Output level to poweramp.

H

Hellburner

Member
Hello.

I wonder if there is a way to determine the optimal output level to the poweramp? I find its very hard to know. I have a tube poweramp, Marshall 9100. I want to push the poweramp at a "normal" level.

I am volume adjusting on my poweramp and i have the vol nob on the "axe-fx 2" to noon.
Can i connect something else to compare? I do have 2 channels.

Id love som help with this.

/Christian Bernhall
Uddevalla
Sweden
 
depend on the power amp. Some like a -10db signal and others a +4db. Occasionally they want a 0db signal. Ultimately though it doesnt really matter as long as the input signal isnt so hot you clip the input (at which point you'd know).

A power amps level/volume control is an attenuator. The amps rated output is what you get with the amp full, and the input signal at the level in the amps specs. If you increase the input signal, then the amp reaches its max output before full on the volume control - it then starts to clip the output (which you'd hear as power amp distortion or the horrible SS clipping if its a SS amp). If the input signal is lower than the amp expects, it doesnt reach its max output even with the volume at full.

So - as long as you have the volume you require, without the distortion resulting from clipped input or clipped output its good, and doesnt really matter where you attenuate the signal (AFX output, amp vol control). There at he same point in the signal chain.

FWIW - I tend to aim for 0db if I can.
 
I am using my Axe Fx with a tube power amp, a Fryette Power Station, and I have the Axe's output at noon as well. Just seems to be a good output level so I can run my power amp at 11 o'clock at gigs. With a tube power amp you probably don't want to run the tubes hard enough where they are breaking up ( or maybe you do, haha).
 
Steve73 said:
I am using my Axe Fx with a tube power amp, a Fryette Power Station, and I have the Axe's output at noon as well. Just seems to be a good output level so I can run my power amp at 11 o'clock at gigs. With a tube power amp you probably don't want to run the tubes hard enough where they are breaking up ( or maybe you do, haha).
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Im using a PS as well. I run my AFX volumes full, with the patch levels peaking at 0db (in utility menu) then control volume at the PS. I tend to run it between 10 and 12 o'clock. At home I do the same, but I use OP 2 which has a -12db reduction in the global EQ - and generally between 1 and 3 db reduction at the FX loop send (to volume match patches - which when quieter need different adjustments). I run between 9 and 11 at the PS.

I have found that at 1 o'clock (live - so 0db on the meter and flat EQ gain) I run out of clean headroom on the PS - so I could quite happily run the AFX lower (or with lower patch levels) and use the full sweep of the PS, but I decided against that after some testing. There is more background noise the higher you wind the PS up - so keeping the input signal as high as it can go without clipping the inputs (I believe they clip at +4db input) and running the PS lower keeps the signal cleaner.
 
It's really a matter of preference. There have been so many suggestions in other discussions. It may depend on whether you want some tube saturation or a whole lot of clean headroom. Of course solid state would be different. I experimented with various levels and now run my Axe output at 30% (using the AXE meters) and my 2:90 tube power amp is at around 50% (12 o-clock), with presence at about 10:30. This gives me a great balanced tone with nice warm tube saturation. When I run the AXE volume all the way up, I have to turn the 2:90 down to 2 or 2.5. It gets sterile sounding to me. But of course other amps will have different results. My amp is all tube and rated at 90 watts each channel. So it's clean. A 50 or 20 watter would have different sweet spots. I have a Mesa Fifty/Fifty and my tone is totally different then when using the 2:90. I prefer the 50:50 weight, but I'd rather have the better tone.
 
shouldnt make any difference to the level of tube saturation which ever way you run it.

Tube saturation will occur when the power values are trying to put a signal out that is approaching or above its max rated clean level. Because the volume on power amps is pre the power tube (ie it attenuated the input signal not the output signal usually), it wont matter whether you attenuate the signal just before the power amp (at the AFX output) or immediately after its entered the amp (amps vol level). The output signal strength would be the same either way for the same given output volume - and the amount of tube saturation would also be the same.

Of course if the power amps volume knobs attenuated the output signal AFTER the output tubes - then it would make a difference. I dont know how the Mesa (or any other) valve power amp works in that respect TBH, but its not normal for power amps in general to work like that.
 
paulmapp8306 said:
shouldnt make any difference to the level of tube saturation which ever way you run it.

Tube saturation will occur when the power values are trying to put a signal out that is approaching or above its max rated clean level. Because the volume on power amps is pre the power tube (ie it attenuated the input signal not the output signal usually), it wont matter whether you attenuate the signal just before the power amp (at the AFX output) or immediately after its entered the amp (amps vol level). The output signal strength would be the same either way for the same given output volume - and the amount of tube saturation would also be the same.

Of course if the power amps volume knobs attenuated the output signal AFTER the output tubes - then it would make a difference. I dont know how the Mesa (or any other) valve power amp works in that respect TBH, but its not normal for power amps in general to work like that.
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Maybe I should have used warmth instead of saturation. Most people think saturation only means pushing the amp to overdrive the tubes into distortion. In my 50 plus years quest for tone, I've owned just about every guitar tube amp. They all have a couple of different sweet spots, depending on whether you want warm Fender like cleans or Marshall/Mesa distortion. If I was looking for warm clean, I would turn down the pre amp and turn up the power amp, until I got the warmest tone before breakup. I would do the opposite depending on how much breakup I was looking for.
With the AXE, I wanted to achieve maximum tube warmth before natural breakup. I wanted a warm clean stage level coming out of the power amp, using whatever signal was going in. I had a stage volume decibel level in mind. The more I turned up the AXE and turned down the amp, the more sterile it sounded. And it didn't sound good when I turned the power amp all the way up and turned down the AXE to 5 or 10%. So I trusted my ears, walked around while playing and kept adjusting until I found what I feel is the sweet spot for what I was trying to achieve. I could probably turn the AXE down to 25% and bring the power amp up more. But I was extremely happy at 30% for the AXE and 50% for the amp.
My cleans have a Fender like warm tone. My over-driven presets have a fluid natural warm tone.
 
paulmapp8306 said:
shouldnt make any difference to the level of tube saturation which ever way you run it.

Tube saturation will occur when the power values are trying to put a signal out that is approaching or above its max rated clean level. Because the volume on power amps is pre the power tube (ie it attenuated the input signal not the output signal usually), it wont matter whether you attenuate the signal just before the power amp (at the AFX output) or immediately after its entered the amp (amps vol level). The output signal strength would be the same either way for the same given output volume - and the amount of tube saturation would also be the same.

Of course if the power amps volume knobs attenuated the output signal AFTER the output tubes - then it would make a difference. I dont know how the Mesa (or any other) valve power amp works in that respect TBH, but its not normal for power amps in general to work like that.
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In a perfect environment, this is true. However when you add noise and interference into the equation, gain staging has a big impact on the overall signal to noise ratio. When running signals over long cables you want to run the hottest clean signal possible in order to maximize the signal to noise ratio. From a noise perspective it is usually better to send a loud signal and then attenuate it at the destination because doing so also attenuates any noise that is picked up along the way, resulting in a better signal to noise ratio.

Lets say you need a 1 volt signal fed to your power amp to get the output volume you want. You could set your preamp to output that 1 volt signal and then turn your power amp's volume all the way up (no attenuation) and get the level you want. However for the sake of argument, lets say that the cable between the preamp and power amp picks up 0.25 volts of environmental noise along the way (that would be a huge amount but it's just for illustration). That means the total signal at the amp's input is now 1.25 volts so you turn it down a little to get back to 1 volt. With that setup you end up with 80% signal and 20% noise (1V signal to 0.25V noise). That's a poor signal to noise ratio. Now instead, say you set your preamp to output a 10 volt signal. Along the same cable it again picks up 0.25 volts of noise. Now the total signal at the amp's input is 10.25 volts. Since that's way to loud, you turn the amp's volume way down to get back to 1 volt. You end up with the same level from the speakers, but this time you have 98% signal and only 2% noise. It's a much better signal to noise ratio. Again the numbers are totally not realistic, but they illustrate the concept of signal to noise ratio.

That said, there's sometimes a rub. Some tube amps have treble bypass capacitors on their input volume controls (Bright or High Treble Channel). The caps have the side effect of bypassing more treble when the control is set low and less treble when it's set high. That usually means that the tone gets brighter the more you turn it down. In this case, sending a really hot signal and turning the power amp's volume way down might result in an overly bright tone, so sometimes you have to find the best compromise between tone and signal to noise ratio. Using good quality cables that are very well shielded and avoiding ground loops will give you more margin of error when it comes to signal to noise ratio.
 
I want posting from a STN ratio POV to be honest. The is exactly why I run the AFX hot and the PS lower - because it eliminates background noise (not just from the input signal but also any generated internally during the amp stage).

The bright caps do come into play - and maybe thats why TT prefers his set up as he does. The point is its almost certainly nothing to do with the actually tubes/amp stage adding anything more to the mix.

I believe the PS does have a bright cap (or at least a low pass filter network), and the new Mk 2 versions have this switchable, so set to taste.
 
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