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Phono stage w/automatic Load-Impedanance.

Yes, automatic load impedance! The WLM PHONATA offers very high dynamics as a result of its very special design (see below)

A few years ago i purchased a slightly used demo unit from Australia. It was reasonable priced (mint- condition) WLM PHONATA reference MM/MC phono stage from respected WLM Acoustic brand (made in Europe). I use it since that day in my system.

a picture of the wlm phonata linked below:
http://audioaddiction.net.au/wp-content/uploads/2012/05/Phonata_3XL.jpg
http://audioaddiction.net.au/wp-content/uploads/2012/05/Phonata_4XL.jpg

When i bought mine demo it was newly released and totally different for previous WLM model (which was a smaller tube stage). The reference WLM Photana is not a tube stage. I'm not sure what's happened after, but probably it was not widely distributed, maybe they made first run and stop the production of this nice unit. They never updates their own website with info about this new unit. It's impossibe to find any reviews online and i assumed there are not so many users.

I wonder if anyone on AudioGon aware of this ice nproduct. I'm sure most of you familiar with amazing range of WLM speakers and different Tube Amps.

But do you know anything about WLM Photana Referense Phono Stage MM/MC ? It has some interesting features such as AUTOMATIC LOAD IMPEDANCE and 2 RIAA CURVES. It comprises pinnacle circuitry and design features that have never been realized before.

The PHONATA works with two-stage amplification:

• An inductive voltage amplification stage (for MC cartridges) using high
performance professional audio step-up transformers.

• A solid state current amplification stage, using specific MOS-FET transistors with tube-typical harmonic distortion characteristics.

The PHONATA offers utterly precise RIAA equalization:

• RIAA equalization is implemented across two amplification stages (within current amplification), providing a frequency expansion from 10Hz to 50kHz (Subsonic cut below 10Hz). Selected components (1% tolerance) are used.

• RIAA equalization can be selected from two positions with a switch at the back of the unit:

- Position “high” for records produced before 1965 or to improve the performance of somewhat “darker” sounding cartridges at higher frequencies. This position provides +3dB equalization as from 5kHz and +6dB as from 10kHz.

- Position “low” for all other records The PHONATA offers automatic adjustment of Load-Impedance:

• You don’t have to adjust the load-Impedance of your cartridge (plus the interconnect-cable between cartridge and Phono-Preamplifier). It goes automatically thanks to one ingenious piece of circuitry.

• You don’t have to adjust the source voltage of your cartridge as well.

• There are no micro-switches or any other mechanical contacts in the signal-path.

Technical Data:

MC-Input Impedance Range: < 100 Ohm to 50kOhm
MM-Input Capacity: 100pF
THD (Total Harmonic Distortion) @ 1kHz: 0.01%
SNR (Signal to Noise Ratio) MC: >72dB
SNR (Signal to Noise Ratio) MM: >85dB
Max. Input Voltage for MC-cartridges (theoretical value): 1200mV @ <1% THD
High Performance, Professional Type Step-Up Transformers.
chakster
atmasphere's avatar
atmasphere
12,158 posts
 
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.
chakster's avatar
chakster OP
6,144 posts
 
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.
thekong
204 posts
 
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!
larryi
4,334 posts
 
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.
fleib
1,124 posts
 
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,
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