vinyl distortion and cone flap - help!

My vinyl set up (Gyro Se, Techno arm, Ortofon MC15, Diablo) was working fine until recently. I'm now getting distortion and a horrible cone flap, where the bass cones pulse in and out wildly on the record run in. I did have one clumsy pick up incident where the needle slid across a record, but can't think of anything else that's happened or changed to give rise to this, and visually the cantilever etc still look OK. I loathe vinyl set up tweaking, so before I start taking off and resetting up the cartridge etc, is there any likely cuase that I should be looking at first? As I said, this didn't happen when first installed, so it's not something inherent in the equipment like cartridge/arm mismatch.

 

Cone flap is quite common if you don't have a subsonic filter, unless they're about to fall off its fine.

Needle sliding across shouldn't have hurt it really unless the mounting bolts were loose or something, I'd check alignment first

 

You could do to have a really good look at the stylus, can you take it off, or is it an all in one?
Get it in really good light, and use a magnifying glass, you might be able to see any obvious damage. It does sound like damage to me if you're getting distortion. i don't think the cartridge body will have moved. Have you tried giving it a really good clean?

 

Its happened to me before, if its miss-aligned it can distort, took me ages to track it down. That why I'd check everything before taking it off.

 

It may be common but it's not fine and shouldn't occur.

You need to examine the stylus, if the cantilever looks straight then it's probably OK. But you may have chipped or damaged the stylus.

Failing that perhaps you've had a coincident failure of the MC input on your amp? Is this both channels?

Paul

 

Thanks for the advice. It's a new symptom - ie it didn't happen on the same records a couple of weeks ago, so definitely a change somewhere rather than lack of subsonic filter. It does affect both channels. Both amp and phono stage are less than 6 months old so I'd hope it's not a fault there. Sounds like I should look at the stylus first, then realign the cartridge. God, I hate doing that stuff!

 

Its as much a question of confidence as anything. Be careful and methodical and you will be fine.

 

I though RIAA phono stages have sub-sonic filters built into their equalisation curves anyway???

 

Some do, some don't.

 

Cone flap happens if you get the arm mass / cartridge compliance maths wrong, i.e. a too massy arm for a cart's compliance rating. As yours was once right and now, after an accident, isn't one of two things has happened: a) you have broken the cartridge (i.e. made it more compliant by damaging the mechanical workings) or b) you have accidentally knocked the tracking weight up much too high. If it isn't b), which is easy to check, then it is a) and the cart needs replacement.

Tony.

 

so have I always been fobbed off with it happens with ported speakers then?

 

It is more noticeable with ported speakers as they are freer to make large excursions, but the math is the same. The only other reason for cone flap that I missed earlier are decks, especially suspended ones on wobbly supports, i.e. a LP12 on a stand on loose floorboards will flap the cones if you walk over the floor as it simply can not deal with the lateral movement.

Tony.

 

Shouldn't be that, I'm wall mounted. According to the morch table thing I have the correct arm tube for my cart, downforce is well within what it should be

 

When do you see the cone flap? If it is just on significantly non-flat vinyl then that is largely acceptable.

All you need to calculate it is this graph:



The mass figure includes the arm, cartridge and mounting hardware. Blue is good. The goal is to keep the resonance below the audio band and above warp frequency and any subchassis suspension the deck may have.

Tony.

 

IIRC our esteemed Mr Saab put a thread up on this very matter a little while ago. May be come pointers there.

Jeff

 

all I had time to do tonight was to give the stylus a good clean and tighten a bit the collar where the arm goes into the arm board (sure there's a technial term for it...) which was very loose. I also recentred the motor standing inits cut-out hole - I thin kthis might have been what cuased the flapping as any lateral movement would have brought cotnact... the cones no longer flap but there is quite a strong channel imbalance, with not much coming through the right channel (still a phono issue as the cd works fine). connections are all good, so maybe I'll need to realign the cartridge - I'll give it a go tomorrow night