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Wish Extend range of headroom meter above 0dB

Rex

Legend!
Can it also show how much (within reason, maybe max +10dB) 'into the red' the power amp is being driven?
So you want the meter to show you how much headroom you'd have if you had more headroom. :)

The Headroom meter corresponds exactly with plate voltage at the power amp. It physically can't go above 0 dB. It's the behavior of that voltage as it dances with the ceiling that tells you what the power amp is doing to your gain structure. IMO, that's more valuable than a "what if" meter that doesn't correspond to what the amp is actually doing.
 

Admin M@

Administrator
Fractal Audio Systems
Moderator
I imagine that Kent probably misinterpreted this as a conversation about a physical 3rd party power amp.
 

Joe Bfstplk

Fractal Fanatic
So you want the meter to show you how much headroom you'd have if you had more headroom. :)

The Headroom meter corresponds exactly with plate voltage at the power amp. It physically can't go above 0 dB. It's the behavior of that voltage as it dances with the ceiling that tells you what the power amp is doing to your gain structure. IMO, that's more valuable than a "what if" meter that doesn't correspond to what the amp is actually doing.
What is being requested is insight into how far beyond the available headroom you are pushing it i.e., how much is it being overdriven.
 

Rex

Legend!
What is being requested is insight into how far beyond the available headroom you are pushing it i.e., how much is it being overdriven.
You get that information by watching it’s behavior. Does It slam into the rail only on signal spikes, or does it hover near the rail? Or maybe a combination of those things? Or does it never approch the rail at all? The fact that it never quite reaches the rail — that can tell you something about what Sag is doing.

These are all indications of what the power amp is doing with your signal. And that’s what really matters. That’s much more useful information than the knowledge that “my signal would be 8 dB louder if I had a bigger power amp.”
 

IronSean

Experienced
@Rex I see what you're saying, and you can use some of those details and close examination and testing to determine if you're deep into power amp distortion or just tickling it.

But from playing with amps, some of them don't start running out of power amp headroom until 7-8, but the Recto amps are already running low at 3. If the meter showed you your peaks were tickling up to +3 in the red on one amp vs going up to +20db in the red on the other it would be an immediate indication that one of those is deeply into poweramp distortion.
 

Joe Bfstplk

Fractal Fanatic
You get that information by watching it’s behavior. Does It slam into the rail only on signal spikes, or does it hover near the rail? Or maybe a combination of those things? Or does it never approch the rail at all? The fact that it never quite reaches the rail — that can tell you something about what Sag is doing.

These are all indications of what the power amp is doing with your signal. And that’s what really matters. That’s much more useful information than the knowledge that “my signal would be 8 dB louder if I had a bigger power amp.”
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.
 

Joe Bfstplk

Fractal Fanatic
Maybe make it a dual meter with similar display to a stereo L/R meter, and have one side able to show drive signal up to +10dB with red beyond 0dB, and the other showing what is currently shown. Kinda like in/out metering on a compressor. For us non-MV amp users, how far over-the-knee is useful info....
 

Joe Bfstplk

Fractal Fanatic
You ain't 'splained it yet. ;)
Actually, I did:

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.
:p
 

Rex

Legend!
Actually, I did:


:p
No, you ain't. :p

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.
True.


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.
Non sequitur. The question stands. What makes it more useful than the current implementation? How would you use that information to dial in an amp? 'Splain?
 

Joe Bfstplk

Fractal Fanatic
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.

For example: to get a better sound for classic rock out of a Mark-series Boogie, it helps to use the graphic in a way that doesn't scoop out so much midrange and boost so much bottom and upper mids, and to turn up the master until it is just over the threshold into power amp distortion, so that as the notes decay, the bottom and upper mids bloom a bit, similar to how a cranked vintage low-gain amp works, but with more drive in the preamp. Doubtless the amount of drive is only a few dB before it starts sounding farty. 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....
 

JoKeR III

Power User
If the Headroom meter cannot/will not ever go over 0 dB, what is the purpose of having it read to +10 dB, or any level above zero?
Is the request for a different way the meter would show the headroom?

I messed around with it last night and it was pretty self explanatory: it's a ceiling for the signal. Max the Input Drive and Master Volume, turn on the Boost and you stay at the ceiling (-0.2 dB in my case). Turn off the boost and use different settings on the Input Drive and Master Volume and the varying, corresponding levels of how much below the ceiling (headroom) is visible. All readings respond to playing dynamics if the Input Drive and Master Volume are not set to 10.
 

Joe Bfstplk

Fractal Fanatic
If the Headroom meter cannot/will not ever go over 0 dB, what is the purpose of having it read to +10 dB, or any level above zero?
Is the request for a different way the meter would show the headroom?

I messed around with it last night and it was pretty self explanatory: it's a ceiling for the signal. Max the Input Drive and Master Volume, turn on the Boost and you stay at the ceiling (-0.2 dB in my case). Turn off the boost and use different settings on the Input Drive and Master Volume and the varying, corresponding levels of how much below the ceiling (headroom) is visible. All readings respond to playing dynamics if the Input Drive and Master Volume are not set to 10.
The current meter is basically analogous to the output level of a limiter. 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.
 
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