replacement resistors for esl57 crossover

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
options

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.
 
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.
 
quad_transformer2.jpg




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
 
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.
 
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.
 
Kiwame carbon film resistors are rated at 1200V and come in both 2 and 5 watt ($1 and $2). The 5 watts won't quite fit between that tabs on the transformer but are very close and could fit with just slightly bending the leads. The 2 watt ones would easily fit but i don't know the required wattage. Anyone know the wattage rating of the originals?
 
Kiwame carbon film resistors are rated at 1200V and come in both 2 and 5 watt ($1 and $2). The 5 watts won't quite fit between that tabs on the transformer but are very close and could fit with just slightly bending the leads. The 2 watt ones would easily fit but i don't know the required wattage. Anyone know the wattage rating of the originals?

Any news on this old topic ?
Quote from OneThingAudio: "Whereas the "wattage" ratings of resistors are not critical, it should be remembered that each resistor should be capable of handling instantaneous peak voltages of at least 3kV".
VR37 series should be fine. They are rated for 1/2W & 2.5kV RMS (3.5kV DC).
But hard to find: listed only on Digi-Key.
 
Why would someone replace the original resistors, unless their ceramic case is broken because of mishandling?
But I am thinking of replacing the original 6x 560pF 3kV ceramic capacitors, because I don't like ceramics for audio. Would these SBE capacitors fit the purpose?
 

Attachments

  • 718p719p.pdf
    91.4 KB · Views: 108
Why would someone replace the original resistors, unless their ceramic case is broken because of mishandling?
But I am thinking of replacing the original 6x 560pF 3kV ceramic capacitors, because I don't like ceramics for audio. Would these SBE capacitors fit the purpose?

Yes. The SBE caps would work great in this application.
Even with a 100W amplifier (30Vrms/8ohm) the voltages would be well within the capability of the SBE capacitors.
 
I was unsure because the originals are 3kV and the SBEs are 1.5kV rating for AC. Given the 292:1 turns ratio (found this value by Googling) the primary can be driven by 5V which seems insane... Or is that not the full AC goes to the capacitors? They seem to filter the AC signal going to the stator of the mid and high section; there is no DC polarizing voltage on them.
 
I was unsure because the originals are 3kV and the SBEs are 1.5kV rating for AC. Given the 292:1 turns ratio (found this value by Googling) the primary can be driven by 5V which seems insane... Or is that not the full AC goes to the capacitors? They seem to filter the AC signal going to the stator of the mid and high section; there is no DC polarizing voltage on them.

Capacitor voltage ratings
The 3kV rating on the ceramics is a DC voltage rating. The AC rating is an unknown, but would be no more than 1kV. (VDCrating)/(2*sqrt(2))

The 1.5kV rating for the SBEs is an AC rating. The DC rating for the SBEs is 5kV. What is important in this application is the AC rating.


Transformer step-up ratio and applied voltages
The full transformer ratio is about 290:1, but the mid-tweeter section only gets about 90:1.

The two paralleled 650pF caps feeding the tweeter will, worst case, only see half of the total step-up (45:1) at low frequencies since the 270K resistor references to the center tap, not the opposite phase side of the winding.

The 650pF cap feeding the midrange section forms an AC voltage divider with the midrange ESL capacitance, which is 200pF. So, worst case, the 650pF cap will see about 1/4 of the total voltage coming from the 90:1 winding.
 
Last edited:
Capacitor voltage ratings
The 3kV rating on the ceramics is a DC voltage rating. The AC rating is an unknown, but would be no more than 1kV. (VDCrating)/(2*sqrt(2))

The 1.5kV rating for the SBEs is an AC rating. The DC rating for the SBEs is 5kV. What is important in this application is the AC rating.


Transformer step-up ratio and applied voltages
The full transformer ratio is about 290:1, but the mid-tweeter section only gets about 90:1.

The two paralleled 650pF caps feeding the tweeter will, worst case, only see half of the total step-up (45:1) at low frequencies since the 270K resistor references to the center tap, not the opposite phase side of the winding.

The 650pF cap feeding the midrange section forms an AC voltage divider with the midrange ESL capacitance, which is 200pF. So, worst case, the 650pF cap will see about 1/4 of the total voltage coming from the 90:1 winding.
Can I use 600V rated capacitors if I don't exceed 10V AC input?
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.