Nottingham Analogue Spacedeck / Kuzma Stogi S / Benz Micro Ace S L
Lenco L-75 / Carl Ellis Plinth / Ortofon AS-212 / Ortofon SPU Classic GM E MkII
Ortofon ST-7 SUT / Nick G Modded Lentek Head Amp / Croft RIAA
Cambridge Audio CXU / Theta DS Pro Prime
Classé Model 30 / Luxman M-383
Usher Compass X-719
May contain opinions that others find disturbing.
The '2-15K' in-line SUT (kabelübertrager), has a step-up ratio of 1:80.
Inspection of the data sheet for the SL15 (http://theartofsound.net/forum/showt...turers-Ortofon), shows the output from the SL15 alone is 0.025mV (at 1 cm/s) and is 2mV via the 2-15K SUT, so the step up ratio is 2/0.025 = 80. This tallies with the impedance ratio: the SUT has the designation "2-15K" because when the SUT is loaded with the 2Ohm impedance of the cartridge, the output impedance is 15KOhm, hence the step-up ratio is sqrt(15000/2) = sqrt(7500) ~= 87.
Barry
It's more a question of gain, rather than impedance. What is the gain of the phono-stage of the EAR amp in both the MM and MC mode?
I expect the "3Ohm" setting refers to the coil impedance of the cartridge, rather than the input impedance of the amp. This is a Japanese convention; the actual input impedance is more likely to be 33Ohm or more.
Barry
Not sure the stats are available in this form. The preamp gain on the EAR 912 is 14db.
Re-reading Stereophile's review the step-up gain is published in db, not in 1:XX - so that's 30db (not 1:30) for the input marked 3 ohm, 26 db for 6 ohm, 23 db for 12 ohm and 20 db for 40 ohm - not sure how ratios can be calculated from that.
There is an additional transformer with three positions (0db, -6db and -12db) in between the phono section and the preamp, providing attenuation for gain matching purposes. I suspect that this complicates things when it comes to calculating gain. Without any attenuation the output on the lower impedance settings can be pretty high - keeping the phono output at appropriate levels is what the VU meters are for. When I first got it I thought I could detect a degredation in quality when the intermediate transformer was used but I'm satisfied now that that's just an artefact of the gain drop and that with levels matched, it can't be heard. Most of my cartridges are pretty low output though so it's not needed that much.
What I have found is that's it's possible to get a good sound out of every MC cartridge I've tried in it from 2 ohm at the coil right up to 100 ohm, at a variety of outputs from 0.05mv to 1mv, while the 47k ohm MM stage on its own is also superb. It really is a Swiss army knife of preamps and I've been delighted with it. I was actually skeptical before Petrat brought his down and we compared it against my Hashimoto HM7 + Aurorasound Vida + Modwright 36.5. But within a few weeks of hearing his I had tracked one down on the French-Belgian border and drove over on the chunnel to buy it.
Specs as published:
Input impedances, phono: 47k ohms, moving-magnet; labelled 3, 6, 12, or 40 ohms, moving-coil.
Output impedance: 600 ohms.
Line-stage gain: 14dB.
Phono-stage gain: 50–80dB
Signal/noise ratio: 68dB phono (ref. 2.4mV), 90dB line (ref. 1V).
Frequency response: 20Hz–20kHz, –0.3dB.
Distortion: <0.1% at 1kHz, 3V output.
Interesting (and informative as usual) write-up, Tom
I'm not surprised that the 'baby SPU' sounds good, as I had both it and the elliptical version, before going for the (then) top model, the Royal GM MKII, and enjoyed them both, although marginally preferring the spherical version, which I considered to be more musical sounding.
One small upgrade you can do, which I found significantly beneficial, is upgrade the stock (thin) internal headshell wires (unless Ortofon have done so already on the new #1 model), with these: https://www.ortofon.com/lw-6n-p-437
I found it 'tidied up' the sound overall, which as you've described is already very good, but the 6N copper lead wire removes a slight opacity, and notably 'fleshes out' the bass, curing the issue you've outlined above (one I can also relate to, as I heard the same thing myself).
It's a nice little upgrade and simply finishes things off nicely, releasing the full potential of the cartridge. Don't be tempted to go for the silver version of the leads, as they make the cartridge sound a little bright, and impacts adversely on musicality. The copper versions are the ones to go for. Once fitted, don't forget to reset VTF, as the new leads will be considerably heavier.
Enjoy!
Marco.
Main System
Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.
Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.
Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.
CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.
Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.
Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.
Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.
Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.
Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.
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Thanks for your detailed reply Tom.
True it is not easy from the published specification of your EAR preamp to relate the input impedance settings with the corresponding gain, but they are only loosely related: cartridges having a low output tend to have a low impedance because they have fewer turns on the coils.
Looking at the spec, the gain of the phono stage is 50dB when in MM mode, and up to 80dB when in MC mode on the "3Ohm" impedance setting. The additional gain of 30dB corresponds to a voltage step-up ratio of 1:31.6, which tallies with the 1:30 of the Cinemag SUT you have tried.
So what about the 1:80 ratio of the Ortofon SUT? Well the increase in gain is by a factor of 80/30 = 2.6, which translates to a gain increase of ~8.5dB and will be noticeable, unless you have adjusted the interstage transformers that you mention.
Whatever the speculations, the fact that you enjoy using the Ortofon devices is all that matters; it is far too easy to become obsessed with specs and figures, and not "hear the wood for the trees" (apologies for the 'bent' metaphor).
Barry
Cheers Marco, I am in the habit of using better leads but I haven't got round to swapping these ones out yet. Will give it a shot. I took a bet on the spherical for instinctive reasons, though I'm sure the eliptical must be pretty good as well.
I believe the SPU Royal N which I have is the same cartridge, without the Ortofon headshell, as the Royal GM MkII (same gold coils and Replicant 100 stylus). I consider it an out and out bargain in terms of performance/sound per pound.
I actually have a Royal GM headshell for it that I picked up on ebay but somehow it sounds better to me in my favourite Fidelity Research FR-S3 headshell, I also have a few of these for my mono Miyajimas (with nice headshell wires natch).
I've taken Marco's advice and purchased some of those copper leads. Should be here after the bank holiday, will let you know
Nottingham Analogue Spacedeck / Kuzma Stogi S / Benz Micro Ace S L
Lenco L-75 / Carl Ellis Plinth / Ortofon AS-212 / Ortofon SPU Classic GM E MkII
Ortofon ST-7 SUT / Nick G Modded Lentek Head Amp / Croft RIAA
Cambridge Audio CXU / Theta DS Pro Prime
Classé Model 30 / Luxman M-383
Usher Compass X-719
May contain opinions that others find disturbing.
Installed. They do seem to have led to more clarity and openness, though it's marginal. Not unhappy though
Nottingham Analogue Spacedeck / Kuzma Stogi S / Benz Micro Ace S L
Lenco L-75 / Carl Ellis Plinth / Ortofon AS-212 / Ortofon SPU Classic GM E MkII
Ortofon ST-7 SUT / Nick G Modded Lentek Head Amp / Croft RIAA
Cambridge Audio CXU / Theta DS Pro Prime
Classé Model 30 / Luxman M-383
Usher Compass X-719
May contain opinions that others find disturbing.