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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
chakster's avatar
chakster OP
6,144 posts
 
@lewm You are right, i thought it was a current-driven because of the "Automatic Load Impedance" feture advertized by the manufacturer, and because of the comments in the beginning of my post (from 2015). But never too late to learn. As we noticed now the real current-driven phono stage works best with cartridge with very low impedance.

But based on a comment from one of the WLM owner (from 2015): "The Phonata works very well between 25 - 100 ohm cartridges".

And base on info from the manual: " MC-Input Impedance Range: < 100 Ohm to 50kOhm".

This is definitely opposite to the current-driven phono stages.

In the beginning of this thread two people made two different comments:

@hdm

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.

@larryi

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.


So i think Larry was right. The question is which SUTs step-up ratio i have to choose now when i will replace WLMs internal SUTs if my cartridges are all low impedance (under 8 Ω estimate ) and low output (under 0.25 estimate) ?
lewm
13,719 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.
chakster's avatar
chakster OP
6,144 posts
 
@lewm Yeah, i know you like Ralph prefer 47k for LOMC
I can do that too with my Gold Note PH-10 or with JLTi phono stages, but this is another story.

I have separate vintaage Luxman toroidal silver SUT for carts with 3 Ω (DC Resistance) or less.

But for that god damn WLM Phonata i have to choose an appropriate Lundahl SUTs to replace stock SUTs on PCB. I have no idea about parameters of the stock SUTs i have in it. That "Automatic impedance" confusing me.

I’ve checked the article here and there to understand.

I know that 1:10 is safe, but my cartridges are lower in output than 0.3mV:

0.050 mV (Ortofon MC2000) / DC resistance 3Ω
0.15mV (FR PMC-3) / DC resistance 8.6Ω
0.2 (Klipsch MCZ Ruby) / DC resistance 2Ω
0.24mV (FR-7fz) / DC resistance 5Ω

Which step-up ratio of the SUT would you choose for example for your Ortofon MC2000 ? 1:32 or more ?

I’ve checked K&K Audio for which Lundahl SUTs installed in their kit. There are two kits (basic and premium).

Basic with LL9226 http://www.lundahl.se/wp-content/uploads/datasheets/9226.pdf

Premium with LL1931 http://www.lundahl.se/wp-content/uploads/datasheets/1931.pdf

Maybe i have to choose one of these SUTs from Lundahl to soldeg them in my WLM instead of the cheap stock SUTs i got there now.







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