replacement resistors for esl57 crossover

[Audiofool]

What type of resistors should be used for replacement of the originals on QUAD esl57 crossover?

The resistors pass the full amplifier signal after the step-up transformer, so common sense tells that they should be rated for high voltage, but the originals seems to be regular 3W carbon comp.

Any ideas?



Quad esl57 schematic

[moray james]

should think Peter W. had the wattage value all figures out so safe to stay with stock values. Metal film resistors will most likely sound a little cooler than the carbon. Carbon in film or solid sound a little warmer. The difference will be one of flavor. Will not cost you much to try out both and see what you like best. Have a very happy Christmas and a happy Honica. Regards Moray James.

[Audiofool]

Thanks Moray for the greetings : I wish you and all forum members happy holidays.

I'm also sure that P. Walker figured out the type of resistors to use, but unfortunately he is not around to be asked about it...neither the schematics mention the wattage or voltage requirements.
And well, cost is an issue if you consider the fact that each speaker have 9 resistors and that high voltage resistors are not cheap : at least 5$ a piece*18=90$.
reasonable amount of money if you have it correct from the start, but not a sum I would like to play hit & miss with...
What I was meaning to ask is if "regular" resistors would survive in that position, or should I look only for high voltage resistors.

[hilbren]

if you want a cheap high voltage resistor just buy some cheaper (low voltage ones) and put them in serie.

or is that just to simple?

[Audiofool]

Interesting : if you look at the schematic, you will see that QUAD used three 180k resistors in series (instead of single 540k) on the low-pass lines to the bass panel stators, which gets the highest voltage : Perheps P.J walker was thinking the same as you about this...

Your idea is really nice and simple, but the resistors are mounted on a tag board inside the tranny box, and I doubt there will be enough place for long resistor strings.

TAG BOARD LAYOUT

[Brian Beck]

While some type of high voltage resistor, or a series chain, might be the safest bet, plain carbon composition resistors are pretty rugged and can handle momentary over-voltages rather more gracefully than can, say, metal films. Also, please note that resistors in series with the ESL stators will not drop the full secondary voltage except at very high frequencies at full power, the kind of signal that would toast a panel to begin with. This is because at most audio frequencies the capacitive reactance of the ESL element will exceed these values of resistors, and the resulting simple voltage divider will cause most of the voltage to be dropped across the ESL. This speaker would be dreadfully inefficient if most of the signal power were wasted as heat in resistors rather than transferred to air motion.

[testlab]

Running the resistors in series overcomes the breakdown voltage of the individual resistors. This is very common in HV supplies. While the total wattage rating of a resistor may not be exceeded, the BV of those id in the 200 to 300 volt range.

If you are concerned about their electrical integrity, Caddock offers suitable high voltage resistors. You can find them at Newark/Farnell.

[hilbren]

i use the same trannies for my diy esl's, i can confirm there is enough space to use more the 10 extra resistors

[testlab]

If you go to the Caddock website, you should be able to find resistors with higher voltage ratings. You will probably be able to reduce the total number of resistors and simplify construction.

[TimA]

I believe Quad's original carbon resistors were rated at 1.2kV.

Tim.