Replacing / Upgrading Transformers

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JonFo

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I’ve been helping another member upgrade his Quest audio step-up transformers via a series of PM’s (since we both speak French, much of the conversation is in that language). But I figured it’s worth sharing with everyone and if there are corrections or enhancements other members contribute on this thread, then we can all benefit.

So the goal of the exercise is to update the (very old) transformers in a Quest ML. Many of the older ML’s had sub-optimal transformers by today’s standards. The newest transformers improve upon their performance a good bit.

Now, there are some theories that the less than accurate (in the high-frequencies) transformers were used to essentially cause a high-frequency rise in system response as a side-effect of their ringing at >10Khz. And that using the newer transformers might actually decrease overall system HF response. So be forewarned.

My take is that even if the response is a bit lower in the high-end, it will be cleaner overall. Actual measurements show a bit smother response as a result.

OK, so which transformers to use?

The common consensus over on DIYAudio is that the Amplimo’s from Holland are the best choice for a ML.

The 1:75 transformer should do fine on most panels, although the 1:50 would also work and give an even greater HF headroom.

So, how to connect it into a ML?

First, carefully document the existing transformers hookup and create a plan for which old wires will go to which new wires before disconnecting anything.

Also, it’s important to understand the basic layout of an ESL.

So to recap, the basic topology is to take the audio input signal (after crossovers) and feed the input side of a step-up transformer. The outputs of which will drive the stators of the ESL.

Note that the Center tap output on the transformer is used to provide a ground reference signal to the diaphragm high voltage energizer circuit (EHT) . (although I have SL3’s that do NOT do that, instead using the Neg signal to provide this).
 

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Replacement wire mapping

This is the critical step, so please ensure to get this right.

Reading the docs on the transformer, I’m thinking the following is correct:

First, follow their instructions:

Always connect the five blue wires together
Always connect the five black wires together

You are the left with:

Inputs
Black – Source signal - Neg
Blue – Source Signal – Pos

Outputs
Yellow – Step up output - Pos
Red - Step up center tap
Green – Step up output Neg

These would map to the Quest as follows:

Transformer inputs:
Black to the ‘High in’ Neg signal input (a black wire that does not go through the crossover)

Blue to the output of the crossover (whatever color that is in your speaker – typically red).

Transformer Outputs:
Red goes to earth ground (a wire that goes to the high voltage board)

Yellow goes to the additional resistors that feed the rear stator (note: not all ML’s have rear stator resistors)

Green goes to the front stator. (no additional components between it and the wires to the stator).


I’m fairly sure this right, but please review carefully.

Once the connections have been mapped, you can proceed with the replacement.

I’ll be replacing the trannies in my 1992 vintage Sequel II's in the coming year (as I also rip out the passive x-over), and will document that process carefully.
 
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JonFo,

With your electrical knowledge and my machining work. We could really do some neat stuff. :D We should work on something....
 
JonFo,

With your electrical knowledge and my machining work. We could really do some neat stuff. :D We should work on something....

JWTrace, sure thing man. I've got some cool ideas, but need a good bit of interesting and intricate metal work to pull them off.
 
With the two of your electrical knowledge and My building ,woodworking Knowledge I think We could build a dream speaker. I have dreamed of a multi panel speaker like a cls panel for mids and mid bass and a Sl3 or that narrow type for the highs . Imagine a wider and a bit taller CLS frame with a SL3 stator on the inside separated by a wood style then you have the CLS panel . Like a Magepan look with Stators and a wood rail separating them. It would look like the CLS with a another smaller panel next to it !

I ran this idea by ML while out there , It was absorbed a tad !
 
Well, let's get goin'. I'm still working/finishing my latest. The design/solid model is done. Now just the expensive part....soon though.
 
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This is an interesting thread..

If any of you are near Detroit in early May, attend the AKFest 2008 and stumble into a listening room hosted by "Cosmos" (me), you might see M-L Odyssey panels paired up with several modified KLH Nine bass panels.. for a full range, bi-amped, active crossover system. That is, if I can have them done in time for presentation.

So far, early tests indicate this is going to be a nice sounding setup. There might also be some homemade panels involved as well.. we'll see...
 
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This is an interesting thread..

If any of you are near Detroit in early May, attend the AKFest 2008 and stumble into a listening room hosted by "Cosmos" (me), you might see M-L Odyssey panels paired up with several modified KLH Nine bass panels.. for a full range, bi-amped, active crossover system. That is, if I can have them done in time for presentation.

So far, early tests indicate this is going to be a nice sounding setup. There might also be some homemade panels involved as well.. we'll see...

Ill be there for sure ! Its a 1 hr drive for me ! May bee I can drag a few other MI members !
 
Ill be there for sure ! Its a 1 hr drive for me ! May bee I can drag a few other MI members !

Cool! Make sure you introduce yourself.

Last year, I had 2 pair of virtually stock KLH Nines running. I thought about bringing 4 pair this year, but not sure that I'd have room for all 8 panels.. (Each listening room is a hotel room). Besides, I have wanted to do something like this for a while.. I hope I can get it done...

Has anyone tried winding their own step-up transformers?
 
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This is an interesting thread..

If any of you are near Detroit in early May, attend the AKFest 2008 and stumble into a listening room hosted by "Cosmos" (me), you might see M-L Odyssey panels paired up with several modified KLH Nine bass panels.. for a full range, bi-amped, active crossover system. That is, if I can have them done in time for presentation.

So far, early tests indicate this is going to be a nice sounding setup. There might also be some homemade panels involved as well.. we'll see...
How did you mod your KLH 9's? A friend just got a mint pair and I thought he might be interested. Thanks,
Neil
 
How did you mod your KLH 9's? A friend just got a mint pair and I thought he might be interested. Thanks,
Neil

Neil,

How do his sound? If they were ok presently, I'd guess someone has worked on them recently.

There are several aspects of Nines that are open to modding, but it sure as heck isn't easy..

The power supplies are potted in wax, which makes doing anything to them a project. However, there are rewards to be had.. Just updating the caps and resistors as well as replacing the selenium rectifiers, which are probably way out of spec is a great step.

Further, I think the crossover point and parameters leave a little to be desired.

50 or so years after their development, there are other improvements to be made as well. While the bass/mid panels are stellar, the tweeter panels do not weather well over time.
 
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I’ll be replacing the trannies in my 1992 vintage Sequel II's in the coming year (as I also rip out the passive x-over), and will document that process carefully.

Hey jon I was wondering about this my self - I have SequelII and want to replace the transformer with a pretty serious Torodial....so I was wondering where you are in the process?? And have you got any ideas about what the specs are for the the Trans?
 
Need help with ML CLS transformer

I’ve been helping another member upgrade his Quest audio step-up transformers via a series of PM’s (since we both speak French, much of the conversation is in that language). But I figured it’s worth sharing with everyone and if there are corrections or enhancements other members contribute on this thread, then we can all benefit.

So the goal of the exercise is to update the (very old) transformers in a Quest ML. Many of the older ML’s had sub-optimal transformers by today’s standards. The newest transformers improve upon their performance a good bit.

Now, there are some theories that the less than accurate (in the high-frequencies) transformers were used to essentially cause a high-frequency rise in system response as a side-effect of their ringing at >10Khz. And that using the newer transformers might actually decrease overall system HF response. So be forewarned.

My take is that even if the response is a bit lower in the high-end, it will be cleaner overall. Actual measurements show a bit smother response as a result.

OK, so which transformers to use?

The common consensus over on DIYAudio is that the Amplimo’s from Holland are the best choice for a ML.

The 1:75 transformer should do fine on most panels, although the 1:50 would also work and give an even greater HF headroom.

So, how to connect it into a ML?

First, carefully document the existing transformers hookup and create a plan for which old wires will go to which new wires before disconnecting anything.

Also, it’s important to understand the basic layout of an ESL.

So to recap, the basic topology is to take the audio input signal (after crossovers) and feed the input side of a step-up transformer. The outputs of which will drive the stators of the ESL.

Note that the Center tap output on the transformer is used to provide a ground reference signal to the diaphragm high voltage energizer circuit (EHT) . (although I have SL3’s that do NOT do that, instead using the Neg signal to provide this).

My ML CLS transformer was burnt. I want to find the replacement. Please help me where I can order the replacement. I don't mind to upgrade to toroidal type.
 

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