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Old 17th February 2009, 03:02 PM   #1
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Location: Irondale, AL
Default New Phono Stage

Papa, we need nice new phono stage to match B1, PLEASE!

Seems Pearl parts getting hard to source.


Thanks , as this would make for complerte Pass system, except main speakers.

Pretty please with a nice wine sauce on top!
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Old 17th February 2009, 07:19 PM   #2
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The problem is that the Toshiba JFETs used in the Pearl (and Ono) were pretty much the only obvious choices for low noise parts. From where I sit, it appears that semiconductor manufacturers are dumping through-hole parts as fast as they can.
There are a few low noise bipolar transistors available, but that may or may not be a viable solution, as they're likely to be discontinued in the near future if the headlong rush to surface mount parts continues.
No, there aren't any really stellar surface mount JFETs out there. At the moment, those who need low noise parts are pretty much left to their own devices (ahem...). Hopefully that will change.
A number of people here have bought the Toshiba JFETs, but are not likely to ever use them. See if you can find someone who will let you have some of theirs.

Grey
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Old 18th February 2009, 12:28 AM   #3
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Default RE:

Iwas hoping Papa would come out with a new one in 2 levels of tweakiness, BP Regular and BP Extra
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Old 18th February 2009, 02:49 AM   #4
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If by BP you mean bipolar, then yes, there are a few options. Unfortunately, a 'regular' bipolar (or JFET) solution will force you to choose between Scylla and Charybdis. Will it be an annoying level of noise or low gain? Your choice. You might be able to live with low gain if you have a high enough output cartridge, but moving coils will suffer.
I recently e-mailed Nelson about the bipolar end of things. He suggested the ones that he used in the Ono. I'd already looked at those, but found that NEC (the manufacturer) doesn't list the 2SC1844/2SA991 anymore. In fact, if I'm remembering the right company, they no longer list any through hole parts at all.
I'm sure you can find some on the retail end if you scratch hard enough, but once it gets to the point where you're getting the last few drops out of the distribution pipeline, you're not building a circuit for widespread DIY use. It's effectively obsolete the day it's published.
I'm not saying circuits can't be designed, but you're faced with a dilemma:
1) Design for low noise parts that are no longer made
2) Avoid circuits--like phono stages--that require low noise parts
3) Design compromised circuits with available sub-optimal parts
I've got a number of circuits that I've played with, but haven't presented here because the parts aren't readily available. Unfortunately, the way things are going, that's going to be true for nearly all small signal through-hole parts in the near future. My fingers are crossed that Toshiba, et. al. will come out with high performance surface mount parts. Not that I'm anxious to start with surface mount stuff, but it'll be better than nothing. Weighing heavily against this will be the economic crash. What we've seen so far is just the beginning, and the sort of parts we're interested in are a niche product for the semiconductor manufacturers. They are not going to invest in tooling up a production line for something they can't make a profit on.
Lean times ahead.
For what it's worth, I'm using the Toshiba 2SC2240/2SA970 bipolars at the moment. They're still available, not unreasonably priced, and perform well. They aren't listed in the low noise portion of the catalog, but they appear to be the equals of the official low noise stuff (which are not available).

Grey
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Old 18th February 2009, 03:53 AM   #5
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Default BP

No, was making a pun. B for latest series from 1st Watt, P for phono. Regular and Extra were references to grades of BP-Amaco gasoline.
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Old 18th February 2009, 04:01 AM   #6
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Well, then I suggest you try the name BOno...
...Or perhaps better still...FOno...

Grey
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Old 18th February 2009, 09:48 PM   #7
gl is offline gl  United States
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I have purchased between 25 and 100 of the various Toshiba dual and single JFET's and have every intention of using most of them. In fact I'm well on my way. Those I don't use will serve to give me peace of mind.

Thank you.

GL
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Old 19th February 2009, 03:30 PM   #8
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The 2Sk170 Toshiba JFET is still in production, so there is not really a component problem to make low-noise input stages.
They can be bought from many places.

Even the 2Sj74 is availbale.

So,
go ahead and design some low noise MC-RIAA amps!





Sigurd
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