Has anyone here read the OP’s previous thread?
What is your point here @deKay?
It is almost surely a magnetic field.
I would do the test with the mat alone, and the record alone, but cannot fathom a mat being magnetic, however the fridge magnets are plasticy.
One could put a mark on platter and mat, and then try the mat at a few phase angles.
Or get a new mat, or degauss the current mat, or put a blocking capacitor somewhere.
A new mat is what I would suggest
|
A capacitor does not “block” a magnetic field.
__ ____ Sherlock… but it blocks 33-1.3/60 Hz, as well as DC
but that’s not so much of a problem, because there cannot be a magnetic field generated from the Funk Firm Acromat, because it is completely non-metallic, let alone non-ferrous.
Those fridge magnets are also plastic.
(See the FF website.) I know there are some who believe that records can become magnetic and need to be degaussed periodically. I am not one of them, but even if it were so then we would all be having this kind of problem, and we don’t.
Agree
Furthermore, a magnetic LP would attract the magnets in a cartridge, and could be disastrous for the suspension, but that doesn’t happen either. Furthermore, if LPs could be magnetized, they would become uniformly magnetic; the magnetism would not be patchy across the LP circumference so as to cause the phenomenon the OP observed.
As I said above and still believe, I think the story that goes with the observation (removing the platter mat and LP cured the problem, etc) is a red herring. If the phenomenon was to be further investigated, in other words, all that bit would be seen to have had nothing to do with the actual cause.
The OP could for an instance use a compass to see if it has the periodic needle jiggle. Or hold that mat next to the compass.
For example, it is possible that the phono stage has the potential to oscillate at a low frequency when in balanced mode. Such an oscillation can easily be a some time thing; in other words it comes and goes. In the story, the OP had to shut down the turntable to remove the platter mat and LP. This might stop the oscillation that is really going on in the preamp, just by chance alone. When he switched to SE operation, that too would require shutting down the phono stage, and it could easily be the case that the premp does not oscillate at all in SE mode. If you have ever tried to chase down and cure an oscillation in a piece of audio gear, as I have done, you would know what a royal pain in the arse it can be. Took me over a year with an amplifier, and that was with help.
this is possible, but the mat suggests that it
|
It is super interesting.
Do you access to a compass like hikers use?
I think even an iPhone with its magnetometer built in might work as a way to see if the mat is somehow magnetised.
Sure, it is possible, that it is somehow related to wiring… but I doubt it.
When I had a 50 Hz hum it was also from a magnetic field, and the coils in a MM or MC cart are effectively a magnetometer.
If it is only doing the pumping when the mat is on, then I would think that removing the mat would be a possible strategy to use to ameliorate the pumping.
|
Not everyone is focused on magnetism. Have you read any of my posts? I’ve just grown weary of contradicting Holmz, who IS focused on magnetism. I let his last fantasy stand as is, because I did not want to appear to be picking on him.
Like I have said three or four times, my best guess is that the system is oscillating at a very low frequency when the preamplifier is hooked to the cartridge output in balanced mode. When the OP switched to single ended mode, the problem went away. The bit about the platter mat and LP is a red herring, as per my earlier definition. The fact that it seemed to make a difference can possibly be due to the fact that when you power down an oscillating electronic device (in this case, the preamplifier or the amplifier would be oscillating due to input from the TT), the oscillation of course ceases. When you then restart or power up the same electronic device, even with the same input and output loading, the isolation may or may not reappear. In order to remove the platter mat and LP, in this instance, the OP had to shut down power to the TT and then power it up again in order to demonstrate the "no platter mat, no LP" condition. So lets say the cartridge is picking up something from the TT motor that intermittently causes either the preamp or the amplifier to oscillate but only in balanced mode. The intermittent nature of an oscillation is what confounds the investigation of its cause, let alone trying to fix the problem. And beyond that, we really do not have enough data to speculate further. Maybe the OP will eventually come forward with some additional information, but I don’t blame him if he does not want to be bothered and is perfectly happy to operate in SE mode.
Magnetism, shmagnetism.
Yeah @lewm I am guilty as charged.
Your posts are usually pretty thoughtful, so I would probably be OK with being picked on.
WRT the air currents and wind, just blowing on the stylus would be more that it would see from currents, and if that does not move the stylus then to get LF movement would be pretty hard.
And resonance of the stylus/cantilever should be much higher freq, that the <1 Hz.
So I am thinking the causal mechanism is doubtful to be mechanical… which leaves electrical and magnetic as two forces.
@mitchellcp I have lost that ball a bit, but we may want to see of it pumps moving the TT patter by hand, or as the thing is spinning down right after the motor stops getting power.
If it does it with only the motor being on, or regardless of whether the motor is powered, then that would be “more clues.”
@lewm I am starting to come around to your hypothesis, as it seems like it what is known as motorboating.
It looked like it was sync’ed to the platter position, and platter speed.
I am wondering if the pumping is faster at 45RPM than at 33-1/3?
|
It’s kind of reproduced except mine needs a record or synthetic mat or both.
So it pumps with a record and not a mat, but no pumping with just the platter?
@byang12 I’m confused, could you restate that
There is pretty much electrical field and magnetic field.
I am having a hard time with an electrical field that is at 1/2 RPM… and a magnetic field should not be affected with just a piece of vinyl on top of the alloy platter.
It is either coming out of the cart itself, or it needs to be tied to the ground wire, like making some differential voltage between the ground and the cart, which is tied to the platter phase.
But those mechanisms should not be tied to rely on a mat or piece of vinyl.
I could imagine Lewm’s idea of electrical being tied into the electrical side.
@mitchellcp previously I think that you mentioned that there NO ground wire running to the electronics… and the PIn-1 is not tied to ground.
I am wondering if pin-1 should be tied to the ground at the TT end.
|
In connecting a cartridge in balanced mode, to a balanced phono stage, ground is left to "float". As you know, the cartridge has no ground connection, per se, except for a very few older designs, like (I think) old Decca cartridges, and those cannot be hooked up for balanced drive. The shield on the phono cable itself, if there is one, can be attached to phono stage ground lug, but I have three TTs operating in fully balanced mode, and in no case has it been necessary to ground anything to anything. I don't see any problem with Mitchell's wiring scheme, certainly not one that can account for the phenomenon. And it's not confusing.
I don’t see a problem either, but to attach the shield to ground, seems worth taking a lark on trying?
Someone else very early on mentioned the Hall Sensor, which is very likely used in the drive system of the Yamaha, because it has a DC coreless motor. On my Kenwood L07D, also coreless and also DC, the Hall Sensor is fixed to the plinth surface under the platter, but there must also be a signalling device built on the underside of the platter itself that rotates with the platter and triggers the sensor if there is a speed error. It seems possible that in balanced mode the phono stage is picking up a signal from the cartridge, as the Hall component that is fastened to the platter rotates under the cartridge. This is causing an impulse from the cartridge to push the woofer in concert with TT speed. But why this happens only with platter mat and LP in place, I do not know.
Yep -it wakes little sense how the mat and LP could contribute
One idea why the problem only occurs in balanced and not in SE mode might be that in the latter case, both channels ARE connected to audio ground, so maybe the signal never gets to be amplified to drive the woofers. It would be interesting to hook the output to a 'scope and see if one can detect the spurious signal on hot or ground in SE mode
If the signal was sneaking in on the ground, then the SE is tying the phono stage to the TT. And the pin-1 being disconnected, is not tying the XLR to ground.
But this also would suggest that the XLR at the TT side may not be wired as push/pull and maybe has the out of phase side tied to ground?
|
…
Next up, Static Electricity. I forget who (sorry) but it was suggested that wiping a record with a dryer sheet might affect the pumping. I observed the pumping with only the mat to get a visual baseline, then applied the dryer sheet while the platter was spinning. The amplitude of the woofer excursions diminished visibly while I was wiping the mat, I’d say by 80 to 90 percent.
It would appear that the correct answer is, levels of static electricity not enough to arc but enough to influence the Hana ML while operating in balanced mode
This makes zero sense to me…
The cart is generally a thing that generates a current, and the electrical field would seem to be difficult to get into a twisted set of differential wires.
And to get enough charge on the LP to merry-go-round in a pile of electrons, and generate a magnetic field, would be difficult.
And to do it with Every LP you tried?
And even a just with a mat alone?
And never without a mat or LP?
I think I am back to the @lewm idea of oscillation in the phono stage. That would either need some different loading, or to block the low freq with a high pass capacitor in-line. The later could ameliorate the problem, but it does not illuminate the mechanism.
|
The idea that the ES charge is concentrated at one area on an LP or on the mat is contrary to data collected by Shure Corporation, when they studied ES charge in vinyl reproduction, albeit many years ago; they suggested that charge distributes evenly across an LP surface. However, I could perceive that there might be some assymmetry to charge distribution due to fingerprints or other oily or watery deposits on the LP surface. So perhaps the data you cite would contradict their earlier findings. I will take a look.
How does a static charge and electric field manifest itself in the signal?
And we still have not had an answer as to whether the 18Hz high pass filter on the preamp was engaged during all of these investigations. If it was engaged, then I would expect there to be little to no woofer pumping when the platter is spun at speeds below 18Hz. Yet I thought the OP reported he can spin the platter by hand at speeds well below 33 rpm, and still visualize the phenomenon.
If it was say the magnetic field from a Hall effect sensor or the motor, then as long as the thing is localised to a small fraction of a rotation, then it will appear like >18Hz.
In XLR configuration, positive attaches to Pin 2, negative to Pin 3, Pin 1 is vacant and the shield is attached to the shell. The shield is floated at the TT end.
^As you have said^… that is pretty much the main difference, and hence why I suggested that you could try attaching Pin-1.
|
… DC into your woofer might burn up the voice coil but won’t move the diaphragm…
@lewm
That is false… DC will make a constant magnetic field that will then push the diaphragm off center.
It would need to be a pretty high offset to deliver enough energy to move it to overload the woofer thermally.
If it is not moving the diaphragm, then there is no AC and no DC.
Whatever the source is that’s moving your woofer it is an AC signal doing the work..
Yes AC, but AC that is at a low frequency.
Hence my earlier suggestion of a DC blocking capacitor, which blocks low frequencies.
But the freqs needing to be quashed, maybe higher than 20Hz as the table is turning at ~2Hz and the think is rising and settling over a small angular extent.
The problem isn’t solved really. That woofer pumping should not occur to that extent. I believe there is a problem with the ELAC PPA-2 balanced input. Both single end inputs function fine. I’ll be looking into it this weekend. I bought to unit on US Audiomart so no warranty for me.
Even more troubling @mitchellcp is that the causal mechanism is not known.
It would be interesting to try another phono stage that is balanced to help identify you hypothesis of the ELAC. But it seems like a rational conclusion.
A pragmatic person might just chuck in the RCAs.
|
Constant DC of one polarity will eventually damage the voice coil.
Only if the DC wattage is enough to cause the VC to rise beyond its temperature capability. A small amount will only slightly warm the VC… R*I = power and those electrical watts are the same as thermal watts.
I suppose intermittent DC pulses could appear as if a low frequency AC source, but….The question is whether the preamplifier and amplifier can pass DC from the TT to the speakers. And DC of sufficient magnitude to move the woofers.
Yeah we talked about blocking caps back on page 2 or 3.
And now whether the frequency is low enough to use a blocking cap to also block close to DC would likely work, as the excursion is not really heard. But maybe some doppler distortion can happen?
Since we do not know the causal mechanism, we are sort of jumping the gun for a solution, as we do not understand how to ameliorate the causal mechanism without knowing the causal mechanism.
I do not think we need to know the amp, as the system does it only with XLRs and the RCAs do not exhibit it.
So it is most interesting thread in ages.
|
@lewm It is not DC… by definition is like a sine wave or really more like a wavelet that is at a period of 33.3/60 of a second.
However it is maybe not a 1/2 Hz sinewave, more likely it is a flat line, with a heart beat that is happening over a just a fraction of the 360 circle.
So maybe it is a 5 or10 Hz thing that happens “at a rate or period” that is 33x/minute.
If it was DC the cone would be pushed out, but the cone was “pumping” and that is a verb or action word that describes something that is not steady-state… and not what a blocking cap or servo is designed to control… assuming that they are used for steady-state control.
…. So, I am dubious that DC generated somehow from the cartridge is causing the problem. But it did occur to me today that maybe the servo in the OP’s preamp is defective when operating in balanced mode. All bets are off.
The thing is perfectly synced to the platter, and the signal has to be coming from the cart, or has to be coming from the ground.
There is no other way the phone stage etc can make the speaker pump perfectly in sync with the platter.
Maybe it could be an intermittent DC shift on the ground, but the “no vinyl” “No mat” discounts that. And a servo will not remove it.
it is a conundrum.
|
Nothing that has been offered as solutions seem viable. Static is random, forget about it. The only suggestion that makes some sense is the the possibility on a weight sensor on the table to detect record weight. The Achromat is much lighter than the rubber stock mat on my old SP-15.
Agree @waltroman - but ignoring a solution, how does the static manifest itself into the signal wires?
I would think that both the + and - wires would be elevated equally and in the balanced sense they should then cancel out with the CMRR of a balanced approach.
|
