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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
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Old 8th November 2017, 10:39 PM   #411
super10018 is offline super10018  United States
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I have an A90 in pretty good condition and love it. One thing I complain about is the stylus guard. The guard is not well designed. So I bought a guard for A 95. The new stylus guard is better but it is still not too good. Ortofon charges USD$2,200 for the service of PW and above. They say they don’t re-tip. They change the whole motor and stylus.
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Old 8th November 2017, 10:45 PM   #412
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by AVWERK View Post
It would be interesting to see a schematics and construction details of the Stax.
This was reviewed I believe in the Absolute Sound magazine way way back. Could be wrong.

I use similiar components Quads, Vandersteen sub, 100 class A monos
I purchased 2 pairs of 57,s with the intent to stack them also but reasoned time alignment would suffer and I don't listen loud anyway.
Quads do downward dynamic range like no other speaker. You just don't need extreme loudness with these.
Just purchased 988,s and one needs work, so these are being modded and reworked for comparisons sake.

Kevin's circuit sounds so good and has plenty of gain your light speed attn. would be a perfect match

Regards
David
All I cloud find quickly was this, looks like there was a couple of models.

Freq. Response: 10-40kHz; 10-50kHz for Type2
Channel Separation: 22db(1kz); 24db for Type2
Effective Tip Mass: 0.3mg
Compliance: vetical - 10
horizontal - 20; 15 for Type2
Optimum Tracking Pressure: 1 g.
Stylus shape: 0.2 x 0.8 mil; 0.3 x 0.8 for Type2
Vertical Tracking Angle: 15 degrees
Weight: 9.5g; 8.5g for Type2

And these link to some good pics.

The Rare Stax CPY/ECP-1 electrostatic phono cartridge & equalizer | Audiokarma Home Audio Stereo Discussion Forums

Stax CP-X Electrostatic Direct Pickup System - Vinyl Engine

Cheers George
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Last edited by georgehifi; 8th November 2017 at 10:50 PM.
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Old 9th November 2017, 04:17 PM   #413
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
Super rare for sure.. Operating principles are not at all similar to the strain gauges I designed this pre-amp for. I need to research this further, but in thinking about it I suspect an electret/capacitive transducer is in fact velocity sensitive so very, very different than the displacement sensitive strain gauges.

Edit: Well it actually ppears to be displacement sensitive with surprises me a bit based on comments in the Audiokarma thead. There are a couple of jfets in the cartridge body as well which at least one person recommends be replaced.

The current phono pre-amplifier design has very rudimentary EQ which puts it into the realm of reasonably correct if not what I would call precise RIAA equalization. I'm actually working on something that is theoretically a slight improvement. My experience so far is that everything that looks like a theoretical improvement in fact has proved not to be.

There are a couple of optical "strain gauge" cartridges that have appeared on the market over the past year or so:

DS-Audio

Phaedrus

So far I only know of three people besides myself who have either built or are in the process of building the pre-amps. None of the others have posted here about what they are doing which concerns me because I expect both questions to arise and mistakes to occur in the building in at least some instances.
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Old 9th November 2017, 11:25 PM   #414
AVWERK is offline AVWERK  United States
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I had no issues first time turn on and with burn in and adjustments.
The only issue is leaving it on over night and one 6C3N-eb going bad with some nasty D.C. Thumps thinking it was the headshell connection.
Other than that , no issues and a straight forward build. Your instructions were spot on.

You must be using a passive or extremely low gain pre and traditional line stages and might need R 10-11 shift points adjusted for more range from a bigger build audience down the road. IMHO

Your circuit brings out any small changes to the cartridge end showing a detailed transparent circuit design.
It was easy to hear the stiffer mod to the u channel cantilever post. The sound stage pushed slightly back with more depth layering and imaging of each instrument tightened up with more focus. Female voice outlines became the size of a real person in space.

I am just getting started and haven't even tranfered to my SLT arm yet , taking advantage of testing with removable headshells to find the one worthy enough to transfer over and finding one for an autopsy and new stiffer housing.

You really did an exceptional circuit design for this cartridge.
2 big thumbs up here !

Regards
David
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Old 14th November 2017, 03:30 AM   #415
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
Thanks Dave! I just saw your comments. This is definitely one of my more worthwhile endeavors, and I am delighted that people like you were willing to trust me at my word about the quality of this design, and fork over significant money for the boards and power transformers even at cost. Factor in the cost of the many other parts and the cartridge(s) it's not a modest investment particularly in the case of the many participants here, none of whom except GTHICM and Shooter know me personally or have presumably heard any of my designs.

My original intention was to try and recoup some of my investment in the original set of PCBs. I never imagined that 22 more sets of boards would go out the door as result of my sharing the design and my journey.

So thank you again, it means a lot..

In all fairness Panasonic created a monster and then apparently dropped the ball, this cartridge technology could have been the ascendant cartridge technology regardless of whether Quad and CD-4 were commercially successful. Instead it became a dead end and a curiosity for people like me to explore. I was pretty dismissive based on the existing commercial examples I heard, particularly given their relatively stratospheric price point.

I had the opportunity to hear a vintage Panasonic strain gauge cartridge under much more favorable conditions on my last visit to Dallas (home of a very vibrant tube diy culture btw), and received several with a challenge to figure out how to make them sound really good. I was not sure it was possible, but it looked like fun.

My goal was something simple and relatively inexpensive which nonetheless did not cut corners in terms of performance capability. Since it was for me and since my system comfortably accommodates sources with relatively high output levels (I design for 2V + sources) the high gain was not an issue.

SNR was sort of important (as you might gather from the performance of your unit) since I use high efficiency speakers with pretty extended LF response and everything else is also very quiet, so it was critical in my mind that it be quiet.

Tradeoffs were made, apparently I will need to figure out how to reduce the gain further for those who need less. (It's excessive for my needs too, I run mine on the -6dB gain tap.) I made no effort to invert one amplifier channel relative to the other because I don't need to do so. My plan was to recommend transformer coupling for those who need to invert or want balanced outputs. Logically a transformer with 2:1 or even 4:1 step down could be useful for those wanting less gain.
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Old 14th November 2017, 03:36 AM   #416
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
Now just a couple of quick observations..

I have done Dave's other suggested mods with blu tac (aka blue stik) and found that this resulted in further improvement.

I have also found with care that the OEM stylus may give very slightly better results provided you are playing clean records, and have done all of the other things previous discussed by Dave and I, otherwise it most definitely will not.
The Bliss is much less fussy, but still needs very careful set up to achieve its best.
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Old 14th November 2017, 03:41 AM   #417
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
And I just bought another EPC-451C on eBay, this one might even be NOS. (It came out of a store, new and never used according to the seller) Can't wait to get it.
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Old 16th November 2017, 03:57 AM   #418
super10018 is offline super10018  United States
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Kevin,

I ordered R7 56Ω. But they sent me 1/4W not .5W. Are they ok to use? Thanks!
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Old 16th November 2017, 12:55 PM   #419
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
No..
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Old 17th November 2017, 05:54 PM   #420
kevinkr is offline kevinkr  United States
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Playing With Panasonic Strain Gauge Cartridges (And A Dedicated Phono Stage)
Quote:
Originally Posted by super10018 View Post
Kevin,

I ordered R7 56Ω. But they sent me 1/4W not .5W. Are they ok to use? Thanks!
Are you sure they are 1/4W or just look like 1/4W? Modern metal films are considerably smaller than the venerable RN60 part.
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