I am working on a pair of 1980's Quad ESL 57. They sound quite well, with a reasonable volume level.
I am using a QUAD 405/1 with the 1k8 resistor as limiter, so not to overdrive the ESLs.
To be on the save site, I ordered a Gas Discharge Tube GC3 1.5 (1500V) and soldered it to Pins 7 and 9 of the ESL Audio Transformer. (Following Sheldon Stokes advise)
After that, I experience crackling distortions, specially when strong bass volumes are in the music.
I see the GDT lightning when the crackling noise occurs.
That already happens at quite low volumes.
Here comes my question:
There also exist Protection Clamp circuits, which should cut the voltage at approximately 3000 Volt, so just before the treble panel is in danger of arcing.
The GDT starts to fire at 1500 Volts - so what is the design decision to use a 1500 Volt GDT instead of e.g. a 3000 Volt GDT ?
What was the intent ?
I can see, that using the 1500V GDT, the panel is certainly protected, but the output level now is far below normal listening levels.
Can anyone discuss the sense behind the decision to use a 1500V GDT ?
Anyone have experience using a GDT with a higher rating (2700....3300 Volts) ?
Or - are my ESL 57 to old to deliver the volume ? The EHTs are ok, I actually modified it by adding the Enquist circuitry.
Many thanks,
Rgds, Thomas
I am using a QUAD 405/1 with the 1k8 resistor as limiter, so not to overdrive the ESLs.
To be on the save site, I ordered a Gas Discharge Tube GC3 1.5 (1500V) and soldered it to Pins 7 and 9 of the ESL Audio Transformer. (Following Sheldon Stokes advise)
After that, I experience crackling distortions, specially when strong bass volumes are in the music.
I see the GDT lightning when the crackling noise occurs.
That already happens at quite low volumes.
Here comes my question:
There also exist Protection Clamp circuits, which should cut the voltage at approximately 3000 Volt, so just before the treble panel is in danger of arcing.
The GDT starts to fire at 1500 Volts - so what is the design decision to use a 1500 Volt GDT instead of e.g. a 3000 Volt GDT ?
What was the intent ?
I can see, that using the 1500V GDT, the panel is certainly protected, but the output level now is far below normal listening levels.
Can anyone discuss the sense behind the decision to use a 1500V GDT ?
Anyone have experience using a GDT with a higher rating (2700....3300 Volts) ?
Or - are my ESL 57 to old to deliver the volume ? The EHTs are ok, I actually modified it by adding the Enquist circuitry.
Many thanks,
Rgds, Thomas
I really don't like the gas discharge tube as a protection device. The voltage is not well enough defined and you don't want to have 1500V or 3000V. They have limited life span as well so some day you may be relying on protection that is not there anymore.
My advise is to make or buy a zener clamp board, it is a better solution and will not affect the sound.
My advise is to make or buy a zener clamp board, it is a better solution and will not affect the sound.
Solved: Clamp-Board made it
Hello Arend-Jan,
thanks for your advise. I created my own clamp-borads using 4KV Diodes (GP02-40) as bridge rectifier and 11 Zeners (BZT 03 C200). I added a Neon Bulb lamp in series with 100k as clipping indicator in parallel to one of the Zeners.
It works great, compared to the GDT/1500V solution.
Thanks again,
Rgds, Thomas
Hello Arend-Jan,
thanks for your advise. I created my own clamp-borads using 4KV Diodes (GP02-40) as bridge rectifier and 11 Zeners (BZT 03 C200). I added a Neon Bulb lamp in series with 100k as clipping indicator in parallel to one of the Zeners.
It works great, compared to the GDT/1500V solution.
Thanks again,
Rgds, Thomas
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