see what's inside (Phonata in the production line):
https://c1.staticflickr.com/7/6139/5955227066_d440161037_b.jpg
https://c1.staticflickr.com/7/6138/5954669505_61ea0a5e6b_b.jpg
besides their own WLM equimpent they got some nice vintage stuff at their office https://www.flickr.com/photos/56576807@N05/ |
There's ONLY one parameter that counts.
So, how does it sound? |
The Phonata works very well between 25 - 100 ohm cartridges. Only very low impedance cartridges like classic SPU or modern ZYX sounds better with sut or pre-pre (headamp).
Manufacturer recommend the MM input with an step-up transformer for the very low impedance carts. My headamp is Zyx CPP-1.
For cartridges with 25-100 impadance range i use Phonata MC input, my Argetnt MC500HS sounds fantastic with this phono stage.
But i would like to know who else on agon use this stage? |
i prefer mc stages with no sut. |
Czarivey, that's why i have Zyx CPP-1 (26db) which is not a sut, but a decent headamp. In this case i use only MM input in WLM Phonata and ZYX CPP-1 provide extra gain. But not for all cartridges it's a better solution.
Arthur Salvatore @ high-endaudio.com said:
“This is, most likely, the finest head-amp I’ve ever heard. I state this because it is competitive with the finest transformers I’ve had, while all the many other (external) head-amps I’ve heard are simply not in that league." |
Czarivey - I'm with you. No SUT, just a silent high-gain mc input stage.
Chakster - Are you in any way associated with the company or designer that produces this unit? |
Bpoletti, absolutely not, i'm just a user of both products from two different companies and i paid for both units ( i do not sell them and i'm not ever reviewer). I use several different cartridges and found the "Automatic Load-Impedance" an interesting option. Would like to hear feebdacks/thoughts from agon members. Or maybe about any other MC/MM stage with "Automatic Load-Impedance" option ?
After few years of using WLM i just noticed this stage is under radar which is very strange, their speakers and tube ams are well known. |
SUT or not SUT for very low impedance MC cartridges ?
depends on which SUT - no ?
Here Mr.Salvatore tested his PASSIVE class A Bent TX-103 Silver SUT against battery powered ACTIVE headamp ZYX CPP-1
source: http://www.high-endaudio.com/RC-Step-ups.html |
My cartridge sounds best at 1000 ohms....tried 4 or 5 different settings... |
There have been other "auto load impedance" designs made.
Example Classe' DR-6 MK-I, MK-II pre amps and probable others of a certain time line when it was popular. |
Stringreen, which phono stage do you use to adjust load-impedance ? |
My cart sounds it's best at the highest cartridge loading available on my phono stage. AT OC9/II and Herron VTPH-2. |
Bpoletti, my AT ART2000 Ltd (similar but slightly different from your AT cart) sounds amazing with ZYX CPP-1 headamp connected to MM imput in my WLM Phonata. With direct connection to MC input on WLM Phonata it is not so chrystal clear as with ZYX headamp. |
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Chakster, You seem to use the term "impedance" interchangeably to talk about both the voltage output of a cartridge (usually expressed in mV in relation to a stylus velocity of either 3.54 or 5.0 cm/sec) and its internal resistance. Thus it is not the low internal resistance/impedance of an MC cartridge that necessitates a SUT so much as it is the low signal voltage that these cartridges typically generate. However, in a way you are right, because the low internal resistance makes an MC cartridge more of a current generator than a voltage generator; the SUT merely serves to trade off current for more voltage.
As to this feature of auto-loading, thanks to Totem for reminding me of some of the other now vintage products that once offered this feature. I think most of us favor choosing the load to suit our musical taste. I prefer a phono stage that allows me to select the load resistance, and for MMs, the load capacitance, most conveniently. I've given up on the purist approach that says no switches in the signal path, but if I have determined what load R and C I prefer, I might then hard wire the parts in circuit, bypassing the switch. |
I definitely need to compare my Automatic Impedance Load phono tage to some other phono stages with Manual Load options if i can invite someone with such stage to my house to check this out (and drink some wine).
I have no idea how it works with Automatic Load Impedance, but i try to understand the process and need for manual load (when you don't have 10 cartridges).
What did the improvement in sound of very low coil impedance (4-6 Om) cartridges is my external cpp-1 headamp for such cartridges as ZYX or Ortofon SPU. Lewm, 4 Omega is very low coild impedance - right ? And the ouput of these cartridges also very low (about 0.24 mV).
At the same time my AT Art2000 MC cartridge impedance is 12 Omega and output voltage is 0.4 vM. Absolutely no problem with 47db gain of my WLP stage. Sounds good with auto load, but with connected external headamp cpp-1 (between cartridge and my MM input) the sound is more like on steroids.
With high output MC like 1.9 mV Argent (don't know the coil impedance) my auto-loading stage sounds simply amazing and no need to change anything. |
Where you at Chakster? I've used the Zyrtec headamp w Azusa and now I have a Doshi all active gain mc phono stage. If you're in the Northeast U.S. We could run them both sto compare. I'm in CT (but not this week). |
Swampwalker, thanks for your kind offer, that would be great, but we have a problem... I'm in Saint-Petersburg (not in Florida). |
Cartridge loading of low output moving coils is almost of no consequence unless the preamp is unstable or unhappy with ultrasonic or Radio Frequency bursts at its input.
If you find that loading is making a difference with your setup, its an indication that the preamp has stability problems. This is because the cartridge is entirely unaffected by load at audio frequencies. You hear a difference because the load resistance is detuning the resonant circuit created by the cartridge inductance and the cable capacitance. So if the preamp is unaffected by this the loading will have no effect. |
Atmasphere, seems like it's your answer to Lewm who prefer different load for different catridges?
I have no ability to change load, this is automatic option with my WLM MC 47db gain stage with build in suts. I just noticed the difference (positive) with some mc cartridges when i use additional device (active headamp with 26db gain by zyx which compete with top suts). Nakatsuka-san made it for his own cartridges and using Zyx Airy and Zyx 4D with or without his headamp i prefer to use them with his headamp (it was an improvement even with additional cable).
Zyx headamp + WLM mm stage is better for low output Zyx Cartridges than my WLM MC stage with build in suts and automatic load impedance option. |
Can anyone tell me how this “automatic load impedance” works? Does the phono have a sensing circuit checking the internal impedance of the cartridge? Thanks! |
It may be the case that "automatic" really means "fixed." There are some manufacturers that don't think that any sort of precise setting of loading is important and so they go with a reasonable fixed value, typically somewhere around 125-150 ohms (e.g., Linn).
With the phonostages I have worked with, I like relatively little loading (high value resistor such as 47k) or no loading at all. Over a huge range of values, I don't hear that much change except for an undesirable loss of top end "air" with values lower than 125 ohms.
A friend had a Hovland preamp that had only a few options. It turned out that the factory default setting was 100k (virtually NO additional loading). He had RFI problems at this setting, but, aside from that kind of problem, I am in the less-loading-is-better camp. |
Thekong,
I was wondering that myself. I suspect autoloading is simply the use of SUT for MC gain which will cover a range of input (cart) impedance.
In the case of this WLM stage, the SUT seems poorly chosen for most high end MC's:
*MC-Input Impedance Range: < 100 Ohm to 50kOhm*
Is it surprising a 4 ohm (or whatever) ZYX sounds better through a ZYX head amp?
A SUT must be appropriate for both gain and impedance. For example, a Cinemag 1131 set for 1:20 (26dB) will have an effective input impedance of 118 ohms. Set for 1:40 (32dB) it's 29 ohms.
The notion of one size fits all MC input impedance is entirely phono stage dependent. With many solid state stages it will make a noticeable difference. In the case of the 1131 SUT set for 32dB, the effective impedance will be below the output impedance of some carts (DL-S1). This is usually considered undesirable unless you're suppressing RFI. On some more revealing IMO solid state stages, loading makes a noticeable difference, noise notwithstanding.
Tubes are inappropriate for a high gain stage. They're too noisy, so they employ either a SUT or a solid state high gain stage.
Regards, |
The Phonata operates in current mode with MC cartridges. Not anything really new here. I've been using an Aqvox for about 7 years now which operates similarly.
The loading is not fixed. From the Stereophile review on the Aqvox:
"MC cartridges may produce tiny voltages, but they output decent amounts of current from a source impedance that is both low and resistive. This is ideal for use with a current-mode input because such an input is nearly a short circuit. Different MC cartridges react differently to being plugged into a current-mode input, in part depending, of course, on the internal impedance, but the short-circuit loading means the cartridge is inherently damped and resistive loading becomes a nonissue."
The BMC (like the Aqvox, also designed by Carlos Candeias) is another current mode stage. From the Stereophile review on the BMC:
" Because the input uses current instead of an MC cartridge's ultralow voltage, the input impedance is very low, less than 3 ohms. There is no need, therefore to damp the cartridge's ultrasonic resonance with energy-destroying resistors in parallel with the input."
Some have suggested that current mode phono amplifiers tend to work better with very low impedance MC cartridges and there may be some truth in that.
I've used the Aqvox with a couple of cartridges, most recently a rebuilt Ortofon MC 20 Super with a 5 ohm internal impedance and there does seem to be particular synergy there. Aqvox themselves market a couple of cartridges that appear to be, for all intents and purposes, clones of the MC 20 Super (at least if appearance is any indicator) and do claim great synergy with the current mode input, but I'd expect almost any low impedance MC to work very well. |
How can a cartridge be autoloaded when the manufacturer specifies a particular load to voice a cartridge? (Sounds like more audio hooey and snake oil to me.) |
Bpoletti,
The contention seems to be that current gain, rather than voltage gain is inherently better for MC's. This does not seem to be the case with Chakster's low impedance carts.
The Stereophile quote probably just echos the mfg. blurb, and I suspect does not reflect the whole picture. Current gain can be controlled by the use of feedback or controlling circuitry, but current gain is dependent on source resistance. To say, "but the short-circuit loading means the cartridge is inherently damped and resistive loading becomes a nonissue." is misleading.
Apparently the phono stage was designed for the MC20 Super. Other than that, YMMV.
Regards, |
Just a clarification. The Aqvox was NOT designed for the MC 20 Super. Aqvox only started marketing cartridges a number of years after they had introduced their phono preamp and it is only speculation on my part that their cartridges are based on the MC 20 Super.
I pointed out the use of the MC 20 Super only in light of its lower internal impedance (5 ohms) as many have suggested that current mode phono preamps tend to give their best with low impedance cartridges (say in the 1-10 ohm range).
In any event it is my experience that phono stages like this can offer up pretty good performance (there are also multiple positive reviews on the Aqvox and BMC, some of which probably delve more into the technical aspects of the current mode and the "non-need" for adjustable loading as a result of this design). I don't really miss or feel the need for adjustable loading under the circumstances.
Others with more technical knowledge than I can make the case for adjustable loading being necessary but the designers/manufacturers of current mode stages (as non-standard and as quirky as they are) obviously feel there are some legitimate technical reasons to take this track.
I was just putting the info out there to shed a bit more light on this as, for the most part, it seemed that most involved in this thread were not really aware of this type of design. |
Tubes are inappropriate for a high gain stage. They're too noisy, so they employ either a SUT or a solid state high gain stage. This statement is incorrect. We have been using all-tube phono sections for LOMC cartridges for about 25 years and they work fine with 0.2mV with no SUT, only 2 gain stages and passive EQ. The trick to getting silence out of tubes is very similar to how you do it with transistors- fully balanced differential with 2-stage constant current sources to get the proper differential effect with high Common Mode Rejection Ratio (CMRR) values. How can a cartridge be autoloaded when the manufacturer specifies a particular load to voice a cartridge? The answer is that no manufacturer 'voices' a cartridge in the way you are suggesting! The load is there to sort out an unstable phono section, not the cartridge. One aspect of loading that is not discussed so far is that fact that in order to drive a load, energy is required. So the more you load down a cartridge, the more energy it has to produce the drive the load. This **has** to have an effect on the cantilever, which is in motion to drive the transducer. Think 'damping factor' as in an amplifier and loudspeaker and you've got the right idea. The implication is that low impedance loading will affect the performance of the cartridge somewhat; that it will be better able to follow the groove modulation if not so damped. This is a profound argument for a stable phono section that does not require loading! |
Atmasphere is correct. A tube circuit can be designed to be low noise, components can be specifically for their low noise. Noise is NOT a drawback to tube design.
And Atmasphere's last paragraph and last sentence speaks volumes! Dead center on the facts. |
Free advertisement over?
This thread isn't about tubes or the viability thereof. The Phonata is solid state and the discussion is now about current vs. voltage amplification.
**The answer is that no manufacturer 'voices' a cartridge in the way you are suggesting! The load is there to sort out an unstable phono section, not the cartridge.**
This is BS. All phono stages where one might prefer a load other than wide open, is unstable? Suggested loads are usually a minimum value or for SUT impedance matching.
We've been through this before. In the absence of noise one might prefer to load down a MC because of preference. Damping a cantilever/generator might improve focus and detail, while wide open might increase stage and size.
The analogy to amplifier damping is a bad one. The goal is to make the speaker play accurately with a high damping factor. A phono cart is an electro mechanical transducer on the source end, but no electrical damping isn't necessarily better. Mechanical performance is the overwhelming determinant of cart performance, something that many EE's don't get. Loading, electrical damping can be a way to balance factors other than amplitude response and noise.
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I just emailed to Herr Frick of WLM (Austria) with a link to this thread.
Really hope he can join' discussion and explain more about his product.
It's getting hot.
i just want to remind to everybody in this discussion that WLM released TWO phono stage:
1) PHONATA TUBE is their old model was available in 3 different versions such as MM ONLY, MM/MC or MM/MC with Lundahl step-up transformers.
2) the latest model is PHONATA REFERENCE (MM/MC) in a bigger cabinet. "This unique preamp has automatic impedance matching so that the input impedance for the cartridge is perfect each and every time."
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Fleib, with all due respect, rather than calling my comments BS, why don't you look into the matter? I suggest you look at the comments of JCarr (Jonathan Carr of Lyra, who is active on this forum) about the effects of cartridge loading. Or how about reading this article? http://www.hagtech.com/loading.html(the closing summery of which is that 'Load resistance tunes damping'...) In a nutshell you will see that I am correct. Loading of LOMC cartridges is one of the more prevalent myths in high end audio LP reproduction; I was under the same illusion until years ago I tried to make a box that would determine the correct loading for any LOMC cartridge. It was during that research that I discovered that loading of the cartridge itself had no effect at all on the output waveform at audio frequencies. The reason is simple enough: the inductance of the cartridge is rather slight. Its impossible for a load to have much effect other than reduce the cartridge's output at audio frequencies in extreme cases. What is happening is that the inductance of the cartridge, in parallel with the capacitance of the tone arm cable, forms a resonant circuit, as Hagerman's article outlines. This can be simply ultrasonic but might be at several MHz. If the phono preamp is unhappy with this sort of signal at its input, you will hear effects, effects of which are easily controlled with a 'loading resistor' which damps the oscillation by detuning the resonant circuit. IMO/IME it is better if the phono section is stable and therefore immune to such things in the first place- it sounds better that way and its a lot less trouble. |
Atmasphere, thanks for the link and your comments.
This is amazing! |
Atmosphere,
You should have quit while you were behind. I've read Hagerman's article and I could point out some erroneous assumptions, but they pertain mostly to MM's. If you're interested you should read the VE thread, Cartridge Loading Explained.
But we're talking MC's here and one HOMC with a solid state phono stage, and I still fail to see where your comments pertain. I know about the tank circuit on the output. I'm also familiar with high frequency overload or oscillation and the possible need to load down the preamp shunt resistance.
Apparently you think this is the only reason to load down a cartridge. If so, you're wrong. I've already explained that wide open is not always better. Maybe it is in your preamp, I wouldn't know, but we're not talking about your preamp.
If you have something to say about current amplification on the front end, that might be helpful.
Regards, |
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If you go to WLM Acoustics they only show the tube phono available in 3 different configurations with SUT for MC gain. Specs to be announced.
http://www.wlm-acoustics.com/
Fremer reviewed the BMC MCCI phono stage on 8/13. This uses current amplification on the MC front end. The unit looks remarkably similar to Chakster's link for the solid state Phonata.
http://www.stereophile.com/content/bmc-phono-mcci-phono-preamplifier
Results seem different from what Chakster said, especially concerning cart impedance, and it's unclear if these are the same.
A couple of guys who post on the MM/MI thread own Atma-Sphere MP1 preamp. They each have high end systems in the extreme and think highly of the MP1 phono section.
Our disagreement is mostly one of appropriateness and in no way is a reflection on the product.
http://www.atma-sphere.com/Products/#MP-1 |
Yes, no updates on WLM website for a very long time :(
no reviews on new Phonata Reference which was the neхt model and released after their tube phono stage.
This is a google doc link to MANUAL of Phonata Reference:
https://drive.google.com/file/d/0B7SnhzDV__cCc2lfQ0NYRnVuRlE/view?usp=sharing (anyone with this link can download .pdf file) |
Apparently you think this is the only reason to load down a cartridge. If so, you're wrong. I've already explained that wide open is not always better. Maybe it is in your preamp, I wouldn't know, but we're not talking about your preamp. I am not talking about MM, where achieving the critical damping value is important for best performance. I am talking about the fact that if you hear tonality change with a LOMC seemingly due to loading, its on account of the behaviour of the preamp and not the signal from the cartridge. I had a conversation with Jonathan Carr at the recent Munich show. He mentioned the same phenomena that I did in a prior post- that when you load a cartridge with a lower impedance, you are asking it to do more work. Since the cartridge is a magnetic transducer, the lower the impedance of the load the more work is being asked of the cartridge. For this reason he was very interested in developing a phono stage that had a high impedance input so as to minimize the work that the cartridge is doing. This would leave it more free to follow the modulations in the groove. Re. current gain inputs: due to their inherently low input impedance, the mechanical loading issue as pertains to the above paragraph is likely not optimal, however you certainly would not have to worry about what the load impedance actually is since the electricalresonance would be well-damped. |
**I am talking about the fact that if you hear tonality change with a LOMC seemingly due to loading, its on account of the behaviour of the preamp and not the signal from the cartridge.**
I know that's what you're talking about. I made it clear that tonality change is NOT what I was talking about. What don't you understand? |
*the lower the impedance of the load the more work is being asked of the cartridge.*
What do you mean by "more work"? Are you talking about the cantilever/rubber suspension interface being stressed more?
I enjoy you posts. |
Many cartridges that make 0.2mV into 100 ohms can do so into 50 ohms as well. Its a small amount of wattage, but you can see in this example that in the latter case it would be making twice as much power as the former. This has to come from somewhere (the groove walls) and as such means that the stylus has become slightly harder to move. I know that's what you're talking about. I made it clear that tonality change is NOT what I was talking about. What don't you understand? Fleib, maybe you could outline what you *are* talking about as it is not clear from your posts so far. |
Atmasphere, From this thread:
*In the absence of noise one might prefer to load down a MC because of preference. Damping a cantilever/generator might improve focus and detail, while wide open might increase stage and size.*
*A phono cart is an electro mechanical transducer on the source end, but no electrical damping isn't necessarily better. Mechanical performance is the overwhelming determinant of cart performance, something that many EE's don't get. Loading, electrical damping can be a way to balance factors other than amplitude response and noise.*
Why does Jonathan Carr recommend for Kleos: *Recommended load directly into MC phono input: 95.3ohm ~ 816ohm* ?
http://www.lyraconnoisseur.com/Products/Products_Analog/kleos/kleos3.html
If you say that's because of inferior phono preamps, I say it doesn't matter or it's an inappropriate response. It doesn't matter because this isn't about you, it's about the Phonata. It's an inappropriate response because your examples and consequences are misleading at best.
Do you really think Kleos will start tearing up grooves if loaded at 100 ohms rather than 47K ? That's what you imply. Is every cantilever optimally damped? A MC cantilever is usually damped just enough to suppress mechanical high frequency resonance to between +3 to +7dB @ 20KHz. Of course usual isn't always and there are exceptions, like no cantilever or short ones. This is way outside the scope of this thread, but no-load always being better is a wrong assumption IMO. It's not right for any preamp all the time, and certainly not all MC's.
Regards,
|
My comments are based on an objective understanding (measurements, calculations, and simulations) of what a low-impedance cartridge generator is, what an interconnect is, what happens when the two are combined, what happens when resistors of various values are added to the mix, and what happens when extra capacitance is added. A low-impedance cartridge has an inductive generator, while a phono cable has significant capacitance. Put the two together and you get a huge spike at ultrasonic frequencies. These frequencies are much too high for any human to hear directly, but fall in a band that is likely to impair the linearity of the phono stage in much the same manner as excessive RF. When we "load down the cartridge", for the most part we don't affect what the cartridge does at all (unless the value of the load approaches or drops below the internal impedance of the cartridge). What adding resistive loading at the phono stage input accomplishes is to dampen the resonant energy of the ultrasonic spike, and give the phono stage an operating environment isn't so likely to trigger any latent non-linearity tendencies that the phono stage circuitry may have.
For the reasons given, the phrase "cartridge load" is misleading. "Phono stage input terminator" is a better description of what really happens. The above comment was from jcarr, which seems to agree with what Atmasphere is talking about. http://www.whatsbestforum.com/showthread.php?15077-Cartridge- |
Can someone please tell me how this resonance in the MHz range is being excited?
dave |
*The above comment was from jcarr, which seems to agree with what Atmasphere is talking about.*
Even if you agree with JCarr and Atmasphere about Lyra, does this apply to all carts? What about those which are underdamped?
Once again, this thread is about Phonata and I don't recall a Lyra being mentioned other than JCarr being used as an authority. He uses some kind of double damping system. Is this common to all MC's?
Atmasphere,
You seem to horn in on multiple threads seeking a free advertisement. Aren't you supposed to identify yourself as a manufacturer? I noticed the Liberty Audio guy took some flack about this.
Beside theoretical objections to wide open ALWAYS being better, there are plenty of real-world examples of that being untrue even with the MP1 or Herron phono stage. Don't some people load other than 47K ? Don't you offer a loading modification? I've read about Herron users preferring other loads.
Now you're implying benefits with consequences based on generalizations which may or may not be true. Elitist minded scare tactics? You ought to have an ad saying, You're Cartridge Working Too Hard? Tearing Up The Grooves?
Regards, |
A lot of back and forth going on here but I'm not sure it's related at all to what the OP posted on.
I've used the Aqvox happily for about 7 years now. I had a chance to audition it and there was clearly something pretty special going on (at least to me and relative to the phono stage I was using previously) in the fully balanced current mode.
I'm not really a technical guy, and because current mode phono preamps are relatively rare, there is not much discussion on them.
Manufacturers of them claim there are advantages in presenting this "short circuit" type of interface with the cartridge and perhaps the discussion should be more on the technical merits (or lack thereof) of this type of interface relative to loading the cartridge on a voltage input. I've never really seen that type of discussion before.
I won't be changing phono preamps any time soon but would still be open to hearing that kind of discussion. As I said earlier, there's been a generalization out there that current mode inputs do tend to work better with low impedance designs (at least from reviewers-not all but some, the TNT review on the Aqvox for example suggested a number of higher impedance moving coils also worked quite well with it).
As the impedance at the current input seems to be quite low in these designs I always wondered whether the supposed working better with low impedance MC's was more a result of most phono stages with fixed or even adjustable loading simply not having settings low enough to really maximize performance with very low impedance cartridges or if there is something more at work here technically? |
Hdm, current gain designs often tend to work with a slightly different principle. In tubes, one means is called 'grounded grid' as the cathode of the tube is used as an input. With transistors, the emitter device of the semiconductor becomes the input. In any event the input impedance is quite a bit lower. This prevents any chance of resonance from the cartridge/cable circuit from occurring.
While LOMC cartridges don't make a lot of voltage, they do qualify as a low impedance source as they have no troubles whatsoever driving a 100-ohm load, unlike most preamps, which would have difficulty doing the same thing.
So its the inherent low impedance input that is why loading isn't an issue. Many preamps do have provisions for very low impedance loads, but if you are working in the voltage domain, bypassing the cartridge output with a very low impedance will simply serve to reduce the output of the cartridge. |
Thanks Ralph. So in theory, at least, there are some technical advantages to this approach.
I'm only guessing that it has not become a bit more popular as a result of being "off the beaten path". That perhaps and the fact that the advantage is only realized in the MC domain.
My Aqvox, for example, tries to be a bit of a "jack of all trades" in that it offers typical voltage amplification, and both MM and MC compatability including adjustments for both capacitance and load, through its single ended inputs. While it's adequate I suppose through those inputs, that's about all I could say for it; I would not have purchased it based on its performance as a voltage amplifier.
In the current mode (fully balanced) its performance is very impressive though and I've been more than satisfied with it. But I think for many audiophiles using MC cartridges it is difficult to get their head wrapped around not being able to "load" the cartridge-I think this is perceived very negatively. Hence this type of phono preamp is probably a harder sell in the marketplace. |
" Intactaudio
Can someone please tell me how this resonance in the MHz range is being excited?"
The output of a cartridge has inductance as a property of that output. If you draw the circuit, the voltage of the cart has its self resistance and inductance in series with it (voltage).
The capacitance of the preamp + cables is in parallel with preamp input impedance (resistance), and they go to ground.
This creates a resonance tank circuit, the frequency of which depends on the value of component parts. Because a LO cart has low inductance (reflected in its impedance), the electrical resonance will be at a very high frequency.
It's commonly thought that capacitance doesn't matter with a MC. It does or might. Higher capacitance will lower the frequency of electrical resonance. This electrical resonance effectively gives the cart output (noise) at a frequency where there is no mechanical output.
You can calculate the frequency at the Hagerman link.
Amplifying current avoids this potential problem, with low input impedance. The BMC MCCI has MC input impedance of 3 ohms. The Aqvox 2Ci is 10 ohms.
Regards, |
But I think for many audiophiles using MC cartridges it is difficult to get their head wrapped around not being able to "load" the cartridge-I think this is perceived very negatively. Hence this type of phono preamp is probably a harder sell in the marketplace. Yes, the importance of loading the cartridge and how that all works is one of the more prevalent myths about LOMC cartridges. Once you get what is really happening though, you see that being able to load the cartridge or not really isn't a problem- so long as the phono section has either a very low input impedance or is stable with ultrasonic noise or RFI at its input. The advantage of balanced operation is that the interconnect between the arm and cartridge will not have any sonic artifact. This is really helpful as the cable is at the very source of the signal path- if it messes things up, there is little you can do about it downstream. So insuring that it works right is important and balanced operation can do that. |
