Originally Posted by
Primalsea
Im not too sure that the set up is optimal for measuring bearing noise...
Do you have some kind of solid puck that you could sit next to the platter and lower the stylus onto it so that any vibrations can be transferred from the body of the TT into the stylus?
Using a test record you would need to isolate the noise from the record surface and the phono stage and this will most likely be quite broadband. Audacity has filters that you can apply. You could try a 250 hz lowpass filter to start with. You should maybe also apply a reverse RIAA too.
Another option could be to place a mic on the TT close to the bearing. You can also buy stethoscopes on Amazon for a few quid. These actually work and are great for a bit of roll play as well
I agree. I don't honestly think that my preference are set up correctly. If you have any hints, tips or suggestions I would be eternally grateful. Well I don't think we can isolate noise from the records surface, that's always going to be there and using a filter might be a good alternative, but can you explain why I specifically need a 250Hz lowpass filter. In fact what is a loss pass filter? I understand what a reverse RIAA is and I can see where this is useful but at the moment I'd just like to keep things simple and then start more complex as my knowledge increases.
Originally Posted by
cre009
Hopefully find attached some spectral views from a couple of transfers I did earlier this summer for comparison. The views are for a few seconds from the start including the lead in grooves to where the music starts. The LP was an old bootleg with a fair degree of surface noise.
The first image was for a transfer using an LP12/Ekos/AT-F7 into a Nakamichi CA5E preamp. The second was for an AR XA with Linn K9 into a Kinshaw Perception SA phono stage.
The LP12 version starts with just the phono stage hiss followed by a thump/clicks when the tonearm is lowered onto the record. There is then a degree of noise due to vinyl roar and crackle and towards the right the music starts to fade in. For the XA version there is some horizontal banding mixed with the hiss. This banding is a very low level hum that is only audible if I turn the volume to max but has proven annoyingly stubborn to remove. Rumble if present would be most pronounced and visible at the lower frequencies during the lead in.
[IMG]
[/IMG]
[IMG]
[/IMG]
Many thanks. These are the sorts of things I'm interested in. And it explains quite a few things, if you have any others please post them.
Originally Posted by
Barry
The spectrogram shows a noise/rumble level of better than -27dB. But what is 0dB? Is there a test tone of a known reference level available?
As it stands a rumble level of -27dB is not that good. One would expect an unweighted rumble figure of -40dB or more.
Barry, as ever thanks for your input. My knowledge is limited but getting better. I now know that 23Hz is where the motor can be found 5-10 Hz is the tonearm and 50/60 Hz the mains supply. I'm also led to believe that 2nd harmonics from the mains supply can occur at 100-120 Hz range. So I now know that I have to produce a Spectral analysis of between 0-120Hz if I want to see information with respects to these turntable components. Do you know of any other specific Hz ranges which would be of interest? Does the bearing have a Hz range for example? Finally I'm a little confused with respects to dB ranges. Am I correct in saying that a (-) value i.e. -50db is better than a +50db for example?
I wonder if I could ask another questions (SORRY). Lets say if I wanted to assess the effects of a new upgrade to the turntable. Please correct my methodology if I'm wrong. I would need to first measure the old components Hz range and dB levels then compare the same Hz and dB range against that of the new component. I large -dB value would indicate an improvement in vibration reduction whilst an increase into the +db range would indicate the opposite?
SS
CD Teac VRDS25X(Audiotuned) DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10
VALVE
PRE Croft Epoch(Modded) AMP Sondex S100 (Modded) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Ref XO + Batpure supertweeters DECK Garrard 301 Mat Teunto Bearings 401(Bastin) Plinth Bamboo Arms 3009/3012 PSU Eagle+Tachometer MC Ag Meister II/FGS + Ortofon SPU MONO CABLES Arm Yannis 420.5 Litz+ SpeakerPC Tripple C+WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostages Paradise(4 Box Mega-Modded) / Croft Musicmaker