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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

Showing 8 responses by lewm

lewm
12,566 posts
 
I want to make sure we are talking about the same thing.  Cartridges have a fixed DC resistance (DCR) if you measure the resistance between hot and ground connectors for each channel using a simple ohmmeter.  Cartridges also have an output impedance, which would be the DCR + any changes in impedance with frequency of the audio signal.  However, we are typically not told much about the frequency-dependent resistance, except usually we get a figure for "inductance", which is very low for most LOMCs.  Anyway, I usually would go by the internal resistance (DCR) in order to choose a load resistance on the phono stage side or in thinking about an SUT.  Rule of thumb says you want the ratio of the output impedance (in this case, the DCR) to the input impedance to be at least 1:10 or thereabouts.  Also, in choosing an SUT, we need a certain minimum turns ratio to guarantee that the signal at the secondaries of the SUT will be sufficient to drive the downstream phono circuit.  The turns ratio then has to interact with the load resistor at the phono circuit input, usually 47K ohms.  As you know, the impedance "seen" by the cartridge will be equal to the phono load (e.g., 47K ohms) divided by the square of the turns ratio.  So, if the turns ratio is 1:10, affording a voltage gain of 10, then the impedance/resistance seen by the cartridge would be 470 ohms (47K divided by 10^2 or 100).  Any typical LOMC can drive the 470 ohm load, because any typical LOMC has a DCR <47 ohms, which exceeds the desired 1:10 ratio of output to input impedance.  If your LOMC cartridge makes at least 0.3mV, the net signal voltage after the SUT would be 3 mV, enough to drive most MM phono circuits with at least 40db of gain.  (This also depends upon the input sensitivity of downstream components and the efficiency of your speakers.)

I have two very different phono stages, but both have sufficient inherent gain for any LOMC that I can imagine.  I now find that I prefer to listen to most LOMCs with "wide open" loading, setting the load R at 47K.  That cannot be done with an SUT, because of the obligatory effect on impedance, in relation to the square of the turns ratio, that is a property of any SUT.
lewm
12,566 posts
 
So the Phonata is not, in fact, a current-driven phono in the way that the Aqvox and BMC MMCI and several others are. Somewhere I thought you said it was.
lewm
12,566 posts
 
So the Phonata is not, in fact, a current-driven phono in the way that the Aqvox and BMC MMCI and several others are. Somewhere I thought you said it was.
lewm
12,566 posts
 
There is another thread of much more recent origin around current-driven phono stages. But in any case, by definition, a current-driven phono stage with so-called automatic impedance loading would not require an SUT. As I think I wrote elsewhere, these stages try to offer zero input impedance to the cartridge, and they only work really well with very LOMC cartridges that have very low internal resistance, less than 10 ohms. (This is based on my own understanding of what I can find on the internet. I am not an EE; I only pretend to be one on Audiogon.) So, the first tube or transistor of the phono stage itself acts like an I/V converter to drive the downstream phono circuit with voltage output. It’s really not so complex. This circuit would work but less well with LOMCs that have internal resistances above 10 ohms, would not be recommended at all for HOMCs or MMs. But I guess the Phonata has separate dedicated MM inputs. I am curious to try one myself. Which is to say that I am curious to try a current-drive phono stage, not necessarily the Phonata.  I've had my eye on the BMC MCCI.

Conversely to my description, if the Phonata does incorporate an SUT in its LOMC circuitry, it probably is not a current-driven phono stage in the technical sense, although I suppose you could say correctly that a SUT converts current to voltage too.
lewm
12,566 posts
 
Dear Chakster, maybe I should read more of this thread before writing this, but I am confused. If the phonata is a current type design, why would you even be using any SUT? An LOMC cartridge with low internal resistance should plug right into the MC inputs. I am sure I am missing some point you must’ve made back there in 2015.
lewm
12,566 posts
 
Allen Wright wrote in his Preamp Cookbook that he could hear the difference when his RTP phono stage was "rolled off" at 750,000 Hz, vs when he fixed the problem allowing it to go much higher in frequency. Of course, that kind of subjective statement is impossible to dispute, but I am dubious that what he might have been hearing was due to bandwidth and not something else. On the other hand, he was smarter than I, in this area for sure.
lewm
12,566 posts
 
All good points. Nevertheless, he wrote in favor of very extended bandwidth. I will try to find the quote; perhaps I mis-remembered. He might have been referring either to the linestage section of the RTP or to one of his amplifier designs. Anyway, his point was that although the roll-off was occurring at frequencies impossibly high by any rational analysis as regards any effect on the audio bandwidth, there was in fact an audible (to him) "trickle down" effect, because the roll-off created distortions down in the audio range.
lewm
12,566 posts
 
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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