|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
17.207.199.172
In Reply to: RE: Then you need to adjust your parts values posted by mobiasloop on September 15, 2014 at 09:07:54
Then, do any of you ever use a plate choke in the power supply if the current demands are really low? (Massive Henries, high DCR, low current)
Follow Ups:
Yes, I do that often in preamps
Thomas
Thomas,
I was planning on using Lundahl chokes. I asked Per about it and he indicated, "Today all our chokes for power supplies are wound using paper insulation, as we have experienced that this makes the chokes more quiet. Technically, yes you can use the LL1668 in a power supply. However, they MIGHT not be as quiet as our dedicated supply chokes." Have you had any issues or noticed this? Part of the reason I was looking at their products was for ease of placement and the other was the lower inherent noise and radiated fields. With 50-100H chokes available, it's very easy to get a low noise supply with small value caps.
Do you think it's worthwhile to make separate legs for left and right? Or it's not important especially if it's all in a single chassis?
Kindest regards,
Chris
Hi!
For preamp voltages you will not have issues with buzz from the plate chokes.
> > > Do you think it's worthwhile to make separate legs for left and right? Or it's not important especially if it's all in a single chassis? < < < <
See my post above, this heavily depends on your circuit (PSRR).
I usually feed each channel and each stage with a separate RC or LC leg
Thomas
"do any of you ever use ... Massive Henries, high DCR, low current."
Large inductance, yes. Low DCR isn't beneficial in a preamp if all the circuitry is Class A.
--------------------------
Buy Chinese. Bury freedom.
It's a single stage DHT preamp. Class A.
Class A always draws the same average current, so RMS regulation from the perspective of loading is not an issue. Also, the instantaneous values within the average should be supplied by the last capacitor in the chain feeding each stage. The primary goals for the PS in a low-current Class A preamp should be ripple reduction and isolation. The latter includes isolation between the channels as well as stage to stage (if more than one) within each channel. Low DCR is not necessarily beneficial to these functions, and many multi-voltage preamp supplies use resistors instead. Personally, I would consider it a waste of resources to use high inductance, low DCR chokes for this purpose.
--------------------------
Buy Chinese. Bury freedom.
Counterpoint I believe did it in one of their more expensive preamps. Shure had a vacumn tube phono preamp (almost identical to a Dyna PAS3X except it had transformer coupled balanced outputs) that used a choke in a seperate chassis power supply. So yes it's just the designer's choice and how well the parts are employed. I see little need for separate power supplys/chokes for each channel. You just need to choose circuits with very good PSRR and choose a well designed power supply.I looked up the Westrex RA1479 power supply used in a recording mixer and it's ripple content at a DC output of 275v B+ does not exceed .001v at it's specified current draw up to .055A . Moe Bias
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: