To what level of "top" phono stage are you referring? The Graham Slee Reflex is a dedicated MM phono stage. (Yes, you can use HOMC cartridges with it but it's designed specifically for MM cartridges.)
Tom |
Should have done my homework... The Reflex isn't even in the same league as a Jadis.
But for those on a budget, I guess the Reflex is one (dedicated MM stage) to consider.
Tom |
The new Bottlehead Eros kit is quite something for $1000 professionally assembled! |
This question is something I tried to get at in a prior post. I, too, am interested in hearing about really top flight phono preamps that are designed for high output coils or moving magnet designs. The benefits would be analagous (sp?) to going with a really high quality monitor that doesn't try to plumb the deepest bass. In other words, the designer saves the money that would need to be invested in a larger cabinet, additional drivers, internal bracing, ETC in order to focus on getting superior sound within the 50hz and up frequency range. Surely someone has got to be making reference quality phonostages that are intended to be used only with high output cartridges--NO? |
Hi Dodgealum,
I think you got my point right on. We all know there are SO MANY phono-stage that ALSO do MM, like BIG DEAL.
It is the TOP effort that becomes of interest. My ML326S modules are doing pretty fine -- BUT I think there can be better to be had, and I think in terms of a tube design. But not another one yet that "sounds really good for the money".
Arthur Salvatore (may he be mentioned here?) insists the best has to be (happens to be e.g. Jadis) inside the pre-amp in any event. So if we take it outside it better be the best --- what ever THAT would be.
Axel
PS: Next we'll be crucified being elitist, I hope not! |
Maybe have one custom made by Juicy Music, Hagerman, Wavelength, or similar for 3-6mV output only. |
http://www.decware.com/newsite/ZP3.htm
Try Decware ZP3 this is very high quality class A Tube
for $895.00 fully assembled and comes with a 30 day trial as well.
I am not affiliated with them. I have their integrated power SET amp and love it alot,But I'm not into vinyl anymore,But have purchased their Tube cd player instead.
Don C. |
Yes, if you get the match right. Start with the cartridge end and find out which pre's work best with the pre. |
Hi All,
has anyone experience with an Allen Wright 'Vacuum State' phono-stage at all?
Axel |
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. |
Hi Lewm,
sorry for having nicked your question, not that I knew. It just becomes the next relavant issue after you get 'closer' with the 'MM prered' thing.
>>> 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 <<<
Now you nicked MY question, it's actually behind the 'Allen Wright' inquiery. He apparently has some VERY well thought out designs. I think your point is a good one, and that's what I'm planning to do. Build my own and meanwhile listen to my 326 phono-boards (and use them as a referance to improve on)
Thanks,
Axel |
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? |
Lewm
>>> Does he sell it as a kit? <<<
I have actually send him an email.
I'll see what comes back.
Thanks for the feedback also.
Axel |
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. |
Hi Lewm,
following FYI, (in answer to my query to A.W.):
>>> The balanced phono stage with "floating" RIAA is not usable as a stand alone unit, as it cannot drive a interconnect cable, and requires a fixed 50k ohm loading to have correct RIAA eq. <<<
And:>>> What is your favorite MM cartridge? <<<
Well, I tried to answer that, and even with the few MMs I have it is not so easy to tell. Right now I've switched to a 'Townshend Elite EEI 500 (parabolic)' and it immediately shows, it can do punchy bass and pretty clean treble.
So now, what's your favourite MM cart?
It'd be just interesting to hear, since I've buried the SUT for the moment :-)
Axel |
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. |
Lewm
>>> probably a Sumiko BluePoint, originally <<< oh, oh, :-) but that's also an MC?
about time if you get a bit restless to check on MMs, I say...
I have listened to A&R P77, Empire S1000 ZE/X, Shure V15 III VN35MR, Elite EEI 500, AT-140LC, and some bottom of the line AT with conical stylus (not actually much more than the $20 you pay for it).
All this has confirmed for me in my system everything that Raul is on about.
I have also had in my system, DV 20X-L, DV 10x5, Kontra-Punkt A, Jubilee, Windfeld, Dorian, Transfiguration Axia, Orpheus what I recall.
I mention this as I can not lay claim to some 100 plus carts MC and MM, Raul is working with.
Yet, other than that el cheapo $20 AT basic --- every MM was more fluid, musical, and had more 'magic' (for lack of a better word) in my system than ANY of the mentioned MCs.
This obviously made me wonder why?!
Raul, thinks it's just by the nature of the different construction that, given a decent phono-pre, make that difference.
What I'm learning also, there seem NO 'special' MM phono-pres in today's offerings, as all are -can do MM too-.
What I was looking for is a MM stage, differential, floating RIAA, tube, 100, 75 50 (47)k ohm input impedance, 100, 200, 300, 400, 500pF C loading. XLR outputs, Differential (wired) RCA inputs.
No such a thing for only up to 40dB for all I can see.
My current boards are, differential, SS (op-amps 2x) 1 for 40dB plus on for 69dB, no C loading (OK two parallel binding posts), 47k ohm only impedance. It sound pretty good, as it uses the clean power of the ML326S' power supply and is INSIDE the pre-amp.
So, I guess all there is, is to find some 'oldie' pre-amp? Not so sure I actually want to change my 326S (to darn convenient :-)
--- End of enquiry? Could well be...
"At least nobody can say I haven't tried"
Axel |
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. |
Well Lewm,
thank you for sharing. Now with 3 'tables why not give a NICE MM a try and let us hear what would be your finding.
It could be most interesting (didn't say rewarding... :-) to have another take by someone of your long standing anlogue background. If only to have some more prespective, and for under $1000 it be just as well :-)
Thanks,
Axel |
Hi Axel and Lew. I'll go out on a limb and recommend a unit I've not yet heard. One of my local audio buddies (he introduced me to Raul, literally during a visit) who has since built up a stable of at least two dozen MM carts uses a phono stage from Emotive Audio. Apparently the good folks at EA, while normally designing tube gear, feel nothing they've found betters this ss design. I hope to hear it for myself soon as my friend is a very observant listener.
Since the JLTi was mentioned, I'm using one with a custom, fully regulated power supply. It offers selectable 40/60 dB output so is not a dedicated unit but has beat out a few other ss and tube phono units with my Grado Reference.
Your findings should be interesting so I'll keep watch of this thread. |
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. |
The two that come to mind for me are the K&K Audio kit and the original Hagerman Trumpet. |
Hi Lew. I can solder but have no ability to design circuits.
I previously used a Threshold FET-10 (a unit I still endorse and a great bargain at $7-800) and an audio buddy built a regulated power supply for that for me. I changed to the JLTi mainly because it offers external gain and loading selection, but when he converted the RPS to my JLTi (which started life with a wall-wart), it offered some audible benefits as well. So yes it is custom and no I don't have a schematic.
The same friend with the EA phono stage just picked up an AT 170(something), one high on Raul's list.
Good luck in finding a few of these "hidden gems". |
Hi, Axel. Given the replies to the original post, I'll let my first question stand: To what level of "top" phono stage are you referring?
The discussion seems to be about phono stages in the range of $1000 to $2000 USD and thus, the Graham Slee Reflex is an example of what you were asking about. (It's clearly designed for MM cartridges.) The Jadis phono stage reference was a bit misleading. Or is the Jadis the "top" level you were originally asking about?
Tom |
G'day all, this quite simple to build design is amazing! This is my preferred MM phono preamp. http://sound.westhost.com/project06.htm I have built several of these. Regards, Fap. |
Hi Tketcham
>>> To what level of "top" phono stage are you referring? <<<
Simply the best, - second best I already have.
>>> ... is the Jadis the "top" level you were originally asking about? <<<
Raul got this, he is thinking "Essential 3160"...
The Jadis is a still current, just as an example, that's why I mentioned it.
There 'where' other great 40dB stages but ALL gone by now.
I'm really NOT asking about any 'wall-wart' power supply pre's. I thought that was implied. Why even bother to ask then? Like: "Go get one (any one) and call it a day..." :-)
Greetings,
Axel
PS: There are squat (current) 'top' 40dB tube phono-pres out there, and that is already something useful to know. Makes it a proposition to build one's own... a new market gap? |
Hi Fap, Tketcham
>>> ..this quite simple to build design is amazing! <<<
OP-Amps, not part of the spec I'm thinking of.
I realize it's maybe time to go into more detail.
Also, the 'Jadis' would be single-ended also not part of the idea, good as it my be.
Rough spec. would be:
- 40dB
- tube gain stage (max. to gain stages)
- 1 JFET gain-stage? Maybe, to get minimum tube-rush/noise
- or e.g. Lundal trannies to get the first 20dB?
- shunt regulated power supply
- differential circuit (XLR out-puts, differential wired RCA inputs)
- no volume control
- floating RIAA (between + and - of the differential circuit)
- one box design (if at all possible, by use of good screening)
- No PCBs, screened silver wire for internal wiring.
- Good,e.g. WBT connectors
That should cover the basics. What tubes to use, trannie, resistors (Tantalum, or?) is dependent on the circuit design and implementation.
Greetings,
Axel
|
Ah, now we have a reference. What you suggest seems reasonable for a manufacturer to offer for sale. (You would certainly know better than I.) But I think you answered your own question as to why they don't: The lack of offerings is most likely a financial decision, not a design decision. If they don't see the market need for a high end dedicated MM stage they aren't going to bother. I guess they don't read the posts from you and Raul. '-)
A question for you, Axel: Do you think that a high quality SUT or headamp could provide the gain and loading needed to turn a high end MM stage into a high end MC stage? Or does the use of external transformers or headamps degrade the signal too much to be considered acceptable for a high end phono stage?
Tom |
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. |
Herron Audio makes a tube MM Phono Pre-amp. I have not heard it, but I have been using their MC Phono-pre for a number of years (on my second set of tubes), and I have never (yes, never) heard one that was better. As with all things audio, YMMV.
Dave |
Correction:
I just checked Herron's site and they have discontinued the dedicated MM phono-pre and now have a combination MM/MC with variable loading provided by changeable plugs.
Interesting looking answer to a common concern. |
Hi Tom
you ask:
>>> Do you think that a high quality SUT or headamp could provide the gain and loading needed to turn a high end MM stage into a high end MC stage? Or does the use of external transformers or headamps degrade the signal too much to be considered acceptable for a high end phono stage? <<<
To start, a head-amp will be (generally) providing the lesser quality, compared to a good SUT.
(That's why they fell out of favour, years back already --- and today? ~ No need...)
Now to the SUT, and here I guess it will..., become controversial once again?
It is my current experience that a top MM into a good MM(MC?) phono-pre will beat an MC with an SUT into that phono-pre. Given, that we have a top class match between MC and SUT, and a subject all on its own.
Only, and only, if for various reasons of your own, you love that MC, and that low gain phono-pre (and particularly if its a good one!), would I consider the SUT option.
It will not be a bad mix by any means. You'll have more dynamic depth, more bass punch, a bit more harmonic completeness, compared to MC only... so, nothing to scoff at.
Yet a good MM will very likely do it all with a bit more 'EASE', so far what I have found.
I still think, that most (if not all phono-pres just have to try too hard to get most 'everything' from that puny ~ 0.3mV cart voltage into a harmonically complete reproduction OF WHAT IS ON THE VINYL.
Now offer that phono-pre ~ 5.0mV it is just simply easier to get it right, as close as can be. And that in turn applies to the MC plus SUT match, ... with maybe a little less ease.
What will go missing with the MC / SUT setup is some micro detail swallowed up by the SUT's leakage inductance, parasitic capacitance, etc. it can be noticed by a less sharply carved out image presentation -- some would argue is unnatural anyhow (like stuck with your head in the microphone).
Yet, plenty people find that's what's needed, else it does not qualify for 'Hi-End' and I'm not going to argue...
Now all the electronic fundies are gonna jump up, but counting ELECTRONS (in a phono-pre) literally, if you consider micro-information coming from the vinyl by 0.3mV, 5cm/sec @ 1k Hz is actually one MIGHTY tall order, 'cause a lot is a the 'single electron' level before it is 'pumped up' and equlised. One electron gone missing = information lost.
I hope this answers your question.
Greetings,
Axel |
Funny that no one has mentioned the new Passlabs XP-15 as yet.
It's SS, but seems to be close in a number of other 'parameters' mentioned. Good price too $3'800...
Any comments?
Axel |
Hello Axel . . . consideration of some of the specific requirements of MC vs. MM cartridges was something I spent quite a bit of time with in my own phono stage design, and I very much feel that the usual "change the gain and loading" approach cannot begin to deliver optimum performance from both types. And while my design is specific to lower-output MCs, I designed, measured, and experimented with some MM-specific approaches.
The most important part IMO is the specific noise/impedance relationship between the the input stage itself (NOT just the loading), and the cartridge. MM cartridges have much higher and much more reactive source impedances than MC cartridges, which means they will require an input stage with lower noise current (hence higher noise voltage), than an MC cartridge, which is exactly the opposite. JFETs and vacuum-tubes are the traditional choices here for such an application, though a lightly-biased bipolar can sometimes work well too.
The second input-stage issue for reactive sources like MMs is capacitance, which can be static or dynamic (changing capacitance with signal level), the latter of which will have a big effect on the ultrasonic behavior of the cartridge. Vacuum tubes are pretty good here, as their input capacitance is usually mostly static (like cable capacitance) for the signal levels we're talking about. With JFETs dynamic capacitance is a big issue, and cascoding a JFET input stage is IMO mandatory to keep this under control for an MM cartridge. Bipolars have such a high transconductance that the capacitance is rarely a problem, but they in turn require special attention to input-bias current so a tiny DC current isn't drawn through the cartridge itself.
For the devices themselves, I think it's silly to turn one's nose up at modern monolithic opamps, especially if a JFET input is what's decided upon. In the past 15-20 years, most of the innovations in JFET fabrication have occurred as part of improved monolithic processes, to the point where JFET opamps can be had that beat the noise performance of the very best discrete JFETs available.
The other question is whether or not to have a balanced input from the cartridge, or a simple unbalanced input. This is even a separate question from whether or not a differential-amplifier is used as the input pair, as the latter is frequently used simply for the feedback capabilities from an unbalanced input. For MC cartridges, I think a balanced input is optimum, especially with a transformer input - this is in part because the low source impedance of the cartridge can make the whole system (cartridge, cable, and input stage) very effective at eliminating magnetic hum pickup.
But the balanced input almost always means a noise penalty of 3-6dB when implemented with active electronics (transformers are unsuitable for MM cartridges). And I'm not sure that with the higher/reactive source impedances of MM cartridges, combined with the low-capacitance cable that they prefer . . . really translates into improved real-world noise rejection when used with a balanced input. At the very least, it greatly complicates some of the decisions required to make the input stage tolerant of common-mode noise, and provide proper protection against accidental overload (30VRMS common-mode nose from a bad turntable ground, anyone?)
Anyway, these are just a handful of the overall-picture considerations that can be very different between a phono preamp design that's specific to MM cartridges. |
Hello Kirkus,
I've printed you notes, and will study them.
There is some most valuable information based on your long experience as I can see on some quick glancing through.
Thank you for sharing!
Axel |
Kirkus
I'm not sure I understand your point about dynamic capacitance of JFET vs V/T inputs, and if I do I'm not sure I agree with it.
Assuming that you are talking about junction thickness dependent capacitance varying with drain - source voltage, I thought this effect was pretty well analogous to Miller capacitance in V/Ts. In both cases cascoding reduces the variation in drain / source (read anode / grid for V/T) voltage.
Is there a secondary effect in JFETs I need to know about?
Mark Kelly |
Hi Mark -- yes we're indeed talking about the same thing, its just that the Miller capacitance is usually much lower. The reason I made the (admittedly rather imprecise) statement about vacuum-tube vs. JFET junction capacitance is from some generalizations about exactly how much this capacitance is actually reflected at the input when these parts are used in a circuit.
That is, 2-3 pF from the interelectrode capacitances of i.e. a 12AX7 are significantly less worrisome than the 30-40 pF or so from something like a 2SK389 set up as a diff-amp. I also think that cascoding JFETs (either with bipolars, or more JFETs) is a simpler, more elegant implementation than the vacuum-tube counterparts, which usually involves bootstrapping and multiple/floating heater supplies.
So I would personally always cascode JFETs in this application, but probably wouldn't with most vacuum-tubes. Just my preferances. |
So it seems that a quality SUT, or, a high quality dedicated MC phono stage, is the key for MC cartridges. Since MC cartridge designs include a fairly wide range of output voltages and internal impedances, and thus gain and loading requirements, it may necessitate a range of dedicated MC phono stages if someone wants to listen to a variety of LOMC cartridges.
Too bad, because that sounds expensive. Is the added expense (of having multiple dedicated MC phono stages) worth the perceived improvements in sound?
Tom |
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? |
Lewm, my mistake for not including the intended recipient in my post. (I don't post here at Audiogon very often so am not used to the continuous thread format.) I was trying to get a sense from Axel (and others) if it was worth the added expense of having dedicated phono stages for several LOMC cartridges, each with a unique amplification and loading requirement. That's making the assumption (and the analogy to a dedicated MM stage) that to get the best sound from a phono stage, the design must be specific to the cartridge.
If so, then the question might also be asked: Dedicated phono-pre for (specific) LOMC only?
Tom |
Hi Tom
you say:
>>> it may necessitate a range of dedicated MC phono stages if someone wants to listen to a variety of LOMC cartridges <<<
I can not support that logic as e.g.: all women are people, there for all people are women? :-)
Loading with MC stages and to some smaller degree loading of SUTs (secondary and primary side) takes care of the variations in MC's DCR and output voltage. Of course a mismatched SUT/cart can not be made to work by loading e.g. if it would overload the phono-stage.
Greetings,
Axel |
Kirkus
Thanks for that, I will have a more careful look at the design calculations for my MM only phono amp. The input stage is currently using 2SK389BL as diff amps with simple resistive loads (balanced inputs, there's no need for a feedback connection to the diffamp 'cos there isn't any feedback).
It will be easy enough to change these to cascode.
Mark Kelly
|
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.) |
Hi, Axel and Lewm. My comment on the need for separate MC phono stages is based on Axel's comment that a SUT degrades the signal, thus my assumption that a dedicated phono preamp (for a specific range of LOMC parameters) would be a better way to handle the amplification and loading requirements. One gain/loading setting probably isn't the best way to handle a wide range of LOMC cartridges, not if optimal performance is desired. And if switches must be used to optimize the LOMC signal, it is not acceptable for a high end preamp, which was the premise of this thread. So, it appears that if the logic is used that a dedicated MM stage is needed (to avoid having additional switching for MC cartridge requirements) then dedicated LOMC stages are needed to avoid having additional switching.
I bring this up because it seems that what is implied, Axel, is that MM is inherently a better cartridge because it doesn't require additional switching or transformers. But a dedicated LOMC phono stage would eliminate the need for switching or a transformers as well. Wouldn't that put a MC cartridge on par with a MM cartridge?
Tom |
Tom,
I guess 'switching' means loading in your context, yes?
Loading an MC with 100, 500, 1k ohm for example makes little difference as to the phono-pre used as such.
The mechanical issues involved will.
Soldered Rs are best, than clamped in some binding posts, then the 'mouse-piano' i.e. the switching you seem to refer to.
The same would apply (to the phono-pre) using 47k, 50k, 75k or 100k phono-pre input impedance 'switching/changing' for MMs only.
The issue with MCs is rather to have a phono-pre that "can count electrons" (if no SUT is used).
Apparently only few designs are THAT good after all. Mostly noticeable in the difference of those parameters I mentioned that are improved, when an SUT is used with a Low MC.
Often a lack of dynamics is noted if an MCs output is on the low side - use an SUT, and THAT problem is GONE.
When using an MM there are different things at work.
Mainly due to the 'high' cart voltage output --- BUT also because they are a more 'reactive' load, usually 600 - 3.5 ohm DCR, 700mH as ~ 20uH with an MC and compared to only ~ 2 - 6 ohm with LOMCs).
That is why a TOP MM stage would ask for a different design if strictly dedicated to MMs.
No SUT can be used, single ended (SE) MIGHT be better. I'm as little sure about this as Lewm is and it might have to do with the 3-6dB lesser noise in SE design --- which then again might just be made worse by using common ground that can be noisy.
Also 'floating RIAA' as in a differential circuit between +/- is not an option either.
Greetings,
Axel |
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. |
Hi Lewm,
>>> With an MM phono stage, we should all be using a 100K load <<<
Another reason for this thread's subject.
I mean, WHICH phono-pre, of one-serves-all, has a 70k and/or 100k ohm input impedance option I ask?
I know Raul's Essential 3160 has, but that is a non-main-stream item.
As to 'switching degradation' I had a PS Audio GCPH using some pretty convenient switching, and now a pain-in-the-butt ML phono-module using internal binding posts or some jumpers.
But as you say, how could I have tested the GCPH's performance without the switches for gain and loading?
All I know is, that the ML modules sound better --- but because of the switches?
Raul and Co. might have some contribution in sharing their findings, wouldn't they?
Axel |
Hi Mark - FWIW, my experimentation with discrete JFET MM stages included both the 2SK389 dual, and a pair of 2SK369 singles. I cascoded them with 2N5089 NPN bipolars, and loaded the collectors with 1K . . . there was also a single 2N5089 used as a simple current source for the tail. Rails were +/- 20V, and I put about 8mA through the tail (4mA through each JFET). VDS across the JFETS was about 5V.
I used this circuit in an unbalanced-input feedback amplifier, in the classic "hybrid-amplifier" (JFET-frontend feeds opamp) topology. Instead of a monolithic, I used a 990 discrete opamp, driving a low-impedance EQ network for the 318uS and 3180uS time-constants, with about 20dB of gain at 1KC. This fed a passive 75uS network and another 990 for 20dB more gain, same as my MC design.
I never really put in the time to fully optimize the circuit, but it was very low-distortion, and CRAZY quiet . . . like greater than -90dBV at the output when looking at a 1K source impedance. I think that the 2SK269s had a little better 1/F noise, and even though the offset on the 2SK389 was much better, it didn't really matter for my application. Of course, YMMV. |
Hi Lewm - I will add my vote as well to the higher-loading approach, I think that 100K with minimal capacitance is much better (with virtually every cartridge that I've tried) than the common 47K/150pF.
But as far as commercially-available phono stages go . . . I don't really see enough of them anymore to have really strong opinions. I do think that in general, getting the subtle details right makes more difference than any generalisations about whether it uses JFETs, tubes, bipolars, opamps, etc. etc. There are certainly an unlimited number of ways to screw things up, or to avoid doing so.
I'm currently using my Beogram 4002/MMC20CL with a little phono preamp that's an opamp design, made on a Vectorboard . . . and the case and power-supply from a Lehmann Black Cube. Its a two-stage topology like my MC phono unit, with active 318/3180 in the first stage, passive 75uS, then more gain in the output stage. Opamps are AD745 (input) followed by AD797 (output), both of them use complementary discrete JFET buffers for high-current output, within each feedback loop. |
Daer Axel: I can speak about that switch subject. During our researh and tests on the deign of the Esential 3160 and due that this PHonolinepreamp was/is designed for our ( José and I. ) specifics need in one of the prototypes ( the one battery powered. ) we have six phono inputs through a switch that I use it for several months till I decided to hear the same cartridges with out that switch where every change on tonearm/cartridge means disconnect/connect in manual way each time, well there is a quality improvement with out that switch and we decided to go in this " fashion ".
But the Essential 3160 is not a product thinking on commercial subjects ( facilities for the customer: using switchs instead that manual changes, switchs for impedance changes instead solder resistors, etc, et. ) but with targets of absolut quality performace where less means more and with no trade-offs or trade-offs at minimum. Many times this approach ( no trade-offs on quality performace. ) means that the Essential user has less facilities: switchs.
Regards and enjoy the music,
Raul. |
