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, |
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.) |
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. |
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, |
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. |
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! |
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. |
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. |
Swampwalker, thanks for your kind offer, that would be great, but we have a problem... I'm in Saint-Petersburg (not in Florida). |
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). |
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. |
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. |
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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. |
My cart sounds it's best at the highest cartridge loading available on my phono stage. AT OC9/II and Herron VTPH-2. |
Stringreen, which phono stage do you use to adjust load-impedance ? |
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. |
My cartridge sounds best at 1000 ohms....tried 4 or 5 different settings... |
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 |
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. |
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? |
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." |
i prefer mc stages with no sut. |
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? |
There's ONLY one parameter that counts.
So, how does it sound? |
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/ |
