Mod for Gramophone tonearms to improve SQ

[audioengr]

Sound quality can be improved, particularly vocal intelligibility by adding mass and dampening the upper part of the hollow tonearm on Victor and Columbia Gramophones. This part is usually held-up by a spring loaded pin.

If you lube the upper tonearm and the "wrist" at the reproducer, it makes them decoupled a bit from each other. As a result, they operate smoothly but can also vibrate and resonate. This resonance adds distortion to the output from the horn.

By applying a temporary device to the upper tonearm, one can reduce significantly this distortion improving the output acoustic result. The device that I use is what is called in the great northwest a "slinky". It is typically used as a flexible fishing weight and is comprised of a length of parachute cord with the internals pulled out and then it is filled with a number of lead or steel buckshot. The ends are sealed by applying a flame and squeezing with needle-nose pliers,

This assembly in my application is about 4 feet long. I just wrap it around the swinging tonearm. You can rubber-band it if needed to keep it from unwinding and hitting the records. I have a photo, but I'm not sure how I can insert it here...

[Inigo]

You must press 'select file' , then choose the file from the photo gallery, once selected you press 'add file', adding some descriptive text in 'file comment' if you want. The file then appears as uploaded in another board.
Then finally you go to the end of the text, press there as if you were to add something, and then go to the board where the file appeared and press 'place inline' and a file code is added in the text where you placed the cursor, you can see it. Hope this helps... We need to see a photo of your ingenious device!
This reminds me of what other colleagues do to the intermediate sound conduit of certain machines. The latest HMV external horn models (25, 32, 31a) had a tonearm detached from the horn, each one in one corner of the case. They are linked within the case through a sound pipe, which colleagues discovered works much better if damped, wrapping it in thick rubber bands and then adding plaster bands.. when dried these remain tightly around the conduit, adding mass and inertia, killing the vibrations added by the conduit material. EMG gramophones also have a long internal sound conduit, but this doesn't need wrapping, for they are thick cast aluminium, and very inert by themselves.
I've always played with the idea of damping the tin big reentrant horn of my hmv 194, by means of filling with sand the cabinet, all around the horn (this would make it pretty heavy, though) or using sprayed poly-foam as used in walls for thermal/sound isolation, or simply installing short wooden sticks jammed between the big side panels of the horn and the walls of the cabinet, to cut out the panel vibrations, just as struts fixing the center of each tin panel... These big tin panels add their own sound to the air column, a resonance clearly audible. Perhaps it is easier to make tests using the wooden struts, easy to install and to remove...

[audioengr]

Photo of the mod.

As for making the horn more rigid, I plan to put a dowel with bumpers on the ends inside of the horn. I'll post if this works. Should improve the bass.

[Daithi]

If the horn is steel it can be damped by this stuff perhaps. Its the magnetic rubber they use on fridge magnets.

https://www.ebay.ie/itm/A3-Sheet-VEHICL ... 0632979408

[Inigo]

Thanks for the tip. I think anything similar would work, a tiny chain (covered in rubber or plastic) wrapped around the tonearm, or whatever heavy and dense rope...

[audioengr]

I'm not sure if it's the added mass that is important here or the damping of resonance, but the lead shot provides both.

If it were a tiny rubber hose, like surgical tubing with lead shot inside, this would probably work even better.

BTW, I put one dowel with rubber bumpers on the ends inside my wooden horn and this seems to help. Will try another at 90 degrees.