|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
82.132.223.63
In Reply to: RE: 4P1L preamp DIY posted by sideliner on March 17, 2017 at 11:30:20
'The reason for the better sonic results with the choke, probably stems from the reduction in the upper harmonics, from say the 20th and beyond.'
I really have no idea how you come to that conclusion regarding high order harmonics although I can take measurements using a wave analyser or FFT if need be . In terms of measurement , I do not posses a DVM with the sort of resolution to take such measurements so an HP mV meter was used
As for the rest in cut and paste format . There is no feedback in the filament supply . This consists of LCRC to a Coleman reg (buffered CCS) taking the cathode connection from the 4P1L filament centre tap
George
Follow Ups:
You stated that you heard a sonic improvement with a choke in place preceding the Coleman regulator. I took that at face value and my response was an attempt to explain why you heard such an improvement - that's all.
The reduced upper harmonics, is obviously a conjecture or an educated guess on my part with no concrete proof offered and the language I used reflects that. Having said that, I still think that the quite drastic reduction in the upper harmonic content put out by the choke supply, is responsible for the sonic improvement you hear, irrespective of the filament regulator. On my part I don't understand why you would think that it'd be that big of a leap to even entertain such a hypothesis. It's been common knowledge for decades now that upper harmonic distortion even at very low levels is quite detrimental.
As far as the regulator comment is concerned, I haven't seen Rod Coleman's circuit, but do you know of any regulator, be it either of the voltage or current reg variety, where the core working principle is not based on feedback? Olson's comment as quoted, is very much on the money IMO.
Maybe you misunderstood me, I don't know, but if you haven't taken a close look at the filament supply test that I linked to earlier, I would give it another shot.
The point I am making is that a Coleman reg presents a high impedence and hence a very large degree of isolation from the downstream PSU circuitry . It feeds the filament with a ring of two CCS one side and a gyrator/buffer the other . By using choke input , the measured noise at the filament pins drops by an insignificant amount . In terms of harmonics measured on the FFT , I can't see a difference in comparison to cap or resistor input but there is an unexplained improvement in sonics . Maybe I need better equipment to measure this but as far as I'm concerned , it's not worth it
George
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: