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Little tech questions from your day

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Re: Little tech questions from your day

Postby Tommy on Mon Mar 05, 2018 1:32 pm

Guitar grounding question...

Scenario: guitar with humbuckers has a nasty ground buzz at home that is somewhat reduced (but not eliminated) by touching the metal parts. It is not 60Hz hum. Same deal with different cables and removing pedal board from scenario. Same guitar produces no such ground buzz at my practice space.

What could be causing this/what should I look for? Is there any test I can do with a multimeter/etc. without pulling the pickguard/bridge? I assume testing bridge to cable sleeve should tell me whether the bridge ground is intact...

I'm going to try moving the amp to a different outlet (and testing that outlet as well), but it seems like my problem is specific to some flaw in this guitar.
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Re: Little tech questions from your day

Postby Nate Dort on Mon Mar 05, 2018 2:47 pm

Is the control cavity shielded? Does the buzz come and go if you rotate the guitar around or move around the room?
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Re: Little tech questions from your day

Postby Tommy on Mon Mar 05, 2018 3:29 pm

Nate Dort wrote:Is the control cavity shielded? Does the buzz come and go if you rotate the guitar around or move around the room?


It's a MIM Telecaster Deluxe. Probably just has the pickguard shielded like everything else. I just restrung it (before noticing this issue) so I haven't pulled the annoyingly large pickguard off of it yet. Until I have to. Does not change if I rotate it like single coil hum or a badly shielded cable would.
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Re: Little tech questions from your day

Postby Adam P on Mon Mar 05, 2018 3:33 pm

Other guitars behave similarly with this amp?

What’s the lighting in the room?
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Re: Little tech questions from your day

Postby Tommy on Mon Mar 05, 2018 4:11 pm

Adam P wrote:Other guitars behave similarly with this amp?

What’s the lighting in the room?


No other guitars behave this way. Lighting is via two lamps. One with LED, one with CFL. Turning off light had zero effect. Amp is plugged into a switched outlet and power strip. Power strip showing green ground LED.

Sound is like a bad ground without all of the low end. More similar to constant white noise than hum.

None of this was present when using the guitar last night through a different amp at a different location.
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Re: Little tech questions from your day

Postby Redline on Mon Mar 05, 2018 5:45 pm

Make sure there's a ground to the bridge/tailpiece.
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Re: Little tech questions from your day

Postby Dr Tony Balls on Tue Mar 06, 2018 10:07 am

Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.
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Re: Little tech questions from your day

Postby Nate Dort on Tue Mar 06, 2018 11:20 am

Dr Tony Balls wrote:Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.


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Re: Little tech questions from your day

Postby benadrian on Tue Mar 06, 2018 2:06 pm

Dr Tony Balls wrote:Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.


Could the grid and plate of the tubes be changing physical position inside the glass? It seems like any change in bias current would result in different voltage drops and therefore show a voltage change. Bizarre.
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Re: Little tech questions from your day

Postby Dr Tony Balls on Tue Mar 06, 2018 2:10 pm

benadrian wrote:
Dr Tony Balls wrote:Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.


Could the grid and plate of the tubes be changing physical position inside the glass? It seems like any change in bias current would result in different voltage drops and therefore show a voltage change. Bizarre.


Fully bizarre. I thought about the actual tubes, and im gonna try the same thing with a different set and see what happens.
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Re: Little tech questions from your day

Postby japmn on Tue Mar 06, 2018 2:32 pm

Possible a loose wire or other component is connecting or shorting something when moved?
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Re: Little tech questions from your day

Postby Dr Tony Balls on Thu Mar 08, 2018 12:06 pm

Dr Tony Balls wrote:
benadrian wrote:
Dr Tony Balls wrote:Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.


Could the grid and plate of the tubes be changing physical position inside the glass? It seems like any change in bias current would result in different voltage drops and therefore show a voltage change. Bizarre.


Fully bizarre. I thought about the actual tubes, and im gonna try the same thing with a different set and see what happens.


Sure enough, tubes. Weird soft-failure I havent seen yet.
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Re: Little tech questions from your day

Postby Mason on Thu Mar 08, 2018 1:08 pm

My Music Man has switchable tremolo/reverb, but of course I don't have the footswitch. Which is RCA, rather than the more available 1/4" type.

Anything, electronically, stopping me from taking something like a Boss FS-5L (I only want a switch for the trem) using a 1/4"-RCA adapter? I've seen things about one connection for an RCA "VIB/REV" switch being shielded and the other not, that kind of thing.
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Re: Little tech questions from your day

Postby benadrian on Thu Mar 08, 2018 1:17 pm

Dr Tony Balls wrote:
Dr Tony Balls wrote:
benadrian wrote:
Dr Tony Balls wrote:Here's a mystery....working on a tube amp where the bias changes depending on the physical orientation of the amp! Cathode current of 30mA when the amp is on its side (chassis vertical) and it changes to 37mA when you put it right side up. I've done this live with the amp on and watched the meter change. WTF. Voltages look identical in both positions.


Could the grid and plate of the tubes be changing physical position inside the glass? It seems like any change in bias current would result in different voltage drops and therefore show a voltage change. Bizarre.


Fully bizarre. I thought about the actual tubes, and im gonna try the same thing with a different set and see what happens.


Sure enough, tubes. Weird soft-failure I havent seen yet.


Freaky! Glad it's an easy fix, though.
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Re: Little tech questions from your day

Postby numberthirty on Thu Mar 08, 2018 7:33 pm

Mason wrote:My Music Man has switchable tremolo/reverb, but of course I don't have the footswitch. Which is RCA, rather than the more available 1/4" type.

Anything, electronically, stopping me from taking something like a Boss FS-5L (I only want a switch for the trem) using a 1/4"-RCA adapter? I've seen things about one connection for an RCA "VIB/REV" switch being shielded and the other not, that kind of thing.


Is the "For The Amp" footswitch something like this one?

https://www.amplifiedparts.com/products/footswitch-fender-two-button-vintage-rca-plugs-0
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Re: Little tech questions from your day

Postby PEPPER! on Thu Mar 08, 2018 9:29 pm

the adapter should work. if you don't care about having reverb or trem activated with a footswitch you can just short an RCA plug (ie. connect the two wires) and use the knobs on the amp.
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Re: Little tech questions from your day

Postby bassdriver on Sun Mar 11, 2018 10:53 am

bassdriver wrote:
projectMalamute wrote:
bassdriver wrote:in my home recording set up I have a sound booth with my amps and drums and a room with all the recording gear in it. I usually play guitar sitting in front of my pc. so I have a ten meter cable to my amp inside the booth. this is quite noisy. should I get a 10 meter speaker cable and set up the amp outside the booth or should I try to reduce the noise with 2 DI boxes?


I've used the two DI boxes trick, when the player had a combo amp we wanted isolated. Neither I nor the player heard anything that was bumming us out about what it did to his 'tone'. He did have a pedal board so the signal being sent through the works was probably buffered. I've AB'd with a test tone and if you have two identical DI boxes signal loss should be minimal.

All that said, a long speaker cable will absolutely have no effect on tone or volume given it's of decent gauge and not fucked up. Anybody who tells you otherwise is straight up wrong. It's also simpler and would be my first choice.



Nate Dort wrote:DIY:


I used an Edcor transformer and housed it in a single-gang steel electrical box from the hardware store.


thanks a lot guys. I think I'll pick up a 10 meter speaker cable first and then look into that DIY box. I like the idea of having the amp next to me and being able to vary the sound and distortion while listening back on the monitors.


bought a 10 meter Neutrik speaker cable for 60 bucks. it works perfectly fine. most of the noise is gone!
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Re: Little tech questions from your day

Postby kazoozak on Tue Mar 13, 2018 12:22 am

Just got a new amp in the mail but the pots are scratchy AF. Looking up directions on how to clean them seemed pretty simple enough--remove chassis from the cabinet, spray the contact cleaner into the pot openings and let it drain and dry while moving the pots, then reassemble and see if the problem is fixed. (No, I'm not gonna desolder and disassemble every pot, I ain't got time for that and I have two left hands with a soldering iron.) Probably gonna pick up a can of DeoxIT from Guitar Center on my way home from work, is there anything I should be wary of or should I consider a different brand of contact cleaner?

EDIT: just tried out the amp again and swept each pot several times, and when I turned it on the situation upgraded from “nigh unplayable” to “tolerable”. I really like the sound I’m getting but I may yet go to clean the pots at some point.
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Re: Little tech questions from your day

Postby numberthirty on Tue Mar 13, 2018 1:07 am

kazoozak wrote:EDIT: just tried out the amp again and swept each pot several times, and when I turned it on the situation upgraded from “nigh unplayable” to “tolerable”. I really like the sound I’m getting but I may yet go to clean the pots at some point.


The "Leave It At The Practice Space" rig?
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Re: Little tech questions from your day

Postby kazoozak on Tue Mar 13, 2018 6:15 am

The very same!
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