Roger Modjeski OTL

All i can say is i have not seen or heard any OTL that sounded better than my M60s......DIYed MA2s.........but the Atmasphere's tend to run very hot an here were i live it too........too hot...it just like with ESLs...the sound is great.. some say the best....an i have more than one pr here now...........but lot TLC..........to keep them all sounding there best.......an i can get 90% of the OTL-ESL sound out of Apogee,Magnepan,an tube amps with output tranfourmers.....
For me the sound of a Balanced Differential OTL is the best sounding...
All Sand or tube setup.........Cass A/Ab.....

But this is Ezy for me to say.... i have all these anps an ESLs here.....
But if you dont go you dont know!

So i say good luck to Mr Modjeski on his NEW OTL...........his last OTLs were a bust............All just one mans o-pine

RE: Roger Modjeski OTL, posted on December 14, 2013 at 18:19:56
airheadair Audiophile Posts: 393 Location: California Joined: October 18, 2010	When you say his last OTL's were a bust, do you mean the Counterpoint SA4? Can you say more? It is true that I tried them and wasn't satisfied, but I'm not sure I'd say they were a bust. Second best amps I tried.

RE: Roger Modjeski OTL, posted on December 15, 2013 at 03:31:22

tyu
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If you could get any of the Counterpoint amps to keep working....maybe the OTLs ..... were the best amps thay made...Counterpoint SA4 would eat tubes...i got out of the OTL ASAP....
I was in the Audio biz in the 80-90s....we sold Mcintosh...repire shop was full of the Counterpoint amps for a time....i tryed to like there amps...i had two of the SA220 amps....But Back in the day even the ARC SS amps were week.....so you could say i had bad luck with Counterpoint!
But then i got in to Krell MDA diff amps....i still have some of there old amps an D/A preamps....never had any thing thay made die....go fig.

Hi, Tyu, posted on December 18, 2013 at 07:44:01

Lew
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Location: Bethesda, Maryland
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Happy holidays.
I agree with Tyu re the Counterpoint SA4. I believe the major issue with it was that it was a direct-coupled Futterman-type design, sort of a contradiction in terms. Julius Futterman always used output coupling caps in series with the speaker to block DC. His totem pole topology inevitably presents DC at the output, along with the AC signal. This required a bank of high value electrolytics, in order to pass bass frequencies. If there is any sonic weakness to the Futterman circuit, that's it. One could ameliorate the negative sonic effect of capacitor-coupling by bypassing the electrolytics with high quality film caps, a trick I only learned to do when I was on my last pair of Futterman type amplifiers, a set of Prodigy OTLs. Julius himself ended up using photoflash caps, which were the fastest electrolytics of his day. He stopped making amplifiers only when he died, in either 1979 or the early 80s. I consider him a great man of audio. Prior to owning the Prodigys, I had a pair of "H3aa" monoblocks, which Julius built for me in 1979. Now back to the Counterpoint SA4: The innovation of the SA4 was to eschew the use of coupling capacitors by virtue of some sort of servo mechanism that balanced out the DC at the output. It was unreliable and often led to mini-disasters. The SA4 also used a 12AX7 at its input, rather than the 6EJ7 and 6FQ7, stipulated in the Futterman design. There may have been issues associated with that. There was at least one other design from the midwest or the West Coast, the KSS, which also used such a method to eliminate DC from the output. Those were even worse, in terms of reliability, IIRC. Those two products did more to damage the reputation of "Futterman" amplifiers and of OTLs in general than anything else that actually applies to a true Futterman design.

What I noticed in RM's post is that it seems he is going to use a servo mechanism to block DC in his new product, as well. I guess we have better ICs and other parts available these days with which to do that reliably.

Altho I revere Julius, I have to say that my first pair of Atma-sphere amplifiers blew away the Prodigy amplifiers, and the Prodigy amps were very very good classical Futterman designs, in and of themselves.
In that, I also agree with Tyu.

Tyu, I am playing with a pair of Beveridge 2SWs. Direct-drive is amazing.

RE: Hi, Tyu, posted on December 18, 2013 at 22:36:40
airheadair Audiophile Posts: 393 Location: California Joined: October 18, 2010	I'm a bit skeptical even now of servo's to protect from DC. Roger is also working on creating direct drive amplifiers for ESL's by the way. I imagine you have to have them custom made for your speakers. I may get a chance to listen to some Soundlabs driven by Atmaspheres soon. I'm quite content with my NYAL's though----they have been easy to manage and run quite cool.

RE: Hi, Tyu, posted on December 19, 2013 at 05:51:51
tyu Audiophile Posts: 963 Joined: April 19, 2011	Lets say that i hope that the New OTL works out for Roger.... the more OTL the better............... lew I am playing with a pair of Beveridge 2SWs. Direct-drive is amazing My frist ESLs were the Acoustat Xs....with the Direct-drive tube amps Amazing is right......have fun every day....hohoho

Modjeski and Beveridge, posted on December 19, 2013 at 12:23:49

Lew
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Location: Bethesda, Maryland
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Some sources say RM designed the Beveridge direct-drive amplifiers. However, I read an interview with RM where he disclaims the full credit for the amplifiers. On the other hand, IIRC, my own Beveridge amplifiers bear his hand-written initials inside the chassis, dated "1979". Also, I believe RM offers upgrades to the Bev amps.

It would be wonderful if there were a reliable source for direct-drive ESL amplifiers. However, to some degree they would have to be custom-tailored to the speaker they would drive. For example, you could not just take a dd OTL amp designed for Quads and hook it up to Sound Lab, without some changes. I inquired with a Euro-based company, Inoxx, re a direct-drive amp for the Sound Labs. The conversation went in circles. I am not sure they are for real. Ralph has now and then mentioned his interest in such an amplifier, but I can understand his reluctance to go there: Few would sell, and the potential dangers of such an amp (very high voltages) can backfire on the maker in this litigious age we live in.

RE: Modjeski and Beveridge, posted on December 20, 2013 at 08:36:50
tyu Audiophile Posts: 963 Joined: April 19, 2011	Thanks Lew......for the info on the Beveridge ESL an there direct-drive amps.......All tube?.........I have not got to hear are see the Beveridges speakers..........so how about there sound??...you know up to soundLab OTL combow Sound wize?...........or just like most... just diff.. ?

RE: Modjeski and Beveridge, posted on December 23, 2013 at 07:22:15

Lew
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Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000

The original Beveridge direct-drive amplifiers, used only in their Model 2 and 2SW speakers, have a solid state input and driver circuit and a 4-tube output stage that uses 36KD6 pentodes. There is a lot about the input and driver circuit that I do not understand; it's quite complex. The 4 output tubes are arranged to form two totem-pole type topologies, one for each side of the diaphragm. The Beveridge ESL panels are also quite unique in that the diaphragm carries no static charge, has low resistance instead of high, and is driven by the amplifier along with the two stators on either side. Thus, one could not take the Beveridge amplifier and connect it to a conventional ESL panel, I don't think.

2SW vs Sound Lab 845PX: I am listening to the Beveridges every day, after taking several months to perfect it, asking myself whether they are as good as the 845PX. The beauty of the Bev system is that it is in my basement, and I can listen to it all night long without disturbing my wife. She cannot even hear the music up in our second-floor bedroom. The 845s are up in our living room, under the bedroom, and 11 PM is curfew, as far as she is concerned. This is a factor in favor of the Bevs. So far, it is obvious that the Bevs are superior for stereo imaging, have a much stabler sound stage that does not move around if you move your head by an inch or even several feet, as does happen with the 845s. In fact, the Beveridge image stays solidly in one place, so if you stand up, it is as if you were in the audience and stood up; the image stays where it was; sitting down, you are looking slightly up at the musicians; standing, they are at eye level. It's quite startling. The 845s have a bigger more massive and fuller sound. The Bevs are amazing at revealing inner details in recordings, without being at all irritating or "clinical" sounding. Surely, I could live with the Bevs alone, and I may do that eventually.

RE: Modjeski and Beveridge, posted on December 23, 2013 at 08:45:21

6bq5
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I can answer a couple of points you ask in your first paragraph:

The original Beveridge direct-drive amplifiers, used only in their Model 2 and 2SW speakers,[ -Correct - the model 3 and beyond use SS/transformer power for the stators]
have a solid state input and driver circuit and a 4-tube output stage that uses 36KD6 pentodes. There is a lot about the input and driver circuit that I do not understand; it's quite complex. The 4 output tubes are arranged to form two totem-pole type topologies, one for each side of the diaphragm -[yes - each pair run the stators at opposite pole - on at +1500 VDC and the other at -1500 VDC]
. The Beveridge ESL panels are also quite unique in that the diaphragm carries no static charge - [Correct - the AC-music signal- 'rides' on the conductive Mylar diaphragm and is driven by the alternating charge in the static field set up by the stators]
, has low resistance instead of high, and is driven by the amplifier along with the two stators on either side. Thus, one could not take the Beveridge amplifier and connect it to a conventional ESL panel - Correct - it will not be pretty!
, I don't think.

You also only feed the Model 2 / 2SW amps with line level signal - it is it's own amp.

They are amazing speakers - somewhat limited in total SPLs but wonderful within their range.

Happy listeing
Happy Listening

Dynamic range, Model 2 vs 2SW, posted on December 23, 2013 at 11:25:28

Lew
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It is said (by Rick Beveridge on the current Beveridge website) that the 2SW was developed to counter issues of dynamic range or SPLs that pertained to the Model 2. Harold Beveridge widened the opening in his acoustic lens for the 2SW to increase SPL capability, but this had the effect also of compromising low bass performance. Thus they added a subwoofer for the 2SW, whereas the 2 is full range. (I am sure you and Tyu know this.) So far as I can tell, the Bev subwoofer was a relative failure and of low quality. In any case, while I sense that there is an upper limit to the SPLs that I can get from my 2SWs in my rather large finished basement, so far I have not had to push the envelope in order to enjoy high sound pressure levels. Because the image is so focused, the sensation is of higher SPLs than when I am listening to the Sound Labs, but I think the latter probably have slightly more "dynamic range" if one were to do a formal measurement under controlled conditions.

I am using my own home built transmission line woofers to provide low bass (below 100Hz) with my 2SWs. I am also not using the built-in crossover and woofer amplifier; I am using a Dahlquist DQLP-1 as lo-pass crossover and a Threshold S200 amplifier to drive the woofers. The 2SWs receive signal direct from the preamp via the built-in hi-pass filter on the 2SW amplifier chassis. The Dahlquist also gets its signal direct from the preamp but only provides the lo-pass output to the TL woofers.

RE: Dynamic range, Model 2 vs 2SW, posted on December 23, 2013 at 13:28:59
tyu Audiophile Posts: 963 Joined: April 19, 2011	WOW... this is all new for me...yes i have saw info on the Beveridge ESLs for years....but never had anyone i felt i could trust say how thay sounded....thanks for your time Lew...an to others for any info on ESLs an OTLs .. ....hoho

Interesting...., posted on December 23, 2013 at 14:51:07

AJ
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Posts: 532
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Lew,

I have just picked up a pair of Model 3s that I am refurbishng.. & I have ordered the Modjeski sub system and cross-over apparently designed for electrostats.

The Line array will be initially driven by a Futterman, Berning and I will try the Wyetech 211 Topaz on it (this amp does wonders with the Qyad ESLs). I hope to add the Modjeski DD OTL that he says will drive the Model 3s as well as the Quad ESLs and USA Monitors that I have in house.

I'll let you know how I make out.

ESL panels in the Model 3, posted on December 24, 2013 at 07:07:24

Lew
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Location: Bethesda, Maryland
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I believe they would have to be of the "conventional" type. Correct? Rick Beveridge writes that his father experimented with using a circuit board to build the panels for the Model 3 and that this experiment was a failure. Futterman (or Atma-sphere) would be a great match for the Model 3, for sure.

So, Modjeski does sell a DD OTL???? How does that relate to his announcement about producing a conventional OTL? I guess they are all custom order, one-off products, if he can provide both types.

RE: ESL panels in the Model 3, posted on December 24, 2013 at 09:41:43

AJ
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Joined: February 24, 2001

Hi Lew,

No, the panels in the Model 3s are identical to the panels in the Model 2 and 2sw :Carbon resin stators as opposed to phenolic or FR4 type stators used in most of the Model 5s and up.

Yes, Modjeski has two OTL type products going: 1.) For "conventional" OTL's in the spirit of Futterman for any speaker and 2.) For driving right off the plates like your Model 2 and 2sw with sweep tubes. The latter is what I am going to get. There are stereo and mono models available and he can customize the number of tubes in order to drive greater of fewer panels for the current required. These direct drives can be used with any electostat.. you have to go in and attach the polarizing high voltage directly to the panels.. Quad and Beveridge (needs more current) included.

These Beveridges are what started my journey into electrostats some 30 years ago.. They are the very same speakers I heard back then at a local audiophiles home, he sold them and moved on and I purchased them off of the 80 something year old 2nd owner who wanted them to go to someone who would appreciate them.

I was too young and still in University back in the early 80's to afford the Beveridges so I journeyed through Acoustat X's (never should have sold them) Acoustat Model 3s , and still have multilple examples of ESL 57(I think my favourite midrange of all) and Quad USA monitors refurbed.

I need to purge a lot of collected equipment to make room for more "stuff" I do really want to simplify int he next year or so.. we'll see how the Beveridges fare. If the amps are good and DD has to be better than even an OTL into a step up transformer then I will get rid of all my amps and just keep the SET for a high efficiency set up. .. time will tell,

Wow and thanks..., posted on December 24, 2013 at 11:46:25

Lew
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Location: Bethesda, Maryland
Joined: December 11, 2000

I did not know that about the Model 3 panels. How do they work when driven by a conventional amplifier externally? Did Bev provide some sort of special step-up transformers, in order to drive both the diaphragms and the stators?

That's a great collection you've got there, Audio Research SP3, Marantz 8B, Marantz (something; crossover?), Marantz 7C, Mac 275, etc. Is that a Futterman down on the lowest shelf?

We all regret selling things. I would love to have my Futterman H3aa's back, not to listen with but just to have them in memory of Julius. More than that, I regret selling my Porsche 550RS Spyder, because it's now worth ~$3 million.

Thanks., posted on December 24, 2013 at 13:45:40

AJ
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Joined: February 24, 2001

Wow that Porsche is a true classic.

Yes Futterman H3 on the rack along with all the Marantz collection except the 9s : Model 1,2,5,7,8b and 10b.

Yes, the Model 3 Beveridges have a transformer and a voltage multiplier for the stators. Any amp can be used, but the woofers are said to be the weakest link. Thus, my decision to go with a crossover and 2 subs.

I will have to purge this stuff eventually. It is almost becoming clutter!

RE: Thanks., posted on December 24, 2013 at 21:33:41

airheadair
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Roger Modjeski agrees that the subwoofer used in the Beveridge 2SW is poor; he says his new one is much better. I think he may have also said that the amplifier had reliability issues, but I don't recall. I have read descriptions of the imaging of the Beveridge that sound quite similar to what Lew says about them. I have done very little comparison between the Soundlabs a friend has and my Stax's, but I think I can say that the Stax's create a more focussed stereo image than the Soundlabs, and give a sense of dynamics (like Lew's description of the Beveridges) (without being as loud as the SoundLabs), but you do have to stay in one spot for the magic to work.

Kent McCollum is restoring a pair of Stax F83's and a pair of F81's at the present time; at least one of these may eventually be available for purchase.

RE: Thanks., posted on December 25, 2013 at 01:52:12
AJ Audiophile Posts: 532 Joined: February 24, 2001	The stax are one of the most transparent 'stats ever. I have heard a pair .Severely difficult to drive and inefficient . The don't play loud not even for an electrostatic . The demands placed on amplifiers are incredible but they are one of purest available. I have not heard Soundlabs either... Would love to some day.

RE: Thanks., posted on December 25, 2013 at 07:45:32

Lew
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Location: Bethesda, Maryland
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If you read on the SLOG website, you may find where I and a few others have made a major mod to the "backplate" of the Sound Labs that to my ears is revolutionary. The idea was not mine; it was brought to me by email from a guy in Australia. We removed the hi-pass crossover and the toroidal treble transformer from the backplate and replaced the RC network and the toroid with a full-range 1:90 EI type ESL step-up that is made in Australia. Then we run the AU transformer essentially in parallel with the Sound Labs bass transformer. The only remaining passive element in the original crossover is a 1.5mH inductor, in front of the bass transformer. This and its own limitations sharply roll off the bass transformer above about 2kHz. The net effect is a huge upgrade in efficiency and transparency and elimination of a lower midrange suck-out (because the impedance used to dip to as low as 2 ohms somewhere between 500Hz and 1.5kHz, due to the R in the old RC network). Further Z of the speaker from 50Hz to about 5kHz never goes below about 20 ohms! It's at 8 ohms at 5kHz and rolls off gently from there. This makes the SLs easy to drive with a tube amp. I am quite sure that 50W from a good OTL or other tube amp is all you need to play LOUD.

Sound Lab countered this idea by a re-design of their toroidal treble transformer, such that now it goes down to lower frequencies and crosses over below the midrange, but they still use cursed resistors and more inductors. Nevertheless, their mods also improve the speaker, or so I am told. I am not tempted to adopt the new SL toroid, however, not at all.

OTL Asylum

Roger Modjeski OTL

173.219.77.122