I'm not sure what you mean Raul. Could you restate your last comment?
A Few Turntable Measurements using the RPM Android App
I found this Android phone app for TT rotation. Phone is Pixel 4a. Thought I'd try this app out. I'm skeptical of these phone apps. Accuracy is always an issue.
I have four tables. I took 5 readings for the first table in order to see what the repeatability is. The "absolute" RPM, RPM peak to peak, and 2 sigma range readings were very, very repeatable. Consequtive RPM readings differed by a max of 0.01 RPM. Two sigma varied by 0.01% ( 2 sigma means that 86% of the readings were within the stated value). I personally would use 3 sigma, but that's a personal quibble.
I've measured all four of my tables. I am very certain that the results are very repeatable. I measured with no LP, LP rotating, LP on and Stylus engaged, and phone offset from center. RPM was the same for all cases, The 2 sigma showed a 0.01% rise (really small). The reading at the edge of the LP was different. And scary to do!
Here's the results:
1. DD-40 #1, RPM = 33.32, 2 sigma = 0.07% (63 dB)
2. DD-40 #2, RPM = 33.27, 2 sigma = 0.09% (61 dB)
3. Acoustic Signature WOW XXL, RPM = 33.17, 2 sigma = 0.10% (60 dB). This varied 0.02% from reading to reading (after running the table for 10 minutes, this noise diminishes), but the 2 sigma stayed the same.
4. Denon DP-57L, RPM = 33.25, 2 sigma = 0.02% (74 dB).
I then went back to DD-40 #1. Using the RPM app, I set the mean speed to be 33.25. The strobe on the table was slowly moving! I checked against the strobe on the Cardas test LP and yes, the RPM speed accuracy was wrong. I reset TT speed using the strobe. The RPM app measured 33.23 again. I must conclude that although the RPM app is very repeatable, the absolute accuracy is not. The wow result (2 sigma variation) remains the same.
I measured the 45 RPM on DD-40 #1. RPM = 44.91, 2 sigma = 0.05%, so the 45 RPM is fairly accurate and the 2 sigma is lower.
This app makes no distinction between wow and flutter. It's all reported in the wow reading (wow and flutter are the same thing by nature, the only difference is the frequency range).
I'm surprised by the poor performance of the WOW XXL table. This a modern, belt driven table, with a massive platter. It is 5 years old. There's no way for the user to adjust the RPM. The variation in the speed is similar or slightly higher than the 40+ years old Micro Seiki DD-40 tables, which don't have crystal oscillator driven speed control. The WOW XXL takes about 10 minutes before the very high frequency variations settle. Now, I don't know much about the internal workings of the app. Helpful would be better accuracy (or the AC frequency in my house is not 60 Hz). Bandwidth is not reported.
The DP-57L performance is outstanding!. This TT was made in the 80s. And the DD-40 tables are not bad, but are as good as or better than the WOW XXL.
In summary, in my opinion, the RPM Android App is very useful. The absolute accuracy is a bit off, but the repeatability is very good The wow measurement is also quite good.
- ...
- 76 posts total
Dear @mijostyn : " The comments about the turntable sounding "dull" only for everyone to decide that the reference system was too bright is a characteristic that is legion in high fidelity systems. There is a tendency for us to prefer brighter reproduction, brighter is better. "I don't think that " brigther is better, as a fact the live MUSIC has that " brihtness " characteristic in a Natural way. So there is brighter and " brighter and not always the same word means the same. That " dull " characteristic you mentioned and the reviewer too came from the listening panel and for those old times the reaction of the member of that panel is just normal because when you listen for the first time a LP with vacuum hold-down audiophiles think that that vacuum mechanism suck the sound and from there the " dull " kind of sound but E.Long posted that after some time listening ( he not the panel members. ) to the Sota he was convinced that the sound is not really dull but more " realistic " and I remember that when I bougth the AT666 vacuum stabilizer as an after market item my first impression was exactly that: " dull " and was disappointed with and time latter on I took in count that the sound was nearer to the reality with the room/system I owned in those " times " and that today in many ways is " different. ".
The sibilance issue is a sound characteristic more on female voice and we even listened in some live events and not necessary associated with poor imaging. In the other side we unknow all the recording process of each LP where the sibilance could be developed but on the playback process some phono cartridges tend to sibilance more than others. As with low bass many times room treatment can't make it disappears. To many challenges to defeat in a home systems where exist no perfcetion but the other way around.
R. |
I think that both of you make good points. For 40 years digital has claimed perfection, while getting better every year. It is still too bright for my ears, but an entire generation has been brought up to think that brighter is better. I have noticed that every major improvement to my system, US cleaning, reflex record clamp, Koetsu, air bearings, every one removed copious amounts of high frequency, yet after a few hours, it was obvious that the sound was closer to the concert hall. So I concluded that what I was after was ’smooth’. Raul talks about there being bright in a bad way and bright in a good way, which I also think is quite right. Mijostyn talks about this too. Might both of you be referring to the leading and trailing edges of the signal? Electronically, this performance is dictated by odd-number harmonics (square wave Fourier Series). Unfortunately, distortion of the odd harmonics is notorious for being offensively bright. I think that you are both onto something.
|
Dear @terry9 : MUSIC and MUSIC in a home and its reproduction quality levels belongs to Transient Response. That first MUSIC note and notes attack is what ,for me and my MUSIC life, I think is what defines the step by step MUSIC score we are listen. That transient response obviously develops harmonics. In a room/system where nothing is perfect: where are developed everykind , not only distortions/colorations, of poor transient response according with each system link where something is poor too in some frequency ranges. Your first hand experiences as me and the listening panel in that TT review along the reviewer tell us ( you and me ) exactly the importance of those transient response and what we " losted " through that dull reproduction were only bad distortions right at the " edge " and that now just dissapeared. My last " dull " experience in my system was in the early last year when I decided to change the attenuators/volume in my phonolinepreamp. Years ago I bought those new attenuators that came with the same Swiss mechanism that the ones I used to, difference with the " new " ones is Only that the old ones where builded with true hole resistors and the " new " with SMD resistors. I made the change and was truly dramatic and the first impresion was sad for say the least, yes Dull sound but after a few hours I took again that what I losted were those distortions that normally gives that " over bright " sound. Now those transients are marvelous and obviously puts me nearer to the recording because the brightness is more natural near the live MUSIC brightness. Yes, we are accustom to that wrong brightness. My audio system is full on SS electronics with ( for me ) high resolution . Over brightness lives in many of the audio system links of that system chain. Through the years our ears goes down in its sensitivity and that over brightness is " welcomed " and normally is not our fault till we have that " dull " experiences and then we learn about and take action in that audio room/system. In the other side for several audiophiles that true overbrightness they take as: clarity, transparency and the like when in true are only added distortions what gives that kind of " clarity " and that can happens at both frequency extremes not only in HF.
R.
|
@mijostyn : This was what I posted a few months ago in other thread and was not the first time on that issue:
and this related in other " diferent " thread:
Today on those issues is my overall " take ".
R. |
- 76 posts total