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Grado Hum Database

Sorry. I should have posted these 2 earlier:

Pioneer PL-630 - No Hum
Pioneer PL-610 - No Hum

I actually offer a new Grado Black, as an additional option, with my PL-630 offerings.

Rich P
 
javajam12 said:
Grado Black + Kenwood KD 4033= HHHUMMMMMMM!
Grado Black + Pioneer PL 400 = none to mild hum.
Click to expand...

I would like to amend this as I've recalibrated my Kenwood and changed
to different leads and now it is down to a very mild hum, maybe just a
bit more than I get with the Pioneer.
 
and i thought of getting grados to replace aging audio technica carts for sansui fr-q5 and a pioneer pl-550, kinda makes me weary
 
- Rega 3 w/Grado Sonata on an RB-300 TA with AudioQuest IC feeding several different preamps (McIntosh C-39, Bryston BP-25, Threshold FET 10/pc, Sony TA-E90ES, Sony TA-F808ES).
- Rega 25 w/Grado Sonata on an RB-900 TA with AudioQuest IC feeding several different preamps (see above).
- VPI HW-19 Mk III & Mk IV w/Grado Sonata on an SME 309 TA with AudioQuest IC feeding several different preamps (see above).

Zero hum with these set-ups.
 
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For those who haven't heard of MuMetal, and want to take active steps to quash the hummers, you can use this foil to provide shielding of your turntable motors from your unshielded Grados.
It's thin enough to afix between most platter wells and motors without taking spacing tolerances out of whack (Idlers and DDs).
Belt drive motors would be a case by case application - most likely on the side of the can facing the spindle. The only real caution is not to block motor vents and other design convection channels that keep the motor cool running.
A bit pricey: $10 to $15 a sq. foot. But if you love that lush Grado sound .....
 
Mopic, we discussed the possibility of using MuMetal to shield unshielded tables a while back, but the found suppliers only sold in large sheets, iirc. For those of us who'd only want a little bit, it's still a bit pricey to experiment with. Unless a few want to get in on a group buy of one sheet and then distribute pieces.

- JP
 
I'm going to have to go home and tear open my TT, I've left the Grado in and it sounds fantastic on some of my 50's vinyl. My 440ML sounds great on great disks, but those oldies come across so noisy with it.
 
The DUAL / Grado hum problem is not caused by the motor…. I have / had a DUAL CS 608 and CS 728Q. Both of these direct drive tables exhibited the hum problem with a GRADO Gold cartridge mounted on their ULM tone arms. I had little invested in the 728Q so I decided to experiment. I gutted the 728Q and removed everything but the motor and tone arm from the metal sub-plinth. I mounted this in a 20-pound birch plywood plinth I fabricated. All the speed control electronics were mounted in a separate metal box. A cable runs from the control box to the wood plinth. These signals are the motor voltage, TAC signal, and strobe LEDs. I added a second tone arm, consisting of a Grace-840 with a removable headshell. The two tone arms are electrically separate from each other with a minimal signal path for the left and right channel audio outputs.

The bottom line…. There is no hum at all with the GRADO gold. (The setup sounds Great by the way). Moving the cartridge back to the stock CS608 returns the hum and other sounds that are, let’s say, not complementary to the vinyl that is spinning.

The next step will be specifically identifying the source of hum in the CS608 and see if I can devise some type of shielding to prevent the problem. A Stanton 500E and 681EEE do not hum on this table. That is however a rather simple way to cure the problem.

I can only speak for the DUAL tables in my testing, but I suspect Motors in general may be getting a bad rap for this problem from other turntable manufactures as well. I would suspect a transformer or an unshielded circuit board as a more likely source of electromagnetic interference than a DC Brushless Motor. The search continues…
 
Grado Sonata
output1.5 mv@5 cmv(45)
input load:47,000
inductance: 45 Mh
Resistance: 475 ohms
VPI Scout jmw 9 arm
No hum untill I switched to Klipsch K-Horns.I found some metal tape about 4" wide,(wish I remember where I got it)and put some around the motor.The hum is much better,can only be heard at loud volume.Tommorow I will do the whole motor and see what happens
 
Pioneer PL-L800 w/ Grado Prestige Black: No Hum but it does pick up the flux generated by the tonearm Linear tracking servo motor, when the motor starts, which is regularly as needed. The effect is worse toward the outside of the LP, as the metal shield only extends out to the outer diameter of the platter, and the flux bends around it at the edge. As you get toward the inner part of the LP, the effect becomes less and less. Note that the servo motor is directly under the tonearm, on axis with it.

I put a new stylus in the Pioneer cart and put that in instead, and the gentle, periodic thrum disapeared...its the Grado alright :tears:

Enjoy,
Rich P
 
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