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Are Koetsus worth it?

Discussion in 'audio' started by Tim Jones, Jan 30, 2017.

  1. Mike Reed

    Mike Reed pfm Member

    The SUTs in the 912 are the same as those in his MC4 stand-alone SUT, whereas the pre. below has the 3 tap trannies, or so I believe.
     
  2. Tony L

    Tony L Administrator

    Capacitance is a PITA with MM carts, e.g. my Ortofon 2M Black sounds utterly dreadful into my expensive and otherwise very nice Verdier pre as it presents too a high capacitance and ends up with a really nasty treble spike. I'm actually using a Croft RIAA stage until I figure out how to modify the Verdier for a lower capacitance. I'm sure MM carts get a bad reputation as most people only get to hear them in a compromised situation - if the loading and capacitance is unsuitable the frequency response goes right off the map. Here is a very good website explaining how load and capacitance impact MM carts (link).

    PS I love the idea of that Manley!
     
  3. Mike Reed

    Mike Reed pfm Member

    I'm finding quite different operational differences. The gain rarely moves at -6, whereas the adj. switch for impedance changes between the lower three settings depending which records is being played. With the gain at 0, I can rarely get the impedance switch below -12 to keep the needles in range. AND my cart' int. imp.is one and output is below 0.3 mV. Other cart's are similar.

    I must admit that after a s/s m/c only stage with known impedance plugs to suit my three cart's, I find the 'twiddle for best effect' approach of the 912 a bit annoying, as I'm looking at the meters and adjusting when I should be enjoying the music. Oh well, sounds bloody marvellous regardless !:)
     
  4. montesquieu

    montesquieu pfm Member

    Having owned an EAR MC3 and found it so-so, I'm not sure at all that they are the same trannies as the MC4 - same ratios, yes, but I think they must be higher quality as befits the 912's 'statement' nature. I put my well-broken-in HM7s in against them into the MM stage (used with my usual SPUs and Miyajimas) and the internal setup was notably better which to be honest was a bit of a surprise.
     
  5. Mike Reed

    Mike Reed pfm Member

    Thanks for explanations, G.T. Don't follow the first one, though, as I can't see the relevance of the line level inputs to the phono ones; you either use one or the other.

    Tom (Montesquieu) uses 0dB gain on his cart's, whereas I get a better presentation by using the -6 setting. Odd, when I have cart's with both low internal impedance and output. Have had few valved power amp's before, but only a Quad 22 (?) valve pre., which was even then, abysmal and overly complex.
     
  6. Robert

    Robert Tapehead

    Agreed, cap loading is critical and yet most amplifier designers pay no attention to the issue. Resistive loading too is important for MM, far less so for MC despite some claims.

    The house sound with which many MMs are credited can be changed completely with loading. Shure's can be changed from mellow and full to crisp and lean, ATs from zingy and bright to smooth and sweet etc.

    Having said all that, I think adjustments should be placed inside the case, or tucked away on the back panel. These are set and forget changes (between cart swaps) and a plethora of cart loading knobs on the front panel just encourages fiddling.
     
  7. montesquieu

    montesquieu pfm Member

    I thing G.T means people can use it to match levels (in a broad sense) between phono and CD or other line input, so no shocks when you change input. But as discussed that's not really what it's for - it sits between SUTs and the RIAA stage ... this has masses of gain available for matching all sorts of cartridges, the 0/-6/-12 control is to make sure there is no overload as monitored by the meters.

    Overkill in a way as I've tried to find where it starts to overload and it's way beyond the bump stops on the meters, I never found it to clip yet.

    Having said that all my cartridges like yours are low output, 0.2mv sort of levels.
     
  8. montesquieu

    montesquieu pfm Member

    Some of us change cartridges several times in a listening session or have several arms or TTs connected, for mono, 78, different styles and eras that suit different cartridges. Internal adjustment is a monumental pain in the bum.
     
  9. Vinny

    Vinny pfm Member

    I recently bought a DV-20X2L and was tipped-off after fitting it here, that into 1K rather than 100 Ohm, the sound would be much improved.
    Maybe a slight exaggeration to claim night and day, but it did transform the sound - clearer, more detailed - way different and very much improved SQ.

    Surely 2 simple high quality DIP switches, one for resistance, one for cap', on the back of a phono stage would be the best of all worlds? Simple enough to alter but not tempting enough to fiddle with?
     
  10. andyr

    andyr Registered User

    Agreed, cap loading is critical for MMs - not so for LOMCs.

    The simplest way to allow different cap loadings for MMs is to:
    * use a low value as the default on the PCB. I use 110pF
    * provide a parallel pair of input RCAs for 'cap-loaded' RCA plugs.

    EG. for my Stanton WOS CS100, 275pF is the mfr-recommended cap loading. Which means:
    * 110 pf default in my 'Muse' phono stage.
    * about 60pF for my phono cable.
    * est 15-20pF in the arm wiring (short but highly twisted).
    * and 90pF in loaded caps.

    IMO, it is exactly the reverse. Needing to load MMs down below 47K is rare - but the optimal load for a LOMC will be anything from 50 to 5K ohms.

    This is not a "claim" ... you just need to listen. :D

    Yes, cap loading.

    Parallel pairs of RCAs are the way, IMO. But this can cost serious money if you use good RCA sockets.

    Disagree - they are "play with until you like the resulting sound" changes. Then you forget them - until you change carts. :D

    Andy
     
  11. Tony L

    Tony L Administrator

    Taking the ATs and modern Ortofon MM carts down to 33-39k can be a real plus IME.
     
  12. andyr

    andyr Registered User

    How interesting. I also heard that wood-bodied Grados are also supposed to sound better at 33-35K ... but I didn't hear any beneficial result from doing this. :confused:

    Andy
     
  13. Tony L

    Tony L Administrator

    I'm basing this on the experience of having Rob mod a Quad 34 phono stage. Out of the box with 47k/220uf it is excruciatingly bad with a 2M Black, just unlistenable to my ears with a masive spike around hi-hats, vocal sibilance and surface noise along with no bass. Just horrible and enough to make you want to drop-kick the 34 into the trash. Dropping the capacitance down to 39uf improved it spectacularly, it now sounded like a very decent cartridge and finally dropping the loading down to 39k nailed it to the point it really sounded like a £500 cart and you'd never believe you were listening to a humble (actually rather unfairly underrated) Quad 34. It really opened my eyes to something I'd never given much thought too.
     
  14. andyr

    andyr Registered User

    Tony, I think you have your cap values wrong? MM cap loadings are usually measured in picoFarad (pF) - not microFarad (uF).

    So the Quad 34 had 47K (standard) and 220pF. Then the on-board capacitance of the Quad 34 was dropped to 39pF ... so when you take phono cable and arm wiring into account, you would've ended up with at least 160pF - within the Ortofon recommended range of 150-300pF:
    * Quad 34 - 39pF
    * phono cable - at least 100pF
    * arm wiring - at least 20pF.

    Whereas with the original 220pF, the total would've been beyond the recommended cap load (at 340pF).

    Interestingly enough, some classic MMs prefer 100K to 47K - gives them a lot more top-end air. :)

    Andy
     
  15. Tony L

    Tony L Administrator

    Yes, typo, my apologies, definitely pf! I even bought a cheap little capacitance meter off eBay so I can measure arm leads as my Fluke multimeter isn't sufficiently sensitive.
     
  16. topoxforddoc

    topoxforddoc pfm Member

    Jensen MC transformers contain standard nickel alloy cores - nickel alloy is technically exotic, but no further info - price USD 210-250 each - Hashimoto HM7s are USD1060 a pair, Stevens & Billington TX103 even more expensive, but not sold separately now.

    Describing the Jensen AXT346AXT -

    "The cores in these step-ups are from 14 gauge 80% nickel alloy laminations, and the case sports nested double metal screening."

    http://www.tnt-audio.com/accessories/mc_3xfr_e.html
     
  17. pmac

    pmac lovesrecordplayers

    The quality, or otherwise, of the Jensen transformers is not the issue. I was highlighting the fact that an audio manufacturer was questioning the quality of them on an assumption.
     
  18. Robert

    Robert Tapehead

    Hmm I can't agree with much there Andy,

    Low output MCs have a very low impedance generator - therefore changes to either capacitance or resistive loading have no effect unless extreme.

    MMs have substancial inductance and therefore the results vary greatly when varying both capacitance and resistive loading. For example, taking loading from 47K to 33K on a standard AT or Ortofon MM will alter the response above around 5Khz by 2-5dB. And these are broad changes, not confined to arrow peaks so very audible.

    With typical MM generators (i.e. 95% of them), changing capacitance alters the centre frequency of the HF peak and roll-off thereafter, while resistance alters the amplitude of the peak and general HF response.

    There are exceptions. Grado have quite low inductance (55mH compared to 350mH-700mH for typical MMs), therefore you'd need to go down below 15K or so to start impacting results.
    Many Grado fans run them into 10K Ohms.
     
  19. Mike Reed

    Mike Reed pfm Member

    Surely, only if you have detachable head-shells; set-up on a fixed one is a painstaking job, esp. with 'under-slung' cantilever/stylus.
     
  20. G T Audio

    G T Audio Trade: Distributor and Manufacturer

    I wasn't questioning the quality of Jensen transformers. I did test some years ago but I wouldn't use them because there were better performing transformers made within Europe. Jensen are American made and I try to use UK and EU manufactured parts where ever I can, unless something special appears. FWIW there aren't many transformers I haven't tried or tested over the years.
     

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