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OT's 'widget' schematics for the ESL57
OT's 'widget' schematics for the ESL57
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Old 10th December 2017, 01:01 PM   #1
Nemeske is offline Nemeske  Hungary
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Default OT's 'widget' schematics for the ESL57

Dear Forum,

I do not know if it's O.K. to ask it here, but do anybody knows the schematics for One Thing Audio's "widget" for the ESL 57?
Who knows its purpose?
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Old 12th December 2017, 03:04 AM   #2
stokessd is offline stokessd  United States
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I have no idea, where is it placed in the circuit, that might give a clue as to what's inside of it.
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Old 12th December 2017, 10:56 AM   #3
lcsaszar is online now lcsaszar  Hungary
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What I could make out from OTAs description is that the widget makes an easy load for the amplifier. Some amplifiers do not tolerate the low impedance of the ESL exhibiting at high frequency, and could become instable. How is this impedance correction achived, I have no idea. But I can live without it
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Old 12th December 2017, 11:12 AM   #4
Nemeske is offline Nemeske  Hungary
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Quote:
Originally Posted by stokessd View Post
I have no idea, where is it placed in the circuit, that might give a clue as to what's inside of it.
It puts between the amplifier and the transformer's input
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Old 13th December 2017, 05:07 PM   #5
Nemeske is offline Nemeske  Hungary
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Quote:
Originally Posted by lcsaszar View Post
What I could make out from OTAs description is that the widget makes an easy load for the amplifier. Some amplifiers do not tolerate the low impedance of the ESL exhibiting at high frequency, and could become instable. How is this impedance correction achived, I have no idea. But I can live without it

My plan is to experiment with other amp than the Dynaco ST70
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Old 6th January 2018, 05:29 PM   #6
bolserst is offline bolserst  United States
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Quote:
Originally Posted by stokessd View Post
I have no idea, where is it placed in the circuit, that might give a clue as to what's inside of it.
From pics and descriptions posted on their website: One Thing Audio
  • The ESL-63 widget appears to be intended as a replacement for the RC input components.
  • The ESL-57 widget is likely designed to be placed at the input as well, but component values and PCB traces are not definitively discernible in the pic.
    With carefully selected R & C values some equalization(mentioned in the description) of the slightly sloping response of the ESL-57 should be possible.
Attached Images
File Type: png ESL63_RCinput.png (651.4 KB, 139 views)
File Type: png Widget_ESL63.png (295.4 KB, 129 views)
File Type: png Widget_ESL57.png (232.1 KB, 136 views)
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Old 13th January 2018, 09:49 AM   #7
Nemeske is offline Nemeske  Hungary
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Thank you for your time!


Quote:
Originally Posted by bolserst View Post
From pics and descriptions posted on their website: One Thing Audio
  • The ESL-63 widget appears to be intended as a replacement for the RC input components.
  • The ESL-57 widget is likely designed to be placed at the input as well, but component values and PCB traces are not definitively discernible in the pic.
    With carefully selected R & C values some equalization(mentioned in the description) of the slightly sloping response of the ESL-57 should be possible.
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Old 24th June 2018, 07:04 PM   #8
misterdog is offline misterdog  United Kingdom
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What is the function of the R-C on the input is it a form of Zobel network ?

Click the image to open in full size.
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Old 25th June 2018, 03:20 AM   #9
stokessd is offline stokessd  United States
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That input provides phase shift and a little response compensation. The impedance of the RC parallel pair is about 1.4 ohms at 20Hz and falls to essentially a short at 20KHz. That is is series with the transformer and panels and such, which also have a falling impedance (more or less). That's also a trick in cone and dome speaker crossovers.

In my humble opinion, that circuit has no place on the original ESL.

As an aside, adding about 10uF of film capacitor in parallel with that 220uF electrolytic really helps the sound of the 63's. for the 988's and later there is room under the hood to replace that electrolytic entirely with an enormous solen film cap. But the 63's are a bit cramped for that, and placement is nasty.

Sheldon
quadesl.com
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Old 25th June 2018, 05:29 PM   #10
AVWERK is offline AVWERK  United States
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0D6EEC65-5219-4FDE-B1F0-73376C2A4A0E.jpeg
(Quad 988)
Yes very tight fit. I purchased 5 - 200 uf Non polars to match them along with the wonder cap matching and got rid of the upstream fuse FS2

The stock 220 uf NP cap were quite a bit higher in value when pullled and measured.

I noticed Bennic makes a 220 uf PP film cap also along with the rest. (Solen Etc )
Very pricy and huge in size and can see why back to back electrolytics were used.
I might make up a board to see if there is a sonic difference worth pursuing


Regards
David
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