Choke Position?

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Cressy Snr
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#1 Choke Position?

Post by Cressy Snr »

This comes up every so often, with CLC power supplies so my apologies if it has been answered before but.....

Is there anything to be gained, with a straight LC, choke input supply, fed off a hybrid bridge, by putting the choke in the tail of the rectifier bridge, ie the earthy side, rather than the output end?
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#2 Re: Choke Position?

Post by Cressy Snr »

I've answered my own question by trying it.
In my pink SET it has worked a treat.

I'll update the PSU and post it on the amplifier thread.

This page from Turner Audio helped me:
http://www.turneraudio.com.au/audiofilt ... page2.html
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#3 Re: Choke Position?

Post by IslandPink »

Interesting. I was mulling it over, but got too busy making a piece of MDF to attach a dartboard to a wall !
However the link makes a good point about the potential from the windings to the choke core being much lower in this config. I do remember Thorsten having chokes in both rails of his mad phono amp supply, but based on Nick's rather dim view of this device after having built it, I'd forgotten about the subject recently.
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#4 Re: Choke Position?

Post by pre65 »

I'm waiting agog for information relating to the benefit (or not) of doing this. :)
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#5 Re: Choke Position?

Post by pre65 »

One thing I did notice in the article Steve linked to was this, regarding choke input power supplies.

" especially where the current draw will vary
by a factor of 10 or more as is the case with a power supply for a class AB, B or C amplifier."

So, what is best for class A ?
Last edited by pre65 on Sat Dec 30, 2017 7:29 pm, edited 1 time in total.
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#6 Re: Choke Position?

Post by Nick »

Yep, I was going to post (but forgot to hit post) that the only obvious advantage is the lower choke turns to earth voltage. But not that big a deal on <1kv.

The problem with the Thorston supply wasn't the chokes in both rails, it was the sheer number of them and if you looked at the impulse response of so many identical caps and chokes, it was rather chaotic.
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#7 Re: Choke Position?

Post by Nick »

pre65 wrote: Sat Dec 30, 2017 7:27 pm One thing I did notice in the article Steve linked to was this, regarding choke input power supplies.

" especially where the current draw will vary
by a factor of 10 or more as is the case with a power supply for a class AB, B or C amplifier."

So, what is best for class A ?
Well, one advantage of a choke input supply is the better regulation. There is arguably less need for better regulation if the current draw is constant.
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#8 Re: Choke Position?

Post by Cressy Snr »

Interestingly, the mains transformer gets less warm as does the choke. Mechanical hum is dramatically reduced from both.
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pre65
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#9 Re: Choke Position?

Post by pre65 »

Cressy Snr wrote: Sat Dec 30, 2017 10:23 pm Interestingly, the mains transformer gets less warm as does the choke. Mechanical hum is dramatically reduced from both.
But, how does it affect sound quality ?
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#10 Re: Choke Position?

Post by IslandPink »

Hmmm...
I could do with less noise from the mains on the T-Rex supply ....
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#11 Re: Choke Position?

Post by Cressy Snr »

pre65 wrote: Sat Dec 30, 2017 10:26 pm
But, how does it affect sound quality ?
Too much water has passed under the bridge and there have been far too many rows and too much bad feeling for this writer to make any comments about sound quality, now or in the future. I've had enough for one year.

Let's just say that more music comes out and leave it at that.
That should satisfy even the most cynical among us.
Sorry I can't be more specific, but it's better all round to just hold my tongue and suggest that people try it for themselves, and draw their own conclusions; after all it's not something out of the ordinary I did.
Last edited by Cressy Snr on Sat Dec 30, 2017 10:58 pm, edited 1 time in total.
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#12 Re: Choke Position?

Post by Cressy Snr »

Mark,
Re T Rex
I think you'd be pleased with the subjective effects of the reduction in noise as any reduction always lets more of the music out, or so they say.
The HT went down by 10 Volts in my case, with the choke in the 0V rail.
Maybe it's a case of the rectifier negative end, now sitting on the voltage developed by the DC resistance of the choke that reduces the voltage across the supply, I don't know.
Anyway, I'll put up the revised PSU tomorrow on the 6B4G thread, as there was a change to the the 0V layout required to get the maximum benefit from the "choke at the bottom" method.
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#13 Re: Choke Position?

Post by Paul Barker »

in the old radio ham books they used it as a cheap and simple way to generate negative bias. But they werent working in stereo. For us using dc resistance to generate negative bias robbing total ht to do so is done at the cathode, usually on an individual basis. Fits our purposes better. Only commenting on that element of the discussion. Never tried it for any of the reasons given here so cant comment.

Like all these various options which all pre-existed some way or another, as we play-about with these creations it is always good to try the ideas and adapt according to taste. If I hadnt experimented with permitations when active I would have stopped short of some very nice sounding amplifiers.
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#14 Re: Choke Position?

Post by Cressy Snr »

May as well put the choke in the 0V line schematic on this thread, as it is arguably, more relevant here than on the 6B4G thread. In my particular case, the GZ34/5AR4 valve rectifiers are the only ones that will now give the textbook op point for the 2A3. 5U4Gs and their ilk put the HT lower, so they have been removed from the rectifier list:
Image

I've said I wouldn't comment on the sound quality changes caused by this repositioning of the HT choke, but it does need saying that in the case of my own amplifier (cynics, note carefully, the complete absence of superlatives, this is a serious attempt to be objective and avoid claims of bullshit) there have been clear gains in the following areas:
  • Noise floor
  • Treble detail/tone/texture
  • Midrange detail/tone/texture
  • Bass slam/tone/tune
  • leading edge speed
  • Micro and marcodynamics
  • Soundstage width and depth
  • Image placement
  • The ability to unravel denseness and complexity.
Now as this is absolutely not hype on my part and the gains appear to be genuine, there are obvious questions to be asked, such as:

why and by what mechanism/s
Last edited by Cressy Snr on Sun Dec 31, 2017 2:44 pm, edited 2 times in total.
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#15 Re: Choke Position?

Post by ed »

not sure this is a serious question or not, it being new year and all, but,

which speakers are you using to get clear gains in Soundstage width and depth'

not to mention image placement
There's nowhere you can be that isn't where you're meant to be
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