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Old 24th April 2011, 01:48 PM   #511
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Quote:
Originally Posted by simon7000 View Post
Of course it can be "voiced" with an additional wye resistor to signal common.
ES
How about voice in the desert. Now the bypass caps are in the signal path as well as you have removed all the PSRR of your buffers/whatever, so what have you gained? Maybe an oppurtunity to spend more money.
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Old 24th April 2011, 01:54 PM   #512
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Quote:
Originally Posted by scott wurcer View Post
How about voice in the desert. Now the bypass caps are in the signal path as well as you have removed all the PSRR of your buffers/whatever, so what have you gained? Maybe an oppurtunity to spend more money.
Yes, you do lose PSRR, but there is something you gain and Scott you got this correct before!
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Old 24th April 2011, 01:56 PM   #513
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Quote:
Originally Posted by Joachim Gerhard View Post
He changed to bipolars shortly before he disappeared from this world.
Hardly. Mine had MAT02 in it in about 2003 on Allen's suggestion.
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Old 24th April 2011, 02:01 PM   #514
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Yes, he did that earlier. Sorry for the misinformation. As far as i know the smaller preamp uses one 2SK170 Fet.
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Old 24th April 2011, 02:08 PM   #515
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Something like this :
Attached Files
File Type: pdf Allen Fet-Tube Phono.pdf (80.0 KB, 119 views)
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Old 24th April 2011, 02:09 PM   #516
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Yes, you can put in a say 10n cap before the 1000k resistor and get a 1st order roll-off at around 15 Hz.


Quote:
Originally Posted by MiiB View Post
would it harm to take the first servo out.. and instead capacitor couple..in order to get too much varped record filtered out a bit..
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Old 24th April 2011, 02:18 PM   #517
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Quote:
Originally Posted by Joachim Gerhard View Post
Yes, he did that earlier. Sorry for the misinformation. As far as i know the smaller preamp uses one 2SK170 Fet.
No worries. Thinking back it would have been earlier than that, 02 maybe as I moved in 03. Mine was an RTP3. I'll likely be building another soon, so I'll go with his SSM suggestion.
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Old 24th April 2011, 03:34 PM   #518
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OK, IngemarR, have it your way. I have plenty of P channel jfets, Charles Hansen has many more, Constellation has many thousands, and Parasound uses 100's every month. Sometimes I have to bail them out by selling them a few hundred. However, it is difficult to OEM P channel 2SJ74's, as I try virtually every week, and audiophiles tend to 'cry out' when something increases in price.
Personally, I already KNOW how to design a complementary jfet ultra low noise input in both single ended and differental topology. I work, at this time, on 3 different separate designs that will someday reach the marketplace. However, for the rest here, it can be difficult to make something comparable to a Vendetta with available products. Matching is necessary, and that takes a lot of parts. High current is necessary, because the folded cascode will not work properly without out high quiescent current. That is WHY I select only the top half of the V series for most designs, or parallel twice as many, and get into non-linear capacitance territory. NOW, where are your sources for P channel fets?
What Scott tends to quibble about, such as leakage, or leakage match with P's or nonlinear capacitance in general, I studied and experimented with, 38 years ago, when I designed the Levinson JC-2. I found, even then, that the advantage of the complementary jfet topology overcame some limitations in complementary characteristics for most applications. Bringing it up here, is just to muddle the water.
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Old 24th April 2011, 04:47 PM   #519
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It would be a pity if your Vendetta went into the grave without some DIYers having the possibility to listen to it (their own Vendetta version)!

Finding V-grade is another ball game. Those I have no surce for.

If I show you my sources, I guess you will buy all the JFET:s...

Here you can find 400 pcs 2SJ74.
B&D Enterprises - Electronic Components Distributor

In Germany there is a source that sell 2Sj74 for 2 Euro each.

Now, I am ALSO interested in single ended input MC RIAA amplifiers. Please do not think otherwise. BF862 is another very interesting Nch JFET that has no Pch counterpart.

So, I will not show any more Vendetta versions. Let's focus on Nch only designs.

I am also very interesteed in PS which seems to have been forgotten all together...
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Old 24th April 2011, 06:38 PM   #520
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Quote:
Originally Posted by IngemarR View Post
It would be a pity if your Vendetta went into the grave without some DIYers having the possibility to listen to it (their own Vendetta version)!

Finding V-grade is another ball game. Those I have no surce for.

If I show you my sources, I guess you will buy all the JFET:s...

Here you can find 400 pcs 2SJ74.
B&D Enterprises - Electronic Components Distributor

In Germany there is a source that sell 2Sj74 for 2 Euro each.

Now, I am ALSO interested in single ended input MC RIAA amplifiers. Please do not think otherwise. BF862 is another very interesting Nch JFET that has no Pch counterpart.

So, I will not show any more Vendetta versions. Let's focus on Nch only designs.

I am also very interesteed in PS which seems to have been forgotten all together...
Ingemar. did you build your version of Vendetta phono preamp? Obviously, Mr. Curl does not wish to see any Vendetta clone. He wishes Vendetta to stay status symbol of selected few. He underestimates Mr. Borbely designs as compromised, but they are only with different design approaches compared to Mr. Curl. Kit designs are often consider inferior since are aimed for amateurs to be assembled. There are no reasons why they should be worse than factory made units. Mr. Borbely used folded cascode in the stage of his eb-804/419 ALL-jFET MC/MM phono preamp which I built myself ,including PCB with two ounce copper. It is very similar to Vendetta , so similar that I tried second stage Vendetta on the same PCB with only slight modification. Reading Mr. Curl posts between lines, I chose 15 ma fets in dual diff. stage. Instead of second stage Mosfets, i paralleled two 8ma fets ( X8 and X9 in your diagram)- it is C grade version. RIAA toplogy and values are the same. I put a small heatsink on output J-fets. Borbely circuit uses source follower at the output. Vendetta output changes open loop gain with the various line preamp impedances. All in all, original Borbely circuit is slightly more dynamic in sound reproduction.
There is no need to reinvent the wheel with SE phono stages using only N fets. Pass Aleph Xono is a almost perfect No-feedback MC SE gain stage. HPS 5.1 is also good circuit using BF862 JFets. Pass Lab latest phono preamp XP-25 is a complementary design. They obviously changed their design approach. At the same time they are constructed with SMD components.
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