2. analog
  3. 1432420024

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
fleib
1,124 posts
 
On 6/3 and 6/4 it might look like I was clarifying Atmosphere's response. My posts were delayed for 4 or 5 hours on those days. When I wrote them, there was nothing to clarify. They hadn't yet appeared.

I'm not saying this to be contentious, but the explanation of resonance in the MHz range, came from J Carr, and seems plausible. This is somewhere on Raul's MM/MI thread, around p.200?
Of course a cantilever can't wiggle fast enough to output in MHz and I think this is completely a function of the tank circuit and not a harmonic of 30K (or whatever) noise. Two separate, but related issues or two aspects of the same issue is moot. In a voltage amplifier front end, both the stability and bandwidth of the device come into play.

Some think (Goldmund) a power amp needs bandwidth at least to 200K to make speakers play accurately. What about a preamp? Some might not share this opinion, but if wide bandwidth is a positive attribute of analog where's the cutoff point?
Are some phono preamps flawed by having too much bandwidth? Maybe it's a bad cartridge design with a tiny output and relatively high inductance/impedance? Just a bad matchup?
Are any of these current amplifiers considered top rated?
Seems worth pursuing.
lewm
13,515 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.
atmasphere's avatar
atmasphere
12,099 posts
 
I don't know how you would get bandwidth that high given that the RIAA curve is rolling off the circuit at 6db per octave, so he must have been referring to the bandwidth of the gain stages rather than the overall bandwidth of the entire phono circuit.
intactaudio
306 posts
 
Allen was a big proponent of using the "Neumann" time constant in his designs which shelves the response with a corner at 50Khz. Using a "normal" riaa puts the info at 750Khz about 32dB below the value at 20Khz but including the "neuman" drops that to 8dB difference.

dave
lewm
13,515 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.
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