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direct drive or belt drive?

harleyrider

harleyrider

Super Member
My speakers are at least 20 ft from my turntable Realistic Lab 400 (direct drive). My problem is i cant crank it up to loud or even put good bass to it and it starts to humm back through the speakers. Low listening levels 70 -80 db its fine as long as you keep the bass turned down. I love listening to my albums but its ver frustrating when you cant listen to them the way you want. Is a belt drive tt a better way to go? :scratch2: Thanks for any help
 

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That's a very loaded question.

A good turntable will not generally have problems with feedback. A poorly designed unit will. This is pretty-much true regarless of drive method.

However, that said, there is definitely something to be said for the effectiveness of the classicly sprung belt-drive TT (like a thorens) in regards to acoustic isolation.
 
I don't know how well you have your table isolated from external vibrations, but if you have wooden floors you might consider putting it on a wall-mounted shelf and add some more damping...
 
I feel the drive-method has got little or nothing to do with the amount of feedback. Feedback occurs when the TT is placed poorly (too close to the loudspeakers or any other form of vibration) and the design of the TT: mass-loaded, damped, springs....
My own TT is a direct-drive design with three very weak springs, which means the arm/platter will float around like crazy. I've had plenty of problems with the thing, but feedback wasn't one of them.
If feedback is a problem, try removing yout TT away form the speakers, choose a different kind of support, use cones or dampers under the TT or try a thick, rubber mat and a clamp.
 
I guess it has a lot to do with the environment ,
My Sl1210 lives on a solid spiked metal stand about 6 inches from one of the speakers. No feed back at all , I can play pinkfloyd at sound levels that make it impossible to stay in the room , the windows vibrating and that table is rock solid .:banana:
 
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The drive type shouldn't really matter. I prefer direct or idler to belt drive but I'm just guessing that as mentioned earlier, you need to isolate your table better.
 
I'd try some of those cork & rubber isolator "sandwiches."
Not sure where I got them, but maybe somebody can help refresh my memory.
I put mine where my turntable WAS, put another piece of wood on top of those, and put the turntable on that.
This method also worked in my shop, where I have a sub (don't laugh now) directly under my setup, which includes a CD player.
After using the isolator blocks, I can crank it up & the CD player doesn't go nuts, like it did before.
 
There were acoustic feedback problems back in the 70s with all types of tables. My favorite answer to this was to suspend the TT on wire (leveled with turnbolts) anchored to the ceiling. Usually with a wooden support under the table.

That isn't good for most people, me included. I had my TT in a tall cabinet. So I put eye hooks at all four corners and suspended the TT itself from the cabinet sides using braided casting line. I leveled with brass model turnbuckles.

It works, but makes it difficult to handle the table.

YMMV
 
KABUSA sells sorbothane replacement feet. A $20 tweak that might help your feedback issue.
 
harleyrider mentioned the word "humm" in his post.

Could this be a grounding issue vs an acoustic feedback, which (should?) be at very low inaudible frequency?

I've never had either issue hit me yet (fingers crossed), but is there more info harleyrider could provide to narrow down what the issue really is?

What are the characteristics of ground hum vs acoustic feedback?

I'm asking so I will also know in the future as well, but it just seems the posts so far are perhaps jumping to a conclusion.

If it is acoustic feedback, what about a cartridge/tonearm mismatch?
 
Kencat said:
harleyrider mentioned the word "humm" in his post.

Could this be a grounding issue vs an acoustic feedback, which (should?) be at very low inaudible frequency? . . .

What are the characteristics of ground hum vs acoustic feedback? . . .

If it is acoustic feedback, what about a cartridge/tonearm mismatch?
Click to expand...

Good questions. I think if it is hum, it will be there when the stylus is off the record. If it is acoustic feedback, it will be only when the stylus is in the groove.

Hum is usually either 60 Hz. or 120 Hz. The acoustic feedback I have experienced is lower. Often described as a low growl. And it makes the woofers go crazy!
 
Thanks everyone, the TT is 20 ft from my speakers. The TT is also setting on top of a rack with a piece of carpet padding sandwiched between you can see this in the pic. My room is carpeted, when the system is turned on and tt engaged tone arm up no noise (even if you tap on the housing) as soon as you drop the arm down in the groove thats when i have the problem . Not until i crank it up with some good bass though. But even at low almost no volume with the tone arm in the groove , you can very so lightlytap on the TT housing anyplace and hear the thump through the spkrs. When listening it can get scary...... I really would like to avoid hanging this from the ceiling. My bass isnt so heavy that it shakes the walls or anything but i do enjoy it loud and rich. I know it would be hard to detect but when listening you can put your hand on the top of the rack and cant really feel much if any vibration. Will the spikes mentioned help with this issue? thanks
 
Sounds to me like the problem is related to the tonearm/cartridge/base relationship. Drive rumble doesn't sound like the issue. Maybe there is an issue with the cartridge/needle/mounting itself?

Do you have a subsonic filter you can engage in the amp? That might tell you something about this as well....
 
harleyrider,

is this a new TT for you? If not, has it ever worked ok for you, and if so, what circumstances changed to make this so sensitive?

What is the cartridge and is it new, purchased NOS or used, etc.

What gear is the TT plugged into?

The more you discuss everything around the issue from the cartridge through to the amp, the answer might just pop out, or jiggle someones memory banks about a similar situation:yes:

Just for reference, I have an ole Technics SL-20 (botl) about 1 foot from my Infinity Q2 speaker, sitting on a metal frame/glass shelf rack which is on a bare wood floor (man, can it be a worse scenario :sigh:) but the thing plays as quiet as can be, tracks ski hills, and I can knock on the plinth with nary a sound. Had an Realistic metal plate spring suspended TT in the same place as well with no errant noises.

There's definitely something not right with your setup. Just gotta find it :scratch2:
 
Ive had the TT for a long time but never used it like i am now . Im on carpet with the best padding you can buy on top of hardwood floor. Never changed anything on TT since ive owned . Has a shure trac stylus in the original cartridge . My system is all in a metal framed rack with glass shelves (i have pics of it on the forum here). All Pioneer Spec 1 preamp -Spec2 amp and TX 9500 tuner with the SG 9800 EQ. I do have a phono2 level knob -12db to 0db which helps but im just cutting back the volume with it is all that does ?
 
So what are the changes compared to when you were able to use it without having this bass sensitivity? Was it in storage for a while before hooking up again?

With the tonearm in the up position and a little volume on, what happens if you tap the arm or headshell? Try some different items: pencil, pen, fingernails, hammer (just kidding :D).
 
I ve owned this since about 1990 or so... so ya it was stored for about 10 years or so. Its very clean and ive always taken care of my equipment. As far as the tone arm up and tapping on the cartridge housing or anyplace for that matter . Nothing until you drop the arm down in the groove? Then you have to be careful , itll play just dandy until you crank it up and put some bass into it. Myabe ill have to but some of those Sorbothone replacement feet mentioned? thanks alot guys
 
might be acoustic feedback :scratch2:...try to isolate the deck by placing something like small pieces of foam under the feet..or try a square sheet of mdf or particle board with three spikes...three screws through the top will allow some levelling adjustment..
try playing with the lid removed...also try placing spikes / stands under your speakers...
the above should help pinpoint if the feedback trouble is external/internal
 
Are you spinning with the dust cover open in the back. This can promote a band shell feedback effect, as will a TT position close in a wall corner. Sonic transmissions that produces the quick graduating control loss in the bass can occur both through solids and the air.
- Mario
 
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