I am happy to report that NFB is still going strong and still producing good work. They have a dedicated streaming app that lets you access their archives for free.
I notice most of the suggested tracks are mostly steady state, which is what you want for measurements, but what about something more bursty? Like a track of tone bursts, or maybe a steady tone in one channel and periodic tone bursts in the other? That could capture some information about cart/arm resonance and it's effect on pitch stability, etc.
Yes!
And, if the repetition rate (or period) for the tone bursts were to be at the mass/compliance resonance frequency, the dynamic variation in stylus drag when alternating between the modulated and unmodulated condition could trigger FM distortion of the steady tone channel. This would be subjectively audible and objectively quantifiable. The observed and measured data from such a test would be useful in evaluating tonearm geometry and tonearm damping, as posted earlier in this thread by myself and LD. The tone burst rep rate could be a slow sweep from say 4Hz to 20Hz, or individual bands of discreet frequencies from 4Hz to 20Hz (easier to use, IMO). There should be a 'Left' channel test band and a 'Right' channel test band. Any performance differences observed between these two bands could reveal mechanical asymmetries in the tonearm design that require attention. I believe these test bands would not be real-estate critical, and would be happy allowing other tests to have priority for the inner or outer portion of the LP.
To my knowledge, no test record previously made or currently available has such a test tone. I understand that the proposed Test LP has to have certain standard reference tones that all test records have, but I am concerned that the group-buy test LP has been drifting towards becoming a ho-hum collection of test tones that I (and others) already have. I vote for giving ourselves test tones that we can't get anywhere else!
Ray K
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My mats are cork, rubber and lead on one and cork and rubber on the either, but I use record weights or clamps depending on arm. The large bearings and unsuspended chassis of the 124s makes weight relatively unimportant. A 1kg - 2.2kg record weight is not going to faze them. The Souther clever clamp is great on suspended tables as it is quite light. I would never play a record without one or the other.
Hi Kevin,
I hear you. That's why I like my sticky mats. It becomes one big mass, and that will not change speed quickly.
As for tone bursts. They would be more valuable as crosstalk information, and even then a steady state tone would be best so you could measure it. For tone arm resonance, you might want various tracks with information at those frequencies. However, once you excite the right frequencies, you might mis-track and damage that section of the test record. There is very probably a better way to do this and it may not depend on a recorded track at all. Even a silent track with the tonearm excited with an external source might damage that section of the record.
Is this a calculated or measured value. If measured, what is the industry accepted way to do this?
-Chris
I hear you. That's why I like my sticky mats. It becomes one big mass, and that will not change speed quickly.
As for tone bursts. They would be more valuable as crosstalk information, and even then a steady state tone would be best so you could measure it. For tone arm resonance, you might want various tracks with information at those frequencies. However, once you excite the right frequencies, you might mis-track and damage that section of the test record. There is very probably a better way to do this and it may not depend on a recorded track at all. Even a silent track with the tonearm excited with an external source might damage that section of the record.
Is this a calculated or measured value. If measured, what is the industry accepted way to do this?
-Chris
The fact that we were able to adjust the VTA through and past serious mistracking with only minutes between plays makes me question some of the mistracking/permanent damage folklore. IMO a large body of the vinyl wear knowledge base is myth.
Hi Scott,
I was thinking if you allowed the stylus to lose contact with the groove, it may well make small impacts on the sides when it makes contact. This would be a problem for a silence groove for signal to noise, or vibration testing.
I don't know, so I thought I would throw it out there.
-Chris
I was thinking if you allowed the stylus to lose contact with the groove, it may well make small impacts on the sides when it makes contact. This would be a problem for a silence groove for signal to noise, or vibration testing.
I don't know, so I thought I would throw it out there.
-Chris
Well I hope not for most folks. One would hope that most people using this have a decent soundcard that they can use with some software, including some written just for this LP. When this gets made will be 18 years into the 21st century, right?
Hi Pano,
People use what they have. I trust my HP 339, but not my sound card for numbers. The RTX will be different of course, but most people will not have one of those. If I had my Leader, I would be constantly adjusting the frequency and phase until it was in rang of the auto function. Even then it takes time to settle and you have to manually downrange. The 339 is a lot more automatic, but I still have to watch it settle, then downrange.
-Chris
People use what they have. I trust my HP 339, but not my sound card for numbers. The RTX will be different of course, but most people will not have one of those. If I had my Leader, I would be constantly adjusting the frequency and phase until it was in rang of the auto function. Even then it takes time to settle and you have to manually downrange. The 339 is a lot more automatic, but I still have to watch it settle, then downrange.
-Chris
I didn't really mean that the tone bursts had to cause mistracking. I think a sudden, fairly high-level tone burst, not necessarily space at arm/cart resonance, can put enough energy into the system to excite a resonance and show pitch modulation. I have heard this on records with a bad scratch, so I assume it would be measurable at somewhat lower excitation levels. One also hears a lot about sudden amplitude changes causing increased stylus drag and momentarily slowing rotational velocity of the platter. I find that unlikely, but I think a test band with, say, a -20dB 1kHz tone and then +6dB bursts at, what, 315 Hz, would reveal whether there was a sudden slowing of the platter. If the effect is real then the track could provide a useful metric.
The arm/cart resonance is stimulated by pretty much anything. Just look at the FFT of any test track and see the hoofing great peak around 10Hz. To look at impulse response B&K took a saw to a record to create a step, certainly beyond anything that can be cut. It's on my list to put a scratch into an unwanted test record to try and see what can be done without getting medieval.
Absolutely correct, so a track with an impulse or tone burst should clearly show fm effects on pitch of a steady tone. Different lp playback systems will exhibit this to different degrees, so I think a track that clearly shows it, without driving the system into mistracking, could be useful. Speaking of which, how is your damping trough coming along? 
We had an HP distortion analyzer at work that I had a chance to buy. It was really nice, but comparing it to my sound card for analysis and for generation, it just wasn't that great. I did like the high output levels. As cool a piece of kit as it was, I passed on buying it for the good price of $100.
There is soooo much that can be done with a modern soundcard and some good software. There are requests for certain special tracks on this LP, like arm resonance, that show up in an FFT of just about any groove. (As mentioned recently). Let the computer and the software be your friend, your very powerful friend.
Me too which is why I only have an Amber 3501A on the bench for very casual THD measurements and primarily as a signal source.
I currently have a loaner QA400 as well, quite a nice little test device.
I have a lab grade Keithley 2002 DMM with 2MHz rms converter that I can use to accurately calibrate the system for gain and for distortion measurements not relative to dBFS. The RTX is calibrated from the factory so for a year at least this will not be a concern.
I have had all sorts of test equipment, but as Scott can attest I do not have a lot of space to spare and anything that gets to stay has to earn the space it occupies.
I currently have a loaner QA400 as well, quite a nice little test device.
I have a lab grade Keithley 2002 DMM with 2MHz rms converter that I can use to accurately calibrate the system for gain and for distortion measurements not relative to dBFS. The RTX is calibrated from the factory so for a year at least this will not be a concern.
I have had all sorts of test equipment, but as Scott can attest I do not have a lot of space to spare and anything that gets to stay has to earn the space it occupies.
Hi Kevin,
You should have bought the instrument !!!
I know what you mean by space. In my case I created the space vertically. Less efficient 19" rack type modules were my choice. Stacked instruments in a pile is what I got away from.
I still find use for some pretty old instruments. I'm even going to restore an HP 3580A, and a 3581. Not for every day use of course!
Hi Scott,
The main difference with the newer instrumentation is money. There are things I have to do and I can't afford the newer gear. Hell, I'm overjoyed when the piece is new enough to say "Agilent" instead of HP. A new "Keysight" generator or 'scope would be dreamland for me, and most others around here.
I get what you are saying, and agree with you. But then that money thing rears it's ugly head. I'm not going to believe I have a current instrument until the RTX actually arrives here and works. I'll pinch myself then.
-Chris
You should have bought the instrument !!!
I know what you mean by space. In my case I created the space vertically. Less efficient 19" rack type modules were my choice. Stacked instruments in a pile is what I got away from.
I still find use for some pretty old instruments. I'm even going to restore an HP 3580A, and a 3581. Not for every day use of course!
Hi Scott,
The main difference with the newer instrumentation is money. There are things I have to do and I can't afford the newer gear. Hell, I'm overjoyed when the piece is new enough to say "Agilent" instead of HP. A new "Keysight" generator or 'scope would be dreamland for me, and most others around here.
I get what you are saying, and agree with you. But then that money thing rears it's ugly head. I'm not going to believe I have a current instrument until the RTX actually arrives here and works. I'll pinch myself then.
-Chris