Forte' audio model two preamplifier

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#24
... since 25 years I move from analog to digital... in this era I listen vinyl on Oracle... I never sell my vinyls (1000). Today I try to re-listen my collection and I re-discover many smalls problems affect vinyls listening.


Thanks for your response... I begin my quest to find a more "rumble" free turntable.
 
#27
No. I try 2 differents cartridges and the "rumble" is similar. Also, I note the "rumble" is more intense at the beginning of the record and is less audible near the spindle at the end of the record.

This "rumble" sound increase at the same level when I increase the volume.
 
#29
cdebien said:
No. I try 2 differents cartridges and the "rumble" is similar. Also, I note the "rumble" is more intense at the beginning of the record and is less audible near the spindle at the end of the record.
This "rumble" sound increase at the same level when I increase the volume.
Click to expand...

Does the bottom of the cartridge ever touch the record, like on a warp?
Does the bottom of the arm ever touch the cue bar when playing (near the back of the arm)?
Is there still noise when the arm is on the record, but the platter is not turning?
 
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#30
Does the bottom of the cartridge ever touch the record, like on a warp?
No

Does the bottom of the arm ever touch the cue bar when playing (near the back of the arm)?
No

Is there still noise when the arm is on the record, but the platter is not turning?
No, but I'm trying this. Needle on the record, platter don't turn. No noise. I start the motor and the sound begin slowly and he reach expected level when the motor reach it's normal rotation speed. It's appear this is a friction problem...
 
#31
cdebien said:
Is there still noise when the arm is on the record, but the platter is not turning?
No, but I'm trying this. Needle on the record, platter don't turn. No noise. I start the motor and the sound begin slowly and he reach expected level when the motor reach it's normal rotation speed. It's appear this is a friction problem...
Click to expand...

Now leave the power off, remove the belt, spin the platter (in the correct direction!) by hand,
to roughly the right speed, cue the stylus on the LP, and listen. Is there noise now?

If there is noise, perhaps it's the bearing or suspension. If no noise, perhaps it's the motor or belt.
 
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#33
cdebien said:
No noise when I spin the record manually. It's appear noise is generate by the motor itself. How to solve this problem? A faraday enclosure around the motor or simply replace the belt?
Click to expand...

Is the noise more like hum, buzz, scraping, etc? Take a good look at the belt, pulley, and platter drive surface. Also some cartridges are unusually sensitive to AC fields, try another standard sort of cartridge with good shielding (Shure, etc). Also make sure the tt ground wire works by disconnecting it, which should make a lot more noise.

I do have some mu metal if worst case. However, if it were the motor, the noise should increase toward the spindle, which you said was not the case, so this is not proven.
 
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#34
with belt still removed , put record on platter , place needle on record

power on motor , power off

try to conclude - is hum there while motor is powered , or hum is there while motor is still spinning , even without power

if latter , hum is mechanical , not generated by flux

if not later - hum is generated by flux
 
#37
Hi all,

Sorry for the delay (long night in Montreal).

@ Rayma
The noise is audible hum. I clean belt with R2 and the pulley also. I switch my Acutex cartridge (LPM 315) for a Shure (M97ex). And the hum is always present. The ground is ok. Effectively, the sound is less audible near the spindle.

@ Zend Mod
I try all of suggestion and the noise is only audible when the belt is in place and the needle is on the record and the motor is on power. The problem appear to be "mechanical".

@ Rayma
No noise.

After all off the tests you propose, I note a small vibration inside the motor itself... I investigate on this way. I expect now this is not a flux problem but a mechanical problem.

I dismantel my TT this weekend and I investigated.

Many thanks to everybody.
 
#38
cdebien said:
... Thanks for your response... I begin my quest to find a more "rumble" free turntable.
Click to expand...

What Oracle do you have? I have an Oracle Delphi, and there is never any detectable rumble at all. I have played poorly recorded records that exhibit unpleasant low frequencies and rumble, but never rumble from the turntable itself.

I previously had a Music Hall 9.1 that picked up resonance from the speakers when the lid was down (it wasn't stable when left in the up position), which was also amplified through the carbon arm. Your Oracle should be pretty immune to rumble, but if you also put the cover down when playing records, try keeping it in the up position.

However, if you still suspect the turntable is the source, you don't need to find a different turntable in my opinion. Instead, pull the platter and inspect the thrust plate on the bottom of the spindle bearing, the ball bearing on the tip of the spindle, and check the oil level. If it's empty or the thrust plate is bad, you'll get rumble. Also inspect the belt, however, I can't imagine a belt in poor enough condition to transmit noise to the platter would not have broken by now.
 
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