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Old 6th December 2012, 10:24 AM   #8791
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by nicoch58 View Post
................... "voltage overhead" means poor regulation ie bad design ..................
No. You misunderstand. A regulated supply requires a higher transformer voltage than an unregulated supply. Typically use a 12Vac transformer for a 18Vdc supply when unregulated. Use a 18Vac transformer for a "normal" regulated 18Vdc supply. A Salas Style Shunt regulator uses a 20Vac to 22Vac transformer for a 18Vdc supply due to the requirement that the CCS must never see a voltage drop of less than 5V and preferably more than 7V. This is nothing to do with "bad design" !!!
Quote:
..................EI with split ................ are best too..................
You have understood capacitive coupling properly. But best ONLY for capacitive coupling or at least for reducing that.

Another unhelpful post ?
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Last edited by AndrewT; 6th December 2012 at 10:40 AM.
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Old 6th December 2012, 10:29 AM   #8792
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Originally Posted by Salas View Post
................ You need 11mA K369BL as it is noted. ..................
2nd tier quality solution is the 2x K170BL 8mA example I had posted. 2 junctions and more 1/F noise, but +2dB gain. Not bad at all in the end, still not the reference design exactly.
How would a 11mA k170 compare?
Not enough transconductance?

Maybe a 13mA or 15mA V grade?
Would a cascode solve the dissipation that ensues?
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Old 6th December 2012, 10:35 AM   #8793
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Quote:
Originally Posted by AndrewT View Post
No. You misunderstand. A regulated supply requires a higher transformer voltage than an unregulated supply. Typically use a 12Vac transformer for a 18Vdc supply when unregulated. Use a 18Vac transformer for a "normal" regulated 18Vdc supply.
Another unhelpful post ?
No. You misunderstand ! I mean the trafo we speak about r-core cinese not the regulate psu power like Salas shunT !

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Old 6th December 2012, 10:39 AM   #8794
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We are in a Salas Topic Thread !
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Old 6th December 2012, 10:54 AM   #8795
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I will be taking the dual 170 for the first build, as it is a Christmas present for my brother. If i am blown away, /i will try the 369 version. The whole thing may be beyond my ability to hear and I am only building because i have built other Salas stuff and enjoy his taste. The toroid option will be used for the first build and I will look into other options for my personal build. Components are in route.
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Old 6th December 2012, 10:57 AM   #8796
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How would a 11mA k170 compare?
Not enough transconductance?

Maybe a 13mA or 15mA V grade?
Would a cascode solve the dissipation that ensues?
369 had noise advantage that even paralleled 170 does not have. Borberly used 4 in a row(which would be better), but all else changes. I may try BF862 with second build, just for kicks and to worry Salas
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Old 6th December 2012, 11:04 AM   #8797
Salas is offline Salas  Greece
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Quote:
Originally Posted by AndrewT View Post
How would a 11mA k170 compare?
Not enough transconductance?

Maybe a 13mA or 15mA V grade?
Would a cascode solve the dissipation that ensues?
One=not enough Yfs and more hiss. 2 K170=enough+ mS, about same hiss, still not the 1/F under 300HZ quality of a 369. Caution, small IDSS changes will not let it centre properly with same resistor values around. This one is much more peculiar for total bias current feed and spare for BC560 bias. There are two branches now, the normal simplistic has one current branch. Heat builds up normally on the Fet(s), only the BJT on top gets a dissipation benefit in the folded.
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Old 6th December 2012, 11:11 AM   #8798
Salas is offline Salas  Greece
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Originally Posted by buzzforb View Post
369 had noise advantage that even paralleled 170 does not have. Borberly used 4 in a row(which would be better), but all else changes. I may try BF862 with second build, just for kicks and to worry Salas
He had much more capacitance also and a telescopic cascode. Different beasts.
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Old 6th December 2012, 11:19 AM   #8799
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Originally Posted by Salas View Post
He had much more capacitance also and a telescopic cascode. Different beasts.
Didnt seem like you were getting enough of a workout, lately. Ill finish my first one before reinventing the wheel
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Old 6th December 2012, 11:28 AM   #8800
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Good morning Gentelmen !
I think the point about the R-cores is...
...low-field & low P-S coupling.
Obviously, the toroids windings, are snug as a bug.

I don't see toroids as any cheaper, by any reasonable margin either.

Voltage-overhead...
...not bad design.
Just get one with enough to drop.

Some guy moaning about Chinese R-Cores in another thread...
...bought a 18v one & expected to get 18v out of it after a couple of regs...
...Dddeeeeer ?

Easily done getting too few Volts...
...having said that, you don't want too many; just to burn-up in your regs.

Beam me up Scotty....................................

Cheers.

Si.
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