Trade: Wakefield Turntables
Location: Yorkshire
Posts: 9,321
I'm Andrew.
Interpreting spectrum analysis
This is my first attempt at trying to measure bearing rumble and I need some help. Ideally I'd just like to be able to say that my bearing has X number of dB but how the heck do you interpret this ?
Untitled.jpg
I used Audacity (Nov 2nd release) with a brand new Hi-Fi news analouge test LP, track 6 from size 2. This was a 20 second grab using the U-Phono UFO202. I selected the data went into the ANALYZE tab and then plotted this spectrum. Hopefully I did things ok.
Any ideas?
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
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Fount Master & Moderator
Location: Essex
Posts: 31,976
I'm openingabottleofwine.
Image not working for me.
Barry
Trade: Wakefield Turntables
Location: Yorkshire
Posts: 9,321
I'm Andrew.
try again!
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
Fount Master & Moderator
Location: Essex
Posts: 31,976
I'm openingabottleofwine.
What is the reference level?
Barry
Trade: Wakefield Turntables
Location: Yorkshire
Posts: 9,321
I'm Andrew.
Barry, I'm not sure what you mean, sorry! I must admit that Audacity is a little more complicated than I first thought and I think my preferences and Hz range were way off. I shall post some more, hopefully, meaningful plots over the next few days.
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
Trade: Beresford Media & Electronics
Location: http://www.homehifi.co.uk
Posts: 6,288
Did you lubricate the bearings before taking that measurement? And if not, what about taking a couple of measurements before and after the lubrication? That would be a good way to see what the effects of lubrication are.
As for the graph itself, first impressions are that the bearing has the worst noise performance at about 100Hz.
If you are interested in the IEC specs and how measurements are interpreted, see http://www7a.biglobe.ne.jp/~yosh/recspecs.htm
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Trade: Wakefield Turntables
Location: Yorkshire
Posts: 9,321
I'm Andrew.
The bearing is in pretty good nick. The plot was just something that I produced to make sure the software and hardware were working, no thought went into preference selection so for all I know the plot could be a load of rubbish. I've done a little more research and understand things a little better now. Thanks for the link that information looks invaluable. I need to understand which bits of the turntable "get excited" like tonearms, motors, IEC mains etc. I'm getting their (VERY SLOWLY)!!!!Originally Posted by StanleyB
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
Senior Member
Location: Bristol
Posts: 111
I'm Clive.
I have no doubt the link provided by StanleyB will provide a lot of useful information but for myself I would start by just comparing spectral views for different decks. By spectral view I mean an overview of the track that shows the spectrogram over time. I think the audacity image shown above is just a very brief snapshot. Towards the left will be low frequency sounds associated with the stylus moving on the grooves but will include other low frequency noise such as rumble if present. Towards the right of the image will be higher frequency noise probably dominated by phono stage hiss.
As an iZotope RX user I find the spectral views provided by that software are a really good way of visualising whether different decks (and phono stages with or without subsonic filters) are producing artefacts. Unfortunately even the entry level of RX is expensive. Not sure if Audacity does that kind of view without crawling through the manual. The freeware Ocenaudio does however readily provide an equivalent view that would do the same job of visualising the artefacts as in iZotope RX.
Pishanto Specialist & Super-Daftee
Location: Dagenham Essex
Posts: 11,215
I'm Allen.
Looks mighty confusing to me
[
Senior Member
Location: Suffolk, UK
Posts: 1,473
I'm Paul.
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
~Paul~
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