Dear Axel, You stole my question from the MM cartridge thread, but I am glad you did, because no one really responded to it over there. Ideally, I would build an MM phono stage myself, based on a single-ended LCR type of RIAA equalization or based on a true balanced circuit design. There are several schematics available for either topology. But in the interim (because it will take me 6 months or more to build such a thing), I would like to find a dedicated MM phono stage to use. Some of the above suggestions do sound appealing. I would like to spend less than $2K and to buy something used in that price range. One candidate would be the cheapest Allnic preamp, the H-1200. Others are Hagerman, Graham Slee, Vacuum State, Pass, Whest, Aqvox, etc. I would love to hear from anyone with actually experience of these or other candidate units.
My regular phono is a highly modified (by me) Atma-sphere MP1. It sounds wonderful on MCs, and I know how to modify it to reduce phono gain for MM, but I would rather not do so, because it would involve the insertion of a switch in the signal path which might particularly degrade MC performance. |
Allen has publicly disclosed his FVP5 and RTP3D designs. In fact, the front end of his RTP3D (using the MAT02 transistor that he mentions in TPCB2), is the prototype for the input stage of my phono section these days. The FVP5 is single-ended and the RTP3D is balanced. So far as I know he has not messed around with an LCR equalization stage. I've never heard the RTP3D or later version per se, but based on my own results with a facsimile of its phono gain stage, I would predict it is one fabulous piece. He uses a pair of resistors between the emitter(s) of the bottom transistor(s) (MAT02 or other) in the input dual-differential cascode and the CCS to control total phono gain. (Believe me, with the MAT02, which has a Gm of 500!!!, you will have gain up the wazoo.) The FVP5 would be easiest to build and may be all one needs for great MM reproduction. Does he sell it as a kit? |
I see no mention of an FVP kit on the Vacuum State website. I do see mention of a new phono stage, the SVP2, but it is rather costly for use as a dedicated MM phono section. Has anyone heard the JLT1? The price is acceptable, but I know nothing about how it sounds. |
I personally have not heard any MM cartridge in my system since I stopped using my Grado TLZ in favor of some MC cartridge (probably a Sumiko BluePoint, originally), about 2 decades ago. I have nothing much to go on except Raul's opinions. |
Axel, What I wrote was that the Sumiko Blue Point was probably my FIRST MC cartridge, back in the late 80s or early 90s. I got away from that pretty quickly. Then I owned Benz Glider, followed by a Transfiguration Esprit and then the Esprit II, only one at a time in succession over a period of probably more than a decade. These were all mid-price HOMCs, and in retrospect neither one "rang my bell". (I would never have thought of either spending more than $1000 for a cartridge OR buying a used one.) Then about 5 years ago, I bought a Koetsu Urushi (via my son in Tokyo), which was a total revelation vs those others. I now own the Urushi, an Ortofon MC7500, and a van den Hul Colibri (both of the latter purchased used off A'gon). I have not yet heard the Colibri. Of course, now I have 3 turntables, too. You could say that the disease vinylosis is advancing in severity as I get older. |
Tom, I did not get that message (that the range of output voltages and inernal impedances of MC cartridges presents a problem per se) from Kirkus' long post. I will have to re-read it, but I think he is saying that the much higher output impedance and reactance of an MM cartridge poses a problem for MM phono pre design.
Kirkus, Given your depth of knowledge of this subject, are there any commercially available phono preamps that seem up to snuff for use with MM cartridges exclusively? |
Hi Pryso, This is the second time someone has recommended EA to me. Since you are a more credible source than the other person, I will look into it. I did also think about buying a basic JLTi, second hand, and upgrading the power supply myself. Did you build the custom supply for yours? If not, do you have a schematic?
Curses, I just lost out on an auction for an AKG P8ES cartridge on eBay. Why? Because I was so busy all day I forgot to increase my bid, which I knew would not withstand the assault of last-minute bidders. i do have my old Grado TLZ, and that is the first MM I will try in the new era. What about the AT150mlx? That seems to be liked by most. |
Axel, you and I are thinking along the same lines, save for the fact that I would not use a transformer anywhere. The desire for a balanced circuit is a real sticking point as almost none of the commercial products offer that. There is the Aqvox, but as far as I can understand from their very confusing ad copy (where they say in one para that it is balanced and in another that it is SE), the balanced circuit, if present, is used only for MC cartridges. If you use the MM inputs, the circuit is SE. The ad also contains some mumbo jumbo about MMs being voltage generators that prefer a SE circuit topology (as compared to MCs). I don't "buy" that logic. The new K&K phono is I think balanced, and I intend to look into that one.
The IC design is interesting, but the ICs used have been surpassed for audio in recent years; I am wondering whether one can just plug in one of the later better sounding ICs, without a re-design. |
Axel and Tom, if you can change load resistors, I see no reason to lust for a separate MC phono section for each cartridge. The LOMCs are not identical to each other, but they are similar enough. Anyway, IF one needed a different circuit for every different LOMC, that is where I would draw the line. I would not ever do that.
Mark, If I understood Kirkus correctly, he maintains that a balanced input is not optimal for an MM cartridge, which was news to me. The Aqvox preamp makers make a similar claim; their product is balanced for MC cartridges and SE for MM cartridges, because the latter are "voltage generators", in their parlance. Yes, MM cartridges are voltage generators as compared to LOMCs, but why does that negate the positive attributes of a balanced input? (Apparently you chose a balanced input for your MM phono stage, for example.) |
Tom and Axel, I heretofore have had only one LOMC cartridge, which seeems optimally loaded by a 100R resistor, which I soldered in place myself. But I recently purchased a (third) LOMC that will probably do best with 1000R. I have contemplated installing a switch, so I can change between 100R and 1000R, when I want to change cartridges. Obviously there is a risk of introducing noise at the switch. But in practice, have either of you, or anyone else, actually perceived degradation of the sound with such an arrangement? Many commercial products incorporate such switches in this critical part of the circuit, so most people would not know if they are losing anything in the way of S/N ratio as a result.
But this is off-topic. With an MM phono stage, we should all be using a 100K load, according to Raul. Based on very limited data, I have to agree with him; several years ago, I made a similar accidental observation with whatever MM I owned at that time. It sounded better with a 98K load compared to the standard 47K load, and the diff was not subtle. |
Raul, Do you mean to say that every time you change from an MC that likes to see, for example, ~100R to one that needs significantly higher R, you actually take the 3160 to the workbench and solder in the required higher R? Or do you use some plug-in system that obviates the need for a switch but still puts mechanical (i.e., unsoldered, pressure-based) contact points in the signal path? Or do you still have a switch for load resistance? (Your post suggests you eliminated switching between input jacks, rather than between load resistors. Even with a single pair of inputs it would be desirable to be able to switch load resistors.)
Kirkus, I just paid too much for a B&O MMC20CL off eBay. I hope I will be happy. The AD797 is one of the ICs I had in mind when I noted that the op amp-based schematic that was posted above might be upgraded with later, better chips. (The schematic used TL072, I think.) |
Raul, Just another one of life's compromises.
Kirkus, Would you care to comment in more detail on your earlier statement that a balanced input is per se not ideal for an MM cartridge? At least I think that is what you meant to say.
By the way, thanks largely to Kirkus' input I am beginning to learn some things about MM phono stages and phono stages in general that I did not know. |
That's a review of the Vinyl Reference, their more expensive phono stage, driven by an MC cartridge, so its relevance to the present discussion is limited. |
In my view, one of the hard to resist features of the 3160 (Raul's product) is the completely separate MM and MC phono stages, not to mention the fact that both are balanced circuits (or at least I know that the MC one is balanced).
Raul might respond to Tom's question about why "high-end" phono preamps have switchable load resistances by saying that there is a demand for it among end-users, for the sake of convenience, not optimal sound quality. Most end-users of such products want remotely switchable everything, so they don't have to get off the couch. Raul wants optimum performance as his end-all and be-all. What I meant to infer when I said that most of us would not know whether switches degrade the sound is that most of us have not done the experiment properly in order to make a judgment. Most of us have one phono stage which either does or does not have switches in the signal path. And no one (other than Raul) has come forward to say that removing switches from phono inputs has made an audible improvement in sound. Or that adding same caused a deterioration. For my part, I own an Atma-sphere MP1 in which I have made considerable mods to the phono stage. The MP1, like Raul's preamp, has no switches in the phono input, but one can change load resistance by installing resistors between two screw terminals on the outside rear of the chassis. Purist that I am, I have never used those screw terminals for loading or for anything; I solder my load resistors right at the grids of the input tube (or the gates of an MAT02 NPN transistor, in the case of my modified unit). Oops, I am off-topic.
One thing that comes out of this so far, thanks to Kirkus and Quiddity, is the concept that there truly IS a difference, primarily at the input voltage amplifier stage, between an ideal MM phono and an ideal MC phono. One topology does not ideally fit all. I'd still like to hear more from Kirkus on balanced mode with an MM cartridge. Anyway, I've decided that I do want a separate dedicated MM phono stage, which is kind of where I started but now I have more info to go on. |
Kirkus, I would like to try to re-state your argument in short form, to see if I understand it:
For the reasons cited, it is much more difficult to obtain a true balanced signal from an MM cartridge as compared to an MC one. Feeding a signal with an imbalance of noise on one phase vs the other to the balanced gain stage will result in the amplification of that noise, i.e., it will not be rejected because it is not identically present on both phases.
Is that more or less correct? Why is the noise to which you refer not similarly amplified by an SE topology? (It's that "3 db" boost of the noise that I don't quite get.) Noise is noise(?) In a good SE phono stage for MM, is the "ground" isolated from chassis or earth ground? That would seem to be a good idea. |
Kirkus, Thanks for your patience in preparing a detailed response to my questions. Your take is very interesting and thoughtful. Meantime, I am wondering whether we should all be beating the bushes for vintage phono stages to use with these vintage MMs. But that would partially negate the premise that we can get more out of them now than ever before with modern well designed preamplification. Here are low-priced products that jump out at me as being possibly well suited to MMs: the new K&K, the Aqvox (SE for MMs, balanced for MCs), the Herron dedicated to MM and now out of production, any of the Hagerman products (I have high respect for his design capabilities), the Allnic products (they add on a SUT for MCs, so maybe they would work well for MMs, especially the H1200), the Whest2.0, possibly older Audio Research phono stages (maybe a tweaked SP3 would be great). Raul's 3160 may be at the top of the heap if price is no object. Any other ideas, guys? |
Axel, You wrote:
"As to hum caused by 'unbalanced' MM cart output impedance. Well, I think that the more expensive carts we are speaking of (Raul mostly), those have always excellent channel balance, often better than more main-stream MCs with an e.g. <1.5dB spec."
I am pretty sure that Kirkus was not referring to differences between channels in his comments on the impedance properties of MM cartridges. I think he was referring to the generally much higher and more reactive impedance of MMs and the fact that these parameters may not be identical for each phase of the output in a SINGLE channel, using a balanced circuit. This creates a noise that cannot be cancelled by the balanced topology and is instead amplified. Channel balance has nothing to do with it. If I am full of baloney, perhaps Kirkus will correct me. |
I guess this thread is on its last legs, or already dead. I for one would love to hear from anyone who is using a vintage phono stage with an MM cartridge. |
Axel, perhaps one reason you don't have "hum" is that the noise that might result from Kirkus' theorem would not necessarily be in the spectrum that we recognize as hum (60Hz or 120Hz, in the US; 50Hz or 100Hz in Germany). The noise he is talking about could be random in frequency (I think) and might not be audible as noise until one took steps to eliminate it and listened for the difference. |
In my list of candidate MM phono stages posted 6/26, I neglected to include the Graham Slee Gold Era Reflex (hope I got the long name right). The Reflex was specifically designed for MM and HOMC. Further, it got great reviews from some respected sources, including M Fremer. It's a bit odd in that it uses active RIAA equalization, but Kirkus has espoused that approach also. (The more common gospel is that passive RIAA is better sounding than active.) Earlier in this thread, someone dismissed this or one of the other Graham phono pres as not being "as good as" a Jadis, without naming the particular Jadis preamp he was referrring to. As I have never been a fan of any Jadis product, I am keeping an open mind on the Graham. Has anyone been able to audition this product (the Gold Reflex) in a system driven by an MM cartridge? (There is an optional accessory, the Elevator, which adds the necessary gain for an LOMC. One would prefer to know what the Reflex sounds like without this add-on.) Thanks for any comments. |
Rockinrobin, I am going to guess that your experience is an overall endorsement of the Reflex. If it were not doing a good job, you might not hear a big difference between the two cartridges. Now you should try the Reflex alone driven by a Grace Ruby, Garrott P77, AKG, AT, B&O, or etc. Let us know how such a combo compares to the Elevator/Kontrapunkt source. Maybe some one of us can lend you one of those gems. (Just kidding...., but it would help the cause.)
Tom, what Jadis preamp did you have in mind? The last top end product from them that I am aware of was the JP80. By now there must be newer models. They have been really quiet in the US market, as in "absent". |
Pablovila, Your list of candidate MM preamps looks like the one I posted on 6/26. I consider it incomplete. Below $1500 we also have the PS Audio GCPH and the Graham Slee Reflex, discussed above. Just to make it more confusing, I wonder how some of the highest end preamps from the "good old days" would fare if one were to upgrade the power supplies and the parts in the signal path. I am thinking of early Audio Research, for one example. |
Did not know that existed. I have never seen one advertised that was MM-dedicated. Thanks for bringing it to our attention; have you heard it? Can you compare it to anything? |
Art Audio Vinyl One, MM only = $2400, new. It's a little above budget but I bet it's very good. |
