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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.
128x128chakster
fleib
1,124 posts
 
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,
hdm
1,056 posts
 
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.
atmasphere's avatar
atmasphere
11,633 posts
 
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!
bpoletti
1,531 posts
 
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.
fleib
1,124 posts
 
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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