio enthusiasts.) Common cartridges are usually crashing at these frequencies anyway.
You can actually get very close and since polystyrene and polypropylene are relatively stable over time, temperature and voltage you can get close, and long term stability seems good in my somewhat limited experience.
Selection is also required for solid state designs operating at low voltages due to tolerance issues with the parts and a desire for tight conformance to RIAA.
I always aim for +/-0.1dB conformance to RIAA over 20Hz - 20kHz.
I think the IEC eq curve is a total waste of time, deal with rumble in the turntable rather than compromise the bass response of vinyl playback. I have similar feeling about the "Neumann pole" in the HF response, not part of the RIAA standard and was intended to cancel rising HF response far outside of the audio band with a specific line of cutters. (This is somewhat controversial amongst a certain crowd of audio enthusiasts.) Common cartridges are usually crashing at these frequencies anyway.
To be fair i'm unsure whether to spend about 3 to 5 Euros for a vinyl LP to clean and digitize - they don't even return a 192 khz 24 bit digital master just a audio CD- or invest in a new preferably high output moving coil cartridge and new phonostage as a 192/24 soundcard is built in.
On various occasions with but rather few examples i found a CD cannot catch up with vinyl in sonic quality by far not. But i got an enormous improvement when the ic based RIAA is operated from battery thus that is a condition that must be met.
On various occasions with but rather few examples i found a CD cannot catch up with vinyl in sonic quality by far not. But i got an enormous improvement when the ic based RIAA is operated from battery thus that is a condition that must be met.
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I believe you may be referring to Andy Grove, he has worked for a few compaines. A phono preamp of his design was published in HiFi World magazine in about 1998, it might be the one you are looking for.
Does anyone have a copy?
Cheers,
Mike
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