Decoupling a cart from the headshell

[Trackside]

I've made a 'cartridge isolator' for my DL-103 by cutting a 3mm thick plate of aluminium and bonding this to the top of the cart with some 1mm thick double sided adhesive foam tape sold for attaching car number plates. I made threaded holes in the plate to bolt up to the headshell so the foam is the only connecting medium. On my SL-1200 MK2 (Sumiko headshell + 5G mass load /KAB damper/heatshrink on armtube) I was already using this plate as a simple spacer so it's just adding 1mm which I added to the VTA at the arm pillar. I recorded the 30 second pink noise track on the HFN test record through my EMU 0404 USB into Adobe Audition before and after the mod and ran a frequency analysis at the highest FFT size but could see no difference in any of the frequency range. Listening tests reveal it sounds a bit less 'dynamic' however I've noticed that on some 'climactic' passages particularly in piano music sound a lot less aggressive and 'clangy' and more controlled. Without direct comparison to the master tape it's difficult to say if this is reducing resonances and cleaning up the sound or lowering fidelity. One school of thought is that the DL - 103 being a low compliance (stiff suspension) cart it throws a lot of energy into the arm which can be detrimental to the sound in a number of ways. The other is that any movement of the cart relative to the arm is very bad as it prevents the stylus reading the groove. I guess it depends on what cart, the arm and what the characteristics of the compliant medium you are separating them with. It was a cheap and easy mod so I'll live with it for a while and see.

[bauzace50]

Trackside,

this notion is totally controversial and calls for technical measurements for final validation, in addition to listening comparisons.

My initial reaction is that the cartridge/headshell interface should be solid, without intervening materials, regardless of some testimonials favoring the insertion of various materials in that interface.


Interesting to see measurements to validate this notion.

Good luck,
bauzace50

[cats squirrel]

if the bolts connect the headshell with the aluminium plate, it is not decoupled! Decoupled in this case means the headshell and cartridge plate move independently, yours seem to move together, so are coupled, though it may depend on the type of tape and glue used.

[Trackside]

The difficulty is what's important to measure. I can zoom in to the frequency plots and see small variations between the 2 recordings in the higher frequencies but these look quite random and there are no obvious 'signature' peaks or troughs where the frequency response differs. It may need much more sophisticated audio analysis tools. All I can say is there does not seem to be any major or obvious resonance either attenuated or exited by this mod. Certainly nothing as obvious as changing the loading on a MM cart changes the treble response or mass loading of the arm moves the resonance peak around. What I do know is how much physical energy ( esp the DL-103) throws out - you can feel it with your finger on the arm. Now you have a choice then of letting the arm resonate and this getting back into the cart in a delayed time as it bounces up and down the length of the arm or letting just the cart resonate on it's own where any energy that's bouncing around it's body going be far less time delayed when it gets back into the stylus - just a theory.

[Trackside]

if the bolts connect the headshell with the aluminium plate, it is not decoupled! Decoupled in this case means the headshell and cartridge plate move independently, yours seem to move together, so are coupled, though it may depend on the type of tape and glue used.

Aluminium plate coupled rigidly to headshell with bolts, cart coupled less rigidly to plate with double sided foam. Obviously complete decoupling is impossible and practically undesirable.

[tomytoons]

The DL103's are supposed to sound completely for the better changing the body material on them. Being wood or aluminum they are out there.
I would and have used super glue to attach the 3gram weight that Isokintic sells and is very good. I would not use foam double sided tape because of not having control of the exact equal tightness of the screws. I also am of the thinking to rigid attach the cart to the headshell.
I would not like a piano sounding clangy. Listen carefully.

[Trackside]

The DL103's are supposed to sound completely for the better changing the body material on them. Being wood or aluminum they are out there.
I would and have used super glue to attach the 3gram weight that Isokintic sells and is very good. I would not use foam double sided tape because of not having control of the exact equal tightness of the screws. I also am of the thinking to rigid attach the cart to the headshell.
I would not like a piano sounding clangy. Listen carefully.

Yes I've seen the body mods and may look at doing one in the future. The bolts don't touch the cart - only the foam. Clangy sound gone when this mod applied.

[tomytoons]

The foam tape has to create a sandwich between the headshell and the cartridge. I thought a bout using "Herbies" grunge buster material but it would compress as the tape would when tightening and just rigid mounted here on an RB700.
Hey whatever works for you.

[Trackside]

There's no point if you are still using the bolts to hold the cart in place - it would be like keeping the transit screw in place on a suspended subchassis turntable.

[jake]

Trackside is on it.
Mapleshade sells some kind of nano-spacers that supposedly isolate the cartridge from the arm for un upgrade/tweek, they look like teeny tiny tiptoes, but why? Isn't the arm damped properly? Aren't you losing rigidity in a place where you would like to have some? Rigidity is the reason we have tonearms without removable headshells.

[Trackside]

Not saying this is a universal mod - if you have stiff well damped tonearm and a medium to high compliance cart then stick with a rigid fix between cart and headshell. With an old low compliance cart and a less than structurally perfect arm a different approach may be worth experimenting with.

[Catcher10]

If the mod sounds good then you are successful......right?

[Ldg]

Jeeps ! As if cart/arm mechanics wasn't hard enough to work out, we need another spring/mass/damper system in there ?

Once one allows the cartridge to vibrate in the headshell, one can pretty much give up trying to analyse or predict what might be going on. Especially when the materials are non ideal, in tension, and held by rigid bolts which allow compression but not extention. Good luck, the outcome can really only be assessed imperically !

One global prediction: all effects arising are likely to be at LF, and affect stability. That's not to say there aren't knock on effects in the audioband, but LF response and stability are most likely to be affected in my book.

One has to ask 'what problem are we trying to solve' with such mods. It's a long shot, but it just might work trying to match underdamped cart/arm situations, or where res f is too low for stability. But pretty obviously, it's generally ad-hoc as to outcome.

Just about all the descriptions of 'energy flowing into the arm' are enough to invoke apoplexy really, it's nonsense. Such things are always diabolically described, even if imperically they have an effect.

Decoupling the cart from the arm is a true act of last resort, in my book. But hey, it's still legal

[Trackside]

If the mod sounds good then you are successful......right?

I'll need some more listening before I pronounce on that - I'm not sure if what's gained makes up for what's lost.