Noisy reverb on amp


awoodfield
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awoodfield
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05/20/2017 4:59 pm

[br]I've just got a new amp and I've noticed that when pushing the spring reverb passed 3 o'clock ish it starts to create a bit of noise, like white noise. At 3pm onwards it's quite a lush/ heavy reverb sound but it still sounds nice so I'd like to see if there is a way of making this quieter or if this is just normal?[br]It's quite an expensive amp (a Bad Cat Cub iii) and is tube driven spring reverb (12AX7). I have replaced both preamp valves and also tried turning the reverb tray the other way.

Thanks![br]Andy


# 1
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05/22/2017 7:35 pm

Hi awoodfield,

Noise from your amp can be from the outlet, the electric transformer and other signals that may interfere with your reverb tank. If you tried turning the tank 180 and it still makes a bit of noise, then you might want to add metallic shielding. From what I understand reverb tanks are kind of like pickups, so they'll pick up some of the interference from other electronics too.

If it's white noise, would you say it sounds more like a hum? Or is it more of a buzz?

Billy


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# 2
awoodfield
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awoodfield
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05/25/2017 3:56 pm

Thanks Billy for getting back to me.

I think it's more of a hum than a buzz, it's usually when I get to about 3 oclock at lower settings but kicks in earlier if I turn up the K-master and gain. I turned the reverb tray 180 and also in different positions whilst on and it didn't make any difference

Could you let me know how I'd go about adding metallic shielding - what to use, how to do it etc? Sorry if this is something quite basic but I have no idea - hopefully this is quite easy to do? It is in a tolex bag screwed to the bottom of the cab.

I've also noticed that in between the RCA cables (at both ends), there is a plastic wire with what looks like copper or something inside. It rests into a tiny hole next to the input in the input tray and at the other end it's just floating next to the inputs but not going anywhere. Is this some sort of ground, I'm not really sure if it serves a purpose but even in the input tray it's not really connected, just balanced in a small hole. You can see the the two holes next to the input on the actual reverb tray here http://www.mojotone.com/amp-parts/ReverbTanks_1/4AB2C1B-Reverb-Tank-Fender-Marshall-Ampeg-2-Spring

Many thanks,[br]Andy


# 3
JeffS65
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JeffS65
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06/14/2017 10:18 pm
Originally Posted by: awoodfield

Thanks Billy for getting back to me.

I think it's more of a hum than a buzz, it's usually when I get to about 3 oclock at lower settings but kicks in earlier if I turn up the K-master and gain. I turned the reverb tray 180 and also in different positions whilst on and it didn't make any difference

Could you let me know how I'd go about adding metallic shielding - what to use, how to do it etc? Sorry if this is something quite basic but I have no idea - hopefully this is quite easy to do? It is in a tolex bag screwed to the bottom of the cab.

I've also noticed that in between the RCA cables (at both ends), there is a plastic wire with what looks like copper or something inside. It rests into a tiny hole next to the input in the input tray and at the other end it's just floating next to the inputs but not going anywhere. Is this some sort of ground, I'm not really sure if it serves a purpose but even in the input tray it's not really connected, just balanced in a small hole. You can see the the two holes next to the input on the actual reverb tray here http://www.mojotone.com/amp-parts/ReverbTanks_1/4AB2C1B-Reverb-Tank-Fender-Marshall-Ampeg-2-Spring

Many thanks,[br]Andy

Is the buzz kind of a steady 'zzzzzzzzzzzzzzzzzzzzzz' as you turn it up?

If so, get some DeoxIT from a local retailer or Musicians Friend and spray the RCA contacts. Give em a spray, give them a shake and then plug the RCAs back in but work them around a bit on the RCA inputs. DeoxIT is a deoxidizer (not shockingly) that removes corrosion and in a way, seals the surface of any micro-gaps. Also, make sure the RCAs are fitting nice and snug too.

I think DeoxIT is about $15. Worth having as a contact cleaner for your gear.

Trying this is a good and cheap way to start since what your buzz sounds like is a contact buzz (....yes, there is an intentional joke in there ;) )


# 4
awoodfield
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awoodfield
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07/01/2017 6:20 pm

Thanks for the suggestion, I ordered a can of deoxit and sprayed all the plugs and jiggled it about a bit but no luck! I've tried swapping the reverb preamp too, but only with others in the amp. I guess a lower microphonic noise preamp like a tung sol might help? They are AX7s in the reverb on the amp. Other than that I have no idea what else to try


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