Who needs a MM cartridge type when we have MC?


Dear friends: who really needs an MM type phono cartridge?, well I will try to share/explain with you what are my experiences about and I hope too that many of you could enrich the topic/subject with your own experiences.

For some years ( in this forum ) and time to time I posted that the MM type cartridge quality sound is better than we know or that we think and like four months ago I start a thread about: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1173550723&openusid&zzRauliruegas&4&5#Rauliruegas where we analyse some MM type cartridges.

Well, in the last 10-12 months I buy something like 30+ different MM type phono cartridges ( you can read in my virtual system which ones. ) and I’m still doing it. The purpose of this fact ( “ buy it “ ) is for one way to confirm or not if really those MM type cartridges are good for us ( music lovers ) and at the same time learn about MM vs MC cartridges, as a fact I learn many things other than MM/MC cartridge subject.

If we take a look to the Agon analog members at least 90% of them use ( only ) MC phono cartridges, if we take a look to the “ professional reviewers “ ( TAS, Stereophile, Positive Feedback, Enjoy the Music, etc, etc, ) 95% ( at least ) of them use only MC cartridges ( well I know that for example: REG and NG of TAS and RJR of Stereophile use only MM type cartridges!!!!!!!! ) , if we take a look to the phono cartridge manufacturers more than 90% of them build/design for MC cartridges and if you speak with audio dealers almost all will tell you that the MC cartridges is the way to go.

So, who are wrong/right, the few ( like me ) that speak that the MM type is a very good alternative or the “ whole “ cartridge industry that think and support the MC cartridge only valid alternative?

IMHO I think that both groups are not totally wrong/right and that the subject is not who is wrong/right but that the subject is : KNOW-HOW or NON KNOW-HOW about.

Many years ago when I was introduced to the “ high end “ the cartridges were almost MM type ones: Shure, Stanton, Pickering, Empire, etc, etc. In those time I remember that one dealer told me that if I really want to be nearest to the music I have to buy the Empire 4000 D ( they say for 4-channel reproduction as well. ) and this was truly my first encounter with a “ high end cartridge “, I buy the 4000D I for 70.00 dls ( I can’t pay 150.00 for the D III. ), btw the specs of these Empire cartridges were impressive even today, look: frequency response: 5-50,000Hz, channel separation: 35db, tracking force range: 0.25grs to 1.25grs!!!!!!!!, just impressive, but there are some cartridges which frequency response goes to 100,000Hz!!!!!!!!!!

I start to learn about and I follow to buying other MM type cartridges ( in those times I never imagine nothing about MC cartridges: I don’t imagine of its existence!!!. ) like AKG, Micro Acoustics, ADC, B&O, Audio Technica, Sonus, etc, etc.

Years latter the same dealer told me about the MC marvelous cartridges and he introduce me to the Denon-103 following with the 103-D and the Fulton High performance, so I start to buy and hear MC cartridges. I start to read audio magazines about either cartridge type: MM and Mc ones.

I have to make changes in my audio system ( because of the low output of the MC cartridges and because I was learning how to improve the performance of my audio system ) and I follow what the reviewers/audio dealers “ speak “ about, I was un-experienced !!!!!!!, I was learning ( well I’m yet. ).

I can tell you many good/bad histories about but I don’t want that the thread was/is boring for you, so please let me tell you what I learn and where I’m standing today about:

over the years I invested thousands of dollars on several top “ high end “ MC cartridges, from the Sumiko Celebration passing for Lyras, Koetsu, Van denHul, to Allaerts ones ( just name it and I can tell that I own or owned. ), what I already invest on MC cartridges represent almost 70-80% price of my audio system.

Suddenly I stop buying MC cartridges and decide to start again with some of the MM type cartridges that I already own and what I heard motivate me to start the search for more of those “ hidden jewels “ that are ( here and now ) the MM phono cartridges and learn why are so good and how to obtain its best quality sound reproduction ( as a fact I learn many things other than MM cartridge about. ).

I don’t start this “ finding “ like a contest between MC and MM type cartridges.
The MC cartridges are as good as we already know and this is not the subject here, the subject is about MM type quality performance and how achieve the best with those cartridges.

First than all I try to identify and understand the most important characteristics ( and what they “ means “. ) of the MM type cartridges ( something that in part I already have it because our phonolinepreamp design needs. ) and its differences with the MC ones.

Well, first than all is that are high output cartridges, very high compliance ones ( 50cu is not rare. ), low or very low tracking force ones, likes 47kOhms and up, susceptible to some capacitance changes, user stylus replacement, sometimes we can use a different replacement stylus making an improvement with out the necessity to buy the next top model in the cartridge line , low and very low weight cartridges, almost all of them are build of plastic material with aluminum cantilever and with eliptical or “ old “ line contact stylus ( shibata ) ( here we don’t find: Jade/Coral/Titanium/etc, bodies or sophisticated build material cantilevers and sophisticated stylus shape. ), very very… what I say? Extremely low prices from 40.00 to 300.00 dls!!!!!!!!!!!!!!!!!!, well one of my cartridges I buy it for 8.99 dls ( one month ago ): WOW!!!!!!, so any one of you can/could have/buy ten to twenty MM cartridges for the price of one of the MC cartridge you own today and the good notice is that is a chance that those 10-20 MM type cartridges even the quality performance of your MC cartridge or beat it.

Other characteristics is that the builders show how proud they were/are on its MM type cartridges design, almost all those cartridges comes with a first rate box, comes with charts/diagrams of its frequency response and cartridge channel separation ( where they tell us which test recording use it, with which VTF, at which temperature, etc, etc. ), comes with a very wide explanation of the why’s and how’s of its design and the usual explanation to mount the cartridge along with a very wide list of specifications ( that were the envy of any of today MC ones where sometimes we really don’t know nothing about. ), comes with a set of screws/nuts, comes with a stylus brush and even with stylus cleaning fluid!!!!!!!!!, my GOD. Well, there are cartridges like the Supex SM 100MK2 that comes with two different stylus!!!! One with spherical and one with elliptical/shibata shape and dear friends all those in the same low low price!!!!!!!!!!!

Almost all the cartridges I own you can find it through Ebay and Agon and through cartridge dealers and don’t worry if you loose/broke the stylus cartridge or you find the cartridge but with out stylus, you always can/could find the stylus replacement, no problem about there are some stylus and cartridge sources.

When I’m talking about MM type cartridges I’m refer to different types: moving magnet, moving iron, moving flux, electret, variable reluctance, induced magnet, etc, etc. ( here is not the place to explain the differences on all those MM type cartridges. Maybe on other future thread. ).

I made all my very long ( time consuming ) cartridge tests using four different TT’s: Acoustic Signature Analog One MK2, Micro Seiki RX-5000, Luxman PD 310 and Technics SP-10 MK2, I use only removable headshell S and J shape tonearms with 15mm on overhang, I use different material build/ shape design /weight headshells. I test each cartridge in at least three different tonearms and some times in 3-4 different headshells till I find the “ right “ match where the cartridge perform the best, no I’m not saying that I already finish or that I already find the “ perfect “ match: cartridge/headshell/tonearm but I think I’m near that ideal target.

Through my testing experience I learn/ confirm that trying to find the right tonearm/headshell for any cartridge is well worth the effort and more important that be changing the TT. When I switch from a TT to another different one the changes on the quality cartridge performance were/are minimal in comparison to a change in the tonearm/headshell, this fact was consistent with any of those cartridges including MC ones.

So after the Phonolinepreamplifier IMHO the tonearm/headshell match for any cartridge is the more important subject, it is so important and complex that in the same tonearm ( with the same headshell wires ) but with different headshell ( even when the headshell weight were the same ) shape or build material headshell the quality cartridge performance can/could be way different.

All those experiences told me that chances are that the cartridge that you own ( MC or MM ) is not performing at its best because chances are that the tonearm you own is not the best match for that cartridge!!!!!!, so imagine what do you can/could hear when your cartridge is or will be on the right tonearm???!!!!!!!!, IMHO there are ( till today ) no single ( any type at any price ) perfect universal tonearm. IMHO there is no “ the best tonearm “, what exist or could exist is a “ best tonearm match for “ that “ cartridge “, but that’s all. Of course that are “ lucky “ tonearms that are very good match for more than one cartridge but don’t for every single cartridge.

I posted several times that I’m not a tonearm collector, that I own all those tonearms to have alternatives for my cartridges and with removable headshells my 15 tonearms are really like 100+ tonearms : a very wide options/alternatives for almost any cartridge!!!!!!

You can find several of these MM type cartridges new brand or NOS like: Ortofon, Nagaoka, Audio Technica, Astatic, B&O, Rega, Empire, Sonus Reson,Goldring,Clearaudio, Grado, Shelter, Garrot, etc. and all of them second hand in very good operational condition. As a fact I buy two and even three cartridges of the same model in some of the cartridges ( so right now I have some samples that I think I don’t use any more. ) to prevent that one of them arrive in non operational condition but I’m glad to say that all them arrive in very fine conditions. I buy one or two of the cartridges with no stylus or with the stylus out of work but I don’t have any trouble because I could find the stylus replacement on different sources and in some case the original new replacement.

All these buy/find cartridges was very time consuming and we have to have a lot of patience and a little lucky to obtain what we are looking for but I can asure you that is worth of it.

Ok, I think it is time to share my performance cartridge findings:

first we have to have a Phonolinepreamplifier with a very good MM phono stage ( at least at the same level that the MC stage. ). I’m lucky because my Phonolinepreamplifier has two independent phono stages, one for the MM and one for MC: both were designed for the specifics needs of each cartridge type, MM or MC that have different needs.

we need a decent TT and decent tonearm.

we have to load the MM cartridges not at 47K but at 100K ( at least 75K not less. ).

I find that using 47K ( a standard manufacture recommendation ) prevent to obtain the best quality performance, 100K make the difference. I try this with all those MM type cartridges and in all of them I achieve the best performance with 100K load impedance.

I find too that using the manufacturer capacitance advise not always is for the better, till “ the end of the day “ I find that between 100-150pf ( total capacitance including cable capacitance. ) all the cartridges performs at its best.

I start to change the load impedance on MM cartridges like a synonymous that what many of us made with MC cartridges where we try with different load impedance values, latter I read on the Empire 4000 DIII that the precise load impedance must be 100kOhms and in a white paper of some Grace F9 tests the used impedance value was 100kOhms, the same that I read on other operational MM cartridge manual and my ears tell/told me that 100kOhms is “ the value “.

Before I go on I want to remember you that several of those MM type cartridges ( almost all ) were build more than 30+ years ago!!!!!!!! and today performs at the same top quality level than today MC/MM top quality cartridges!!!!!, any brand at any price and in some ways beat it.

I use 4-5 recordings that I know very well and that give me the right answers to know that any cartridge is performing at its best or near it. Many times what I heard through those recordings were fine: everything were on target however the music don’t come “ alive “ don’t “ tell me “ nothing, I was not feeling the emotion that the music can communicate. In those cartridge cases I have to try it in other tonearm and/or with a different headshell till the “ feelings comes “ and only when this was achieved I then was satisfied.

All the tests were made with a volume level ( SPL ) where the recording “ shines “ and comes alive like in a live event. Sometimes changing the volume level by 1-1.5 db fixed everything.

Of course that the people that in a regular manner attend to hear/heard live music it will be more easy to know when something is right or wrong.

Well, Raul go on!!: one characteristic on the MM cartridges set-up was that almost all them likes to ride with a positive ( little/small ) VTA only the Grace Ruby and F9E and Sonus Gold Blue likes a negative VTA , on the other hand with the Nagaoka MP 50 Super and the Ortofon’s I use a flat VTA.

Regarding the VTF I use the manufacturer advise and sometimes 0.1+grs.
Of course that I made fine tuning through moderate changes in the Azymuth and for anti-skate I use between half/third VTF value.

I use different material build headshells: aluminum, composite aluminum, magnesium, composite magnesium, ceramic, wood and non magnetic stainless steel, these cartridges comes from Audio Technica, Denon, SAEC, Technics, Fidelity Research, Belldream, Grace, Nagaoka, Koetsu, Dynavector and Audiocraft.
All of them but the wood made ( the wood does not likes to any cartridge. ) very good job . It is here where a cartridge could seems good or very good depending of the headshell where is mounted and the tonearm.
Example, I have hard time with some of those cartridge like the Audio Technica AT 20SS where its performance was on the bright sound that sometimes was harsh till I find that the ceramic headshell was/is the right match now this cartridge perform beautiful, something similar happen with the Nagaoka ( Jeweltone in Japan ), Shelter , Grace, Garrot , AKG and B&O but when were mounted in the right headshell/tonearm all them performs great.

Other things that you have to know: I use two different cooper headshell wires, both very neutral and with similar “ sound “ and I use three different phono cables, all three very neutral too with some differences on the sound performance but nothing that “ makes the difference “ on the quality sound of any of my cartridges, either MM or MC, btw I know extremely well those phono cables: Analysis Plus, Harmonic Technologies and Kimber Kable ( all three the silver models. ), finally and don’t less important is that those phono cables were wired in balanced way to take advantage of my Phonolinepreamp fully balanced design.

What do you note the first time you put your MM cartridge on the record?, well a total absence of noise/hum or the like that you have through your MC cartridges ( and that is not a cartridge problem but a Phonolinepreamp problem due to the low output of the MC cartridges. ), a dead silent black ( beautiful ) soundstage where appear the MUSIC performance, this experience alone is worth it.

The second and maybe the most important MM cartridge characteristic is that you hear/heard the MUSIC flow/run extremely “ easy “ with no distracting sound distortions/artifacts ( I can’t explain exactly this very important subject but it is wonderful ) even you can hear/heard “ sounds/notes “ that you never before heard it and you even don’t know exist on the recording: what a experience!!!!!!!!!!!

IMHO I think that the MUSIC run so easily through a MM cartridge due ( between other facts ) to its very high compliance characteristic on almost any MM cartridge.

This very high compliance permit ( between other things like be less sensitive to out-center hole records. ) to these cartridges stay always in contact with the groove and never loose that groove contact not even on the grooves that were recorded at very high velocity, something that a low/medium cartridge compliance can’t achieve, due to this low/medium compliance characteristic the MC cartridges loose ( time to time and depending of the recorded velocity ) groove contact ( minute extremely minute loose contact, but exist. ) and the quality sound performance suffer about and we can hear it, the same pass with the MC cartridges when are playing the inner grooves on a record instead the very high compliance MM cartridges because has better tracking drive perform better than the MC ones at inner record grooves and here too we can hear it.

Btw, some Agoners ask very worried ( on more than one Agon thread ) that its cartridge can’t track ( clean ) the cannons on the 1812 Telarc recording and usually the answers that different people posted were something like this: “””” don’t worry about other than that Telarc recording no other commercial recording comes recorded at that so high velocity, if you don’t have trouble with other of your LP’s then stay calm. “””””

Well, this standard answer have some “ sense “ but the people ( like me ) that already has/have the experience to hear/heard a MM or MC ( like the Ortofon MC 2000 or the Denon DS1, high compliance Mc cartridges. ) cartridge that pass easily the 1812 Telarc test can tell us that those cartridges make a huge difference in the quality sound reproduction of any “ normal “ recording, so it is more important that what we think to have a better cartridge tracking groove drive!!!!

There are many facts around the MM cartridge subject but till we try it in the right set-up it will be ( for some people ) difficult to understand “ those beauties “. Something that I admire on the MM cartridges is how ( almost all of them ) they handle the frequency extremes: the low bass with the right pitch/heft/tight/vivid with no colorations of the kind “ organic !!” that many non know-how people speak about, the highs neutral/open/transparent/airy believable like the live music, these frequency extremes handle make that the MUSIC flow in our minds to wake up our feelings/emotions that at “ the end of the day “ is all what a music lover is looking for.
These not means that these cartridges don’t shine on the midrange because they do too and they have very good soundstage but here is more system/room dependent.

Well we have a very good alternative on the ( very low price ) MM type cartridges to achieve that music target and I’m not saying that you change your MC cartridge for a MM one: NO, what I’m trying to tell you is that it is worth to have ( as many you can buy/find ) the MM type cartridges along your MC ones

I want to tell you that I can live happy with any of those MM cartridges and I’m not saying with this that all of them perform at the same quality level NO!! what I’m saying is that all of them are very good performers, all of them approach you nearest to the music.

If you ask me which one is the best I can tell you that this will be a very hard “ call “ an almost impossible to decide, I think that I can make a difference between the very good ones and the stellar ones where IMHO the next cartridges belongs to this group:

Audio Technica ATML 170 and 180 OCC, Grado The Amber Tribute, Grace Ruby, Garrot P77, Nagaoka MP-50 Super, B&O MMC2 and MMC20CL, AKG P8ES SuperNova, Reson Reca ,Astatic MF-100 and Stanton LZS 981.

There are other ones that are really near this group: ADC Astrion, Supex MF-100 MK2, Micro Acoustics MA630/830, Empire 750 LTD and 600LAC, Sonus Dimension 5, Astatic MF-200 and 300 and the Acutex 320III.

The other ones are very good too but less refined ones.
I try too ( owned or borrowed for a friend ) the Shure IV and VMR, Music maker 2-3 and Clearaudio Virtuoso/Maestro, from these I could recommended only the Clearaudios the Shure’s and Music Maker are almost mediocre ones performers.
I forgot I try to the B&O Soundsmith versions, well this cartridges are good but are different from the original B&O ( that I prefer. ) due that the Sounsmith ones use ruby cantilevers instead the original B&O sapphire ones that for what I tested sounds more natural and less hi-fi like the ruby ones.

What I learn other that the importance on the quality sound reproduction through MM type cartridges?, well that unfortunately the advance in the design looking for a better quality cartridge performers advance almost nothing either on MM and MC cartridges.

Yes, today we have different/advanced body cartridge materials, different cantilever build materials, different stylus shape/profile, different, different,,,,different, but the quality sound reproduction is almost the same with cartridges build 30+ years ago and this is a fact. The same occur with TT’s and tonearms. Is sad to speak in this way but it is what we have today. Please, I’m not saying that some cartridges designs don’t grow up because they did it, example: Koetsu they today Koetsu’s are better performers that the old ones but against other cartridges the Koetsu ones don’t advance and many old and today cartridges MM/MC beat them easily.

Where I think the audio industry grow-up for the better are in electronic audio items ( like the Phonolinepreamps ), speakers and room treatment, but this is only my HO.

I know that there are many things that I forgot and many other things that we have to think about but what you can read here is IMHO a good point to start.

Regards and enjoy the music.
Raul.
Ag insider logo xs@2xrauliruegas
Lew, I didn't say it's ridiculous not to bypass the fuse. It seems ridiculous to go for an OTL and then have a fuse in line with each output tube. These are OTL and not direct drive so you have transformers on the panels? You have Sound Lab spks?

I don't know the capacitance/power requirements of of your spks, but Roger does make a electrostatic system with direct drive amps. I think it's Acoustat panels. I had Acoustat panels in a biamp configuration with ribbon tweeters. Mine were Acoustat amps, rebuilt by Dan Fanny, formerly of AHT. He had to gut the entire amp except the power transformer. DD is the way to go with electrostats IMO. I know that Roger is currently making these amps and might be able to use it on your spks. Here he discusses the requirements of some diff brands:
http://www.audiocircle.com/index.php?topic=107869.0

Tuning fuses:
http://www.audiocircle.com/index.php?topic=105425.0

Sorry to come off so outspoken, but in truth, I think we're all nuts. (Sometimes I miss those amps though)
Regards,
This is a response from Roger Modjeski re: fuses.

I read with some laughter, dismay and sadness the follow up on Stereophile May 22, 2012. page 109 concerning the latest hype of Tuning Fuses. Besides my opinion that these are a horrible waste of good money I want to let readers know that these fuses can damage your equipment.

I repaired a RM-9 MK II where the owner had installed 8 of the $49 tuning fuses in the individual fuse holders of the amplifier. Besides spending close to $400 the fuses they cost him another $400 in repairs and $320 for a new set of output tubes. When fuses cost more than tubes something is rotten in Denmark (actually they are made in Germany.) Not only had the fuses not protected the tubes but they had also blown a cathode resistor that I have yet to see fail in any other RM-9. Upon opening the fuse I found that it was not of a high-breaking construction. In fact the construction was such that a 10 cent RadioShack glass fuse offered more protection. Whoever designed this fuse evidently does not know about breaking ratings or how to achieve them. To my knowledge they publish none of the essential engineering graphs of time VS current. Furthermore, I can see nor can I find anywhere UL, CE or any of the standard safety approvals. Given their construction, I doubt they could get any.

I called the distributor to see if there was any technical data and he referred me to a white paper on the website which is down for maintenance for a week. Let's have a look at that when it's back up.

I know it's difficult to do, but if audiophiles would take the money they are tempted to spend on useless tweaks and start a savings account for that money, in some time they would have enough to buy something like a better pair of speakers, new amplifier or something that would really make a difference in their listening.

Now that I have had my say, here's something you can do if you want to experiment. Since we know these are made of silver wire you can get a enough silver wire for $40 to make hundreds of fuses that sound even better and will protect your equipment. Since these fuses are only good for the AC line lets look at what a line fuse does and what you have to do if it blows. An AC line fuse will protect your solid state and modern tube equipment (Not your 1960's tube amp or any tube amp where there are no tube or B+ fuses) from further damage if a rectifier, main filter cap or any short in the high current portions of the product. This is a good thing. We don't want a shorted rectifier to cause capacitors to explode or transformers to burn up. However if either of these occurs, it's going to have to go the the shop to replace the shorted rectifier which is a very simple matter.

I have more audio equipment and test equipment in daily use than most of you and I assure you, other than nuisance blowing, AC line fuse replacement is a very rare event in my experience. For those who are unfamiliar with the term "nuisance blowing" it is a commonly accepted term for a fuse just wearing out. It is caused by the simple fact that every time a piece of equipment is turned on, the inrush current, which is many times the run current, expands the fuse wire eventually causing it to break. Usually it takes years and when a fuse fails in this manner one simply replaces it and goes on for another similar period. It is more common with fast blow fuses which are not good choices for line fuses for reasons given below.

Fuses are of particular interest to me and every time I replace a fuse I give consideration to what fuse I would have used had I designed the product. Though cautioned "replace fuse with same type and value as original" I often wonder how carefully the "original" fuse was chosen. I have seen a lot of bad fuse choices and have replaced many a fast blow fuse with a much lower current slow blow which often ends the nuisance failures and improves the safety of the unit. I have found many products where the specified fuse would not protect against a shorted filter capacitor or shorted rectifier because the fuse would not blow under those conditions. Instead the power transformer would overheat and fail, then it would blow the fuse. Now there is a lot of stuff to replace instead of the simple diode.

In the original RM-4 I did many tests to determine that the 250 mA slow blow fuse would protect against every possible failure. I shorted a rectifier to see what happened. I shorted a filter cap. I shorted the main supply which never blows a fuse because, unlike many regulated power supplies it is short-circuit protected.

So, how do you make your own silver fuses. Simply wrap the right size silver wire from post to post of the fuse holder and solder.
« Last Edit: 13 Apr 2012, 06:03 pm by Roger A. Modjeski »
Logged
Thought this might be of some interest.
Fleib, You do have a point; my ESL panels have a step-up transformer, so it might be safe to do away with the fuse, but I believe that the fuse also protects the circuit of the amplifier.

Direct-drive OTL for Sound Lab has been discussed ad nauseam among the small circle of people who care about it. The bias voltage of Sound Labs is very high in comparison to most ESLs, something like 8kV to 10kV, so solutions that work for all other ESLs, with lower bias voltage, will not necessarily be sufficient for the Sound Labs. Believe it or not, I actually did speak to RM about this and about his design for the Beveridge amplifiers, which he is willing to rebuild, at very great expense. Since mine are not broken, I had no desire to drop several kilo bucks on a rebuild, but I am making some mods to the input and driver stages. The Bev panels, for comparison, only need 3200V for bias. I think other common ESLs, like KLH9s and Quads use bias voltages under 3kV. But when you look at the other compromises associated with direct-drive, the use of a step-up transformer is not so bad.

By the way, I misspoke, and I expected to get hammered for it. The 6LF6 does not have an internal fuse. I distinctly remember that Julius Futterman used hair-thin wires as fuses on his OTLs. He always supplied an extra set of these fuse-wires, which he taped to the inside of the chassis of each monoblock. I don't know what NYAL and other makers of Futterman type amplifiers did about fuses on the outputs. And truthfully, I am not sure about the output tubes that Modjeski used in the Beveridge amplifiers, 36KD6s, whether they are internally fused or not.
Lew, Roger says he can build amps that work at any voltage. You should read the first link (above). Current/impedance requirements are also a major consideration.
"Here is the run-down on what my direct drive amp can do. It can be made at any output voltage and I have a high and low current version because some ESLs draw very high currents due to high capacitance and some don't. This is just the same as the fact that speakers can be 2,4,8,16 ohms and anywhere in between. ESL speakers can be low capacitance, mine are just 100 pf. Beveridge model 2's are 4500 pF. That's a 45 to 1 difference, a much larger range than we see in cone speakers. In addition being capacitive the impedance varies inversely with frequency being lower at higher frequencies. When Beveridge went to transformer drive the result was a speaker that went from 100 ohms at 100 HZ to 1 ohm at 16 KHz. We had to find amplifiers that would deliver over 40 amps of current. These speakers were not suitable for most conventional amps tube or transistor. Roger Sanders makes a solid state mono amp that delivers 2000 watts at a cost of $8000 per pair."

"Thanks for report on an excellent comparison. Here are a few contributing factors. If played loud the Futtermans have not the current needed to drive Acoustats, especially ones 3 panels or larger. The impedance of any large, full range panel speaker is going to approach 1 or 2 ohms at high frequencies and Futterman amps put out nothing into 1 ohm nor do the tubes appreciate the task.

It is a long standing myth that OTL amps and ESL speakers were made for each other. This is true in one combination, the Futterman OTL and the KLH-9 which was a 16 ohm speaker that stayed pretty constant over the range. I have a copy of Julius Futterman's impedance measurements in my "Futterman File". He was certainly interested in driving this speaker as he measured its impedance at over 20 different frequencies. The advantage of his amp over others was it had lots of voltage which the KLH-9 needed. I am told that one of the classic listening tests was to compare the Futterman vs the Marantz 9 driving the KLH, particularly on Saturdays at Lyric Hi FI, NYC.

A Futterman can drive the QUADs or the Stax that airhead has but one has to be very careful not to exceed the maximum voltage which is 35 volts peak for the QUAD 57's and about 40 volts peak (100 watts from a 8 ohm amp) for the 63's. I do not know what the peak is for the Stax. I do know that most Futterman amps can put out 150 volts peak and therein lies the danger.

When Acoustat gave up on making their "Servo Amplifier" they went to a two transformer system, a system that is flawed in its very nature,. There is really no way to drive a single panel ESL with two transformers one being for the lows and one for the highs. One can split the band on the input side but they have to re-combine the bands on the output side and that causes the high frequency transformer to "see" enough of the low frequency information to cause saturation at higher levels and significant 3rd harmonic distortion at moderate levels. Although I don't have my measurements of the Acoustat Magnetic Interface handy, I do recall it is not easy to drive. It needs lots of voltage and lots of current.

Although rarely mentioned, the transformers in ESL speakers often eat up 25 to 50% of the drive energy due to their capacitance at the high end and saturation at the low end. When we eliminate them and the output transformer in a traditional amp and connect the tubes directly to the panels there is a great relief of work that the tube have to perform.

As you can see, from both a safety and sonic perspective, direct drive makes a lot of sense. When you can go directly to the panels, an ESL is actually easier to drive than a magnetic speaker."

Did you ever talk to him about Sound Labs? From his post, I got the impression that a Beverdige rebuild would include the complete amps, hence the price.
With your OTL I don't know if the high voltage speaker transformer would protect your amp if a tube or capacitor failed.
Regards,
10-21-12: Rnadell
This is a response from Roger Modjeski re: fuses.
Rnadell - excellent post that everyone should read.
So, how do you make your own silver fuses. Simply wrap the right size silver wire from post to post of the fuse holder and solder.
« Last Edit: 13 Apr 2012, 06:03 pm by Roger A. Modjeski »
I distinctly remember that Julius Futterman used hair-thin wires as fuses on his OTLs.
I did suggest this about 40+ posts ago and was pooh-poohed. Never mind, I'm sure in post number 14684 or thereabouts the same discussion will be had again.