Acceptable noise in new amp build

[dusty712]

I finished building my first amp, a clone of the Sunn Model T (the first revision) and having never heard this amp live (or the Bassman that it's similar to) I was hoping to get some help to understand what's an acceptable amount of noise.

There's a slight bit of hum, but I think that's low enough at this point that I'm not concerned about. The main noise I'm trying to understand if it's expected or not is white noise that's present when the channel volumes are up and the master is up.

I tried to capture the noise with my iPhone and while not great I hope it gives an idea of the noise I'm referring to. In the clip below, I keep the tone controls at 5 throughout and start with channel volumes at 2 and roll the master volume from 0 to 10. Then I repeat with channel volumes at 5 and then at 8. When it's at 8 I keep it at max for a few seconds and then bring up the channel volumes to 10. Throughout the test nothing is plugged in through the front of the amp.

If it's too much (or even if it's not), I'd like some help to understand what the noise may be attributed for those with more experience troubleshooting these issues (is it resistor noise, just tube noise, preamp vs power amp, etc.).

Here is the link: https://soundcloud.com/user-981938832/model-t-noise

Note that the beginning of the clips shows just the background noise in the room and just the iPhone's mic quality. The master is all the way down on the amp, there's no actual noise coming from it other than a slight hum possibly.

Thank you

[tubenit]

I'll offer some thoughts for consideration in evaluating the floor noise (idle level) of my amps. I've built dozens of different designs and currently own 4 amps which are all pretty quiet at idle.

I tend to use 12AY7 or 5751 tubes in the V1 position.

I never run my Subaru Forester with the pedal to the floor for 5 minutes straight. I never run my amps wide open with all the volumes on 10 either. If there is hiss louder than any level I would normally play the amp at home or at an open mic, I'm not concerned about that.

I judge the idle noise floor level at the volume/s I normally will play the amp.

I occasionally when learning a rhythm to a song, dial my amp at a volume that I can still easily hear myself sing unmic'd with the amp on while I'm learning the new tune. This would be slightly louder than playing my Larrivee acoustic guitar.

At that level of volume, I want my amp to be quiet enough that it could be possible to forget that it's on and walk off. 

I want the amp to be quiet enough at idle that I might need to look over to see if the on/off light is turned on if a ceiling fan (set on low) were on.  This would be with my guitar volume at 7-8 with humbuckers not single coils.

I want my amp to be so quiet at idle that I am surprised how loud it is when I strum it.  All 4 of my amps are that quiet.

I'm not saying that amps "should" be that quiet .......... just saying this would be a reference point for how quiet I want my amps.

with respect, Tubenit

[dusty712]

Thank you Tubenit for your thoughts and advice, that does help a beginner try to sort out when to stop and that an amp is good enough. Honestly I think a lot of my question comes from the fact that I'd like to be able to build it "as good as I can" and if there's something I could do better I'd like to learn what that is.

The way you frame it though does make sense and honestly I think my amp right now fits that criteria. If I'm just playing it at home at a loud enough level, with the guitar plugged in, I think it's quiet enough and definitely not hearing any white noise. If I turn it up even more I'll start to get feedback from my guitar interacting with the speaker before I'm able to hear any idle noise. Once I add pedals to the front of it and put on some fuzz/overdrive/distortion then any idle noise I'm not sure is relevant anymore.

I plugged it into my Fryette Power Station to allow me to push the power tubes and I was going to record the signal from the line out as I assumed it would be noisy. But it wasn't noisy at all, even when turning up the master.

Thanks again, I appreciate the advice from this community.

I'll offer some thoughts for consideration in evaluating the floor noise (idle level) of my amps. I've built dozens of different designs and currently own 4 amps which are all pretty quiet at idle.

I tend to use 12AY7 or 5751 tubes in the V1 position.

I never run my Subaru Forester with the pedal to the floor for 5 minutes straight. I never run my amps wide open with all the volumes on 10 either. If there is hiss louder than any level I would normally play the amp at home or at an open mic, I'm not concerned about that.

I judge the idle noise floor level at the volume/s I normally will play the amp.

I occasionally when learning a rhythm to a song, dial my amp at a volume that I can still easily hear myself sing unmic'd with the amp on while I'm learning the new tune. This would be slightly louder than playing my Larrivee acoustic guitar.

At that level of volume, I want my amp to be quiet enough that it could be possible to forget that it's on and walk off. 

I want the amp to be quiet enough at idle that I might need to look over to see if the on/off light is turned on if a ceiling fan (set on low) were on.  This would be with my guitar volume at 7-8 with humbuckers not single coils.

I want my amp to be so quiet at idle that I am surprised how loud it is when I strum it.  All 4 of my amps are that quiet.

I'm not saying that amps "should" be that quiet .......... just saying this would be a reference point for how quiet I want my amps.

with respect, Tubenit