Bravo 112 background noise

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Cleantone
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Joined: Fri Sep 10, 2021 3:39 pm

Bravo 112 background noise

Post by Cleantone » Sat Sep 18, 2021 12:02 pm

I am getting more background noise from my amp than I would like. I play at home at fairly low volumes, mostly using pedals for gain through the clean channel, so the noise is very noticeable and distracting to me. I know that i can expect some noise from a tube amp but am wondering what I can do to minimize it.

As background, I am the original owner, and the amp was essentially unused from the late 90s until last year, though it made several apartment and house moves with me. Less than a year ago I replaced all the tubes with new JJs. Less than a month ago I replaced the stock speaker with a Warehouse G12C (love it in this amp so far!). Other than those updates, the electronics have never been opened, modded or serviced. The issues I'm describing are with no instruments or cables plugged, and not detecting any typical EMF noise from phone, computer, etc.

First, I noticed that the reverb adds a lot of noise. Based on some forum research I disconnected the wires in the reverb tank to isolate it as a possible source. This improved the background white noise level some with the reverb control at 0. But turning the control up quickly adds noise and a hum the same as with the tank connected. This is more pronounced on the Ultra Gain channel. I expected the control to be ineffective with the tank disconnected. Is this a wrong assumption?

With the reverb disconnected, the clean channel is improved and is not too bad up to about 3-4 on volume, then the white noise gets noticeable. Adjusting the High EQ rolls the noise up/down, but the other bands do not affect it.

On the Ultra Gain channel the background noise is much louder even with minimal pre and post gain levels. All the EQ controls affect the noise, especially the Body (middle) control.

If the easy answer is to take it to an amp technician that's fine, given the amp is 30 years old it probably needs it. But I'm on a bit of a DIY kick so would like to rule out things I can do myself - e.g., different tubes, general cleaning/maintenance that doesn't require special knowledge.

The reverb noise is a bit concerning. In the short term I can live without it, but I do want it to work.

Thanks for any advice!

Update:
A correction to the above: The Reverb noise and hum is the same on both channels, not more pronounced on the gain channel.

Also, I fiddled with the knobs some more. I noticed that on the gain channel, with the Pre set at 0 turning the Post up increases the white noise, making me think the power stage is a significant factor. Would different/better tubes make a difference?

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Enzo
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Re: Bravo 112 background noise

Post by Enzo » Mon Sep 20, 2021 8:36 pm

Post up increases the white noise, making me think the power stage is a significant factor.
Think about that. The post control is at the end of the preamp, so before the power amp. If turning it down turns noise down, then that noise is not coming from the power amp.

You have preamp controls. Do ANY of the controls (gain, volume, tones) affect the noise in ANY way? If so which do and which do not?

Cleantone
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Re: Bravo 112 background noise

Post by Cleantone » Mon Sep 20, 2021 10:25 pm

Good point about the power section. Thanks for clarifying.

Yes the clean volume increases the noise after about level 3. The clean treble more clarifies it than changes it.

In the gain channel the Pre amp gain greatly drives the noise, even if the Post is at 0. Unlike the clean EQs, all gain eq controls increase the noise.

Also, the reverb seems to add a separate layer of its own noise as well as a unique and loud hum.

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