Headroom

[Maaak]

I know this is kind of a newbie thing to ask, but I only have a general idea of what Headroom is and I'd like to get a fuller understanding. So far I think its the ammount of signal an amp can take without clipping or distorting, but I'm not sure.

Take my Eden head for example...it has a Gain control and a Master control. Is Gain equivalent to "level" and Master equivalent to "send"? Should I crank the Gain to get more "headroom" and control how much the amp is getting with the Master? Just not sure. Thanks guys!

 

[Happy MurphDay]

Im sure IvanMike can give you a better response but here it goes..

I believe head room is to be extra wattage. Amps clip when the wattage has hit its peak, so if you have extra wattage, then the amp wont clip as easy.

if you have a 100 watt head/amp and a cab that can handle 500, you would need to crank the amp to get the desiered volume. when cranked, the amp will hit its limit easier.

if you have a 1000 watt head and a cab that can handle 500, you wouldnt need to turn the amp up all the way to get your desiered volume, and a cab can handle double(debatable) its rms wattage, thus peak wattage, the amp wont clip as easy because you have significant headroom(extra wattage).

now with the amp, turn it up halfway, then set the master volume on the eden to a little more than half, then adjust the pre accordingly, if you need more volume adjust the amp first then the master(tweaks, not huge twists)

 

[billfitzmaurice]

Pretty close. Headroom is how much power/voltage/dB you have available over and above that which you are using at normal levels. Let's say when you're playing at average levels you are running at 50 watts. You have a 100 watt amp. That gives you 50 watts of available headroom. Sounds impressive, doesn't it? It ain't. That's only 3dB. Let's assume your transient peaks are running at 6dB over your average program power, which is a very conservative figure. Your amp is 100 watts shy of being able to deliver on them. A commonly accepted figure for minimum adequate available headroom is 10dB. So if you play at an average draw of 50 watts you should have a 500 watt amp to be sure of adequate clean power.

The good news is that a 50 watt average draw is very high; most bassists amps average closer to 20 watts average draw, so a 200 watt amp is generally adequate, though having more never hurts.

But that doesn't tell the whole story. An amp rated at 200 watts continuous may be able to deliver 10dB (2000 watts) or more on transients if it has an adequate power supply. How much transient power is available above continuous power is also is referred to as headroom. A cheap amp with a marginal power supply may have only 3dB of transient headroom available. That's a good reason to take wattage claims lightly when comparing amps. An inexpensive high wattage amp probably got to be inexpensive by using a cheesy power supply, and could easily be outdriven by a lower rated amp with more available transient headroom.

As far as gaining more power headroom via adjusting the gain and master controls, you don't. However, to prevent distortion, headroom is required in every stage of the amp, not just the output section. A good rule of thumb is to have both the gain and master set at about the same level, so that neither the preamp or power amp gain stages are overloaded. If anything have the main set higher. With guitar the opposite is generally true; you want distortion, so you set the gain high and the master low so that the preamp stage output overloads the power amp stage input.

 

[Jerrold Tiers]

Take my Eden head for example...it has a Gain control and a Master control. Is Gain equivalent to "level" and Master equivalent to "send"? Should I crank the Gain to get more "headroom" and control how much the amp is getting with the Master? Just not sure. Thanks guys!

Actually, that might give LESS "headroom".

Headroom is usually intended to mean an amount of additional signal available beyond what you are using.

So, if your device can produce a 10 volt signal, and you have it producing a 1 volt signal, you have about 20 dB of "headroom".

Any electronic device has a limit. It might be 10V for an SS preamp using op-amps, or 130V for a tube preamp with a high voltage supply.

In your example, turning up the gain produces a larger signal inside the preamp. That is closer to the limit, whatever it may be.

Then, turning DOWN the master causes a "loss" of signal to bring it down to your desired output. It takes more signal that it used to to get teh same output.

In that case, what was a 1 volt signal internally might be now a 5 volt signal, while the max is still 10V. Then your formerly 20dB of headroom is now only 6 dB before the gain stage clips. Fine if you want "grunge", not so fine if you want clean.

Cranking the master wide open eliminates the "loss" and requires less output from the gain stage. That increases the difference between teh actual level and the max level, and increases "headroom" per the above definition.

You will now be able to get the cleanest signal output right up to the point where the output stage of the preamp runs out of "headroom". The only limit is the power amp capability.

Note that the power amp, internal or external, still requires the same amount of signal for full output. If that is 1 volt, the 10 volt capability of the preamp isn't going to limit output at all.

But, if you start turning down the master volume, at some point a previous stage will have to produce more than 10V to get 1 V at the output of the pre. It will clip before you can get 1 volt output. Then you get distortion, wanted or unwanted, and "headroom" goes to zero...

 

[Happy MurphDay]

thanks for backing me up guys and giving me the low down to

 

[Joe Beets]

Headroom to me is when your rig has enough extra power that you can thump on your "E" string as hard as you want and it doesn't make that fart sound at the beginning of the note.

 

[Maaak]

Thank you very much guys!

\m/

 

[quatre03]

ok so now i have a question...

take a stewartwold 2.1 power amp

2100 watts @ 4 ohms

and a schroder(sp?) 3101212

2100 watts @ 4 ohms

would that give me 0 head room???

or would maxing out a 300 watt amp into a 500 watt cab give me 0 head room??

and is it ok to match up cabs with the same wattage with heads of the same wattage like the stewartwold 2.1 and the schroder??

 

[nicoli]

The relationship between head and cab doesn't matter that much as far as headroom goes, it applies more to amps than cabs. The cab just has to be able to handle the power that the amp puts out.

You'd have more headroom with the 2.1 than with the 300watt head, because you'd be using a lower percentage of the available power of the 2.1. Maxing out the 300 watt head would mean you have '0' headroom, but hitting 300 watts on the 2.1 would mean you have a lot more available power still.

 

[ezstep]

...most bassists amps average closer to 20 watts average draw, so a 200 watt amp is generally adequate, though having more never hurts.

I believe this statement, although I am sure that some won't.

I have a JVC powered AM/FM receiver with a watt meter built in. I have a decent pair of stage monitors for speakers. I swear, I hardly ever turn the volume up over 1/4 watt. One watt is almost too much. Two watts is too loud. It will go to 50 watts per channel, but I have never had it there.

I recently bought a 100 watt combo with CD inputs and headphone output for bedroom practice. Instead, I have used this amp on three gigs as my main amp (small rooms, of course). It is very loud. Much louder than I would have guessed.

I learn something everyday. Thanks, guys.