GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage

Post Subject: About the last distraction cap and transformers.Posted by Romy the Cat on: 8/31/2011

N-set wrote:
Oh, Romy, I meant the air caps in the corrector loop of course!!!
Adjusting PS caps I leave to AA morons and alike.

Believe me or not I did go very serious about the proper choke input operation.
What I meant is that I have to get hold of a scope to check if it all works as it should.
The input chokes were already changed once (once too low voltage rating,
another time too low inductance for a given voltage/current).
The heater/bias input choke is for example 300mH (!), dictated by the tranny
output voltage/heater current (and the Hammond range). Then the LC tanks are additionally damped
with series resistors to bring the Q's down. I'll post the schematics.

I'd strongly desagree that the L-input on B+ is questionable. First of all the choke is dictated
by both the input voltage and the current draw. It's perfectly fine to make a 2mA choke input
supply--the choke will have to have a big inductance, which is easy with low mA's.
Second there are VR's and a serious bleeding resistor down the chain so a small current
drawn by the signal part itself is not an issue. I very much like this implementation of yours. I believe
it helps a lot to stabilize the supply.
Third, and probably most important, L-input is inherently less noisy (provided min current is
met). With such a delicate preamp, the current spikes
emitted by the cap input filter (they depend on the cap size, not the current draw, and could easily go into ampere's range
if the cap is big enough...which would be the case to filter well) could do a lot of harm: may spread all over
the place and trigger ringing here and there. I'd not even consider a C-input.

N-set, I do not want to argue the subject of LC filtration vs. RC filtration. I am a big supporter of LC filtration and all my “own” electronics is a good evidence of it. However, at the currents of 2mA I am not sure that it makes any sense. Sure as an avid LC supporter I can bring many evidence why it might make sense from perspective of circuit operation but I also feel that it might be possible that in practical listening it would be no difference between LC filtration vs. RC filtration if you draw juts 2mA. Do not forget that in my version of LC filtration I do not use the small caps as many SET builders people do. You will not see in my power supplies any 4uf or 8uF caps after chokes, any plastic or paper caps of small values and the rest of the typical DIY Audio idiocy. I do not shape the sound of a devise by wiring or insulation in chokes, or by specifics of rectifiers sound. I leaves that duty to the DIY Audio and I will leave for them to make amps to sound as good as the parts of this PS. In my audio after LCLC, the last caps is a distraction cap, a very large cap that shunt PS at very low frequency, as close as possible to the load and that completely eliminate any contribution to Sound from PS.

Anyhow, I had identically good sound with my EAR 834PT before, what I used the regular capacitive PS and later on when I went with LC and bleeders. Some might feel that gas tubes, the LC supplies are superfluous in this corrector (on B+ side). I would not argue with it and it is possible that it has no practical impact to sound. I made it as it was my “end of the life” phonostage and I did not want to have anything done in none final version.

Regarding your MC efforts - the sound of your step up transformer is 70% of your sound. Do search for a good one. I am not familiar with Tribute phono transformers. Fame and Sound of phono transformers are not necessary goes alone. The phono transformers are very personal thing. Also do not forget that the phonostage that you built has very lash and very polite sound. You need to have very hard reading phono transformer to get the sound that I envision…

Romy The Cat

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