You can use 2SK170-J74 parts for input and second stage parts if you wish.
Many of you do not understand that BEFORE the Japanese devices, there were the J series parts. You know: J107,110, 113, 203, 274, etc. This just meant that the parts were plastic encased, instead of metal, not the polarity of the device.
Many of you do not understand that BEFORE the Japanese devices, there were the J series parts. You know: J107,110, 113, 203, 274, etc. This just meant that the parts were plastic encased, instead of metal, not the polarity of the device.
Mr Curl,
As i can not think of anyone more knowledgeable on Japanese parts, what is your view on the outlook for audio grade semiconductors ?
It looks to me like the top grade Japanese parts manufacturing had a 30 year timeframe, ended as the internal demand in Japan for such parts has diminished in favor of the 'digital/switcher' era.
The concentrated development of high quality semiconductors seems to be shifting back to the roots.
ps: hope my "sense" of humor is still acceptable => @
As i can not think of anyone more knowledgeable on Japanese parts, what is your view on the outlook for audio grade semiconductors ?
It looks to me like the top grade Japanese parts manufacturing had a 30 year timeframe, ended as the internal demand in Japan for such parts has diminished in favor of the 'digital/switcher' era.
The concentrated development of high quality semiconductors seems to be shifting back to the roots.
ps: hope my "sense" of humor is still acceptable => @
Jacco, I don't know what to think of the Japanese parts situation. It is NOT good! I don't understand it, and why Toshiba would pull successful parts from the inventory.
> why Toshiba would pull successful parts from the inventory.
Successful maybe in the technical sense.
They don't bring enough financial return. Better to use the same production capacity to run higher valued parts.
Patrick
Successful maybe in the technical sense.
They don't bring enough financial return. Better to use the same production capacity to run higher valued parts.
Patrick
John,
Assuming that the schematic posted herein is correct, or close to it, why do you use a current source to set the operating voltages for the output cascode? Given that you have flogged the DC rails to within an inch of their lives, a resistor would seem to give as stable an operating voltage and presumably be quieter. Is the output run hard enough that you're using Q17 to thermally stabilize the voltages across R26 & R33?
Grey
Assuming that the schematic posted herein is correct, or close to it, why do you use a current source to set the operating voltages for the output cascode? Given that you have flogged the DC rails to within an inch of their lives, a resistor would seem to give as stable an operating voltage and presumably be quieter. Is the output run hard enough that you're using Q17 to thermally stabilize the voltages across R26 & R33?
Grey
From my understanding of the datasheets, the 2SK240 and 2SJ75 can be replaced by the 2SK389 and 2SJ109 which still exist on earth (however the datasheets state a significantly higher current capability for the 2SK240, also higher dissipation...so one should check that).
Just a thought for the guys who probably want to build this amp.
Cheers, Hannes
EDIT: seems the 2SK140/2SJ75 can still be found somewhere, as are the other parts!
Just a thought for the guys who probably want to build this amp.
Cheers, Hannes
EDIT: seems the 2SK140/2SJ75 can still be found somewhere, as are the other parts!
h_a said:
Depends which Idss grade.
I have eight pairs of 2SJ75BL/2SK240BL, the usual grade to be found is GR.
Same goes for the 2SJ72/2SK147. Grandata and Mark5 still offer these for a pound and a half the piece, GR grade ones.
I've got more than 50 of the 2SK147GR, finding them in BL grade is difficult.
Why Erno BoBo takes you to the cleaners if you need a BL pair.
For small projects, Erno is still a good source for fets. They now cost even more in the open market in many cases. There isn't any clear way to save money or to substitute parts, UNLESS you are very lucky. Think of these devices as if they were discontinued tubes, and perhaps you can gain better perspective.
So I'm curious - has somebody build this phono pre in the meantime?
As I'm no expert, maybe someone could help me a bit to understand this circuit a bit better: the SCP-2A shown here consists of SCP-1 and SCM-2 (though Stereophile claims that SCP-1 is only the power supply, ahem).
How much gain has the SCP-1?
I read in Frederico's notes 40dB@1kHz...is that correct? And as far as I can see there is only 1 RIAA-time constant realized in the SCP-1 with R16||C7, is that correct?
Consequently SCM-2 delivers another 20dB gain to give in total 60dB and further passive RIAA-equalization, correct?
Is there any suitable way to use Moving magnet cartridges with this design?
Thanks a lot for taking the time!
All the best, Hannes
As I'm no expert, maybe someone could help me a bit to understand this circuit a bit better: the SCP-2A shown here consists of SCP-1 and SCM-2 (though Stereophile claims that SCP-1 is only the power supply, ahem).
How much gain has the SCP-1?
I read in Frederico's notes 40dB@1kHz...is that correct? And as far as I can see there is only 1 RIAA-time constant realized in the SCP-1 with R16||C7, is that correct?
Consequently SCM-2 delivers another 20dB gain to give in total 60dB and further passive RIAA-equalization, correct?
Is there any suitable way to use Moving magnet cartridges with this design?
Thanks a lot for taking the time!
All the best, Hannes
The SCP-1 was a separate design that stood alone, for several years. It had a flat linear gain of about 25. Dave Wilson still uses an SCP-1 in front of virtually all of his phono preamps that he has used, over the years.
The SCP-2 includes an SCP-1 board and an SCM-2 board which adds further gain and equalization.
This design is NOT designed for moving magnet input, because it is difficult to control the gain, without changing the frequency response. Also, the input parts have too high nonlinear input capacitance to be driven by any cartridge over 100 ohms in impedance. It is just the wrong design for moving magnets.
The SCP-2 includes an SCP-1 board and an SCM-2 board which adds further gain and equalization.
This design is NOT designed for moving magnet input, because it is difficult to control the gain, without changing the frequency response. Also, the input parts have too high nonlinear input capacitance to be driven by any cartridge over 100 ohms in impedance. It is just the wrong design for moving magnets.
John Curl, thank you very much for your enlightening reply!
Especially your point about max. cartridge impedance I find very interesting and useful!
It's a pity that I wouldn't be able to use a SCP-2 at the moment, but I'm thinking of building it nevertheless, it's such a cute design!
All the best, Hannes
Especially your point about max. cartridge impedance I find very interesting and useful!
It's a pity that I wouldn't be able to use a SCP-2 at the moment, but I'm thinking of building it nevertheless, it's such a cute design!
All the best, Hannes
I expected this thread to be more responsive. After all, Vendetta phono is also the part of Blowtorch preamp which is a subject of a separate, huge thread. Recently,I have bought a few tens of J175 and J112 at a very good price at my local electronic parts supplier,for Vendetta first stage local regulators.They are from the same batch, well matched components,generally to about 3-7 % of Idss. I wish to ask mr Curl if it is good matching for voltage regulators paralleled transistors.
Also, in a previous thread, he mentioned Harris 1A vertical Mosfet used in cap. multiplier/filter circuit. Searching catalogues and datasheets, i was not able to find such a part.
Also, in a previous thread, he mentioned Harris 1A vertical Mosfet used in cap. multiplier/filter circuit. Searching catalogues and datasheets, i was not able to find such a part.
The problem isn't the quality of the design, it's that so many people have abandoned the LP as source material. If you don't listen to records, you don't need a phono stage. It's that simple.
Harris no longer exists as a separate corporation. They were bought out. In fact, one of the more available alternatives, IRF, recently sold their MOSFET division to Vishay. Your best bet at this time is to look for either Toshiba or Hitachi parts that meet the same general specifications, assuming you can find them. If you can't get them, the fallback position is Fairchild.
Grey
Harris no longer exists as a separate corporation. They were bought out. In fact, one of the more available alternatives, IRF, recently sold their MOSFET division to Vishay. Your best bet at this time is to look for either Toshiba or Hitachi parts that meet the same general specifications, assuming you can find them. If you can't get them, the fallback position is Fairchild.
Grey
Well, initially I also thought so.
However it's not so easy. First, the schematic is thought to be correct, but it was never build (at least nobody here said otherwise), so there might still be mistakes. Thus you would want to own some equipment (signal generator+scope) to test it.
Further it uses hard to find parts which need to be matched as well (so you need lots of them). If you start substituting parts, it's not a real Vendetta anymore; however at least you need to know with which parts you can replace the originals.
Next the Vendetta copes exclusively with MCs, so people with MMs drop out of the equation.
In a couple of years I will build one, but I guess that's a tad too far away for you, eh?
All the best, Hannes
On the other hand, you've got people like me who have multiple moving coil cartridges on hand. But I feel no compunctions whatsoever about changing devices around to suit my availability/needs/wants/desires/mood. You can do one helluva job using the 2SK389/2SJ109 and 2SK170/2SJ74 for the main gain parts. The MOSFETs are wide open--Toshiba/Hitachi/Fairchild/IRF/etc. I recently acquired some of the Toshiba MOSFETs (and John thinks people never listen to his suggestions...huh!) and have had very good results in another circuit I'm working on. I have a phono stage going as well--it will receive some attention in due time.
Don't obsess over the parts--work the topology with parts that you can get.
Grey
Don't obsess over the parts--work the topology with parts that you can get.
Grey
