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In Reply to: RE: Dyna PAS3X, SDS PSU Board and some Wine posted by TimeConstant on July 12, 2015 at 04:20:44
Soft recovery (SR) SS diodes - that don't have switching noise problems - do exist and can be used. Because they don't have voltage drop and PIV limitations at switch off, they allow for much stiffer power supplies, which IME is always a good thing.Switching noise might have been a problem for you but needn't have been.
Higher voltages can be adjusted for, but also don't seem to have been here, and extra volts too can have some significant advantages. Valve amps run on supplies of several hundred volts and storage is 1/2 the capacitance times the square of the volts.
The difference in PSU stiffness between 240 volts and even 280 volts is not small. 240X240 = 57600, 280 V (17% more v) sq'd gives a factor of 78,400 (36% more storage) and ripple would be very low.
There is one other advantage, you have just freed up the heater/filament supply to the VR and it can be used, yep even the 5V ones?, to boost your heater supply headroom and even use higher Gm valves. These almost always sound better so less loop NFB is needed, which is a good thing. Still with the logic of this?
A PP amplifier I came to like and even sold on weekends at the shop years ago was a Quicksilver 8417 type using two 5AR4 VRs. Where two ought to have been adequate - from a VR-design-era perspective - and a choke/cap ladder supply.
So, I don't think VRs are a bad idea, I simply know that SR SS diodes can be better. I don't think QS still use VRs.
Any circuit is a system, in any given state it has dependencies, which are state dependent.
I listen at least once a week to live acoustic music performed to a high standard. At home I find that the audible advantages of valves, in reproducing such music for me, lie in their instantaneous headroom, basic linearity, and low amounts of loop NFB, all making timbre distinct.
None of these valvey features depend on the use of VRs and indeed could be restricted by them.
LBNL Valve Rectifier PSUs have 'sag' which IMO does not belong in a hi-fi amplifier.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 07/15/15 07/15/15Follow Ups:
I don't think QS still use VRs."
Yes, Mike Sanders still uses them in the re-issue of his full function pre-amp. I hear increased definition and detailed nuance with valve rectifiers. I do not believe this can ONLY be heard through Khorns, although the difference is not as apparent with my Quad ESL 63's.
The Mind has No Firewall~ U.S. Army War College.
Great... So with a few changes to the Power Supply to account for the offloading of the stock PAS transformer, a pair of high quality FR low noise diodes, the quiescent voltages should park themselves properly for an objective comparison. All good points, all well taken. Appreciate you taking the time to post.
The bitterness of poor quality remains long after the sweetness of low price is forgotten
I think this may be the reason why "I" prefer tubes for classical and solid state for rock-ish type music. Solid state amps can and do have a wonderful sound, when done right.
However, in the end it is a "taste" issue. For me - tubes.
Thanks for that excellent explanation.
charles
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