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Thread: Ortofon SPU Mono GM Mk II

  1. #1
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 171
    I'm Martin.

    Default Ortofon SPU Mono GM Mk II

    I have been assaulting the senses of a forum member for a while so thought I should do the honourable thing and inflict that same pain on everyone......

    I have questions and confusion, no doubt through lack of knowledge, but read as I may I can't seem to get the answer I need.

    You may have seen my thread re a mono setup and I have decided I would like a mono cartridge that I can swap in and out with my stereo one with the minimum of fuss. The stereo one is an SPU 1E so a mono SPU would seem to make sense.

    There are currently three mono SPUs, two of which are not appropriate however the Ortofon SPU Mono GM Mk II could work. The reason I say it could work is that it has an element of vertical compliance so I could use it on stereo records with no fear of vinyl damage.

    Here is my first question..... Given it has vertical compliance then I am assuming it was designed to not damage stereo records or even mono records cut with a stereo head so if that assumption is correct why does it have a 25um stylus and not an 18um version?

    Second question, given it has a 25um stylus is it safe to use for modern mono reissues, in fact any mono record from the 60s onwards? Ignore any crossover records of the early 60s, I am really only referencing modern reissues or records labelled as"Mono" due to the fact they were created in the stereo age and therefore needed to be flagged accordingly.

    Hope that all makes sense and thanks in advance :-)

  2. #2
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,698
    I'm Hugo.

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    Ortofon do not offer mono tips on SPUs smaller than 25um (1 mil). That is safe for all microgroove mono records, but for the most modern pressings the tip will sit higher in the groove compared to a 0.7 mil tip which will 'fit' the groove much better. I do think that a smaller 0.7 mil tip is a better 'all round' choice than 1 mil but identifying earlier, wide groove, pressings is far from straightforward and this article is worth a read https://dgmono.com/2018/04/06/deep-g...width-mystery/ . It's a shame that Ortofon don't give us the choice with the SPU mono cartridges but any of them will play mono much better than a stereo cartridge.

    The SPU Mono GM does have some vertical compliance so as you say it won't damage stereo records, but its 3mV output is a tad low for a MM phono amp. Conversely, the SPU Mono CG models have a very peculiar 1.5mV output and played into a regular MC phono amp or SUT these cartridges sound rather underwhelming; however paired with Ortofon's recommended ST-M25 mono SUT (12dB gain) they really come to life - they are really rather good, if not quite to Miyajima Zero Mono standards.

  3. #3
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 171
    I'm Martin.

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    Thanks Hugo, I'll have a look at the link later.

    Are you therefore saying that even though the Ortofon stylus isn't the 0.7 "ideal" it will still play modern reissued mono records better than the SPU #1E and will not do any damage?

  4. #4
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,698
    I'm Hugo.

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    Maybe 'ideal' is the wrong term - for wider groove mono LPs a 1 mil tip will typically result in better replay quality compared to the smaller 0.7 mil tip, but the situation is reversed for narrower groove LPs. So, it's largely a matter of choosing your compromises! And yes, it should play mono records better than the SPU#1E and its vertical compliance, while not quoted by Ortofon, is much like any stereo SPU so there won't be any danger to stereo grooves.

    It's interesting that Ortofon offer 18um tips on mono models in their 'mainstream' cartridge ranges - they seem to view mono SPUs as being purely old-fashioned things, but mono done well is anything but old-fashioned in terms of sound!

  5. #5
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 171
    I'm Martin.

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    Thanks again that's very much appreciated. Also, yes, I was using the term "ideal" with regards to modern grooves and not microgroove.

  6. #6
    Join Date: Feb 2010

    Location: Berkshire, UK

    Posts: 4,119
    I'm Tom.

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    Just to amplify Hugo's point, mono can be a bit of a minefield as standards were changing throughout the period and it's complicated by reissues over time.

    I have used the Ortofon Mono GM MkII in the past and in my view it's one of the best all-rounders out there, yes with its 1mil tip it is made for the earlier pressings but wide, u-shape groove mono (for which the 1mil tip is 'correct') ran all the way from the early 50s and continued on some masters/pressings right into the late 1960s ... indeed even some reissues can be wide groove. So it's in the 'ideal' bracket for a lot of stuff out there.

    For the most part, wide groove mono only started to disappear when the stereo era began in earnest in the early 1960s. After that point, the narrower, v-shaped stereo groove fairly quickly became standard for most mono pressing as well as stereo, and this is the situation with most mono reissues since that time, for which the 0.7mil (stereo width) is correct.

    Using a wide tip in a narrow groove is not ideal in principle, but it often sounds fine. Conversely a narrow tip in a wide groove in my view is (of the two cases) the less satisfactory (can be noisier) though my view could be coloured byt the fact that in my collection, the vast majority of mono is older stuff, rather than reissues - that may not be the case for others.

    In the end, if you start buying mono in earnest, you might find you need both. Spotting the difference/choosing the right tip especially for 1960s mono either originals or repressings can be difficult or even impossible just by looking ... often the only way really to do it is to try both sizes of stylus and use the one that sounds the best - it should be obvious enough to the ear which is noisier and which is more 'right'.

    In my setup I've ended up with Miyajima cartridges of 1.0mil, 0.7mil and 4.0mil (for 78s) as well as a few vintage ones that can also be fun and a raft of Shure M44 stylii (from Expert Stylus) for 78s of later eras that use a smaller tip.

    But if you are 'only' having one mono cartridge I would say the GM MkII is a sensible option the, only constraint is as Hugo says, the 3mV which is on the low side for MM-level input - so it may not be ideal if your MM input or overall phono + preamp gain is a bit on the weedy side. (For most people this won't be an issue).

    If your mono is mainly later/reissue, its not quite at the same level but you might want to think about something like the AT33Mono which is also vertically compliant but has a 0.65mil tip intended for narrower grooves, but have a good think about what your main mono listening will consist of before purchasing.
    Main: Speakers 'RFC' Tannoy Canterburys / custom crossovers with Tannoy ST50 supertweeters; Amp - Silvercore 833C monoblocks; preamp TBA watch this space; Vinyl: Schopper'd Thorens TD124 MkII + Ikeda IT345-CR1 9 inch and Ikeda IT-407 12 inch tonearms; Cartridges Stereo - Miyajima Madake, Miyajima Takumi, Ikeda 9TT, vintage Ortofon SPU GM and SPU Gold; Mono - Miyajimas - Zero 0.7, Premium 1.0, Miyajima/Edison '78' 4.0 conical, and Shure M44 strapped for mono with several Expert Stylus conicals for different eras of 78s; Phono stage Allnic H7000V used with Miyajima ETR-Mono and ETR-Stereo SUTs; Digital: Audio Note CDT2/II transport, heavily enhanced AN DAC based on kit but aspiring to DAC5 spec.

    Study: Speakers - Tannoy DC6; Amp: Marantz PM-4; Digital: CDP Sony CDP-X3000ES & Arcam rBlink; Vinyl: Garrard 401 with AT 1503 MkI broadcast arm, Ortofon SPU Classic GM, Ortofon 2-15k SUT and Puresound Tenuto platter mat

  7. #7
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 171
    I'm Martin.

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    Thanks for that Tom and very much appreciated too.

    As you rightly point out my mono situation, although it's tiny currently, is the later stuff and yep the AT33 would possibly be a better choice technically but I don't want the aggravation of having to mess about with VTA or anything like that if I want to just play one record to its best ability. I also have no intention of creating myself a nightly playlist and then working out the best logistics of cartridge changes :-) :-)

    That's why the SPU seems to make sense as it's pretty much a 30 second swap over with my stereo SPU and I could handle doing that on a record by record basis if that makes sense.

  8. #8
    Join Date: Feb 2010

    Location: Berkshire, UK

    Posts: 4,119
    I'm Tom.

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    The GM MkII will play reissues perfectly well. For a while (before I got the Miyajima bug) it was my only mono cartridge. I would say go for it.

    I used to trim the weight of SPUs with little bits of lead blu-tac'd inside so that when swapping I didn't even need to change the VTF. (They can vary slightly from being a straight swap over). VTA/alignment etc of course as you point out are all the same between SPUs.
    Main: Speakers 'RFC' Tannoy Canterburys / custom crossovers with Tannoy ST50 supertweeters; Amp - Silvercore 833C monoblocks; preamp TBA watch this space; Vinyl: Schopper'd Thorens TD124 MkII + Ikeda IT345-CR1 9 inch and Ikeda IT-407 12 inch tonearms; Cartridges Stereo - Miyajima Madake, Miyajima Takumi, Ikeda 9TT, vintage Ortofon SPU GM and SPU Gold; Mono - Miyajimas - Zero 0.7, Premium 1.0, Miyajima/Edison '78' 4.0 conical, and Shure M44 strapped for mono with several Expert Stylus conicals for different eras of 78s; Phono stage Allnic H7000V used with Miyajima ETR-Mono and ETR-Stereo SUTs; Digital: Audio Note CDT2/II transport, heavily enhanced AN DAC based on kit but aspiring to DAC5 spec.

    Study: Speakers - Tannoy DC6; Amp: Marantz PM-4; Digital: CDP Sony CDP-X3000ES & Arcam rBlink; Vinyl: Garrard 401 with AT 1503 MkI broadcast arm, Ortofon SPU Classic GM, Ortofon 2-15k SUT and Puresound Tenuto platter mat

  9. #9
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 171
    I'm Martin.

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    Perfect Tom thanks, just what I wanted to hear. That's a great tip of extra weight too and will minimise, if not eliminate, the faff. Looks like I have a winner!

  10. #10
    Join Date: Feb 2010

    Location: Berkshire, UK

    Posts: 4,119
    I'm Tom.

    Default

    Main: Speakers 'RFC' Tannoy Canterburys / custom crossovers with Tannoy ST50 supertweeters; Amp - Silvercore 833C monoblocks; preamp TBA watch this space; Vinyl: Schopper'd Thorens TD124 MkII + Ikeda IT345-CR1 9 inch and Ikeda IT-407 12 inch tonearms; Cartridges Stereo - Miyajima Madake, Miyajima Takumi, Ikeda 9TT, vintage Ortofon SPU GM and SPU Gold; Mono - Miyajimas - Zero 0.7, Premium 1.0, Miyajima/Edison '78' 4.0 conical, and Shure M44 strapped for mono with several Expert Stylus conicals for different eras of 78s; Phono stage Allnic H7000V used with Miyajima ETR-Mono and ETR-Stereo SUTs; Digital: Audio Note CDT2/II transport, heavily enhanced AN DAC based on kit but aspiring to DAC5 spec.

    Study: Speakers - Tannoy DC6; Amp: Marantz PM-4; Digital: CDP Sony CDP-X3000ES & Arcam rBlink; Vinyl: Garrard 401 with AT 1503 MkI broadcast arm, Ortofon SPU Classic GM, Ortofon 2-15k SUT and Puresound Tenuto platter mat

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