Mono Tetrad vs. Astatic 89T

[radiotvnut]

As some of you know, the Astatic 89T was a popular plug-in needle/cartridge combination that was mainly used in institutional record players from the mid '50's until about 2007. So, we're talking about a cartridge that was in service for a good 50 years. Back in the day, these were cheap (about the same price as a needle alone) and when the cartridge or needle became damaged or worn, all you had to do was unplug the old one and slide a new one in the holder. These came in both diamond tipped and sapphire tipped versions, with flippable LP/78 versions and LP/LP versions. Up until the early 2000's, I was still buying the gold colored ones from the parts house for $5 and some change.

In recent years, these cartridges have become scarce and expensive. In fact, I just communicated with Gary Stork (www.thevoiceofmusic.com) and he said that the 81T/89T family of cartridges was well on their way to extinction and that the old style originals with dual tips are getting hard to find. The most current variety are the red Pfanstiehl 911-D7 (single sided diamond LP tip) and the 911-S3 (green single sided 78 rpm tip). In order to play both types of records, you need to order both cartridges and that's well over $30. Also, I don't like the idea of physically having to swap cartridges around and run the risk of losing or damaging one of the cartridges and/or holder from excessive handling.

These cartridges are advertised to put out about 1.3 volts and I can tell you from experience that the .5V Pfanstiehl P226 does not work well. They will work; but, the volume is lower and the tonal quality is not as good. Also, another problem I've ran into with the 89T's, especially when mounted in cheaper plastic tonearms that are often found on later classroom record players, is that they skip all over the place on records that contain heavy bass and they can wreck a styrene 45 on the first play.

In recent months, Gary has announced a mono Tetrad cartridge (white body, light green socket) that is advertised to put out close to 1V. Several months ago, I ordered one of these (about $28). Last night, I decided to use it in a Hamilton 915 classroom record player from '97. This model uses a cheap plastic kiddie style tonearm and with the 89T, I experienced the problems that I just described.

When I first installed the mono Tetrad, the tonearm tracked fine and didn't carve up styrene records on the first play; however, I could tell that the cartridge was not quite as hot as the original 89T. This record player uses a low powered amp that might put out a watt of audio. The output stage is an IC and there is a single transistor that serves as a driver ahead of the IC. In this model, the cartridge was shunted by a 100 Kohm resistor. From past experience, this value seems a little low; but, it was probably used to pad down the output of the 89T cartridge. I removed the resistor from the circuit and the record player now sounds just as good, if not better, than it did with the 89T.

I don't know how many of these mono Tetrad cartridges are in stock; but, Gary said he was very fortunate to get them and that he bought up every one that was available.

So far, this Tetrad mono cartridge has been the best solution that I've come up with for replacing an older mono cartridge; however, depending on your amplifier design, be prepared to make amp modifications if the cartridge does not seem quite hot enough for your needs. This amp mod may include altering or removing the cartridge shunt resistor or capacitor, etc.

Now, I wish Pfanstiehl would get on board and start making universal cartridges that put out a solid 1V because we all know that the green mono Tetrads won't last forever and once Gary is out of them, that will likely be it.

If you get on Gary's site and look at Tetrad cartridges, you'll see the one I'm talking about. Three big advantages to this cartridge is that it tracks better, has a replaceable stylus (the initial cost may be high; but, a new stylus will run only a few dollars, as opposed to spending $25+ for a new 89T every time the needle wears out), and the actual needle (not the whole cartridge) flips. I've fixed many school record players where the wires had broken off from the cartridge holder from it being flipped back and forth once too many.

So, just a heads up - if you need a higher output more recently made mono cartridge, you might consider the mono Tetrad from Gary.

[Olorin67]

I might have to grab one, I play a lot of mono 45s and 78s.

[radiotvnut]

I just discovered something about this cartridge. Normally, when playing a stereo record with a mono compatible cartridge, both channels are combined to produce a mono signal. I was just playing a stereo record with this cartridge, a record with good stereo seperation, and it sounded like that only one channel was coming through. I played the same record on another unit that contained an 89T cartridge and both channels came through. The wiring harness with the mono Tetrad has only two wires (the two unused wires have been clipped where they enter the plug on the wiring harness); so, I substituted a 4-wire harness and wired both channels together. I still had the same "lost channel." I then connected to the unused pins on the mono Tetrad cartridge and got nothing; so, these pins must not be connected to anything. So, this cartridge must be set-up to reproduce only one channel of a stereo recording. If these cartridges are only going to reproduce one channel and are not wired to combine both channels; then, they might not be a good investment unless you are only playing mono records. I'm going to experiment with this some more and then I'll communicate my findings to Gary, since he probably isn't aware of this.

[Electronic M]

Originally Posted by radiotvnut

I just discovered something about this cartridge. Normally, when playing a stereo record with a mono compatible cartridge, both channels are combined to produce a mono signal. I was just playing a stereo record with this cartridge, a record with good stereo seperation, and it sounded like that only one channel was coming through. I played the same record on another unit that contained an 89T cartridge and both channels came through. The wiring harness with the mono Tetrad has only two wires (the two unused wires have been clipped where they enter the plug on the wiring harness); so, I substituted a 4-wire harness and wired both channels together. I still had the same "lost channel." I then connected to the unused pins on the mono Tetrad cartridge and got nothing; so, these pins must not be connected to anything. So, this cartridge must be set-up to reproduce only one channel of a stereo recording. If these cartridges are only going to reproduce one channel and are not wired to combine both channels; then, they might not be a good investment unless you are only playing mono records. I'm going to experiment with this some more and then I'll communicate my findings to Gary, since he probably isn't aware of this.

Even on mono records it is not very good....Most mono records (Edison diamond discs being a notable exception) are laterally cut. So half of a conventional stereo cart (a single magnet/coil optimized to pickup motion at a 45 degree angle to the playing surface) will pick up more vertical surface plane noise from a worn record than an old school mono cartridge (it has the advantage of being able to play both vertical and lateral cut records on the other hand, if you count it as that).

[radiotvnut]

OK, I revisited the new stereo Tetrad cartridge and two things went wrong, as a result of me getting frustrated. 1. I had it wired wrong. 2. The needle was not seated properly. After I corrected these issues, the stereo Tetrad sounds just as good as the mono Tetrad and I now have both channels of a stereo record.

I sent an email to Gary to make him aware of my findings. It will all depend on what he has to say; but, in the future, I'll probably only order stereo cartridges and wire them for mono (unless we determine that the mono Tetrad is defective).