Help! Something's wrong in my analog chain!

[tennisets]

Okay, after a few weeks of waiting, I finally took delivery today of the Radio Shack Phono Preamp (aka the Little Rat). I hooked up my vintage Kenwood turntable (one of the ones with a corian base, a KD-2055, with Grado Black) which I purchased on ebay to the phono stage, hooked that up to my amp, a Jolida JD102B, turned everything on, and put on a classical guitar album.

To my horror, when I turned from the amp to walk to my listening seat, on the first step I took I saw the speaker cone move a HUGE amount. It bottomed out the speaker with a horrible crack. When I stopped moving, I saw that the speaker cone was still moving back and forth a good bit and was humming noticeably, but not a huge amount. I guess I half excpected that because I'm using a Grado and the motor is unshielded but I can DIY a shield and fix that. What I am extremely worried about is the fact that the slightest impact on the floor translates to a huge amount of movement in the speaker cone.

What's going on? The Kenwood is not sprung, and it's sitting on my dresser. Can such small vibrations have such a huge effect on the cartridge? What can I do?

Help, I want to listen to vinyl but I'm afraid someone will walk up the stairs or outside my room and break my speakers!

 

[drminky]

The hum problem is a common curse of the grado carts. Not having one myself, I'm not sure if there's a fix, but the vinyl asylum has endless articles about this problem. Search the archives.

The footfall problem you have sounds pretty extreme. The slightest vibrations can cause problems, usually mistracking or acoustic feedback. Either your floor must be very bouncy, or the dresser very flimsy (don't tell me its ikea!), or both (I assume the cart must have bounced right out of the groove and come crashing down with an almighty thump). Ideally, you want a wall mount for your turntable (if your walls are any better than your floors). If that is not possible, you need to dampen the effect of the footfalls somehow. A sturdier base if you have the room would help. A great trick is sitting the turntable on a half inflated bike tyre tube that's sandwiched between 2 mdf boards (ugly but at least its cheap!), or I've even had success before sitting a turntable on polystyrene from old packing boxes.

This is all assuming you have set the turntable up properly with regards to tracking force, tonearm/cart compatibility, antiskate etc of course.

 

[OakIris]

Quote:

when I turned from the amp to walk to my listening seat, on the first step I took I saw the speaker cone move a HUGE amount. It bottomed out the speaker with a horrible crack.

The "speaker cone" moved and bottomed out because of floor vibration? Or do you mean your tone arm/cartridge crashed down on the record, as drminky interpreted your statement?

 

[daycart1]

This problem sounds electrical to me. Are you sure that the four leads from cartridge to tonearm are all nice and tight?

 

[rickcr42]

sounds like the kenwood uses an unsheilded AC motor-death for woofers used with Grado cartriges without some measure taken.

Some other points :

1-the turntable needs to be absolutely level

2-make sure the turnatable suspension is tuned to (From memory) 8-10 Hz

3-the turnatable itself may need to be attached to and earth ground

4-attach the turnatable ground wire to the phono stage if it is not already

5-make sure the cartridge tracking and anti-skating (if the deck has it) is set correctly.

6-decouple the turntable stand from the environment if the above steps don't work ort buy an Ikea Lack table ,about $10 or so.

If you are still really baffled i can provide some links to turntable set-up