Turnable database with TimeLine

I had my turntable dismantled the last couple of days. I found some bushings at the hardware store that slip over the threaded studs supporting the main chassis. The sub chassis has holes for the studs to go through. These bushings that I found were 1mm smaller in diameter than the holes in the sub chassis. This made them a perfect fit. Where the sub chassis used to cycle up and down several times if pushed (underdamped) it now moves back to position in one cycle (critically damped). I was concerned that the sticktion was too much but using a level on the platter; the sub chassis seems to move back to the correct position every time. I have very good isolation of the whole turntable. I had developed the isolation last year which made a considerable improvement. That surprised me since the turntable is a suspended design and I thought was already well isolated.

I put my turntable back together and set it up to play this evening. After dialing in speed I started listening to some records. The iPhone app showed speed was off by 0.1Hz out of 3150Hz. WoW&Flutter at +/-0.02%. After dialing in 33 and 45 rpm I started playing some music. Right away I was bothered by the difference in the highs. I realized that they are cleaner now, which makes the highs like cymbals more apparent. It took me a couple of records to get used to them. The whole character of my turntable has changed. Nothing has been lost as far as I can tell. The soundstage is more airy. The detail and clarity of the highs are startling. Imaging is more focused. I can't say I hear a difference in rhythm and pace. I don't think speed was off by that much before. The improved speed control seems have affected more subtle things about the music. I have now experienced things that several people have said would happen with improved speed control. Constant belt tension even under micro conditions such as stylus drag is critical. I am a believer now.

I forgot to mention that nearly all play in the horizontal plane has been eliminated. The added bushings took up that horizontal play. Corresponding to this is increased damping of motion in the vertical direction. Like I was saying- before if I pushed on the platter, it would bounce up and down for several cycles. Now it moves back to position in one cycle.

That is awesome, Tony. Congratulations on your efforts. They seem to have paid off. What you say about the highs frequencies, like what you hear with cymbals, is so true. I too was startled when I added isolation to what I thought was already a well isolation turntable design.

Could you share the information about the iPhone app? And which 3150Hz LP band do you use? I think I've missed this if you discussed it earlier. Thanks.

It is the Dr. Feickert iPhone app. It requires a test record with a 3150Hz test tone, or now the app will also recognize a 1000Hz test tone. I happened to have a test record with the 3150Hz test tone; but Dr. Feickert's test record can be purchased at their online shop.

I think this app is excellent. Just start playing the test tone and the app will react to the tone and ask to start recording. It plots frequency versus time and has a bar at the top that helps you to dial in speed. Once you save a plot the app analyzes the data and gives you average speed, raw WoW&Flutter as well as filtered Wow&Flutter. It is easy to filter out the record's contribution to WoW&Flutter due to eccentricity of the center hole since the period is 1.8 seconds. But the app does all that for you. The filtered plot shows you raw and filtered frequency over time. For example, my record gives a frequency plot with the peaks going from 3160Hz down to 3140Hz (my test record center hole is not very well placed). The filtered line or the actual tt performance shows shows frequency right on 3150Hz with slight waves about that line. That is the +/-0.02% or -0.6HZ/-0.7Hz variation that the chart shows me.
I tried this app with my CD player too. I had a test disc with a 1000Hz tone. The app showed a perfect flat line at 1000Hz with WoW&Flutter at 0%.

Just for the sake of argument about calibration of the iPhone's microphone. I downloaded an FFT app a few years ago. FFT is a method of analyzing a noise spectrum. It plots frequency vs. amplitude. I was at an automaker's NVH lab one day a few years back. This is a Hemianechoic chamber for measuring noise levels and frequency on a car. (If you are amazed at how quiet your car is, then I may have had a little something to do with that on one little component. If you are not too pleased with the sounds your car makes, well then someone else must have worked on that model). They had their B&K calibrated test tone source used for verifying microphone amplitude calibration sitting there. It generates a 1000Hz tone. So I turned it on and checked my iPhone's calibration (just for frequency, not amplitude). The app was dead on. These apps utilize the iPhone's internal oscillator/clock for calibration. Frequency accuracy should not be a problem for an iPhone app; but amplitude (SPL) is a different matter. I would not count on the iPhone's mic for exact amplitude measurements.