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Preamp for EPC-450CII and semiconductor / strain-gauge carts

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Preamp for EPC-450CII and semiconductor / strain-gauge carts

Postby flavio81 » 21 Jun 2010 06:03

Hello my friends,

I just wanna report that:

(1) I have four (4) Panasonic EPC-450CII cartridges, three of them brand new (new old stock) in their original packaging, all of them with their very nice, Panasonic/Technics original, nude-mounted* square shank shibata stylus.

(2) After extensive research, i have successfuly built a special preamplifier for using them (they require a special preamp) so the output goes to a standard "LINE IN" amp input, no RIAA preamp required.
I'm using the special correction/equalizing reverse-engineered from the Panasonic/Technics CD4 decoders that contained a preamp for this kind of cartridges.

(3) It sounds wonderful!!! I'm amazed!!!

(4) I will sell one or maybe two of the NOS cartridges to forum members that are interested. Of course, i'll include schematics of the preamp or maybe i'll sell it with a preamp, although it's time consuming to assemble one without having a PCB for it. I need to do more testing with the preamp, though, to make sure residual noise is low, etc.

* (Haven't checked with a microscope, only with a loupe, and it appears to be nude mounted. If it's a square shank stylus, most probably is nude.)

For the uninitiated

Strain-gauge (or "semiconductor") cartridges (like this one):

- Have 0hz-50Khz+ frequency response, perfect for CD4 playback
- are immune to magnetic fields/hum (like ceramic cartridges),
- are also immune to cable capacitance and loading effects (like MC cartridges)
- do not require a RIAA compensation network
- are reputed to give great sound quality.

A curious note: Soundsmith currently manufactures a strain gauge cartridge. It costs more than $10000!!!
flavio81
 

Postby flavio81 » 21 Jun 2010 06:20

My schematic was based on this one:
http://yasshin.hp.infoseek.co.jp/boron'sdiary6.05.htm

(the last schematic on the page). I only modified some filter values for more exact EQ compensation and added trimpots for fine-tuning the EQ.
flavio81
 

Postby flavio81 » 21 Jun 2010 06:22

Picture of the cartridge (from another forum member):

1883

The EPC-460C looks almost the same but tracks at a much higher VTF:
Image
Image
flavio81
 

Postby flavio81 » 21 Jun 2010 06:40

Comment on sound quality

This is from the quadraphonicquad forums. The comment is from Lou Dorren who is the person responsible for designing many CD4 demodulators on the 70s:

"Quadfather, The EPC-451C is one of the best pickup cartridges I have ever tested. Besides being probably the best CD-4 cartridge price performance wise, it has the feature of not being a generator pickup. It is a strain gauge type which has a DC bias applied and is a variable resistance. This makes a low impedance device which improves high frequency response and left to right separation at high frequencies (>45 KHz). I have 3 of these and 2 450c versions. I would recommend buying several replacement stylus. By the way the new demodulator will support these cartridges. My opinion is that the EPC450C and EPC451C way outperform the AT440MLa and the AT14S."
"

Way out-perform the AT14S? Strong praise indeed.
I'm still testing mine. So far is the best pickup i've heard!!
flavio81
 

Postby funflyer » 22 Jun 2010 05:43

I just bought a 351 on bay. Now looking for a suitable preamplifier. The link above won't work for me - it goes to a Japanese language page "info seek" but no schematics. I am certainly interested in your preamplifier solution as an alternative to finding a demodulator/power supply from the past!
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Postby funflyer » 22 Jun 2010 05:43

I just bought a 351 on bay. Now looking for a suitable preamplifier. The link above won't work for me - it goes to a Japanese language page "info seek" but no schematics. I am certainly interested in your preamplifier solution as an alternative to finding a demodulator/power supply from the past!
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Postby flavio81 » 22 Jun 2010 07:58

Copy the full url and paste it on your browser, don't click on it:

http://yasshin.hp.infoseek.co.jp/boron'sdiary6.05.htm

What is a "351" cartridge?
flavio81
 

Related link

Postby sregor » 23 Jun 2010 03:49

A brief discussion of strain gauge cartridges and history: http://www.audiokarma.org/forums/showth ... p?t=293090
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Postby flavio81 » 23 Jun 2010 17:51

Ok i've made more listening tests with the EPC-451CII cartridge.

Now i can safely say it is -by far- the best cartridge i have. I've made listening tests comparing them to the following carts:

- Shure V15-IV with original Shure VN45HE stylus (my previous favorite)
- ADC XLM II Improved (also excellent sounding, another classic)

These two cartridges are classics and -according to some people- as best as a MM cartridge can get. But the Panasonic is even better!!

Transients are clearly defined, and the sound has a sense of immediacy/realism that is not on the other cartridges.
The sound is CD-like (in the good sense of the word!!)
Vocals, cymbals, everything with a high frequency content is more clearly defined than the carts above mentioned. The sound has a significatively greater "punch", too.

I think the increased realism might probably be thanks to the absence of the need for a RIAA equalization network, which introduces undesirable phase shifts. I have some quotes from a Soundsmith expert on strain-gauge cartridges, will paste them in a few minutes.

The downsides are that this cartridge can't track the Telarc 1812 overture "torture" disc, while the Shure V15-IV can do it with no problems. The ADC is distinctively softer, smoother sounding, which can be a benefit when you don't want to rock the house.

I also haven't tested for groove noise yet. The ADC a champ in this respects.

But ALL comments i've read on the internet about semiconductor cartridges are praise, praise, and more praise. Now i know why.

---------------------------------

These comments are from Peter Ledermann, Chief engineer for Soundsmith corp, responsible for the audiophile Soundsmith strain-gauge cartridges that get rave reviews.

User name "retipper" on this and other forums. This is about what i (and him) believe it's one of the major sonic advantage of this kind of cartridges: The absence of the need for a RIAA compensation network, and thus the absence of additional phase shifts.


Displacement devices have an INHERENT 6dB/octave curve, very similar to the RIAA (not an accident, BYW)....they DO deviate slightly from the RIAA at two points, BUT, we do NOT correct for this, for doing so would ruin the beauty and simplicity of the device; the one super clean gain stage between you and the music we designed is almost one too many. More than one (to "fix" small anomalies) would be death to the magic. We do compensate passively for the low end roll, as required.
(...)
The subject of human response to amplitude and phase is an interesting one; the standpoint often determines the course of design choices for those of us in the audio design and manufacturing field. I, for one, strongly believe that the human ear is much more forgiving in the amplitude domain than it is in the time domain. After all, many amplitude deviations are the direct result of phase interaction due to resonance, both summation and cancellation, making "amplitude" perturbations audible and potentially objectionable in speaker drivers and cartridge/tone arm systems.

(...) The phase shifts introduced by the RIAA recording curve are further modified by the varied individual characteristics of the equipment used to cut the master. So, where does that leave us? The Strain Gauge is without much phase shift at all.

(...)
My experience is that severe phase perturbations over a narrow region are very audible, while those that are spread out are much less objectionable. It may well be that this is one of the positive differences one experiences when listening to the Strain Gauge. That, in combination with the general standpoint of multiple stages being inferior to a single stage, makes one think that possibly that too, is a motive for using a "simplified" strain gauge system. (...)


This one is very interesting, on the lifespan of the Panasonic/Technics/Matsushita Semiconductor cartridges.

What I can say is that the Matsushita carts I own from the time when I was a design engineer at RAM audio 35 years ago, and produced a SG preamp sold with the Matsushita SG, have not changed at all

(...)Reliability?? I will wager that an SG cart will last far longer than most MC's due to HOW the SG are built, how stable they actually are compared to MC's, and the fact that my many SG carts are more than 30 years old and still perform flawlessly.



Source: https://www.vinylengine.com/php.....r=Retipper
flavio81
 

Postby flavio81 » 23 Jun 2010 17:54

More on the absence of need for RIAA:

Retipper wrote:Please also refer to the graph near the top of Mr. Galo’s excellent article called Figure 1;

https://img.photobucket.com/albums/v716/flavio81/vinyl/RIAArecordingcharacteristic.gif

It refers to this graph as the “typical” RIAA response; in reality, it is far from the “ideal” response that one gets from the theoretical filters due to interaction of those filters. This, not the “ideal”, is what we have all been listening to for years with magnetic cartridges! Superimpose a 6dB/octave curve (Strain Gauge) and you will find that it deviates less than plus or minus one dB.


My comments: As you can see they almost require no RIAA compensation. Only one at around 50Hz to correct the bass and also -very important- remove the DC bias voltage from the cartridge.

The deviation around 1Khz is left uncorrected in the Soundsmith system:

Please observe the "real" RIAA curve in Galo's figure 1, and superimpose a 6dB/octave line on this "real" world RIAA graph, referencing both at 1Khz. The greatly simplified result is that in the response below 1KHz, the SG would be slightly boosted, and above 1K, slightly attenuated. For a cartridge with 70Khz bandwidth and immediate speed of the Strain Gauge, this slight upper end attenuation is not missed at all as there is a definitive acoustic signature that many notice, which more than makes up for this slight "loss".
flavio81
 

Postby Guest » 23 Jun 2010 21:42

flavio81 wrote:Ok i've made more listening tests with the EPC-451CII cartridge.

Now i can safely say it is -by far- the best cartridge i have. I've made listening tests comparing them to the following carts:

- Shure V15-IV with original Shure VN45HE stylus (my previous favorite)
- ADC XLM II Improved (also excellent sounding, another classic)

One has to sit up and take notice of flavio81 posting this. Really !
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Postby flavio81 » 23 Jun 2010 22:27

ld wrote:
flavio81 wrote:Ok i've made more listening tests with the EPC-451CII cartridge.

Now i can safely say it is -by far- the best cartridge i have. I've made listening tests comparing them to the following carts:

- Shure V15-IV with original Shure VN45HE stylus (my previous favorite)
- ADC XLM II Improved (also excellent sounding, another classic)

One has to sit up and take notice of flavio81 posting this. Really !


Sadly i don't have an OC9MLII, or an AT150MLx or even an AT440MLa to compare, but IMHO the Shure V15-IV is similar in performance to the 150MLa. Not better, but similar.
flavio81
 

Postby joseaugusto » 23 Jun 2010 22:36

Schematics of the preamp for Panasonic EPC-450CII cartridges:


Image
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Postby flavio81 » 23 Jun 2010 22:50

joseaugusto wrote:Schematics of the preamp for Panasonic EPC-450CII cartridges:


Image


Yes, i posted the link. I already have built it. I will experiment deleting the R6/C2/R5/C1 filters, since they're not really needed.

BTW, Noise is too high (still usable, but high) with a cheap TL072. Probably because of the use of the 1.68M on the feedback path.
flavio81
 

Postby joseaugusto » 23 Jun 2010 23:22

Flavio:
How did you get these cartridges in Lima?
Is the same guy who sold you the Shure V15IV?
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