 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
144.131.102.48
In Reply to: Ray, the whole point of using a choke input filter... posted by Allen Wright on May 6, 2007 at 03:18:51:
Hi Allen,I understand your point. Since the main purpose of Satoru Kobayashi's PS design was to avoid the use of a heavy and expensive choke, I wonder if reducing the size of the input C before the MOSFET could help to minimize the spikiness to any useful extent? Or would a small inductor << 1Hy before the input C, as proposed by Jeff and experimented with by Henry, help to neutralize the RF? BTW, did you find this to be a problem in your own PP-1C?
Follow Ups:
Huh? the schema I have of his amp (GA #4/1999)uses a 300mA/10H choke - which isn't small/light by anyone's standards, followed by a MOSFETregulator for the B+.Are we talking about the same thing?
My PP-1Ccircuit was always intended to be a very low cost unit to be sold in malaysia as a kit. In it's original form it even used a 25 watt toroidal power transformer as an OPT.
Later versions used good James OPTs and became something rather nice - but when it grew into the PP-2C with a choke input filter - it stepped up several levels of perfomance with no other circuit or parts changes.
QED!
Regards, Allen
Allen, the design I'm talking about can be seen at the link below. There is no choke and in the text Satoru-san explains that he wanted to avoid using one, to save weight and cost. And thanks for explaining your findings with the PP-1C.
...both power and output traffos, even a high end Lundahl choke would add a very small percentage to both the cost and the weight - and minimally to the already gigantic (to me at least) size.I like my chiropractor, but hate the time between a strain and an open date at his office - hence I only ever build monoblocks!
Never saw that article - only the huge P-P one I referenced.
Regards, Allen
"even a high end Lundahl choke would add a very small percentage to both the cost and the weight - and minimally to the already gigantic (to me at least) size."
Well, I tend to agree, but I'm just quoting what he said in his article. Maybe, with all the cost, space and weight he'd already incurred, he felt that a smoothing choke would have been the last straw?As I explained to Tre', I wasn't crusading against the use of chokes, just interested in this alternative approach. From your replies and others, it seems a choke-input filter (a real one!) is a hard act to follow. Thanks for your interest.
That is my experience, without any reservations, across 30 years of actual work.Talked at length with Tim de Paravancini at last year's European Triode Festival, and we found we both agreed on the importance of choke input filters. But he's even more emphatic about this than me. I told him that in the "TubePreamp CookBook" I write that the choke should be at least the same physical size/weight of the power transformer - and he contradicted me: "No - it should be twice the size/weight!"
Regards, Allen
Hi Allen,Our mutual friend, the late Bob Fulton, used to tutor me in about 1973 on the use of " twenty ohms or less DCR for the chokes " which IS a large unit. Now - in 2007, I have changed to ten ohms or less DCR, and under 1/2 a HY, and Low C.
Even if this is may not intuitive to you, it is worth a build and listen Allen!! Use a couple Triad C-40Xs and two 50 uF ( or 40 uF ) caps, high quality, and heavy AWG high-quality hook-up wire. L/C/L/C.
Have fun listening to that! It is "something else" on dynamically recorded music, especially when all the musicians play at once !!
Refreshingly good to hear. A whole new performance level, one that we never even had before in audio.
The " proof " many of you seek of this build approach is very simple, ........ it is in the listening Allen.
Cheers,
Jeff Medwin
Ray,IMO, the place for a high current/low DCR RF choke is AFTER the 1st filter cap. and in front of the regulator. The "hash" is associated with the triangular wave form cap. I/P filters ALWAYS exhibit.
Eli D.
| ||||||||||||
| ||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
