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Thread: Suggestion for Valve phonostage to play MONO records only

  1. #1
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 9,295
    I'm Andrew.

    Default Suggestion for Valve phonostage to play MONO records only

    I'm looking at getting or having made a valve phonostage for mono only records so that I can get the best out of my SPU mono. Any suggestions?
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  2. #2
    Join Date: Jul 2010

    Location: Cheltenham

    Posts: 982
    I'm Charlie.

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    How about this? Purpose built valve mono phono stage with different EQ options and custom built to order. Won't be cheap though.

    http://www.tron-electric.co.uk/phono...o-phono-stage/
    R2R: Studer A820 1/2 inch 2 track; Otari MTR-12 1/4 inch 2 track; Sony APR 5003; Sony APR 5002; Studer A807/II. Vinyl: Platine Verdier Allaerts MC1B/Schroeder Reference & Model 2 Decca C4E/Hadcock 228 TRON Seven Reference phono. Keith Monks MkII RCM Other analogue source: Nakamichi Dragon with ANT4066 mods. Amplification: TRON Meteor preamp TRON Voyager 20B SET power. Speakers: Avantgarde Duo. Digital: computing at last with Prism Sound Lyra 2 A2D converter

  3. #3
    Join Date: Mar 2015

    Location: Berlin

    Posts: 50
    I'm George.

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    As I understand it the SPU mono is not a genuine mono system, just only a converted stereo cartridge with coils rotated 45 degrees to reduce vertical sensing. So why bother..? SPU = Stereo Pick Up.

  4. #4
    Join Date: Jun 2011

    Location: Skien, Norway

    Posts: 932
    I'm Jostein.

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    Another top-end one in somewhat the same price range as the Tron:

    https://hagerman-audio-labs.myshopif...e-phono-preamp
    My hifi system:

    Turntable: Technics SL-1200 MKII, Ortofon 2M Bronze cartridge, Mike New bearing, MCRU PSU (c), Oyaide HS-CF headshell, Oyaide MJ-12 TT mat, Vantage Audio Copper mat, Isonoe Isolation Feet, Isodek IF-2 isolation platform, Furutech Monza LP stabilizer, Herbie's Hal-O JR damper Phono Stage: Hagerman Cornet 3 (prototype) Amplifiers: EAR 868L Preamp, Transcription Audio 211 Heaven Power amp, Bob Carver Cherry 180 power amp CD Player: Ear Yoshino Acute Tuner: Magnum Dynalab 90T Speakers: Vandersteen 2CE SigII, Townshend Audio Super Tweeters, Transcription Audio Speakers Cables and stuff: LFD Audio interconnects and speaker cables, Mark Grant G2000HD, BlackCat Electronics, Van Den Hul Clearwater, Black Rhodium mains cables, Black Rhodium mains block, Finite Elements Resonator, Townhsend Stella Speaker stands, Pro Audio Bono hifi rack, Herbie's spike gliders, Herbie's Ultravox and Hal-O tube dampers, Super Black Hole CD mat Record Cleaning Machine: Loricraft PRC4

  5. #5
    montesquieu Guest

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    Quote Originally Posted by REXTON View Post
    I'm looking at getting or having made a valve phonostage for mono only records so that I can get the best out of my SPU mono. Any suggestions?
    Ortofon seem to have changed its description over the years ... despite the fact that the specs haven't changed ... it used to say this:

    Continuing its commitment to supporting older formats, Ortofon’s SPU Mono GM MkII is specifically designed and engineered solely for the playback of early 25µm monaural recordings. A relatively high output, moving coil cartridge, the Mono GM MkII employs a spherical stylus profile,and its signal output makes it suitable for use with a medium-gain step-up transformer or standard gain phono pre-amplifier. The true-mono design also means that the cartridge can be used with a single step-up device, rather than requiring a stereo unit.

    Now it says this:

    The SPU Mono GM MkII is a high output Moving Coil cartridge a with a spherical stylus profile, for the playback of early 25µm mono recordings.
    The SPU Mono GM MkII provides an authentic method of playing back these early vinyl recordings with remarkable level of sonic accuracy, and its high output negates the need for a moving coil transformer.


    However, it does include the Mono GM in its list of True Mono cartridges, which I believe settles the matter:

    https://www.ortofon.com/hifi/cartrid...nges/true-mono

    I have seen the odd random post claiming it's not true mono, with no particular evidence presented. As someone who has owned one twice at different times, I believe from the performance of it that it's a single coil design, it's very good and I only sold mine when it was replaced by a Miyajima Premium.

    When I had the Mono GM MkII I found it worked perfectly well into the MM input. I had a Carver SUT at one point that had a 100 ohm setting (I think it went 6, 12, 40, 100), but I could hear no difference between moving the MM input - volume and tonal balance didn't change - this was surprising initially.

    On the phono stage point, I once had a single input, single output phono stage made for me by Nick Gorham, it also had turnover and rollof controls for adjusting equalisation. I ran this with a single speaker mono system (Quad 63, Leak TL12+). It worked well enough but to be honest I prefer mono produced by stereo speakers, among other things, it creates a better illusion of front to back depth. For this you don't need a mono phono stage as you are outputting the same mono signal into both channels.

  6. #6
    montesquieu Guest

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    Quote Originally Posted by topoxforddoc View Post
    How about this? Purpose built valve mono phono stage with different EQ options and custom built to order. Won't be cheap though.

    http://www.tron-electric.co.uk/phono...o-phono-stage/
    I use an earlier version of one of these, in the tape loop of my preamp, so it's not always in circuit. I had the opamps and wiring upgraded and I also had a good linear PSU done for it. Works very well indeed and you can use it with any phono stage (there's also the option to use it in-series).

    https://www.esotericsound.com/elect.htm


  7. #7
    Join Date: Mar 2015

    Location: Berlin

    Posts: 50
    I'm George.

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    Quote Originally Posted by montesquieu View Post
    Ortofon seem to have changed its description over the years ... despite the fact that the specs haven't changed ... it used to say this:

    Continuing its commitment to supporting older formats, Ortofon’s SPU Mono GM MkII is specifically designed and engineered solely for the playback of early 25µm monaural recordings. A relatively high output, moving coil cartridge, the Mono GM MkII employs a spherical stylus profile,and its signal output makes it suitable for use with a medium-gain step-up transformer or standard gain phono pre-amplifier. The true-mono design also means that the cartridge can be used with a single step-up device, rather than requiring a stereo unit.

    Now it says this:

    The SPU Mono GM MkII is a high output Moving Coil cartridge a with a spherical stylus profile, for the playback of early 25µm mono recordings.
    The SPU Mono GM MkII provides an authentic method of playing back these early vinyl recordings with remarkable level of sonic accuracy, and its high output negates the need for a moving coil transformer.


    However, it does include the Mono GM in its list of True Mono cartridges, which I believe settles the matter:

    https://www.ortofon.com/hifi/cartrid...nges/true-mono

    I have seen the odd random post claiming it's not true mono, with no particular evidence presented. As someone who has owned one twice at different times, I believe from the performance of it that it's a single coil design, it's very good and I only sold mine when it was replaced by a Miyajima Premium.
    Either you have a true mono cartridge with a basically one coil generator that translates lateral movement in the record groove into one output signal or you have a "fake" mono cartridge that is actually a stereo cartridge with 45° -2 coils arrangement providing 2 signals for stereo and internally wired in parallel to deliver mono output signal. Sort of "Mono" -switch inside the system. In the second case you can also use a true stereo cartridge, run both output signals through a phono stage with a "Mono" switch, press the "Mono" button and it is exactly the same as with "faked" mono cartridges.

    "claiming it's not true mono, with no particular evidence presented."

    You can only see by opening the cartridge, getting through to the generator to get an idea of the coil arrangement which means "smashing up" the cartridge to find out. Such online discussions -mono, not mono- emerge because cartridge manufacturer do not provide detailed information. Likewise you can also say: manufacturer claim true mono, with no particular evidence presented.

  8. #8
    montesquieu Guest

    Default Suggestion for Valve phonostage to play MONO records only

    Quote Originally Posted by forsell View Post
    Either you have a true mono cartridge with a basically one coil generator that translates lateral movement in the record groove into one output signal or you have a "fake" mono cartridge that is actually a stereo cartridge with 45° -2 coils arrangement providing 2 signals for stereo and internally wired in parallel to deliver mono output signal. Sort of "Mono" -switch inside the system. In the second case you can also use a true stereo cartridge, run both output signals through a phono stage with a "Mono" switch, press the "Mono" button and it is exactly the same as with "faked" mono cartridges.

    "claiming it's not true mono, with no particular evidence presented."

    You can only see by opening the cartridge, getting through to the generator to get an idea of the coil arrangement which means "smashing up" the cartridge to find out. Such online discussions -mono, not mono- emerge because cartridge manufacturer do not provide detailed information. Likewise you can also say: manufacturer claim true mono, with no particular evidence presented.
    I don’t think you understand what you are talking about matey. It’s perfectly possible (as with the Lyra monos) to have a true mono cartridge with two coils, so long as the coils are oriented to pick up a signal only in the horizontal. The coils can then be summed or not as required. Soundsmith do a mod for the Denon 103 that rotates the coils to turn it into a true mono cartridge - I used to own one.

    As it happens I use single coil Miyajimas for mono which not only detect only in the horizontal, but also have only horizontal motion (leading to potential damage if accidentally used on a stereo record). But that is NOT the only definition of true mono. Indeed a single coil can cause its own problems - into some stereo phono stages there is a risk of ground loop hum unless the loop is closed via a mono button.

  9. #9
    Join Date: Mar 2015

    Location: Berlin

    Posts: 50
    I'm George.

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    Quote Originally Posted by montesquieu View Post
    I don’t think you understand what you are talking about matey. It’s perfectly possible (as with the Lyra monos) to have a true mono cartridge with two coils, so long as the coils are oriented to pick up a signal only in the horizontal. The coils can then be summed or not as required. Soundsmith do a mod for the Denon 103 that rotates the coils to turn it into a true mono cartridge - I used to own one.
    I don’t think you understand what you are talking about mate. You can align a cross shaped coil system -as intended for stereo where both coils are in 90° to each other- in any position by rotating it, beginning at 0° position. In 0° position if the groove is only laterally modulated (mono) one coil picks up signal resulting from lateral groove modulation the other from vertical modulation. As there is no vertical groove modulation with mono records the only thing the second coil can pick up is dirt in the groove causing pops & noise. Thus any signal that the second coil is able to pick up is to be rejected. Or you do it mechanically by blocking the vertcal degree of freedom. In case of Soundsmith modification the "original" Denon cartridge is stereo thus it can't be said that is a true mono cartridge after having rotating the coil system from 45° to 0° position. It doesn't matter if you had it -as everything else- or not.

    The reason why alignment at 0° and vertical + lateral groove modulation for stereo playback is not used -theoretically it could be- lies in the record itself: vertical groove modulation causes more distortions than lateral and large amplitudes are not possible.

  10. #10
    montesquieu Guest

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    Quote Originally Posted by forsell View Post
    I don’t think you understand what you are talking about mate. You can align a cross shaped coil system -as intended for stereo where both coils are in 90° to each other- in any position by rotating it, beginning at 0° position. In 0° position if the groove is only laterally modulated (mono) one coil picks up signal resulting from lateral groove modulation the other from vertical modulation. As there is no vertical groove modulation with mono records the only thing the second coil can pick up is dirt in the groove causing pops & noise. Thus any signal that the second coil is able to pick up is to be rejected. Or you do it mechanically by blocking the vertcal degree of freedom. In case of Soundsmith modification the "original" Denon cartridge is stereo thus it can't be said that is a true mono cartridge after having rotating the coil system from 45° to 0° position. It doesn't matter if you had it -as everything else- or not.

    The reason why alignment at 0° and vertical + lateral groove modulation for stereo playback is not used -theoretically it could be- lies in the record itself: vertical groove modulation causes more distortions than lateral and large amplitudes are not possible.
    Whatever the mechanics (and the above is a useful observation which would suggest that where the coils are rotated as in the Soundsmith approach, then only one coil is used for output) it's pretty clear that when Ortofon write True Mono in caps and have a special page for all their cartridges, they are obviously NOT talking about simple strapping of a stereo cartridge. Likewise Koetsu who do the same (and who like Ortofon don't have a Miyajima/vintage-like approach with single generator and horizontal only motion), and Lyra who have two mono coils (their approach is documented, Jonathan Carr has several write-ups out there). And Audio Technica whose AT33 monos are true mono as well (I've also owned these in both LP and SP form).

    Or do you claim to know more than the engineers behind these illustrious companies? Are they all putting lies out there?

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