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Old 13th January 2009, 11:09 PM   #601
Salas is online now Salas  Greece
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Quote:
Originally posted by ikoflexer
I'm hoping the MCM manufactured ones from Newark don't totally suck. One question though, since this is my first foray in jfet land, do the jfets need to be matched position-wise (left-right channel correspondence)?
Thanks. This phono has been done with tube logic and comparison, right from the start. It will not let down some tube oriented guy.
I don't think that the Linear Systems LSK170B will let you down either because ''Jonners'' from England used them for our phono already with no problems. Position wise matching (left & right per stage) is the best strategy indeed. The strongest for Idss pair, better be reserved for 1st stage. Bypass your batteries with a 10.000uf 35V capacitor. Batteries are not that good although there is an urban legend that they are special. Good thing is that they are virtually floating so they don't give such a hard time with not so good grounding, and don't emit hum fields. When you are about to make a PSU, don't reinvent the wheel, go directly for the shunt. We will be happy to learn about your progress and help out.
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Old 14th January 2009, 07:20 AM   #602
jonners is offline jonners  United Kingdom
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Hi!
Yes, the LSK jfets seemed fine to me. And I would definitely plan to go for the shunt reg psu eventually. Batteries have never really done it for me .
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Old 14th January 2009, 08:03 AM   #603
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ampslab ,very fast and good price (complementary too,no LSK)
better have a small bags of this original pearl , as out productions

or if you want the best go for borbely audio for mached- V grade and/or dual j109/k389
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Old 14th January 2009, 10:12 AM   #604
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Default row psu

Salas I see that pedja in my dac put 10r beetwen diodi -caps ,can be better to avoid doubling the caps......
the same for power amp (0,47r)?
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Old 14th January 2009, 01:34 PM   #605
Salas is online now Salas  Greece
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Default Re: row psu

Quote:
Originally posted by nicoch46
Salas I see that pedja in my dac put 10r beetwen diodi -caps ,can be better to avoid doubling the caps......
the same for power amp (0,47r)?
Someone must plan why and what values, knowing the particular raw PSU details. Such small resistors are probably there to cut initial rough edges on the charge cycle that translate into unwanted harmonics. They certainly can not create problems if you use them. If the capacitors are very good like Nichicon KG, and not that large in value, maybe doubling is not too efficient in cutting much self inductance and esr, because it may be low enough in the first place. Doubling can be very anti economic when using expensive capacitors...
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Old 14th January 2009, 01:42 PM   #606
Salas is online now Salas  Greece
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Quote:
Originally posted by nicoch46
or if you want the best go for borbely audio for mached- V grade and/or dual j109/k389
No V grade in our phono. Only BL. V needs all the circuit values to be designed again. Also the gain will sky rocket.
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Old 14th January 2009, 02:02 PM   #607
AndrewT is offline AndrewT  Scotland
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The bottom end of the V range is below what is available from the top end of the BL range.
Why do we need to redesign?
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Old 14th January 2009, 02:33 PM   #608
Salas is online now Salas  Greece
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Because they will bunch at about middle V range and I have designed at about middle BL range. Practically someone will end up with double the Idss I have designed for.
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Old 15th January 2009, 02:40 AM   #609
iko is online now iko  Canada
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Honestly, I have no idea who makes the jfets sold by MCM. In time I'll get some Toshiba originals, thank you guys for all the pointers.

We all know simulation isn't reality, but it's fun. I've attached a simulation file any one can run on the freely downloadable ltspice. I've included the regulator in the simulation, with a 1V p-p ripple, DC bias 30V going into the regulator, and out coming an impressing almost zero ripple at 24.7V. Also nice, a bit of distortion analysis with .027% THD, of which 99.91% is second harmonic.

Now, can anyone see why I'm a bit peeved that the jfets are on back order and I have to wait another two weeks to get them?

Actually it seems I can't attach this type of file, so it can be found here

Right click on the link and then save the file to a place where you can open it with ltspice if interested in playing with the schematic.
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Old 15th January 2009, 03:25 AM   #610
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Default get yr 2SK170's on ebay

Just do a search on ebay- that's where I've bought my 2SK170BL's. I get the 'matched' quad sets from Audiotek; usually around $4-5 including shipping. The 2 sets Ive bought were fine.

Idss, set 1-
8.18 8.13 8.09 8.00mA

Idss, Set 2-
7.72 7.40 7.25 7.09mA

Matched? Good enough for me. The first set was better. I put trimmers for my source R's to bias them all for ~8.2v on the drains. Coming from tubes, these cost peanuts to me!

-Kent
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