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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
atmasphere's avatar
atmasphere
11,953 posts
 
But I think for many audiophiles using MC cartridges it is difficult to get their head wrapped around not being able to "load" the cartridge-I think this is perceived very negatively. Hence this type of phono preamp is probably a harder sell in the marketplace.

Yes, the importance of loading the cartridge and how that all works is one of the more prevalent myths about LOMC cartridges. Once you get what is really happening though, you see that being able to load the cartridge or not really isn't a problem- so long as the phono section has either a very low input impedance or is stable with ultrasonic noise or RFI at its input.

The advantage of balanced operation is that the interconnect between the arm and cartridge will not have any sonic artifact. This is really helpful as the cable is at the very source of the signal path- if it messes things up, there is little you can do about it downstream. So insuring that it works right is important and balanced operation can do that.
fleib
1,124 posts
 
" Intactaudio
Can someone please tell me how this resonance in the MHz range is being excited?"

The output of a cartridge has inductance as a property of that output. If you draw the circuit, the voltage of the cart has its self resistance and inductance in series with it (voltage).
The capacitance of the preamp + cables is in parallel with preamp input impedance (resistance), and they go to ground.

This creates a resonance tank circuit, the frequency of which depends on the value of component parts. Because a LO cart has low inductance (reflected in its impedance), the electrical resonance will be at a very high frequency.

It's commonly thought that capacitance doesn't matter with a MC. It does or might. Higher capacitance will lower the frequency of electrical resonance. This electrical resonance effectively gives the cart output (noise) at a frequency where there is no mechanical output.
You can calculate the frequency at the Hagerman link.

Amplifying current avoids this potential problem, with low input impedance. The BMC MCCI has MC input impedance of 3 ohms. The Aqvox 2Ci is 10 ohms.

Regards,
intactaudio
302 posts
 
I have simulated it using J_carrs model and indeed considering the simple ideal model a MC cartridge can in theory resonate with cabling capacitance in the Mhz range. However in spice, you are feeding a signal from a generator that has no problem creating a 0.2mv (or whatever) signal at the resonant frequency in order to excite it. I want to know is how a physical cartridge is generating its full rated output at these high frequencies in order to cause these issues.

dave
atmasphere's avatar
atmasphere
11,953 posts
 
^^ The cartridge itself provides the excitation and it does not have to do so at its rated output by any means (that is the nature of resonance- it does not take a lot of excitation to get it going). Harmonics of signals on the LP or noise in the LP surface is all it takes.

I think many people don't realize that one of the reasons the LP sounds better than digital is that it has a lot more bandwidth.

We run an LP mastering operation; we can record a 30KHz tone on a lacquer and play it back on a modest stereo (Technics SL1200, Grado Gold and H/K 430 receiver from the 1970s) with no worries at all. Cartridge manufacturers only show 20-20KHz response on their spec sheets but the cartridge always goes much higher than that. There is also noise that appears in the grooves of many LPs that is ultrasonic, caused by the pressing process itself.

So its pretty well guaranteed that the resonant peak is going to contain some energy.
fleib
1,124 posts
 
Dave,
The cartridge is not physically generating at these frequencies. It's an electrical resonance at a particular frequency which can cause overload or oscillation. This occurrence will also intermodulate and affect the mid/high frequency range with an overtone coloration.

A common example of this occurring is with the DL-S1 MC going straight into a phono stage with extended bandwidth. The cart has very low output (0.15mV) due to the coreless design, but its impedance is 33 ohms. This low output requires extraordinary gain and makes the problem more likely to occur.
To deal with this, a prominent poster on Asylum loads his DL-S1 below the impedance value of the cart (22 ohms I believe). Apparently his phono stage has enough gain to compensate and he's happy with results.
Not all phono stages will be thus affected. If a design is more bandwidth limited, then this overload is less likely to occur. If phono preamp response rolls off at 100K, it probably is immune to resonance in the MHz range.

I've read about tonearm cables for MC's with very high capacitance. More capacitance will lower the frequency of electrical resonance and might be a bad idea.
A phono cart generates output with magnets and coils. The internal cart resistance reflects the size of the coils. Some coreless designs have stronger magnets inside the cart and lower impedance/inductance. The AT 50ANV and ART7 are such designs. Output is still extremely low, but so is inductance.
Regards,
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