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Old 24th March 2016, 04:52 PM   #1
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Default Tube power amp bad fit for ML?

I am looking into building a Tubelab spp power amp. It delivers about 20 watts. I think the power is more than enough for my Martin Logans (I am using a 35 watt amp at the moment and never turn the volume up more than about 75 degrees), but I wonder if the varying impedance of the MLs would pose a problem.

The Martin Logan is a hybrid electrostatic speaker, mine uses a conventional woofer up to 500 hz and then the electrostatic panels for the rest. I have attached a graph of the impedance vs frequency. The yellow line is the impedance. The red line is phase.

Will the varying impedance cause any problems? If not which tap would I use on the OPT (my guess is that 4 ohm would be the closest).

Would I be better off just sticking to SS?

Thanks for any input on this.
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File Type: pdf ML- impedance.pdf (115.5 KB, 53 views)

Last edited by jazzzman; 24th March 2016 at 04:54 PM.
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Old 24th March 2016, 07:45 PM   #2
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Talk to Mike Samra. He uses ML speakers and H/K Cit. 2 amps.
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Old 24th March 2016, 08:18 PM   #3
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JM
I have the CLXs which are the larger 2 panel ones and I am using a pair of McShaned Citation 2s in parallel to drive them from 55hz on up.The Martin Logan pair of Descent subs are handling everything down to 17hz. In your case,I'm not sure which logans you have but I redid a citation 2 for a guy 4 months ago and he is running it on a pair of Summits and loves it..I added some film caps for added decoupling as well..One amp can drive my big logans but being mine go lower I like to run two..Since your speaker panels are probably crossing over at 270hz or 370hz,a rebuilt Citation 2 would be marvelous on your speakers.
Now,the Mc240 or a Citation 5,both with the McShane type upgrades will be more than sufficient but more than that,the Citations and the Macs are ideal for ESLs because they are ultra wide bandwidth and low distortion,the two things ESLs really adore.
The Citation 2 was actually designed to drive speakers like the KLH9 and the quad ESL63s which many are doing as we speak.
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File Type: jpg MC240.JPG (412.8 KB, 175 views)
File Type: jpg cit2.jpg (214.2 KB, 167 views)
File Type: jpg cit_v_4.jpg (988.4 KB, 164 views)
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Old 24th March 2016, 08:56 PM   #4
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Thanks for the replies.
Mike, mine are the ElectroMotion ESL's. They cross at about 500 hz. Given my impedance response, would you recommend I use a 4 ohm tap?
Thanks again.
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Old 25th March 2016, 04:00 AM   #5
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Default I would use the 4 ohm tap because it it closer to the 1 ohm impedance

that the speaker can hit at certain frequencies..I parallel my 4 ohm taps to give me two ohms but I'm using a par..Now,you can also use 8 ohm taps and they will sound excellent on the Mac amps or a Cit 2 or Cit..The key to a tube amp doing well on ESLs is to have wide bandwidth,low distortion,and a stout power supply.. I also run my Mac Mc60s and my Mc275 on the Logans with no issues. I also have a couple pair of Altec 1570s done with the Tutay mods and running SV572s giving me 200 watts of triode power from 50hz on up.Without getting exotic,I would look for a Citation 2 or Citation 5 or an Mc240 and do the McShane power supply and signal upgrades and you will be happy as a pig in slop.You also get the bass signal from the tube amp to drive the solid state built in subwoofer amps.
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Old 25th March 2016, 08:22 AM   #6
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Quote:
Originally Posted by michaelsamra View Post
The Citation 2 was actually designed to drive speakers like the KLH9 and the quad ESL63s which many are doing as we speak.
It was designed to drive speakers which would not exist for another three decades?
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Old 28th March 2016, 05:09 PM   #7
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Thank you, Mike. That is very helpful. The Citation II looks great. Maybe someday . . .
Right now, I am thinking of building something relatively simple.
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Old 28th March 2016, 05:54 PM   #8
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Quote:
Will the varying impedance cause any problems? If not which tap would I use on the OPT (my guess is that 4 ohm would be the closest).
Impedance dips at high freqs. are not particularly troublesome, as power demands are low. OTOH, low freqs. have high power demands and the dips are troublesome.

I agree with the 4 ohm idea, given the dip around 300 Hz.

Talk to George (Tubelab) and ask him if the PCB you're considering will yield a respectable damping factor. You definitely need decent damping. Among tube amps, the H/K Cit. 2's damping factor is huge.
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Old 28th March 2016, 07:54 PM   #9
gofar99 is offline gofar99  United States
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Hi, I use ML Vistas full range on the amps in the link below. Stunning sound IMO.

KT120 Push-Pull Tube Amplifier Schematic (Oddwatt Audio OBHO)

They are wide band low distortion and 40 watts rms. No issues with the 1 ohm HF load. I don't want to go into any more as I am a share holder in a company that sells kit versions of them. The DIY project will permit you to build ones that are equal to the commercial ones. A very similar fully assembled version was favorably reviewed on Analog Planet about a year ago.

(moderator...if this is too close to commercial please delete it, I try rather hard not to wander into that region)
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Old 28th March 2016, 08:06 PM   #10
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I have a pair of ML Aerius speakers and use a slightly under 10W PP all differential tube amp. I don't really think I need more power. The ESL's, even with the curved panels, are still fairly directional and the SPL at my seat is loud enough for me. I run them on the 4 ohm taps.
Happy amp hunting,
John
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