New Posts New Posts RSS Feed - DC on the mains
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Welcome to the Graham Slee Audio Products Owners Forum

 

Open to all owners plus those contemplating the purchase of a Graham Slee HiFi System Components audio product and wishing to use this forum's loaner program: join here (Rules on posting can be found here)

This website along with trade marks Graham Slee and HiFi System Components are owned by Cadman Enterprises Ltd


DC on the mains

 Post Reply Post Reply Page  <1 345
Author
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298
Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2022 at 11:41am
Originally posted by CageyH CageyH wrote:

A more compact version of what I ended up with.
I am happy with the lack of humming traffos now. Does it make a difference to the sound quality?

I have no idea…

I think it does, but "downunder friend" doesn't quite see things my way, and so I tend to keep my mouth shut, but this time it's different.

It is difficult to "see" the workings of this, yes, even for me, but something that would otherwise steal transformer magnetising current each half cycle, isn't going to be much good for the amplifier it's powering.

By "centering" the waveform, then the relationship of mag current to reservoir capacitor charging current becomes "even".

OK, the reservoir charging current is per every 100Hz (120Hz elsewhere) and the musical waveform is everywhere else, and the current drawn each conduction angle is not the mag current, which occurs at a different angle within the 180 degrees, but DC is not DC in the strictest sense.

All analogue amplifiers are cap coupled as "downunder friend" does actually say, yes, even the DC coupled amps are cap coupled, because the current into the reservoirs only conducts for part of the mains cycle. At all other times they are supplying energy all by themselves.

So if the signal demands current (which it does) and the mag current is offset, then it's out of balance compared to the next 10mS. The relationship to mag current is due to the non-linear capacitive filter rectifier load, and transformer winding harmonics, which can increase the mag current, unless it isn't there because of interference.

So basically, the naysayers say it can have no effect. That depends on whether you over analyse things like I do, or you deny that little things have any effect. It used to be said that if you look after all the little things, then big things would follow. Perhaps I'm old fashioned in that respect.

Anyway, the 1W distortion fell from 0.009% to 0.007% so something about it works.

That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298
Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2022 at 11:50am
Originally posted by Graham Slee Graham Slee wrote:


Anyway, the 1W distortion fell from 0.009% to 0.007% so something about it works.


Or even the reduction in noise.
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
CageyH View Drop Down
Senior Member
Senior Member
Avatar

Joined: 30 Apr 2012
Location: Toulouse, Franc
Status: Offline
Points: 1678
Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2022 at 1:07pm
I am a great believer in “every little helps”.

My amplifier is based on the LM3886, and apparently has the following specs:
Output power: 360 W (4 Ω) – 240 W (8 Ω).
Ultra-low 0.00026 % THD+N (140 W, 8 Ω, 1 kHz).
Ultra-low 0.00048 % THD+N (100 W, 4 Ω, 1 kHz).
Kevin
European loan coordinator, based near Toulouse, France.
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298
Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2022 at 1:45pm
With that amount of NFB - about 30dB available at 20kHz for a voltage gain of 20 - then distortion and noise simply vanishes (fig.47 LM3886 datasheet). The point though is what it does within the first watt, where most of the detailed listening takes place. No matter how good a circuit is, external factors can be more prominent. Not that a power supply should be considered an external factor, but is often considered that way.
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
 Post Reply Post Reply Page  <1 345
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.125 seconds.