What to do with a stereo phono cartridge and mono LP's?

Consider this: you've got mono records in your collection, but your turntable is fitted with a stereo cartridge.  Can you listen to them with a stereo setup?  Will they sound good?  How can the sound be improved?

Of course, you can listen to your mono records on your stereo setup, but you've probably noticed that they're overly noisy and have a strange sound, almost like bad chorus effecting the entirety of the signal.  This is a consequence of your stereo cartridge picking up elements of the groove that aren't meant to be heard on a mono pressing.

A mono cartridge generally has a stylus which is larger and rounder than a stylus for a stereo cartridge.  Additionally, a mono cartridge is wired in such a way that only horizontal movement creates current; vertical movement makes no difference.  This means that a stereo cartridge tracking in a mono record will be picking up dust and noise through vertical movement, noise that would never be heard through the use of a mono cartridge.  Because the stereo stylus is smaller, it's also tracking in a way that a mono stylus would not (and generating more noise).

Also, a stereo cartridge tracking a mono record still generates two channels of sound; the left and right channel should, in theory, be the same, but in reality they may be slightly different due to noise patterns.  This amounts to the strange chorus effect that can be heard when playing a mono record on a stereo system.

mono switch

If you have a mono switch on your vintage hi-fi receiver, a single channel (generally the right side) is pulled and spread to both channels.  This doesn't help with the increased noise off the cartridge, but it does get rid of the chorus effect.

On newer receivers, however, this may not be an option.  Many new receivers have a stereo-fold-in option which is referred to as mono.  In essence, the two channels are folded into a single channel, and that channel is then spread to left and right.  It's not a true mono mode; it doesn't take care of the chorus problem, and in some cases can make it worse.

the paper clip fix

Use this one at your own risk, and only if you've got the proper equipment to make it work.  Crucially, you'll need to own a tracking force gauge to ensure that you don't ruin your mono records with this trick.  If you do own such a gauge, however, this can be a good way to save a couple hundred bucks on a mono cartridge.

If you've got a vintage receiver with a true mono swtich on it, you'll want to leave it on, even when using this fix.

The premise is simple: on a stereo cartridge with a standard mount, the four wires which connect cartridge to tone arm and their contacts are exposed.  A mono cartridge has only two wires.  This trick amounts to shorting two of the four wires on the back of a stereo cartridge, essentially shutting off the cart's ability to track vertical motion, making it a mono cartridge with a narrow stylus.

Of course, this means having some way to short the contacts easily without permanently modifying, or worse, damaging the cartridge.  And that's where the paper clip comes in.

By shorting the white and red wires on the back of the cartridge, as shown above, a stereo cartridge is converted electrically to a mono cartridge.  Notice, however, that the paper clip must ride along with the cartridge, thus increasing the tracking force.  A paper clip generally weighs about 1 gram, and thus a cart which normally tracks at 2g will be tracking at 3g (!) after the addition of the clip.  This is where the tracking force gauge comes in.

After installing the clip and shorting the wires, set your cart on your tracking force gauge and measure.  It should be nearly 1g heavier, and you should thus adjust the weight on your tone arm to 1g lighter, so that you are back at the recommended tracking force for your cart (often 2g).

Does it work?  Pretty well, in practice.  Noise is greatly reduced.  Sound overall seems a bit clearer.  While it may not match the sonic perfection of a good mono cartridge, it's more than adequate for most people, and it saves you a couple hundred dollars.

going all out

Alternatively, you could go all out and purchase a real, genuine mono cartridge.  Believe it or not, they are still readily available.

LP Gear carries quite a few, one of which is only $80.  Reviews of the Grado MC+ are generally favorable, but I have not tried it personally.  There are other, more expensive options, of course, but the massive variety and price difference in all the available cartridges is for another post entirely.

In my opinion, most people will be more than happy with one of the possible improvements above.  Don't think that they are only suggested because of a lack of availability of mono carts, however; obviously, someone is buying these cartridges, so if you're willing to spend the money, it may be worth it.

final thoughts

Your happiness at it pertains to your mono vinyl will be greatly improved if you can get your system as close as possible to the system they were meant to be played on.  If it means shorting some contacts on a stereo cart, so be it.  You'll be glad that you took the extra 5 minutes to place the clip, reweigh, and adjust.