advertisement


ESL57 question (level matching, bass output)...

The replacement boards I've seen all come with stand offs to mount them where the existing potted EHT unit sits - no need to mess about with wax, but you will need to use a soldering iron.
 
  • Like
Reactions: JTC
I’ll dig out the paperwork tonight, hopefully, to see what was done and when. And, yeah, I will power them down and pop the back off over the next few days to have a look.

If the speakers have the original Bulgin sockets, they were likely not rebuilt by OTA. Their rebuild changes them over to IEC. I can’t imagine a full rebuild of panels not including the power supply.
 
They have the original sockets John, that I can confirm. I do have paperwork for OTA work, but it may be that a previous owner decided not to change what was (at the time) still working?
 
Not at home, but dug this out of my emails from the chap I bought the ESLs from:

in 1993 Quad did a major rebuild including new grilles, protective clamps, new rectifier blocks and all six new panels.
In 2005 One Thing rebuilt the treble panels and replaced the audio transformers
In 2006 One Thing rebuilt all four bass panels


So, looks like everything has been done *except* the EHT. Which kind of makes sense if one has started to go after what might be 40 years of use! I guess the next step is to double check against the invoices (which the seller gave me). Out of interest, though, do te rectifier blocks degrade over time? And what about the clamps? I am thinking that, after 25 years, they might be due a looking at too....
 
I would assume rectifier block = EHT unit :) If they were replaced with potted units in 1993, that’s 25 years and they likely need doing again.
 
I’m tempted to just order up new OTA PSUs as they also let you part-ex the old ones, and are (apparently) better made...
 
I would assume rectifier block = EHT unit :) If they were replaced with potted units in 1993, that’s 25 years and they likely need doing again.
I take it that, other than the bits that a new EHT board would replace, there are no other components on an ESL PSU that would wear out, hence my pair having the older style power connector?
 
All panels renewed 2005/6 so hopefully good for at least another 5-10 years. In contact with OTA today, am going to send PSUs for diagnosis and possible refurb or replacement (if required)...
 
I'm beginning to get paranoid now. I bought my 57s from Pete MB&D of this parish, some 14yrs ago, and have done nothing to them since. I'm not sure how long Pete had them for, or what was done to them when he had them, if anything. They do have the clamps fitted (I think...) so they must have been serviced at some time in the last 50yrs, but as far as I can tell they are working just fine. To be honest, I just don't notice them, they are part of our TV system now, and the sound is so good we just don't think about the sound when watching films and TV, though we don't watch much of either as we listen to too much music.
 
I wouldn't worry. I've had mine 9 years and never picked up a screwdriver. One pair were serviced 1986, the others were built in 1976 and I have no service record. Therefore at least one pair are 30 years the wrong side of a service, the others are anyone's guess. They work fine. I bought a spare pair to plunder for spares if necessary, they are tucked away in a cupboard. I'd pull a cover off to have a look but it's a bit of a rave and while they work I don't want to disturb anything.
 
To be sure, I wouldn’t be messing with them unless I had to. Despite having this bass level mismatch, they still make pretty much every other speaker seem a bit lame. However, I want to bring them back to full performance and it’s sounding very like it’s just a matter of servicing or replacing the EHT unit on one side, though I’ll get both done at the same time so Iknow they’ve been done.
 
I think that the treble panels fade over time, but even faded they are fabulous. And the EHT units decay measurably. If they decay at different rates then the speakers change their outputs. It's not magic and it's easy to fix. The real danger is over-driving, which is especially likely when the EHT droops.

I have a pair of ESL57 which were fitted with encapsulated EHT modules, non-serviceable. Both had drooped, one more than the other, so audible. I changed them to OTA boards. Job done, speakers perked up. I have another four in my office which all have the beeswax jobs and all have different measured outputs. I expect I will rebuild these for the hell of it.
 
Update: As it turned out I had 2 PSU blocks in each speaker, I sent 2 off to get serviced/rebuilt. They arrived back yesterday with new EHT boards and much cleaner too (plus gone are the Bulgin connectors, replaced by modern IECs). After some fiddly refitting - mainly complicated by a lack of wire for the earth feed, plus the need to renew the grill earth cables - they are now back up and running and sound *incredible*!!!!

I am very happy!!!
 
I've concluded that as ESL's are driven by the mains transformers as much as by the signal from the amp, that they respond better to improved mains supplies.

Mine have responded well to introducing a balanced mains transformer and now a DC blocker capable of removing 3/4 Volts of DC.

lRBIbjbNQo9WjBUS0siCPasmoC8TkJ6yktESexodCAFlOzqKzd04nWxHynRzjXEaWaxC1U6OizoBM_f84oXrycDfLYlc_MJhufW1DGRbcJJRPxdA2MoeMPQq3c5Le4ZeXLQjrPFmMUg9VHMyhJZBX_snFS9sV9HIFamQqT8j1USn5cGWF8BPNN683cj8WK-jiqvKCqf3KNs_LVKaW_ww7QAIaR3pa--GmDZAB6TL7ctVkdw-houxz169umKrLxGqlKIh92KvvOtAE-CqSurhu8zDrF22bliIo-BORHImcolt9BFFGVd4nvG4bjOvJwGSmOoKPw3JqMbr7egyiMsdxrJcwuWkCdp-sNLZ-AwRQqTsumCY5FP6WFhOmLSLbbwBWrHaYAI6fkozHjDb4GaP07goRE9OXofYY7bO6mkvRnSuk7jOmwyXE27ziEiaIWWTt2PI6FHqdrN4GKF9U4cZnRMUGPhCJIQ-xeGraWrcdvu1HfbhmspgsleKRqMeE7EBj65KswSNWzLDjBbBMi8kT1zYUP3w6ko7f5SjGtf6oUveh6m5mB-KaMtHpNxLNnyPrTsCZlw9srlHBSOIVzzKinFLWhGIhhJ7LtoMJ2U=w884-h663-no
 
Having missed the group buy, I've just ordered the parts: the idea was to stop my Meridian amp buzzing, but it seems I may need two more.:)
 
More info on the above, please :)

The signal from your amplifier is providing a signal at around 15/20 Volts depending on volume level.
This signal is then being boosted to several thousand Volts in order for the ESL's to work.

If improvements to the incoming mains supply have a beneficial effect on an audio amplifier, though maybe only small depending on how good your amps PSRR is. Then benefits to the ESL's mains supply will possibly multiply the advantages by using good clean mains.

I've ordered a spare DC blocker to send out for people to try, as it has been a success for two of us on here. More so than just reducing transformer hum.
DC on an AC supply causes distortion of the waveform and is a form of distortion.

As for the balanced mains transformer, this is the one I use

https://airlinktransformers.com/category/standard-balanced-power-supply

I think the DC blocker had as much effect, though I should try it without the BMU.

Pm. me if you wish to try the DC blocker.
 


advertisement


Back
Top