• Welcome to ASR. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Fun with vinyl measurements

How did you find that!?
I
was given one but the suspension was stiff/dead
 
It seems quite healthy. Remains to be seen if suspension has survived.

IMG_0463.jpeg
 
How did you find that!?
I
was given one but the suspension was stiff/dead
Used at Swedish ReHiFi store. Could not resist.

Measurements are up.
 
Acoustic feedback effect on turntable ...
I put a stationary record on the TT and lowered the stylus onto it. I then play Pink noise from the speakers, while recording the cartridge/pick-up signal. This is what I get

Turntable 1 Michell Gyro SE, SME V AT-OC9MLii at 59db gain /200 ohm. No platter mat used,

1749477409848.png


Then another TT Denon 51F with Shure V15 IV Jico SAS-B at 39db gain /47k added to the plot=blue curves
1749478026617.png
 

Attachments

  • 1749477605750.png
    1749477605750.png
    203.7 KB · Views: 42
  • 1749477784571.png
    1749477784571.png
    212.6 KB · Views: 42
Last edited:
Acoustic feedback effect on turntable ...
I put a stationary record on the TT and lowered the stylus onto it. I then play Pink noise from the speakers, while recording the cartridge/pick-up signal. This is what I get

Turntable 1 Michell Gyro SE, SME V AT-OC9MLii at 59db gain /200 ohm. No platter mat used,

View attachment 456587

Then another TT Denon 51F with Shure V15 IV Jico SAS-B at 39db gain /47k added to the plot=blue curves
View attachment 456590
Did you measure the pink noise SPL above the TT?
 
To find out what compliance / resonance is on a pickup, you need to know what the effective mass of your tonearm is, and what it is with the pickup installed. Usually you take the stated effective mass and add the pickup weight. But effective mass is not just effective mass, is the stated effective mass with the arm balanced with or without the pickup going to make a difference. So to nerd out a little about this, I played around with some math and statics and torque.

It turns out that if you add mass to a balanced arm, the arm must be rebalanced and that entails a change=INCREASE in the effective mass, and after a lot of tinkering and checking and some mistakes and finally correcting the mistake I come up with the following formula:

dEM= Increase in effective mass=CM1+(CM1^2+2*H*CM1)/W

Where:

CM1=PU mass or other change in weight

H= Effective mass of the headshell end of the arm, typically 90 to 95% of the stated effective mass

W= Mass of counterweight

Let's take an example with a stated effective mass of 10 grams and add a pickup of 10 g with screws and all, and a counterweight of two hundred grams (which is quite hefty=high end counterweight)

dEM=10+(10*10+2*(10*0.95)*10)/200=10+1.45=11.45 grams

New effective mass is therefore not 10+10=20 but 10+10+1.45=21.45 grams or a full 3.6% lower resonance frequency, (possibly the same % effect on calculated compliance from test plate resonance Hz). If you have a lighter counterweight, for example 100 grams, the addition is twice as much, almost 3 grams. This may be an explanation for those wondering why the resonance frequency was lower than they thought…


For simplicity I assumed a static balanced arm, but with a static balanced arm the effective mass will be slightly less due to counterweight adjustment, can be calculated from static balance equation…that can amount to 0.2 to 0.3 grams …
There is indeed a lot to worry about regarding vinyl reproduction;)

IMG_7640.jpeg
 
Last edited:
Please report back on the quality.

I will, looks good enough to try it out, Canada was the closest to me and price seems right. I have to confess, btw - Stereophile had an article on the turntables Unitra makes.
Though in my defense, I didn't read the full piece but went to the Unitra website and looked at their products myself, instead.

 
Last edited:
There are two version of the record, standard and lab. they have e good video explaining the content. Looking forward you your review
 
Seems it does not have sweeps for L and R, only L+R.
 
Seems it does not have sweeps for L and R, only L+R.
Haven't found a dealer, from the website of Unitra - that ships the WT-2 or any products from them for that matter, to the US.
I sent an e-mail to Unitra to find out who would be willing to sell and ship. Will take a while longer than I thought, I guess - still on it, though.
 
Fisher MT-6330 turntable speed stability and internal pictures. Not serviced-, but not bad. in fact close to the spec of 0.035 DIN W&F.
(The visual trend and data is very similar to the new Denon 3000NE=
1750094967097.png

It is a good 70usd replacement for my 30usd Sony PS-212 as as kitchen bench TT to try out cartridges and stuff.
Next I will service the simple tings myself , clean pots and set speed control and motor DC bias according to service manual
The slow oscillations once per rev are maybe from too high servo gain, but servo gain is not adjustable as it is on the 6250 model

1750092234756.png

1750092431165.png

img_7673-jpeg.1128045

img_7656-jpeg.1128026



My Denon 51F is serviced and better on speed
1720039710511-png.1036668
 
Last edited:
Back
Top Bottom