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Converting stereo single ended to balanced mono?

Hi, I have three Thiel 3.5 stereo equalizers (bass boosters). These are single ended only. I was wondering about the benefits of trying to convert two of them to balanced mono operation. Is it possible? Is it worth it? What are the options for doing this? What are the pros and cons of these options? Are there any other upgrades that might be considered if and when these conversions might be done?

https://www.stereophile.com/content/thiel-cs35-loudspeaker-measurements

As always thanks in advance.

unsound
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unsound OP
7,332 posts
 

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Thanks for all your responses. I seem to be just as confused as when I first started.

I have considered bi-amping the 3.5's. The 3.5's only come with one set of binding posts per speaker. The earlier 3.0's came with two sets of binding posts per speaker. Perhaps "Coherent Source Service"

https://www.coherentsourceservice.com/

 the company made up of ex-Thiel techs could modify the 3.5's with earlier dual setup 3.0 binding posts. They are currently working on cap replacement/upgrades for the Jim Thiel designs, Unfortunately I'm led to believe that the 3.5 cap replacements are not currently on the front burner of development. I do have a bit of concern about the time delay between the signal that would go through the eq vs. the signal that doesn't. I realized that the time might be insignificant, but time integrity is one of the hallmarks of Thiel designs (and a handful of others). Heck, the cross-overs on the CS 5's were designed to move drivers back as little as 3/8".

https://www.stereophile.com/floorloudspeakers/690thiel/index.html

Furthermore, though bi-amping would help keep the eq out of the upper registers, the degree to which might be less than one might first assume due to the shallow 1st order cross-over. Still, despite the extra expense the thought has much merit.

Thanks again for the responses. I still don't feel like I understand this well enough. In any event I don't have the technical skills to pull this of myself and think I would have to hire some one to complete the task, should I go forward.

 I welcome any other thoughts or considerations.

 As always, thanks in advance.

atmasphere's avatar
atmasphere
11,896 posts
 
You could do this with some modification, but there really isn't a good way to do it otherwise. The problem is that you have to invert the signal to one channel in order for a balanced output to be produced from the pair of channels.
One way do solve that, assuming a single-ended input, is to wire the input circuits of the two channels as a single differential amplifier- with each output then driving their respective channels. This assumes a discrete solid state circuit. And you might need a negative power supply to make it happen.
Another way would be to use an line transformer driving the two inputs. This is by far the easiest way to do this but the transformers that are worth it aren't cheap. Jensen makes the best- its either that or Lundahl. If the secondary driving the input of the EQ has a center tap that would be helpful, but a pair of resistors would do as well.  PM me if you need more info.
unsound OP
7,332 posts
 
Atmasphere, Thanks for your considered thoughts. I was hoping you might respond:-). I’ve always been curious about using balanced configuration, and your previous posts on the subject have been quite compelling. Honestly, this subject seems more and more like it’s way beyond my technical understandings. Still, I’m curious and it might open up options up and down stream in my system if I could resolve the bottle neck.
imhififan's avatar
imhififan
2,210 posts
 
Schematic on diyaudio if interested:
https://www.diyaudio.com/forums/analog-line-level/294911-popping-noises-thiel-cs3-5-bass-eq.html

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