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Grab Luckydog's experimental spreadsheet (VinylEngine near zero capacitance thread) - plug in the cartridge spec inductance, and your load parameters (C, R, I) - remember to set it to 35% reduction factor (the model is still being refined and that seems to be about the right factor for those cartridges measured to date .... which has yet to include a Grado)Good luck with itDavid
Hey everyone,Here is a plot of the frequency response curve of my turntable using Dr. Feickert's Adjust+ software to measure. I'm wondering why this curve is non-flat (peaking more at the high end, with the downward slope from 20-10k). I would figure that a properly aligned turntable with a decent cartridge & preamp could produce a relatively flat curve. Any ideas what device / configuration might be causing this?To measure the curve, you plug the RCAs from the preamp's output into the 1/8 line input on your computer. This means that the cause has to be somewhere between the turntable source and the preamp's output (can't be main amp, speaker wires, speakers, etc.).Gear:-Grado Gold cartridge/stylus-Project Xpression III turntable-DH Labs BL-1 interconnects-Graham Slee Reflex preamp-Standard power supply for preamp-Pro-ject speed box-Gear for calibrating turntable -Feickert protractor -Feickert adjust+ software (to align azimuth) -Pro-ject digital force tracking gauge -A bubble level for VTA -A bubble level for the turntableAs far as I can tell, the turntable is calibrated correctly, but maybe I'm missing something in the calibration that's causing the non-flat frequency response curve, or maybe I need to upgrade a component.Any thoughts / help?Thanks,-Clayton
Neo brought up another thing that reminded me of some other offerings. As Neo stated, the rise in low frequencies is down there in the mechanical noise area, as well as the evil motor hum (60 cycle) and looking at the curve, those elements could easily be the culprit, as well as hum induced noise into the Grado (tho in this case, my be minimal). Using plasticlay will lower the fundamental resonance frequency of the table plinth, of course, other "loose" elements may be also vibrating either in harmony with the motor noise or bearing noise or worse, what ever is being played on the TT. I have found that placing a 1/8" diameter, then flattened out to about 1/16" thick piece of plasticlay about 2" down from the tonearm pivot, on the tonearm tube itself, really reduces inducted tonearm noise, from either end it seems. It's a very cheap tonearm damper, but will not rob the tonearm of needed response or energy intended for the cartridge. Just to make it even more confusing......Wayner
In the end, I found that the best tools for alignment are your ears, a mono album, and a small bubble level to place on top of the tonearm to use as a reference for azimuth and VTA.
I think that a check on SRA (stylus rake angle) may be in order. Grado states that the front face of the cartridge be at 90° to the record surface, but after Mikey Fremer's article in Stereophile regarding SRA, I talked to the folks at Grado (we are a dealer) and they agreed that the 92° SRA would be beneficial. That means, the tail end of the tone arm is up in the air. The inclusive angle from the front of the cartridge to the record surface now should be at 88° (92° the exclusive angle). On a normal 9" tonearm, 1 mm of VTA adjustment (raising the tonearm base) equates to .25°. So once you have put the arm in a parallel position, and using that position as a point of reference (it becomes zero), you would have to raise it an additional 8 mm. Looks kind of funny, but it does work. It may flatten your response, but at the least will give your stylus a better contact area with the record grooves (less wear too).Wayner
