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In Reply to: RE: Addendum posted by KIS on April 26, 2012 at 12:39:12
The cap *would* add to transparency *if* it helps the new transformer in some way to not have the lows moving through it. It might also help as it might help the overall impedance to be higher, which would result in less distortion from any amplifier. That would translate to smoother/more detailed.
Follow Ups:
Ralph
With all due respect, I heard it and you did not, therefore the comment.
But I see your theoretical point of view.
Will
When I installed the 100:1 treble transformers in my friend's U2PXs (formerly my own U2s), I inserted an 8uF film and foil polystyrene capacitor in series with it, which in conjunction with the 70-ohm impedance I measured at 300Hz (across the 100:1 transformer in isolation from the bass transformer) was intended to create a hi-pass filter at that frequency. Based on what you say, I will de-install it next time I get a chance. I was only following recommendations from Rob.
I agree you heard what you heard- no argument there.
What I am saying is that the road may not have ended there- if the impedance can be further raised at high frequencies the door would be open to lower powered amps and lower distortion out of higher powered amps.
In the old days (pre-toroid), you could drive a set of A-1s with 60 watts with no worries. I am wondering if all this work could make that happen again.
Your mention of having a cap in the signal is a two edge sword. Very similar to my experience below:
Years ago, I went down the part of cutting off bass below 100 Hz on my Quads ELS and adding a Sub-woofer for everything below 100Hz. Yes, the system sounded better with bass on a macro level, but suffered in the micro level - meaning that the beauty of the Quad midrange is loss by adding a cap in the signal path.
I tried all types of caps, but none made my Quad ELS sound anywhere close to how it can sound without a cap.
I preferred playing my Quad ELS full range (despite amplification and SPL down sides) and matching my subs to the natural roll-off of my ELS. I have since moved on, as it has its compromises.
Very similar argument to what you had proposed. There are upsides and well as down sides of using capacitors. For me, capacitor sounds too obtrusive and should be avoided where ever possible.
Anyone who persist with ELS (and its many shortcomings) are in it for low level detail and its magical midrange, so I doubt your suggestion of a cap is a long term answer for this group of people.
KIS..You have it right...Thanks for your input... Less is more with ESl an OLts...well any tube setup...But your are left with the socalled...MIXer...That eats power an dropes SPL buy a good 3-4db...MartinLogan setup... That i have moved onto....from Acoustats An soundLabes May in the end be on the right track...with this type setup...For fullrang...an in the clx thay ran two way...one panel for highs an a flat one for mid-base...sounds better too me...Than any other.... an i can get great SPL out of 60 tube watts.....goodluck
TyuI need to get use to your writing style, but you are worth deciphering. Most time I am only guessing at what you are trying to say.
With the implementation of the Au transformer, we can do away with the Soundlab cross-over entirely. This makes the current PX model probably more efficient than your beloved CLX.
As for the mixer cap eating away efficiency, I am not sure how the 0.015uF cap in series with the secondary high frequency transformer can eat away 3-4dB in your thinking. I doubt this, but I am not a trained electrical or electronic expert, so I will listen to your explanation.
Seeing that you have a vast knowledge on ELS and electronics, what are the consequences in removing the mixer altogether? What if I just hook up the two transformers together in parallel to drive one full range panel. What are we up against? Can we design transformers that can handle this?
I know there would be a lot of cross talk, but at lowish volume, it must sound quite exquisite. What sort of damage am I risking?
Edits: 04/27/12
Here it is Ralph has hit it....
There's gotta be some point where if the two transformers have different ratios, they will load each other and both would get warm if they are tied to the same load. Right now that's not a problem.
It When you tie the tranfourmers togather...this is a Problem.. the caps can be what ever....... you lose output in the paraleling of the secdary of the tranfourmers... that cant be over came!....jUST One tranfourmer ..If it was as big as the A1s...maybe?
KIs
What if I just hook up the two transformers together in parallel to drive one full range panel.
No....You need two tranfourmers that are the same..then run them like the ML CSLs setup...Look you may only get the speakers to go down too. 40-50hz...but the gains are well worth it...well to me anyway...
An for what i know about ESL... it just hands on...if i have not done it.. an heard it ...I wont post about what i think.
..The ML setup is the only way to over come this that i see....look i have Acoustat an about 5 pr of ML here an i have redone all the panels it a must....ML makes Big money of saleing panels...thay are set up to fail....thay feed the bias only on one side..i run new bias feeds an the panels come alive... I got out of the SL A1...I new i would spend big money if i keep them.
But i am not in to anyone ESL...thay all work the same...one thing i do Know there a lot of room to get better sound out of the SL an other ESLs the bias is one place i would start with the sound lab.. a better bias tranfourmer would go a long way at geting better sound ...
goodluck..An thanks for any input on geting better sound
Thanks for your great insights Tyu.
Like you, I do not speak about things that I have not heard or tried. Theories often can get unstuck when it comes to reality.
ML set-up:
Having two transformers that are the same would require filters (resistor, cap or inductors) in the signal path to get the frequency response right. More filters less sound.
SL set-up:
Now we have come up with a solution that can do away with all the filters on the primary side of the transformer - which is a big plus. The only filter now is in the form of a small value cap (0.015pF) in series with the two legs of the high frequency transformer.
Lew has already used a 0.01uF teflon cap here instead of a 0.015uF cap without any problems. I will be using 0.0075uF teflon.
Comparing the above two filtering set-up, isn't the SL one less obtrusive now?
Big value cap and resistor is more damaging than small value cap and resistor - all things being equal.
Also I suspect that at 8kV the cap on the secondary is also going to be less obtrusive.
Like you already said, the ML set-up have to give away the low bass which the SL can do easily with its multi-tap monstrous bass transformer.
Will
Tyu, I like your idea of paralleling identical transformers, e.g., two of Rob's 90:1. As you suggest, however, the extreme low bass might suffer. One can only find out by trying. Will has the cojones and the wherewithal to do it.
You also mention a better bias supply. As Rob also manufactures and sells bias supplies for ESL, I wonder what you have in mind. What would define a "better" bias supply, compared to that which SL uses?
There's gotta be some point where if the two transformers have different ratios, they will load each other and both would get warm if they are tied to the same load. Right now that's not a problem.
I've had the idea of a single transformer that does the whole thing for a while but never did anything about it. You wonder how far you can push this stuff. I think it would be neat if a speaker like the A-1 could be driven with lower-powered amps. That is likely going to mean that the impedance get no lower than 4 ohms at 20KHz.
Ralph
I am not a keen small amp believer went it comes to ELS speakers.
As you may well know, more tubes in parallel means lower impedance (if all things remains the same). Even with transformer coupled ones, it makes winding the OPT an easier task.
20kHz is not near high enough. To get really airy highs, a minimum target is 25kHz.
I do not know of any ELS that does not drop its impedance to 1 to 2 Ohms at 20kHz.
Coupled with your (and my) love for zero feedback, small tube amps is but a dream IMO.
Can 1500pF be wound into the secondary of the high frequency transformer? I believe that even 500pF is enough.
Lew, did you measure the Au Transformer secondary winding capacitance?
Don't know about the Quad 57s, but the 63s have a wretched 220uF bipolar electrolytic in series with the input. All those lovely sounds are going through that horrid capacitor, which is in parallel with an equally lo-fi sand cast resistor, to form a filter which I gather protects the speaker from low bass transients OR is needed to equalize the frequency response. Ironic.
With the 57s, they have a 1100pF to roll of the bass.
Remove this cap, and depend on the natural roll off. They sound better this way, but less SPL obviously.
Alternatively, use an air capacitor here. It is as good as having no cap IMO. You can not do this with the 63 and that is one of the reason why many still prefer the 57s. The original 1100pF cap in the 57, is not as bad as the 220uF cap found in the 63.
Yes, I have had the experience with the Quad as well.
My point though is that you are also involving the amplifier, and all amps make distortion. Due to the ear's masking principle, the presence of distortion can mask low level detail- detail that can indeed be transmitted by a cap if executed properly.
So- the idea here is to see if the impedance can be raised (thus reducing amplifier distortion) by examining the way the bass transformer and the new transformer interact at frequencies above the 'cutoff' of the LF transformer. Maybe its not a concern, but it may well prove worth looking into.
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