[neobop]

Hank,
Wonder why it's not extremely popular?   I think it is.  AT is known for offering great value and the OC9II is no exception.  AT probably sold a ton of them.
http://www.soundstage.com/vinyl/vinyl200711.htm

http://www.positive-feedback.com/Issue52/audio_technica.htm

Some people have it mismatched and this can result:
http://www.vinylengine.com/turntable_forum/viewtopic.php?t=27629

You should be okay with the RB300.  Have an arm height adjuster?  Maybe the arm is already at a good height, but the ML stylus is sensitive to SRA - angle in the groove.  I'd consider an aftermarket adjuster if you don't already have one.  There's an outfit in England, Audiomods that reworks these arms and results are said to be stunning.  Maybe you should get it going first. 
neo

[Hank]

Thanks neobop.  I'm actually considering that Audiomods re-do, with adjustable arm height.

[neobop]

Phase.....

On another thread Toni linked to an interview of Michel Reverchon of Goldmund.  Some interesting stuff here, some about structural grounding/stability and some about resonance immune transistors.   The part about bandwidth and phase integrity in amps got me thinking again about phase. 
http://www.symmetry-systems.co.uk/Images/pdfs/Michel-Reverchon.pdf

The contention is that maintaining phase integrity in an amp or pre requires bandwidth of 2 to 200KHz.  I think this is widely accepted even if the need for such is disputed.  Further, an amp requires a bandwidth out to 2MHz to insure correct arrival time from the speakers.  Lots of energy storage from an amp and low output impedance makes the speakers play and controls diaphragm movements, but most amps are limited by their current/voltage capabilities. 

Interesting stuff, but what's this have to do with your source? 
Much of this thread has been about phase integrity in carts.  Ortofon claimed that phase was responsible for spectacular imaging in an undamped MC.  Increased high frequency amplitude response might have contributed, but now I think they're mostly right. 

In an old thread about phase (the one in which Scotty introduced his inductance canceller) we site examples of the importance of phase/arrival time on location clues - hearing research supports this along with our inability to hear relatively greater amplitude errors. 

We know that mechanical resonance/damping defines phase performance of MCs, not electrical resonance.  It's my contention that mechanical also defines it in MMs, only it's modified by electrical resonance.  If we look at the world's only known measurement of phase in carts, why is there no MM resonance (phase) peak at 10 or 12KHz ?  Were all 5 test carts low inductance models?  Not likely.  EE's tell us it's impossible not to have a phase shift at electrical resonance, so where is it, why doesn't it show up on the test?  If you use a SUT why isn't phase hopelessly compromised?  A SUT is nothing but a big inductor with a ton of capacitance at the output, plugged into a MM input.   

If worst case MM phase nonlinearity extends down to approx. 1KHz, and MC200 is to approx. 8KHz, what's the big deal?  1KHz is a critical upper mid frequency and 8KHz is above the primary frequency of musical tones.  Increased amplitude combined with + phase response above 8KHz adds sparkle and can compensate for high frequency losses.  Put a very short or boron/beryllium cantilever on a low inductance MM, and MC200 phase response can be equaled or bettered, depending.
neo

[dlaloum]

You don't have to be extreme about the inductance... you just need to have an inductance/capacitance/resistance combination that doesn't generate a resonance in the audio band - if the rolloff is below critical (ie no resonance just a gentle roll off) - then it can even be within the audio band without generating a big phase change peak.

With 150pf the AT MM's will do fine, as will a range of other MM's.

And the MC200 cantilever is a solid boron rod so pretty similar to the AT150MLx, and the MC200 does not sport a particularly short cantilever.

I think something like the ATML series  with the shorter cantilevers might be superior to the MC200....

The fly in the ointment is perhaps damping - at this point I don't properly understand the interaction between phase and damping - if it is minimum phase, then no big deal, but I have a sneaky suspicion that the reason damping has such a negative impact on sound is due to its phase behaviour being something else....

[neobop]

When you dampen a tonearm what happens to low frequency resonance?  Amplitude of resonance is diminished, but spread over a wider frequency band.
Amplitude of a phase shift is still going to approach 180° but affected area increases.
When the MC200 was damped, the phase discrepancy peak went higher in frequency, but spread over a wider band.  Undamped, the peak was narrow and stayed above the audio band.  Carts must be dampened to control cantilever movement and amplitude response, and the article said that MMs are more heavily damped.  But MM damping was already built into those plots. 

What about carts with tubular boron cantilever or little or no cantilever?  There are some carts with response to 100KHz and even with damping should have no phase shift within the audio band.  Carts with 6mm aluminum cantilevers are going to have phase response similar to the MMs in the report, regardless of whether MM or MC. 
neo

[neobop]

Here it is - lowest tip mass in the known world, so low it's in negative numbers.   

Faster than a speeding bullet.....

http://app.audiogon.com/listings/cartridges-technics-epc-100c-mk-iv-cartridge-king-of-mm-mega-rare-spu-2014-10-25-analog

neo

[neobop]

TOTL AT MM specs:

AT-ML140, 150, 170
impedance 2.5K ohm
inductance 380mH
output 4mV

AT180
impedance 1.4K ohm
inductance 240mH
output 4mV

150 is beryllium/ML   
170, 180 is boron/ML

Curious thing about the AT23, 24 etc.  They all had elliptical tips and were never considered top.  I guess inductance was too low to be practical.
Thanks to Timeltel (Agon) for the specs.
neo

[dlaloum]

Interesting that the top models were Boron rather than Beryllium.... (were they tubes rather than rods?)

On the subject of the AT22 to AT25, although they were all eliptical, their upmarket signet twins had ML's at the top of the line...

The AT22-25 and TK9/10 were a generation earlier, they were more expensive to make due to having true torroidal construction... all the rest of the VM series have always used para-torroidal design - so the earlier generation were magnetically superior - but the difference may have been very minor.

The shorter cantilever on the ATML series made a bigger difference I think, than the torroidal structure on the earlier series...

Seems to me the ATML180 is up there as one of the all time greats.

My own measurements of the TK9 show a noticeable midrange trough (not  a bad one, but not the best I have seen either) - which is caused (I think) by a combination of magnetic losses and cantilever flex losses - the low inductance is reflected in the high end rise to a resonance beyond the audio range (cannot recall right now the frequency - would have to look up my measurements).

The higher inductance of the ATML allows it to achieve a flatter frequency response at the high end - would love to get my hands on one to measure - and see what the midrange trough looks like... I have a feeling it will/would do better than the earlier series or the AT150 - mostly due to the shorter cantilever.

In the Stantering family, the D7500 stylus shows a 3db trough when fitted to a high inductance body, and a 1db trough when fitted to a low inductance body... so magnetic differences can be quite substantial (and get worse as signal rises - the test tracks are at -20db) - the trade off is the flatter overall frequency response with reduced high end rise.... But given the greater importance of the midrange, the XLZ body ends up sounding better than the high inductance XSV... although on the chart, the XSV looks better/flatter.

[neobop]

Sorry, I get the Pickering designations mixed up.  XLZ is low output, low inductance and XSV is regular output like the 3000 or 4000 ?
Is there another series with 3000, 4000 etc ? 

I was looking at the specs (what there is) of the 22 - 25, and was thinking there's no way these could be 85mH.   A toroidal coil is just a more efficient coil with less field?  Inductance should be appropriate value for magnets and output.  Did I remember this wrong?
neo

[Grbluen]

Neo,
I haven't heard much about your explorations with the Signet.  Have you abandoned this one?

[neobop]

Hi Don grb,
You mean the MR 5.0ML ?  The body turned out to be a dud.  It'd decidedly uninvolving.  The stylus sounds great on my 440.  Those two have the same specs, but the Signet was too far off.  I got it for the stylus anyway.  I'm thinking of getting a 100E to play with a 350mH body.  I've been using the 15/20SS and the Genesis, so it's not urgent. 
I'm waiting for a settlement to purchase a few things.  What I really want is a Teres Verus motor/controller for my Sapphire.  It needs a new subchassis and I waited this long so I can wait some more.  If I get the Verus I'll probably have the subchassis machined out of steel or aluminum.  I'll add MDF and lead sheet.  I'll have to incorporate the motor and redesign the armboard and support.  If and when I get to it, I'll post it. 

Get any new carts lately?
neo

[Grbluen]

Neo, I've been away from the hobby for awhile.I've an obstacle with the drive system on my Scout, and I can't seem to get it solved to my satisfaction. I don't listen much, but I do try to keep tabs on the forums.

Grb

[dlaloum]

Sorry, I get the Pickering designations mixed up.  XLZ is low output, low inductance and XSV is regular output like the 3000 or 4000 ?
Is there another series with 3000, 4000 etc ? 

I was looking at the specs (what there is) of the 22 - 25, and was thinking there's no way these could be 85mH.   A toroidal coil is just a more efficient coil with less field?  Inductance should be appropriate value for magnets and output.  Did I remember this wrong?
neo

XLZ is low output low inductace, XSV is regular and yes it is an XSV3000.

I measured the 22-25's and TK9/10 at very close to the 85mH spec (Tk9 was 87.6mH)
Impedance spec was 240ohm, and I measured 227.8 ohm.

Yes it is a more efficient magnetic system, which mean reduced eddy currents, hysteresis, increased linearity - all the good things... also possibly improved wire/coil consistency as per the previous discussion.

[neobop]

Neo, I've been away from the hobby for awhile.I've an obstacle with the drive system on my Scout, and I can't seem to get it solved to my satisfaction. I don't listen much, but I do try to keep tabs on the forums.
Grb

Sorry to read that.  Is it the motor, platter wobble or main bearing?   Aren't you using a recording tape belt?   Why don't you tell us about it?  I have a friend who's a VPI dealer.  Maybe I can get you a part or something (I get a discount).  If it's speed stability there are some new AC motor controllers that might be a hair cheaper than SDS.  Sometimes there are little tricks to figuring out, or solving problems.  If you feel like it, we're glad to possibly help.
neo

[Grbluen]

Neo, I'm struggling with the capstan that I'd made in the machine shop at work during lunch. The piece was fabricated fairly quickly, and it hinted that I was on the right track. The runout is unacceptable, and subsequent attempts have been disastrous. The motor has been changed to a Premotec which has much lower torque compared to the Hurst which was OEM. I've added mass to the platter to give it more of the flywheel effect. I just don't have access to equipment which would allow me to fabricate the capstan to acceptable specs. I prefer the new system to the motor that came with the Scout!

Grb

[Grbluen]

With regard to the controllers, I'd agree. I'm not happy with the prospects of the SDS. I think you really need to do more than lower the voltage to the motor to really optimize the system. But, I have to solve the runout problem first!

[a.wayne]

What material are you using to make the capstan ....?

[Grbluen]

I'm using Delrin. I should add that the lathes and mills were given to our department because they were unsuitable to the other departments!

[a.wayne]

Yes i suspected it was delrin , its too soft hence it wont true up , there is a certain hardeness  required the one you have is too soft, i do  recall different levels of hardness with delrin for machining ...


Regards

[neobop]

Grb,
I don't know much about fabricating capstans, but I saw that Premotec makes some motors designed for turntables.  Couldn't you buy a capstan the appropriate size?   If you increase platter mass you might need the extra torque, depending on how much mass. 

I saw a few companies like Newark Electronics that sell these motors, but I didn't find capstans.
neo