Audax N-20 Cartridge

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Presto Repairs
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Audax N-20 Cartridge

Post: # 33916Unread post Presto Repairs
Thu Feb 26, 2015 6:22 am

Hey Trolls

Does anybody here know if the Audax N-20 cartridge is a piezo, moving coil or moving magnet?

I am in the process of rebuilding a Model Y Lathe & I am about to rewire the tonearm + cart
(Audax N 20)

Its marked for 500 ohm and an AC Test on it gave a reading of 319 ohms with a strong 1 k tone being heard...

I'll soon be looking for a new phonostage to run it and knowing what type of cartridge it is will narrow down my search...

Regards

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gold
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Re: Audax N-20 Cartridge

Post: # 33926Unread post gold
Thu Feb 26, 2015 4:54 pm

A piezo or crystal won't need the RIAA EQ as it naturally does this when loaded correctly (500kΩ?) An MM cart should have a nominal output of around 5mV @1k hz with a 7cm/sec lateral groove. A low output MC would have a nominal output of around 0.5 mV.

I'd think that would be enough to go on.

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Re: Audax N-20 Cartridge

Post: # 33940Unread post Presto Repairs
Fri Feb 27, 2015 8:10 am

Thanks Gold,

Can rule out piezo at 500k because its marked for only 500 ohm and tested 319

Looking at the impedance ratings on some phono stages for both moving coil and moving magnet has leaned me towards believing that might be a moving coil cart

EG: Project phono box S - Dual mono configuration phono stage: MC 10, 100 & 1000 ohm MM 47k ohm

I dont have a separate turntable and stage here to test it further yet, So at the moment I can only assume...
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markrob
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Re: Audax N-20 Cartridge

Post: # 33941Unread post markrob
Fri Feb 27, 2015 8:38 am

Hi,

That's not exactly correct. Many of the cheapy ceramics pickups used in bottom of the line players did little or no EQ to interface to these pickups. But technically, these are amplitude sensitive devices and the required RIAA curve needs to be redrawn based on this. Attached is a nice article covering this subject.

ceramic_cart_1.jpg
ceramic_cart_2.jpg
ceramic_cart_3.jpg
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gold
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Re: Audax N-20 Cartridge

Post: # 33942Unread post gold
Fri Feb 27, 2015 12:18 pm

Thanks. I don't know much about them. There are the Soundsmith cartridges, which look to be crystal, are hideously expensive and boast no need for RIAA EQ.

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Re: Audax N-20 Cartridge

Post: # 33943Unread post markrob
Fri Feb 27, 2015 12:47 pm

Hi,

And also the MicroAcoustics line of pickups back in the day. I think the developers of that came from the Sonotone company. I never had one, but they were supposed to be very good sounding. I think they had the network to convert to a moving magnet type output built in (see the article).

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Re: Audax N-20 Cartridge

Post: # 33953Unread post Presto Repairs
Sat Feb 28, 2015 4:14 am

Thanks again Gold + Markrob

The subject got a little derailed, but the information you have both provided has been a great help...

I've had a bit of a browse over a few different brands of MC & MM carts to familiarise myself a little more with the different types...

Just by viewing a few different spec sheets of both MC & MM carts I am now more inclided to believe that it is a M.M cart...

P.S

The cost of some of the moving coil heads i viewed was frightening... I'd would have to refinance my house...
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gold
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Re: Audax N-20 Cartridge

Post: # 33958Unread post gold
Sat Feb 28, 2015 3:38 pm

Presto Repairs wrote: Just by viewing a few different spec sheets of both MC & MM carts I am now more inclided to believe that it is a M.M cart...

MM's are by far the most common type. Most phono preamps assume you have an MM.

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gold
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Re: Audax N-20 Cartridge

Post: # 35385Unread post gold
Wed Jun 03, 2015 1:41 pm

I just figured out that the NOS Panasonic SE-405 CD4 Disk Demodulator system I have is a "strain gauge" crystal system. I don't have much interest in quad but I'm excited to check out a strain gauge system.

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Re: Audax N-20 Cartridge

Post: # 35387Unread post markrob
Wed Jun 03, 2015 4:36 pm

gold wrote:I just figured out that the NOS Panasonic SE-405 CD4 Disk Demodulator system I have is a "strain gauge" crystal system. I don't have much interest in quad but I'm excited to check out a strain gauge system.
Hi,

That's very cool. What a great find!

The pickup is a resistive device that responds to defelction, not velocity. It uses piezo resistivity and it does not generate voltage on its own. The spec for the pickup indicates its about 1000 ohm and produces a 3mv signal at 5 cm/sec at 1Khz with 4ma. of DC excitation current flowing. Since its a displacment device, they indicate no RIAA is needed as it will be close to correct with no EQ. To be totally correct, you really do need some EQ to correct between 500 hz and 2122Hz where the response is still velocity based. Let us know if you get it running and how it sounds. I guess you'll have to use the decoder for its preamp.

Mark

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gold
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Re: Audax N-20 Cartridge

Post: # 35389Unread post gold
Wed Jun 03, 2015 6:59 pm

markrob wrote:
gold wrote: That's very cool. What a great find!

The pickup is a resistive device that responds to defelction, not velocity. It uses piezo resistivity and it does not generate voltage on its own. The spec for the pickup indicates its about 1000 ohm and produces a 3mv signal at 5 cm/sec at 1Khz with 4ma. of DC excitation current flowing. Since its a displacment device, they indicate no RIAA is needed as it will be close to correct with no EQ. To be totally correct, you really do need some EQ to correct between 500 hz and 2122Hz where the response is still velocity based. Let us know if you get it running and how it sounds. I guess you'll have to use the decoder for its preamp.
Thanks. It was from the shop. Since it was brand new in the box I grabbed it even though I didn't know what I'd do with it. I'm glad I did. There have been a few things I've grabbed from the shop not really knowing why that have turned out to be really cool. It also came with a 7" CD4 calibration record.

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Re: Audax N-20 Cartridge

Post: # 35390Unread post markrob
Wed Jun 03, 2015 9:28 pm

Hi,

I've been working on a software CD4 decoder. It sounds like the calibration record is NOS as well. Any chance you could capture the cal record using the strain pickup and preamp at 192K/24 in a wav file? Not sure if the preamp would filter out the stuff above 20Khz though.

Mark

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gold
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Re: Audax N-20 Cartridge

Post: # 35393Unread post gold
Wed Jun 03, 2015 10:26 pm

The Prism AD2 converter I use tops out at 96k. I have been getting more requests for 192k so I may have to do something about that. Too bad as these sound great, were stupid expensive and bought new less than five years ago. The SE-405 has a pretty good manual. When I get a chance i could scan it if you'd like to see it.

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gold
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Re: Audax N-20 Cartridge

Post: # 35425Unread post gold
Sat Jun 06, 2015 4:23 pm

Hi Mark,

I've been trying to understand these ceramic cartridges. From what I can decipher a Piezo cartridge works in one of two ways. One way, is like the Micro-Acoustics uses the piezo to directly generate a current. It looks like the Micro-Acoustics cartridge incorporates extra resistance to do a current to voltage conversion and some correction EQ. The strain gauge type bias or provide a current source to the piezo which then directly generates a voltage. Is this basically right?

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Re: Audax N-20 Cartridge

Post: # 35431Unread post markrob
Sat Jun 06, 2015 8:24 pm

Hi,

That seems right to me. In the more familiar case, you are using the piezoelectric effect. In the case of the Panasonic strain gauge, its piezoresistivity.

The typical ceramic pickup is a voltage source (due to bending) in series with a capacitor. So, you cannot get a DC signal out due to the capacitance. You connect the pickup to a resistor (preamp input impedance) which results in a high pass filter. As you increase the resistor value (raise input impedance), you lower the breakpoint of the highpass. This sets the low frequency response. Typically, you need pretty large values (1 megohm or so) to get decent bass performance. You also still need EQ to correct for RIAA but not using the velocity based curve you always see. That can be done at the pickup or in the preamp. IIRC, the MA pickup converted the ceramic high impedance higher voltage amplitude response into a low impedance low voltage velocity response so that it could be connected to a standard MM input.

In the case of the Panasonic strain gauge pickup, you are measuring the very small changes in resistance that occur under strain (bending). The voltage is developed down to DC. Given that the specs say the pickup is 1000 ohms and you get a signal of 5mv. with 4ma. of current flow you can surmise that the resistance changes the equivalent of about 1.25 ohms out of 1000 for that to happen. As small as that seems, it is pretty amazing given the small movements that are being sensed.

Hope that makes sense.

Mark

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Re: Audax N-20 Cartridge

Post: # 35439Unread post tubeactive
Sun Jun 07, 2015 9:06 am

Greetings All ! First, all Audax carts were definitely magnetic, which will require gain and proper EQ for your needs. Their first carts were the horseshoe magnet type; evolved into the replaceable styli types that actually predate the GE replaceable styli ! Plus, their styli "resemble" the GE RPX-040 types; but it is really the GE that actually resemble the Audax Polyphase styli. Soon after WWII, the Audax, Clarkstan and Radio Products brands of magnetic carts ruled; besides the RCA and Western Electric, of course. The Polyphase Audax do have that GE RPX sound but a bit more forward sounding in the mids and rolled off at the high treble. These later "flipover" Audax carts, requiring 7+ grams of tracking pressure, are still worthy of some awesome sounding mono playback...

Next, I don't know how this thread became morphed into a strain gauge thread, but strain gauge carts are VERY "fast" sounding. That can mean very detailed with some systems but overly analytical with others. They are rarely ever described as "warm" sounding; as many mm carts can sound very detailed and warm simultaneously. That Panasonic SG cart can be very exciting sounding. All SG carts require a power supply and usually have a cart specific EQ built-in to the "supply" (a la the typical electronics theoretical description "AC rides the DC" or "AC over DC"...). I have used the Panasonic CD-4 SG carts with the Panasonic SE-405 CD-4 Decoder and was very impressed. There was a short-lived company, Ram Labs, that offered an SG Supply/EQ unit which excels. Also, there were super rare Precision Fidelity circuit board "kits" available for a very short time, which included am EQ PCB allegedly designed by Nelson Pass (he was later the Threshold designer). There were also the Win Labs entries of TOTL SG carts; which were allegedly modified Panasonic carts. No doubt about it, the strain gauge carts were briefly at the audiophile state of the art in the late seventies/early eighties. With the new Soundsmith brand of SG carts being offered, at incredibly high prices nonetheless, the SG cart merits might deserve at least an audition...

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gold
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Re: Audax N-20 Cartridge

Post: # 35441Unread post gold
Sun Jun 07, 2015 10:49 am

I haven't auditioned a million cartridges. What cartridge(s) would you describe as fast and warm?

I have a few preferences so far. I generally seem to like a conical stylus. Currently I'm using a Denon 103. My favorite so far is an SPU with a conical stylus but it's too good to keep on the lathe for auditions. I haven't generally liked esoteric MC's. They usually have hyper elliptical stylus shapes so I'm never sure if it's just the stylus I don't like.

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tubeactive
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Phono Cartridge Choices

Post: # 35446Unread post tubeactive
Sun Jun 07, 2015 6:07 pm

What a super coincidence ! I too favor conicals and the Ortofon SPU GT has been my reference since the late 1980s ! Yes, it is a valuable cart; maybe should be reserved for your fave sessions. Their diamond quality is second to none; one of my SPU-GTE was used for over 15 years on an almost daily basis ! I think you might want to consider your real goals, concerning the lathe results versus critical listening versus kick back and relax sessions. While one cart could be great for all, like the original SPU types, SPUs are definitely on the very sweet, warm side. They are so warm, they are considered "too forgiving" by many; which is fine for me and my usual "kick back and relax" sessions.

There is one other early stereo vintage stereo cart I use that actually saves my SPU for more critical sessions. The Pickering Stanton 380, either gold or black body, deserves anyone's attention. It has many attributes of the SPU; seriously ! It is a chore to mount, requiring at least 1/4" tall spacers, plus needing 3 grams to track right. It weighs 14 grams, but any arm that can balance an SPU can work with it for sure. The spacers are no big deal, but while tightening, you might have to "pry" the rear carefully so the bottom of the stylus is parallel with the disc record. I have accumulated enough nude conical styli for a few lifetimes; but there is a caveat these days. Many of the aftermarket styli disregard the color scheme of the original Pickering styli. Originally, the yellow "chicken head" looking styli were for manual tonearms with 2-4 grams tracking while the red and black styli were for changers needing 3-5 grams. If you can find an original Pickering/Stanton stylus with the nude mounted stylus, you will be happiest, IMHO. Before I recommend some "faster" and "more analytical" types for critical sessions, I would also search for an Elac 222 or 240; 222 is green and 240 is gray. The 240 is much sweeter; same styli used in both and aftermarket styli types work fine. I do love the early stereo choices in carts.

A few more mm choices are in order for trials. Besides a Stanton 681EEE or 681A body with a D6800HP conical high output stylus, the Sonus Blue, Red or Green might also deserve attention; at least a trial session...Last mm for today's recomendations is the Grace F9E; sweet and fast but low output. The Grace green stylus is a simple elliptical. BTW, the Sonus Blue has a bonded line contact type while the red is an elliptical, green is conical but good luck finding these...

Now, for some mc choices. Many vintage lower output mc carts had simple ellipticals; a bit more hf detail than their conical counterparts. Two serious contenders are the Supex SD-900- and the Great Americal Sound "Sleeping Beauty" carts. The Supex became the Koetsu black and red after Sugano started using boron cantilevers in the Koetsu shop. Supex have good old reliable aluminum cantilevers; very detailed and sweet. The GAS is a super "sleeper" and can be had with any stylus you or I would want; if we could find them. Many years ago, a Denon 103D was used here for awhile; but the 103C was preferred...

So, rereading my "too many choices" above, if there was only one cart which would meet all our requirements, that honor would go to the Pickering Stanton 380. Everyone I know who tries them keeps using them...ENJOY !

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Re: Audax N-20 Cartridge

Post: # 35449Unread post gold
Sun Jun 07, 2015 8:16 pm

I'll keep an eye out for, a Pickering 380. Do you know why you like a conical stylus? Technically an elliptical should be better. I find the high end presentation of the conical more like the source when I compare.

I have the SPU Classic N mounted in a SME headshell on an SME 3012. It's too forgiving of sibalance the be good for test cuts. It tracks too well too. I use it for transfers. I have two sets of Lundahl step up transformers. One for the 103 and the other for the SPU.

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