Hi Salas,
Thanks for the GB. I was planning to do the simple NJFET Phono Preamp before but was set aside due to no good PCB available then but I have the complete parts for said project. I have Obligato gold .1uf and 3.3uf matched pairs for C3 & C4. I also have the matched pairs of Vishay MKP1837 for C1 & C2 all source from partsconnexion. For R1 I have also caddock 47K. For this project I will use Denon 103R what is the best value for cart loading so I can buy a caddock resistor. I will order some resistor parts for this project as some values have change. I will also wait for the 2sk369 from Mike to arrive so I can include the matching resistor for R2 & R3. I hope to finish my project this time.
Thanks,
Rey
Thanks for the GB. I was planning to do the simple NJFET Phono Preamp before but was set aside due to no good PCB available then but I have the complete parts for said project. I have Obligato gold .1uf and 3.3uf matched pairs for C3 & C4. I also have the matched pairs of Vishay MKP1837 for C1 & C2 all source from partsconnexion. For R1 I have also caddock 47K. For this project I will use Denon 103R what is the best value for cart loading so I can buy a caddock resistor. I will order some resistor parts for this project as some values have change. I will also wait for the 2sk369 from Mike to arrive so I can include the matching resistor for R2 & R3. I hope to finish my project this time.
Thanks,
Rey
It's an explanation, or at least a conjecture, of why a larger-VA transformer sounded better in one circuit, and the example was a change from 100mA transformer to a 10A transformer. Nobody here is disputing that a transformer needs adequate capacity, nor that "adequate" is a lot higher than the load consumption. However, I think there are upper limits to any benefit. Taking his change from 100mA capacity to 10A capacity, and adjusting for the fact that Salas' RIAA circuit consumes something closer to 200mA, and the secondary voltage is nominally 36V, that implies you should use about a 720VA transformer for your phono preamp.
The reason stated in that article is the lower secondary winding impedance of the transformer, hence the ability of the transformer to respond to changing load. However, that has limited applicability in the case in hand. First, if the transformer impedance has that much effect, then the PS is poorly designed, and the regulators have terrible line regulation. Second, in this circuit we have a CCS-fed shunt regulator with a constant current load on the transformer. The transformer does not respond to changing load, because the load the transformer sees is constant. Only the shunt reg error amp needs to respond to the changing load.
So based on things like transformer derating, conduction angles, and a generous safety factor, a pair (pair!) of 30VA transformers, about 5x over-rated for the job at hand, seems like a good compromise. Of course, this is DIY and if you want to use a 300VA transformer (50-times oversized) by all means do so.
All good logic, nezbleu ... but (irrespective of the argument advanced as to why it sounds better) if you want to use theory and don't want to experiment ... well, it's a free world.
My own attitude is the same as (I think it was) Newton's ... who said he "stood on the shoulders of giants", in terms of incorporating other people's prior thinking into what he did and thought.
Regards,
Andy
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All good logic, nezbleu ... but (irrespective of the argument advanced as to why it sounds better) if you want to use theory and don't want to experiment ... well, it's a free world.
In the past i have raised the transformer "sound" effect many times but never got a reasonably convincing explanation. The reason is: too many variables and interactions generally lead to inconsistent conclusions.
Here is what i've heard and learnt:
1. Bigger generally sounds better but there are exceptions. I have used huge 1kW-plus transformers which sounded bad in either power amp or preamp duties.
2. Core type matters soundwise. Some silly observations: R-cores are great but don't seem to ever match the bass power of EI. Toroids are sometimes just as good as EI but often sound a bit "nervous".
Why are these empiric conclusions without much value? Too many possible variables and most of them interdependent.
Is it core size that matters? Is it winding impedance? Is it the geometry and the relultant filtering effect? Is it all due to interactions with the rectifiers and subsequent RLC resonance? Or is it the flux density at which the core operates?
Could anyone please give a recipe for a great sounding mains transformer?
Analog_sa said it all as well as it can be said
One never knows until they try the various components in THAT one circuit.
We wish for hard and fast rules and we are continually disappointed.
WHICH is why threads like this are so great. We are all working on a similar circuit and can come closer to actually discovering what works best AS LONG as we maintain great similarities in our implementation of the phono stage.
"The simple things you see are all complicated" - one of Peter Townshend's great lines of wisdom; we all need to remind ourselves, as soon as something seems simple, we are lost.
One never knows until they try the various components in THAT one circuit.
We wish for hard and fast rules and we are continually disappointed.
WHICH is why threads like this are so great. We are all working on a similar circuit and can come closer to actually discovering what works best AS LONG as we maintain great similarities in our implementation of the phono stage.
"The simple things you see are all complicated" - one of Peter Townshend's great lines of wisdom; we all need to remind ourselves, as soon as something seems simple, we are lost.
To andyr concerning McGowan and transformers
I remember getting the big transformer for my PS AUDIO phono stage when it became available.
Stan Warren was a very open fellow and when he left PS and started his own company he would answer the phone and tell some interesting stories.
I remember him saying that the transformer idea was not shared. I cannot remember which one came up with it - I think it was McGowan because he credited Paul with being the intrepid one - the one who would try things everyone else said was wrong. The "other" was shocked that such a thing would do what it did. This was back when intrepid audiophiles were being shocked regularly that cables sound different and connectors and everything else. Stuff no one (well, almost no one, other than the DIY obsessives) were concerned with. Not too long after LINN showed that a turntable could sound dramatically different.
NO question - PS started the big transformer idea. But this was also running parallel with HUGE cap bank idea which has become discredited in some quarters SO that is why, since this BIG TRANSFORMER idea began over thirty years ago I thought it likely to be ready for revision or at least reflection.
Much time has passed and I would like to think we have learned something in the interim - which, of course, we have.
I remember getting the big transformer for my PS AUDIO phono stage when it became available.
Stan Warren was a very open fellow and when he left PS and started his own company he would answer the phone and tell some interesting stories.
I remember him saying that the transformer idea was not shared. I cannot remember which one came up with it - I think it was McGowan because he credited Paul with being the intrepid one - the one who would try things everyone else said was wrong. The "other" was shocked that such a thing would do what it did. This was back when intrepid audiophiles were being shocked regularly that cables sound different and connectors and everything else. Stuff no one (well, almost no one, other than the DIY obsessives) were concerned with. Not too long after LINN showed that a turntable could sound dramatically different.
NO question - PS started the big transformer idea. But this was also running parallel with HUGE cap bank idea which has become discredited in some quarters SO that is why, since this BIG TRANSFORMER idea began over thirty years ago I thought it likely to be ready for revision or at least reflection.
Much time has passed and I would like to think we have learned something in the interim - which, of course, we have.
~100mA per channel in this implementation, and not recommended to modify. The integrated regs are tweaked, judged, biased and sinked, specifically to this PCB concept. For the raw PSU part beyond the minimal example included in the guide, each one to his own aspirations and budget as also stated in the guide. No harm done as long the raw volatges, fusing and grounding are done right.
Amen. There are just too many factors that are real and make sense, to just adopt an unthinking attitude that "bigger is always better".
No, I do not. I mean that if one follows the "logic" in the cited article, where the transformer in the PS for a phono preamp was changed from 100mA -> 10A (a 100x increase) then (based on my faulty assumptions and arithmetic) it would make "sense" to use about a 720VA (36V x 10A x 2) transformer for this circuit.
Please don't misunderstand me: I think a pair of 30VA transformers, or a single 50+VA transformer, should be adequate for this project. There is no harm going higher, say a pair of 50VA transformers. I personally would never consider using 160VA transformers for a phono preamp, but others here disagree. So be it, more power to them (pun!), to each his own, etc.
Point taken, my bad. I think I read something you wrote in another post, probably about 200mA for both channels. It's not like I actually did the math
Again, point taken, and it was not my intention to tell anyone NOT to use bigger transformers. However, I was concerned that there seemed to be a few posts suggesting that much much bigger transformers were de rigeur. I doubt there are many real "newbies" reading this thread, but it concerned me that some might be getting a false impression of the minimum requirements for this build. I had my say, so I'll butt out now. (Still waiting for my boards, and rewiring a tonearm, so probably a few months away from actually listening to one of these!)