Thanks Scott
I have some homework to do on Audacity Nyquist plug-in (I have never used it)
May be.
I have to tell you that the 48dB/oct I showed before, was the result of using the ready made cross-over slope and not bi quads cascaded in advanced mode
The top flat is less than 1Hz wide, i.e. very good rotational velocity stability.
The arm/ cart resonance is very well controlled (side bands at approx +/-14Hz from 1kHz are just visible)
It seems you have sampled at 96kHz, yes?
This speed accuracy is very good for a synchronous motor/belt driven TT.
My TD160 was 1.7% fast.
I had to tape the sub platter outer diameter for to bring the speed within proper rpm (0.2% low).
By using a thinner tape, one can go closer to 0% difference (then monitor the harmonics instead of the main test tone for better estimation of frequency deviation )
For Fs=96kHz and N=862448 , fifth FFT bin matches your 0.556555294Hz to the fifth decimal point.
Placing the frequency of interest as centrally to an FFT bin as possible is important.
I have become interested on the issue and I will open another thread to discuss this FFT related topic, for not to corrupt this pure analog thread.
George
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For a very affordable turntable that looks pretty impressive.
As the Berkshire dumping ground for abandoned projects I've recently been given a couple more boxes which includes some acrylic sheet. Need to start working out how to make a front damping trough out of it.
Somehow I managed to remove quotes while editing post # 101, making it incomprehensive.
My apologies. It was meant to be like this:
Thanks Scott
I have some homework to do on Audacity Nyquist plug-in (I have never used it)
May be.
I have to tell you that the 48dB/oct I showed before, was the result of using the ready made cross-over slope and not bi quads cascaded in advanced mode
The top flat is less than 1Hz wide, i.e. very good rotational velocity stability.
The arm/ cart resonance is very well controlled (side bands at approx +/-14Hz from 1kHz are just visible)
It seems you have sampled at 96kHz, yes?
This speed accuracy is very good for a synchronous motor/belt driven TT.
My TD160 was 1.7% fast.
I had to tape the sub platter outer diameter for to bring the speed within proper rpm (0.2% low).
By using a thinner tape, one can go closer to 0% difference (then monitor the harmonics instead of the main test tone for better estimation of frequency deviation )
For Fs=96kHz and N=862448 , fifth FFT bin matches your 0.556555294Hz to the fifth decimal point.
Placing the frequency of interest as centrally to an FFT bin as possible is important.
I have become interested on the issue and I will open another thread to discuss this FFT related topic, for not to corrupt this pure analog thread.
George
My apologies. It was meant to be like this:Thanks Scott
I have some homework to do on Audacity Nyquist plug-in (I have never used it)
May be.
I have to tell you that the 48dB/oct I showed before, was the result of using the ready made cross-over slope and not bi quads cascaded in advanced mode
The top flat is less than 1Hz wide, i.e. very good rotational velocity stability.
The arm/ cart resonance is very well controlled (side bands at approx +/-14Hz from 1kHz are just visible)
It seems you have sampled at 96kHz, yes?
This speed accuracy is very good for a synchronous motor/belt driven TT.
My TD160 was 1.7% fast.
I had to tape the sub platter outer diameter for to bring the speed within proper rpm (0.2% low).
By using a thinner tape, one can go closer to 0% difference (then monitor the harmonics instead of the main test tone for better estimation of frequency deviation )
For Fs=96kHz and N=862448 , fifth FFT bin matches your 0.556555294Hz to the fifth decimal point.
Placing the frequency of interest as centrally to an FFT bin as possible is important.
I have become interested on the issue and I will open another thread to discuss this FFT related topic, for not to corrupt this pure analog thread.
George
Nice to hear I am not the only one running such an operation. A lot of unloved stuff ends up here, once in a while there is a gem or two.. lol
I will second the comment on the turntable, quite decent at the price.
Right here in Woburn, I've been tempted to go over at lunch and say hi. It is an interesting exercise in minimalism especially the tone arm which harks back to the original AR. A piece of tubing from smallparts.com and plastic fittings.
wasn't sure whether to put this here or in the rim damping thread, but here goes
John Crabbe: Firebrand Page 4 | Stereophile.com
An interview with John Crabbe where he discusses the fact that if you play a record you can pick up the vibrations with another cartridge on a silent groove. I can see from this why he so loved the VST-V !
But does open up another area where we might need to look at vibrations.
John Crabbe: Firebrand Page 4 | Stereophile.com
An interview with John Crabbe where he discusses the fact that if you play a record you can pick up the vibrations with another cartridge on a silent groove. I can see from this why he so loved the VST-V !
But does open up another area where we might need to look at vibrations.
I've heard the record brush sing, but had not thought about it getting picked up by the cart.
Damping the vibration of the vinyl LP
Billshurv,
It does appear to be another locus for controlling unwanted vibration. John Crabbe’s results show that the stylus excites the vinyl LP to a degree that may be audible at playback. Vinyl has more internal damping than metals (such as aluminium) but it is evidently it is not enough to convert as much of that vibration as we might wish to low-grade heat - it needs help.
Short of re-engineering the chemistry of the vinyl (I am not sure how that might work, let alone its practicality) attention has focused on the capacity of the platter mat to dampen vibration in the LP. There are DIY tweaks such as the Janus platter mat on TNT Audio (Janus: DIY turntable mat) and commercial offerings like Ringmat (Ringmat Developments - The Story of Ringmat).
I wonder if any forum members have results and/or measurements that show the effectiveness (or otherwise) of platter mat damping of vinyl excitation (as distinct from platter mat isolation of the vibration produced by the rotational machinery).
Billshurv,
It does appear to be another locus for controlling unwanted vibration. John Crabbe’s results show that the stylus excites the vinyl LP to a degree that may be audible at playback. Vinyl has more internal damping than metals (such as aluminium) but it is evidently it is not enough to convert as much of that vibration as we might wish to low-grade heat - it needs help.
Short of re-engineering the chemistry of the vinyl (I am not sure how that might work, let alone its practicality) attention has focused on the capacity of the platter mat to dampen vibration in the LP. There are DIY tweaks such as the Janus platter mat on TNT Audio (Janus: DIY turntable mat) and commercial offerings like Ringmat (Ringmat Developments - The Story of Ringmat).
I wonder if any forum members have results and/or measurements that show the effectiveness (or otherwise) of platter mat damping of vinyl excitation (as distinct from platter mat isolation of the vibration produced by the rotational machinery).
I can't remember seeing in this thread any reference or comment on the fact that although most early vinyl records were pressed on 'virgin' vinyl stock, a point came when many many labels began to use re-cycled vinyl.
I knew many people in both UK broadcasting and record companies who at that time were quite convinced that this use of re-cycled stock was responsible for a sudden downturn in record sound quality in the later 70s.
[Others blamed the ever increasing use of compression.]
I knew many people in both UK broadcasting and record companies who at that time were quite convinced that this use of re-cycled stock was responsible for a sudden downturn in record sound quality in the later 70s.
[Others blamed the ever increasing use of compression.]
@bondini: Would certainly be interesting to test. I don't currently have a research turntable setup to do that with 2 Arms, but would love have an excuse to build one!
@brianco: The 74 oil crisis has been blamed for some crappy stuff. And of course the dynaflex disks. Not sure it affects what we are talking about here.
Down with Dynagroove! | Stereophile.com does contain a fine JGH rant on dynagroove, although he does at the end accept that the pre-distortion they add seems to work.
@brianco: The 74 oil crisis has been blamed for some crappy stuff. And of course the dynaflex disks. Not sure it affects what we are talking about here.
Down with Dynagroove! | Stereophile.com does contain a fine JGH rant on dynagroove, although he does at the end accept that the pre-distortion they add seems to work.
There was a LOT of complaining about bad vinyl in the 70s. Then CDs came along and no one cared any more. The LPs I own from the 50s and early 60s are lovely, solid things. From the 70s and 80s? Floppy dishrags. Although some skimpy vinyl sounds OK.
I'd love to see some tests of the anti-vibration mats. Do they quell the stylus induced vibrations?
The LPs I own from the 50s and early 60s are lovely, solid things. From the 70s and 80s? Floppy dishrags. Although some skimpy vinyl sounds OK.I'd love to see some tests of the anti-vibration mats. Do they quell the stylus induced vibrations?
Waking this thread back up as I have been collecting parts for experimentation. I now have most of the cheaply available DD motor types from the 70s/80s to mess around with against some new drive techniques to see what I can find. Turns out there has been quite a lot of work in improving BLDC over the last 10-15 years, some for reducing component count and some for reducing noise as noise in spinny things appears to be a big thing.
Looking back at George's plots and how much cleaner the JVC turntable is I realise now that is only a 2-phase motor. I have a Sony with the same motor (well actually I just have the motor now) but run off a 70s Floppy disk controller chip! this makes it worth getting that setup as well as the 3-phase pancake I just won on ebay.
I have a suspicion that wimpy DD may be the way to go. Whilst hitting lock in a 1/4 turn is handy for DJs I'm not sure it matters much to us other than a party trick!
Looking back at George's plots and how much cleaner the JVC turntable is I realise now that is only a 2-phase motor. I have a Sony with the same motor (well actually I just have the motor now) but run off a 70s Floppy disk controller chip! this makes it worth getting that setup as well as the 3-phase pancake I just won on ebay.
I have a suspicion that wimpy DD may be the way to go. Whilst hitting lock in a 1/4 turn is handy for DJs I'm not sure it matters much to us other than a party trick!
Question, probably for George or Scott. Doing more research I mused about the benefits of getting a Feikert test record, although the PC software is a bit of a stretch for stuff that can be mainly done in audacity. Anyway decided to hunt for any technics DD measurements and found this
Archimago's Musings: MEASUREMENTS: Technics SL-1200 M3D Wow & Flutter - PlatterSpeed + Dr. Feickert's Test LP...
And got myself confused. What it looks like is that you have the 8Hz cartridge resonance being modulated by the 0.55Hz record eccentricity on top of the 3150Hz signal. If this is correct (and it very possibly isn't) I have no idea how the LPF the SW puts in around 1Hz removes the 8Hz signal...
What I can't be sure about is if there is any evidence of motor effects there.
@George: Did you ever start a thread on analytical techniques with Audacity?
Archimago's Musings: MEASUREMENTS: Technics SL-1200 M3D Wow & Flutter - PlatterSpeed + Dr. Feickert's Test LP...
And got myself confused. What it looks like is that you have the 8Hz cartridge resonance being modulated by the 0.55Hz record eccentricity on top of the 3150Hz signal. If this is correct (and it very possibly isn't) I have no idea how the LPF the SW puts in around 1Hz removes the 8Hz signal...
What I can't be sure about is if there is any evidence of motor effects there.
@George: Did you ever start a thread on analytical techniques with Audacity?
For anyone (in addition to me) interested in the FFT thread, I hunted it down, the thread title is "Getting the Numbers Right" and here is the link to it:
http://www.diyaudio.com/forums/software-tools/287089-getting-numbers-right.html
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