Static noise when touching quicking and microphonics, what to do?

[machinehead]

Gents and Ladies,

When I walk up to my Quickie with the rig playing, when I touch the volume knob to adjust it, and discharge the static in my hand to the Quickie
the sound transmits through the speakers.

Do I have a grounding problem, or is this normal since this unit is battery powered and not grounded through the house ground?

I also get tons of microphonics when reach and touch the volume knob, or any of the RCA cables.  Any ideas?

Is there a circuit I can add like a soft start, so that I don't have to turn the amps off prior to turning the Quickie on or off?  My amp switches are in the back and
I generally don't turn them off.

Thanks.

 

[Grainger49]

No manufacturer can make static proof equipment.  If you run a humidifier it will lessen or eliminate that part of your problems.

If you do a quick search in the Quickie posts you will find that microphonics are, for the most part, a tube related problem.  Rolling in other tubes can help.  There might be a couple of other suggestions for helping microphonics.  

In all tubed equipment it is best to turn on the preamp 30 seconds before the power amplifier.  Powering down you turn off the power amplifier, wait, then turn off the preamp.  It is only a few seconds but it is a good practice.  And the green guys will get you for leaving your amps on.

 

[Paul Joppa]

...Is there a circuit I can add like a soft start, so that I don't have to turn the amps off prior to turning the Quickie on or off?  My amp switches are in the back and
I generally don't turn them off.

Thanks.

There is no such device at present.

If you have the stock version, or use choke loads, the amp won't draw current from the high voltage supply when the filaments are cold. So merely bypassing the high voltage switch would cause a short delay while the filaments heat, and while they cool down after switching the power off. That might be good enough, depending on how fast those filaments heat up.

I don't see a problem adding a slow turn-on to the PJCCS. There would probably have to be another mod for a soft turn-off. Some experimentation will be needed before there's a package to offer.

Here are some design ideas in case someone out there wants to play with them ideas before we get around to it:

For turn-off, a capacitor from the high-voltage supply **after** the switch (negative to ground) would let the voltage drop slowly. I think 1000uF would probably be acceptable; I'd prefer a 50 or 60v rating.

For turn on, a capacitor on each channel to slow the C4S bias would be needed. I'd start with one across the 4.02K resistor R1 - that resistor will discharge the capacitor when the am is turned off. But it may come on too soon that way. The alternate idea is to place the cap across both the resistor and the UF4007 diode; in that case you'd need another resistor across the cap to fully discharge it when the preamp is off. You can use the holes that straddle the mounting holes for this RC combination. I would expect something in the range of 1000uF to 5000uF ought to work, with a 20K to 50K resistor. Use a 6.3v capacitor rating.

 

[tbbenton]

I also get tons of microphonics when reach and touch the volume knob, or any of the RCA cables.  Any ideas?

Last two times I had "tons" of microphonics,it was because I failed to solder a couple parts.  They made good enough contact to operate, but I had inexplicable rushing noise sometimes and it sounded like hell when I tapped the chassis.  Note that my experiences are with other bottlehead kits, not the quickie.  But you still might want to check your connections.

 

[Paul Birkeland]

You might try connecting and soldering a wire to the ground buss, then strip back an inch or two on the other and and wrap that around the threaded portion of the pot that goes through the top plate. That may help with the static discharge, but the plastic knob should be enough of an insulator. 

 

[machinehead]

Seems mostly gone after installin the Alps pot, may have been a bad solder joint to ground.