Amp noise test, check it out.

[Wolfeman]

Shameless plug for my amp here, but it's also interesting to just hear how bad some amps are in regards to noise.

Here were the test conditions. I used the same cab (Wolfe 4x12, V30) with the same mic (SM57) for all tests. Mic position stayed the same through out the test, I just switched the cable from amp to amp. Mic pre level stayed constant on each clip. The amps used were my 5150, SLO clone, and the Hellfire. I tried my best to match the gain on each amp, as well as eq and power amp controls(depth/presence), as well as the master volumes (I first matched by ear, then checked the DAW meters to make sure they all checked out equal). All of those controls make a big difference on noise, so trying to match them as best as possible was essential. And to be fair, I must mention that the power and preamp tubes can make a difference as well. In this test the power tubes are all SED =C= 6l6's from a matching lot, and were all biased on each amp to a modest 32mA. The preamp tubes are all Tung Sol 12AX7, with the exception of the phase inverter in the Hellfire which is a NOS JAN 12AT7. Also, to be fair again, the SLO is a homebrew, so I have no idea how noisy a real one from Soldano is. My wiring job could be better, making it quieter than a real one, or vice-versa. Irregardless, I think the test shows how well I designed and set up the Hellfire. I spent a lot of hours trying to do everything I could to get it to be as quiet as possible, since less noise means less crap in your tone, and also requires less gate threshold when playing live, and I don't need to explain why that is good. So listen and enjoy. Once again you just have to trust me that the amps were set up to equal gain and volume.



The 5150 noise is very loud. Not really any dirty hum present, but damn that resistor noise and what not is HORRIBLE. I'm sure everyone with a 5150/6505 knows this noise all too well, as it's been persistent on every one I've heard.



The SLO is a lot less noisy than the 5150, but has a bit of hum in there.





The Hellfire is pretty quiet at a high master volume setting. You can still hear a bit of noise going on, but not as bad as the other 2 amps. The real magic happens with a turn of the noise cut knob. Works very well, and doesn't kill any notes or mess with the amps tone.

 

[TheWinterSnow]

The 5150s design is horrible, their gain stages have way too much gain which must be reduced by some hefty sized voltage dividers, which in return create resistor noise and also microphonic tubes. The first stage of V1 has an Rp of 220k which is just stupid high for a high gain amp and as a result makes the amp to microphonic you HAVE to use a noise gate if you don't want horrid amount of feedback at rehearsal volumes. And where does all that gain go, its bled down through resistors that create more noise on top of the microphonics.

Also do you have a humdinger and is it properly set, that could remove much more hum but you already know that.

 

[Ermz]

The 5150s design is horrible, their gain stages have way too much gain which must be reduced by some hefty sized voltage dividers, which in return create resistor noise and also microphonic tubes. The first stage of V1 has an Rp of 220k which is just stupid high for a high gain amp and as a result makes the amp to microphonic you HAVE to use a noise gate if you don't want horrid amount of feedback at rehearsal volumes. And where does all that gain go, its bled down through resistors that create more noise on top of the microphonics.

If it were redesigned to be more electronically 'ideal', would it still retain the same tone that makes it a world-standard metal recording amp?

 

[kev]

If it were redesigned to be more electronically 'ideal', would it still retain the same tone that makes it a world-standard metal recording amp?

Nice question Ermz :Smokedev:

Im assuming this is where the 5150 III comes in!

 

[Sloan]

I would assume that it's hard to reduce noise in a device intended to create it.

 

[drew_drummer]

Two Q's...

1. Irregardless??? Really???
2. What is the low frequency humming and where it is coming from? They ALL sound way more noisy than I'd ever EVER expect. Or am I misunderstanding the test?

 

[Wolfeman]

1. Irregardless??? Really???

Used to show emphasis on 'regardless'. I know it's not proper, but I use it anyway

2. What is the low frequency humming and where it is coming from? They ALL sound way more noisy than I'd ever EVER expect. Or am I misunderstanding the test?

Maybe you don't understand, I should have been more specific. I had to raise the levels in the end the get the noise to be louder so one can actually hear it. If the levels were set to a playing/recording level, the noise on the loudest amp(5150) would have only been around -20 and you would of had to crank the volume in order to hear the test.

That hum is from the power. Unplug your guitar from your amp, crank the gain, then crank the master to full and put your ear up to the speaker. You'll hear it. If you don't, then you have one damn well built amp, or some awesome power coming into your house

 

[drew_drummer]

Ah, so you mean you normalized the clips? I know the 5150 is pretty damn loud, but the others comparatively didn't seem much quieter. Would be interested in non-normalized clips

 

[Wolfeman]

Ah, so you mean you normalized the clips? I know the 5150 is pretty damn loud, but the others comparatively didn't seem much quieter. Would be interested in non-normalized clips

I just pushed all 4 faders up equal amounts (+10) so they still show the same difference between the clips, just a little more audible. This probably made some of the preamp noise more audible, so this surely isn't a foolproof test. So many variables to account for when it comes to noise. Everyone's results would probably vary.

 

[Sloan]

I think it would be good to compare the noise level versus the average level of a signal to see which one has the lowest measurable signal to noise ratio.

 

[MarkG]

Probably a very dumb statement, but doesn't the amp manual state the signal to noise ratio?

 

[Wolfeman]

Probably a very dumb statement, but doesn't the amp manual state the signal to noise ratio?

Some do, but you never know how they conducted the test. Any slight change in any of the controls will change that ratio. Most of the time, the manufacturer will do whatever they can to get that number as low as possible. So clean channel, gain all the way down, you just never know. That's why I did my test by trying to match the amps as close as possible, to give a 'real world' scenario instead of giving faulty numbers. For all we know, the manufacturers could get that number with no tubes plugged in

 

[LeSedna]

I think it would be good to compare the noise level versus the average level of a signal to see which one has the lowest measurable signal to noise ratio.

+1, next step would be throwing a Di signal of a riff with pauses so that we could evaluate the signal to noise ratio by ear, comparing the guitar sound to its noise floor.

Seems a pretty decent improvement, BTW. That + a Decimator and you're done.

 

[Wolfeman]

Seems a pretty decent improvement, BTW. That + a Decimator and you're done.

Exactly, and it's nice because you can set the gate to a much lower level to begin with. Less note cut off, but still with quick stops when you need it.