Lots of smart EE with ears have tackled the SG equalizer equation and sonics, Iverson comes to mind…
Dustcover Blues
Most of you probably know that I have always championed the use of dustcovers on turntables even during play, the goal being to protect the record from the environment and shield it from sound. For the first time in my audio career I have stumbled into a problem with this and other than not putting the dustcover down I have not come up with a solution.
Yesterday I was playing Herbie Hancock's Secrets and I cranked it on my favotite song. After about 30 seconds the room started to rumble. My subs were putting out a remarkably clean 20 Hz as if I were playing a test tone. Feedback! Just turn the volume down a little and it disappears. Turn the volume back up and within 30 seconds it starts up again. Did I screw up my cartridge set up? I veiwed the tonearm during the feedback and it was rock solid. Usually with low frequency feedback you can see the tonearm shaking. I played the resonance tracks on an Ortofon test record and both lateral and vertical resonance were centered on 9 Hz With the feedback going and the house shaking I wanted a better look at the cantilever. On lifting the dustcover the feedback stopped! The dust cover is attached to the plinth which is isolated from the sub chassis (tonearm and platter mounted on this) by four springs. The resonance frequency of this suspension is 2 Hz. Nothing above 2 Hz can pass directly through to the platter and tonearm. What is going on here? Any of you scientists out there have a clue? My best guess is that I am dealing with a type of Helmholtz resonation. The dust cover is lowered on four hard rubber pads, one at each corner. There is a 1/16" slot all the way around. This combined with the weight and dimensions of the dust cover creates a resonance at 20 Hz. To get it going I have to turn the volume way up.
Today when I get home I'll play around with it to see if I can figure it out. Any ideas would be appreciated.
- ...
- 146 posts total
Thanks, Ralph. All Atma is saying is that a strain gauge needs a little EQ in order to correct for the RIAA pre-emphasis standard used to cut all LPs. I don’t know whether the SS SG phono stages account for this but I’d be surprised if they don’t incorporate some corrective filtering in the 500 to 2000Hz region. |
@lewm , It is a good question I plan to ask Mr Ledermann. I have not seen him mention this. I can do it digitally although replicating the phase shift Ralph talks about won't be easy. @rauliruegas , I viewed Channel D's web site last night. The Lino C 3.0 is now out and it has both MM and Voltage Mode MC capabilities among circuit improvements. It is also up to $6000 if you option it up. It has also lost the simplicity I like. Makes the Loco look better to me. |
Dear @mijostyn : You need to go for the one that match your way of thinking. No one of both phono stages you named are my cup of tea but this is me and that's all.
Look, when I want to listen analog everything that's below my system control must be analog and does not be digital manipulated in any way. Again, that's me and I'm way different to you with different targets and MUSIC priorities.
R.
|
- 146 posts total