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The Myst G-Ohm

Discussion in 'classic' started by misterc6, Jul 14, 2013.

  1. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    I'm not sure if this qualifies as a classic but it deserves a thread for its almost mythical rarity.


    I picked up a Myst TMA3 from a member earlier this year and was impressed by the quality of its construction as well as the sonic performance. As a result I went on to acquire an example of the G-Ohm system.

    There is very little about Myst on the Internet and as far as I can tell there wasn't a single picture of the G-Ohm until the eBay seller I bought it from put it up for sale.


    The TMA3 runs from 39v power rails but the G-Ohm has 52v rails giving it greater power and control. The system is modular with a massive power supply in the bottom box and three small boxes for the preamplifier and two mono power amplifiers. The circuitry has a lot in common with the TMA3 but I'm still trying to figure out what the Erg DIL switches do. I'd appreciate any advice or information that anyone reading this may have.




    It's a delight to work on because with the cases off the amplifier modules you can easily get to both sides of the printed circuit boards.

    Anyone else got one?

  2. divedeepdog

    divedeepdog pfm Member

    I heard a TMA3 recently and was a pleasure. I'd have thought it would run a Nait 2 very close, on a good day a third of the cost.

    Looking forward to any more information ;-)
  3. juz400

    juz400 pfm Member

    I like it! Clean and Simple looking (Aimed at our fair Isles?)
    Some modern Allen/Security type bolts in the front and you could have picked it up brand new yesterday! :p
    Suprised NWRler04 hasnt spotted it yet, Im sure he would like the layout here.

    Seems very well looked after, did it need a majic soldering iron briefly waved over it for aged joints and then power-on?

    How does it sound?
  4. pure sound

    pure sound Trade: manufacturer/distributor

    I replaced a Nait with a TMA3 back in the day. A much better amp. Indeed probably the best amp you could buy for £250 back in the early 80's with the possible exception of the Marantz Pm4.
  5. russel

    russel ./_dazed_and_confused

    Do I get extra points for spotting that the rectifier is made by Marconi Electronic Devices Limited, MEDL?. I have one in my parts box somewhere, I used it in a Linsley-Hood design for for a few years, along with the HPAK FETS used in the Myst. If you do ding the FETS they will be very hard to replace with originals but they are the same die as the 2SK133 /134/135 and the complements 2SJ48, 49 and 50. BUZ905 and BUZ900 from Semelab will be a suitable replacement.
  6. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Well it was designed and built these Isles.

    The insides, as you can see, are remarkably clean. The only fault was that the dropper resistor to the LED indicator on the power supply box had failed so I replaced it with a higher wattage resistor. Strangely this LED was green whilst the ones in the power amps were red. I took an executive decision that the red was much more in keeping with both the era (1980s) and the champagne colour of the panel. Does anyone know what colour it should be? Even the massive 15,000 uF 63 V capacitors seem to be in good order although I'm tempted to drop a pair of Kendeils in there.

    I was much impressed with the construction of the TMA3 and the earlier G-Ohm is along the same lines. The TMA3 is a NAIT killer at a fraction of the cost. I've never seen another G-Ohm changing hands but think that the price I paid was fair for the performance.

    I have an aversion to trying to describe how an amplifier sounds partly because the other elements of the system affect this. I'm using an upgraded Rega P3-24 with the TT PSU, an AO rewired RB251 with Denon DL-110, a Michell Tecnoweight, an Isokinetik metal hub and an Tizo Acrylic platter as the source and Epos ES14 speakers.

    The TMA3 had amazing clarity and dynamic range and had no problem driving the ES14s; the G-Ohm has more of all those things mainly due to the higher voltage power rails. I haven't analysed them fully but the circuitry looks similar between the two models. Another plus point is the relay in each power amp which completely eliminates the switch on thump experienced with other products of this vintage.

    The MM phono stages are very good indeed. MC is a plug in option on the TMA3 but it looks as if you have to change the whole preamplifier box to get an MC phono stage on the G-Ohm.
  7. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Very useful information, thank you!
  8. pure sound

    pure sound Trade: manufacturer/distributor

    I thought I also recalled that Myst were involved with an active loudspeaker system called Wellard.

    Some info here.

  9. Martyn Miles

    Martyn Miles pfm Member

    So, who were MYST ? Did they employ a well known designer for their amplifiers, or was it the ' Cottage Industry ' ( two men in a shed ) type of operation ? Did they branch out into tuners or anything else? So many questions...
  10. Mignun

    Mignun pfm Member

    Wow. Great find. I still have the old Hifi Choice review of the G-Ohm but have never seen a set in the flesh, so to speak. A shame the covers are brown. I would have hoped for the rather funky blue... I'm wondering whether the screws on the front panels are originals - the photo in the review seems to indicate black allen head bolts.
  11. Mignun

    Mignun pfm Member

    I believe it was more like a husband and wife "in a shed". Yes, they did make a tuner to match the TMa3 - quite a rarity. I have a whole article about Myst filed away somewhere. I'll see if I can dig it out sometime.
  12. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    @ pure sound - that's really interesting and implies that they are still going under a different guise. Anyone live close enough to Hereford to see if they have any historic information there?

    @ Martyn Miles - pretty much two men and a dog, see the picture of their offices/factory on the link provided by pure sound. I have a scan of the 1982 brochure which mentions the possibility of other G-Ohm modules but I don't know if they ever came to fruition. The brochure also mentions the "Stage-Life Series" which is described as a top end system consisting of a valve based preamplifier and a hybrid (valves and mosfets) power amplifier. I have neither heard nor seen one of these. The TMA3 came later and there was a matching tuner (TMR?) but no other products as far as I'm aware.

    @ Mignun - The original TMA3 came in blue with a silver panel; pictures here:


    but later changed to black. I've only ever seen a black TMR. You don't see the brown when it's in the rack. I'm pretty sure that the bolts are not metric, I'll check later. Would it be possible for you to send me a scan of the HiFi Choice review?
  13. pure sound

    pure sound Trade: manufacturer/distributor

    I think I once saw pictures of some Myst electronics with valves fitted.

    I really liked the Blue/Silver look of the TMA3 but I suspect sales were slow (perhaps too much minimalism?) & I think the change to black was to make something that looked more conventional. The Black amps simply had freshly painted covers and newly anodised front panels. The chassis was still Blue as may be seen on any rear view photos. A Black TMA3 and matching Black TMR sold on ebay just recently. I was tempted by the Tuner but already have enough tuners!



    I never saw the simpler looking Stage Life models. These, according to this page, were the ones with valves.

    Judging by the outline drawings above the 'slot head' screws in the fascia were original although I'm sure the G-Ohm I saw had black allen bolts.
  14. davidsrsb

    davidsrsb pfm Member

  15. LesW

    LesW Retired at user request

    I once met Mike Maloney and his lady, Mary during a visit to the then Audio Centre in Sheffield - nice folks.

    The amps employed the fabled "Hitachi" mosfet circuit used by many a manufacturer including MF and Perreau to name a couple: http://www.angelfire.com/sd/paulkemble/sound7g.html

    From my days of working on the G-Ohm and the TMA3, I remember them with some affection as being quite exquisitely constructed for the day.
  16. Mignun

    Mignun pfm Member

    Malcolm, pm me with your e-mail and I'll send you a copy.
  17. davidsrsb

    davidsrsb pfm Member

    It looks like Myst got the power supply and layout right, though the Hitachi is a forgiving circuit.
    RS stamped TL071s in the preamp, hmm
  18. Beobloke

    Beobloke pfm Member

    I used to own a G-Ohm setup and it was a lovely little amplifier combo. I also owned a black TMR tuner and both reside firmly in the "why did I sell them?" catrgory!

    Ironically, I've yet to own or hear a TMA3 - maybe one day.

    May I trouble you for a copy, too, please? I'll send you a PM!
  19. pure sound

    pure sound Trade: manufacturer/distributor

    I think alot of it was built with RS Parts. It made the fact they could do it so nicely & still sell it at the price all the more surprising. Either that or they got their sums wrong.
  20. istari_knight

    istari_knight pfm Member

    Do those little black to-92 plastic holder things have a name ? Tried a Google but came up short.

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