• We would like to remind our members that this is a privately owned, run and supported forum. You are here at the invitation and discretion of the owners. As such, rules and standards of conduct will be applied that help keep this forum functioning as the owners desire. These include, but are not limited to, removing content and even access to the forum.

    Please give yourself a refresher on the forum rules you agreed to follow when you signed up.

Wish Extend range of headroom meter above 0dB

Rex

Legend!
Okay, I see what you're saying, @Joe Bfstplk , but consider:

Many of the dirty amps like Recto and Mark-series Boogies put out a rather compressed, peak-free signal from the preamp. The method you suggest for watching how hard/long it hugs the 0dB mark on the meter doesn't really help understand how far they are pushing beyond the available headroom.
It does, though. If the spikes peak out below the rail, you're running the power amp clean. If they run to the rail with a little dwell, you're in light overdrive. If the troughs rise and they dwell a bit longer, you're in moderate overdrive. If you're slammed to the rail, your tone farts like cattle eating silage. :) You can use the same concepts to visualize the behavior of held notes as they decay.


With a compressed preamp signal, the current metering fails to help find that other sweet spot just above the threshold of power amp distortion. It can be dialed in by ear if you have lots of time to tweak and listen, but it is easily measurable, and the propsed metering improvement would show that info....
There is no formula for how much overdrive constitutes any sweet spot. That depends on the amp, the EQ, the signal... It must be determined by ear, whether there's a headroom meter or not. No level meter can tell you how the mids are behaving relative to other frequencies. You have to hear it.

Notice that the signal never quite gets all the way to the power rail. That's because the supply voltage sags to meet the signal. That sag is part of the power amp's reaction to the signal, and it affects the sweet spot. If you allow the Headroom meter to rise above 0 dB, you lose access to that information.
 

Joe Bfstplk

Fractal Fanatic
Okay, I see what you're saying, @Joe Bfstplk , but consider:


It does, though. If the spikes peak out below the rail, you're running the power amp clean. If they run to the rail with a little dwell, you're in light overdrive. If the troughs rise and they dwell a bit longer, you're in moderate overdrive. If you're slammed to the rail, your tone farts like cattle eating silage. :) You can use the same concepts to visualize the behavior of held notes as they decay.



There is no formula for how much overdrive constitutes any sweet spot. That depends on the amp, the EQ, the signal... It must be determined by ear, whether there's a headroom meter or not. No level meter can tell you how the mids are behaving relative to other frequencies. You have to hear it.

Notice that the signal never quite gets all the way to the power rail. That's because the supply voltage sags to meet the signal. That sag is part of the power amp's reaction to the signal, and it affects the sweet spot. If you allow the Headroom meter to rise above 0 dB, you lose access to that information.
Actually, you're wrong when it comes to already thoroughly distorted preamp signals. The peaks are largely clipped, and the signal is fairly well compressed. This is not conducive to your method working beyond the threshold of power amp clipping.

As far as metering, you can hear a thing and note the position of a meter when you hear it, then dial it in repeatedly elsewhere. Metering is not a bad thing....
 

Rex

Legend!
Actually, you're wrong when it comes to already thoroughly distorted preamp signals. The peaks are largely clipped, and the signal is fairly well compressed. This is not conducive to your method working beyond the threshold of power amp clipping.
But that situation is the opposite of the use case that you presented and I was addressing. ;)
 

Joe Bfstplk

Fractal Fanatic
But that situation is the opposite of the use case that you presented and I was addressing. ;)
Actually, if you go back to my original example, it is exactly the use case I presented....

Depends on what end result you are after and what type of amp it is. Many of the classic amps get the dirt by driving the power amp into distortion. Mark series Boogies can do a bit better for classic rock sounds with a little bit higher master volume setting that 'tickles the red' in the power amp and less mid scoop in the graphic. Knowing how far past the 0dB point is useful info that is not always entirely obvious from watching how long/closely it hugs the power supply rail.
 

Smilzo

Power User
Essentially, I am asking for the input meter to go with it, with the 0dB point synced to the point of limiting/clip, for the purpose of determining the optimal amount of power amp drive signal.
There's no way an "optimal amount" complex signal like guitar playing could be determined by a meter between 2 non linear stages.
 

Joe Bfstplk

Fractal Fanatic
There's no way an "optimal amount" complex signal like guitar playing could be determined by a meter between 2 non linear stages.
LOL. Neither triode gainstages nor any stripe of power amp is linear, clean or dirty. By your logic, the existing meter is superfluous.
 

Smilzo

Power User
By your logic, the existing meter is superfluous.
It's a visual indication, like the setting of a knob. If you like the sound, you can have a look at the value/indication. You can learn by the meter that you like lot's of headroom of no headroom. A useful learning tool.
 
  • Like
Reactions: Rex
Top Bottom