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RE: I hate my Quads!

Yes R13 to be specific. The stock value is 61K in the 12 series speakers and this produces a bias voltage which is much too high IMO about 5.15kV.

110K-120K will drop the voltage to about 4.5-4.6kV which is the voltage that is found on early production ESL-63.

Yes I know the schematic states 5.25kV but in reality early production ESL-63 was much lower.

The lower voltage will reduce efficiency slightly, perhaps 1dB, but it puts far less stress on the panels.

QUAD raised this voltage over the course of the ESL-63 production to make them slightly more efficient in the hope they would ultimately play louder. This is speculation on my part. It doesn't really work for several reasons and the result is premature panel failure.

This increased voltage carried over to 98 series with the same result premature panel failure. With the 05 series QUAD reduced the voltage back down to early ESL-63 levels and I don't see panel failures due to drive voltage. Typical failure is glue issues which QUAD solved over a decade ago. I never see glue problems on late production 05 or current 12 series speakers.

Unfortunately and I don't know why QUAD has raised the voltage again on the 12 series speakers. This is a mistake IMO and the results are quite predictable.

Every speaker I service be it 63, 98, 05 or 12 series gets the bias voltage set at 4.6kV. And before I ship any new 12 series speakers that I sell I drop the voltage. After doing this simple change I have had zero issues with panel failures.




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