Shunt vs. linear reg

[Pars]

My previous query(ies) may have gotten buried. Given the somewhat religious fervor this topic seems to generate on other forums (without much technical justification for the most part; just assumption), I would like to know people's thoughts on this. My take from other reading seems to be if not shunt then you are a) a dumb ass, or b ) you just don't appreciate the best. I did read a critique/analysis on topic that discussed shunts presenting a more uniform impedance to the load, but then went into a discussion of a push-pull relationship via a shunt, versus a push only relationship with a linear reg.

My specific interest is in a Salas shunt vs. GRLV plus for a phono stage, but a general discussion is more than welcome, if for nothing more than my education

[steefdebruijn]

Pars,

I guess this is all too familiar for you, but for me the pages at http://www.learnabout-electronics.org/PSU/psu20.php were quite informative about the different topologies.

Steef

[Pars]

Thanks Steef. Yes, those are helpful in getting a basic understanding of the differences.

[Blueman2]

I know JimL designed and built a shunt PSU for the SRX-Plus.  Great article on it in AudioXpress I can send you if you want.   

[Pars]

Sure, if its no trouble. The more reading, the better

[jose]

I am very interested in this question. I was thinking about using the Salas Shunt on my Pearl II but I am very attracted to the idea of using the GRLV.

[JimL]

Horses for courses. As John Broskie of TubeCAD points out, series regulators are well suited for class AB power amplifiers, where the current demand on the power supply can vary from tens of mA to several amps, whereas shunt regulators are best suited for class A amplifiers where the variation in current demand is relatively limited.

 

Arguments about which “sounds better” approach religious discussions, although it is interesting that more designers claim that shunt regulators sound “better” than the reverse – for example, Broskie, the late Allen Wright of Vacuum State Electronics, Richard Marsh, the late John Camille, designer of the Kyrie 211 SET amplifier, Lynn Olson, designer of the Amity, Raven and Karna, Kevin Carter of K&K Audio, and Frank Cooter. I think Kevin Gilmore is one of the few designers who has gone on record saying that series regulators are as good or better. Incidentally, Richard Marsh wrote an excellent basic article on power supplies for Audio Amateur magazine (1983, issue 3).

 

Religious arguments aside, there are pluses and minuses to both approaches.

 

In favor of series regulators, they can have excellent specifications in terms of noise, output impedance, input rejection, etc. For example, the low voltage regulators designed by Walt Jung have a lower output impedance than 0.2” (yes, one fifth of an inch) of 18 gauge wire. Of course, to achieve that performance you would have to incorporate the regulator circuit on the amplifier board, as any intermediate wiring would negatively affect the impedance. Series regulators are frequently more efficient than shunt regulators as they only require a few mA extra current draw for regulation.

 

In favor of shunt regulators, they have a constant current draw from the raw power supply, can both source and sink current, and have a relatively simple path to ground. By using a constant current source in series between the raw power supply and the shunt, this limits the signal currents to the regulator and amplifier area, whereas the varying demands of a series regulator means that some simplified form of the signal current has to circulate between the raw power supply and the series regulator.

 

The argument that a shunt regulator can both source and sink current is thought by some to be a major reason for its sonic superiority. However, this can be abrogated to a significant degree by placing a bleed resistor after a series regulator to bring it up to 50% of maximum load, as first suggested by Richard Marsh. This allows a series regulator to also source or sink current up to the level of its bleed current, but also decreases the efficiency advantage of a series regulator.

 

For a phono preamp, which runs in class A, you definitely want low noise. The GRLV definitely qualifies for that. K&K Audio sells a shunt regulator kit which it claims is suitable for phono preamps, and says it is based on the Salas regulator, so I assume that it is low noise also, though without suitable measuring equipment it is impossible to know how they rank in terms of noise.

[Pars]

Thanks Jim, just what I was looking for!

I already have one GRLV plus built, so I'll start with that (and maybe build a 2nd for dual mono). As mentioned, the Salas shunt regs are on the boards, so if I decided to switch to those, all I have to do is populate them (and build a raw dc supply to feed them).