rjs@hpfclo.UUCP (rjs) (08/06/84)
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I have a feedback problem when using my turntable. I have a
yamaha P350 turntable, a yamaha A700 amp (100 watts/channel),
and bose 901 (model II) speakers. When using the turntable I
find that I can't turn the the sound level above about the 1/3
mark without getting severe feedback! If I use my tape deck I
have no feedback at all. The turntable and amp are on top of a
shelf mounted on a wall in the same room as the speakers (about
10 feet from the closest speaker). Why the feedback? What is my
problem? Thanks in advance.
Bob Schneider
{ihnp4,hplabs}!hpfcla!rjsrjs@hpfclo.UUCP (rjs) (08/08/84)
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Thanks for all the responses. The answers fell into 3
categories.
1) Improper ground
2) Dustcover
3) Coupling through the base of the turntable.
It turned out to be case #3 for me. Thanks for all the help!!
Bob Schneider
{ihnp4,hplabs}!hpfcla!hpfclo!rjsark@rabbit.UUCP (Andrew Koenig) (08/10/84)
Bob Schneider complains about feedback in a situation where his turntable is on a shelf mounted on a wall in the same room as the speakers. This sounds like a classic case of acoustic feedback. As a test, you might try changing something about the acoustic coupling between turntable and speakers and see if it changes the character of the feedback. For instance: put the turntable on several layers of blankets, move it elsewhere in the room, or run it with the dust cover open if it's normally closed (or closed if it's normally open). If this is the problem, there are several products designed to cope with it. Audio-Technica (I think), for example, makes a set of mushy feet to put your turntable on. Someone (I forget who) makes a heavy marble slab on soft feet. For all these doodads, the purpose is the same: to prevent the sound from the speakers from affecting the turntable.