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Old 8th January 2012, 01:01 AM   #1
john65b is offline john65b  United States
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Default Martin Logan CLS Power Supply

Hello all, this is my first foray into the ESL side of DiYAudio. I have been on DIYAudio for a number of years. Built all sorts of tubed and SS amps (Icepower, Tripath, Hypex, Krell KSA-50 clone, Aleph 5 Clone, etc) and preamps (Aikido, Jfet BOZ, etc), and now want to take a dive into an ESL.

I have acquired a working pair of CLS panels. I should have no problem with the frames (got some good ideas already), but am in need of a little help on the bias / power supply.

First question is what is the voltage on an original CLS? 3kv? Are the power supply requirements any different from what I have seen here if the CLS is a full range design?

I have a few CLS schematics, but they are a little vague on the actual component values. I also noticed there is no Bias control or brilliance pot on the CLS that my panels came from. They also do not have a toroidal output transformer either.

BIAS CIRCUIT
I have two designs I have researched - one is a simple basic power transformer to a voltage multiplier circuit with diodes to get to 2 - 3kv (or higher), or just getting a 20VDC supply (plan on a 20vdc 3.2 amp laptop power supply) and running it to a DC to HVDC converter to do the same. Is one design preferred over the other? I know the original PS for the CLS had the diode voltage multiplier (12 stages if I remember correctly)...I will post some pics later of the one I saw....

Thanks in advance!!

EDIT: Also, thinking of leaving the CLS to do 200HZ and above, and leaving the remainder for a Tympani bass panels...
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Last edited by john65b; 8th January 2012 at 01:06 AM.
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Old 8th January 2012, 01:48 AM   #2
john65b is offline john65b  United States
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I am guessing bias around 4.7kv??

And there is a single 10uf cap, two coil inductors, and three 10R 12w resistors in there - this is a crossover? I thought the CLS was full range?

That Opamp circuit - is it a sensing circuit to tun on / off the Bias voltage to keep panel from attracting dust? Don't really need the sensing circuit, as I will just turn it off when not in use...
Attached Images
File Type: jpg photo12.jpg (353.0 KB, 473 views)
File Type: jpg photo8.jpg (346.7 KB, 421 views)
File Type: jpg photo17.jpg (334.3 KB, 414 views)
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Last edited by john65b; 8th January 2012 at 02:05 AM.
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Old 8th January 2012, 02:09 AM   #3
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Default OPAMP

Hi,

Yes that opamp is for the sensing circuit.

Regards,

Audiofanatic
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Old 8th January 2012, 01:57 PM   #4
tyu is online now tyu  United States
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From info i got from ML thay set the last CLS at 3700 bias....I run my CLSs bias higher but i have redone... the panels bias feeds so i get all the CLS panels Can put out....About 3-4db more than stock like you have....The Bias feed is the week link of all the ML panels....It only runup the right side only....thay lov to sale those panels...thay never had Bias control pot ....that i like a lot for any fulrang ESL ...ML Never used a toroidal output transformer either..... but thay dose not mean you cant.....AS for the crossover i just run some res..1-2ohms on the pos input ... an use subs.....An have used Acoustat panels for just the low end.....sound ok ....but to big for me........Goodluck
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Old 8th January 2012, 03:24 PM   #5
john65b is offline john65b  United States
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Default Bias and output tranny

OK, I am thinking of going the "safe" route per Mark Rehorst and use a standard laptop power supply and the Emco DC to HVDC converter per attached for the Bias Supply. There will be two - one for each panel (don't want to string HV wires across my speakers)

Also thinking of an Edcore GXPP15-4-8K output transformer.

EDCOR Electronics Corporation. GXPP15-4-8K

Would this output transformer work out better than the Antek 115-6V toroidal that has been discussed?
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File Type: jpg Bias Circuit.jpg (45.5 KB, 404 views)
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Old 8th January 2012, 04:18 PM   #6
fperra is offline fperra  United States
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Quote:
Originally Posted by john65b View Post
OK, I am thinking of going the "safe" route per Mark Rehorst and use a standard laptop power supply and the Emco DC to HVDC converter per attached for the Bias Supply. There will be two - one for each panel (don't want to string HV wires across my speakers)

Also thinking of an Edcore GXPP15-4-8K output transformer.

EDCOR Electronics Corporation. GXPP15-4-8K

Would this output transformer work out better than the Antek 115-6V toroidal that has been discussed?
That HV supply will work great. I'm using a similar EMCO based supply for my speakers. The LM317t runs a little warm for the Emco's I used and if I did it all over I would have used the TO3 version. Looks like this:

Click the image to open in full size.
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Old 8th January 2012, 04:57 PM   #7
tyu is online now tyu  United States
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I am thinking of going the "safe" .....i would not do anything diff....who runing wires all over??......an the fperra set up look great....Go with that then you no if the panels work....or sound good.....It only your $$$$...goodluck

Fperra Thanks for the pic...
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Old 8th January 2012, 10:43 PM   #8
john65b is offline john65b  United States
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Great work....Does anyone have any input on the output transformer? The Edcor vs the Antek Toroidal? I was going to purchase everything tomorrow...

Going with the Emco G50 (5000V) for a little more bias headroom, as I can always turn the bias down from there...
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Old 8th January 2012, 11:33 PM   #9
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Quote:
Originally Posted by john65b View Post
Great work....Does anyone have any input on the output transformer? The Edcor vs the Antek Toroidal? I was going to purchase everything tomorrow...
If I am understanding you correctly, you are wanting to purchase step-up transformers to drive a CLS. Isn't the CLS a full range ESL? If so, I don't think either of these transformers will work, as their power handling capability would be very limited below 200Hz.
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Old 8th January 2012, 11:50 PM   #10
john65b is offline john65b  United States
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As far as the power/bias, a single Emco G50 per speaker is still not enough? It would be 5000V@ 300ma full load?

I can hold off on both trannys until I hear back....
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