Nominal Input Level and Nominal Output Level

[rogeryu_ph]

Hi Guys,
Most of the Boss pedal i found in their spec has this stated NOMINAL INPUT LEVEL -20dBu and NOMINAL OUTPUT LEVEL
What does this mean?

[John Lyons]

Basically just that the input of the pedal is typically -20 decibels which is "instrument level" roughly.

[rogeryu_ph]

Basically just that the input of the pedal is typically -20 decibels which is "instrument level" roughly.

Hi John, I forgot to indicate it states NOMINAL OUTPUT LEVEL is also -20dBu ! is that also mean the same? And does our guitar level is -20dBu? Thanks mate.

[R.G.]

"dbU" is normally defined as 0.775Vrms, so -20dbU is 0.0775V rms, which is 0.108V peak.

[rogeryu_ph]

"dbU" is normally defined as 0.775Vrms, so -20dbU is 0.0775V rms, which is 0.108V peak.

Yes R.G. you guided me there before and remember -10dBu is 0.245Vrms. What i like to know is the literal meaning of NOMINAL INPUT LEVEL stated in the Boss pedal spec. Even other pedal brand for sure it has it own Nominal spec. Does this means THE LEAST feed dBu level that the pedal could process or handle and below that dBu the pedal may not work? Am i correct? In this case is -20dBu then how do we know we're feeding Nominal or below dBu spec e.g. guitar to my Boss MT2? and what is the Ideal dBu level? Does this have bearing to input impedance our DIY circuit stuff we made, i meant i built many project yet I don't know whats the Nominal dBu input particularlly when someone or a friend ask me. Is there a guide for this.... If i'm totally wrong can you enlighten me more on this, sorry R.G for many question.....

[R.G.]

"Nominal" means "We call it this level, even though we know that it may be different from that. We think it's more likely to be somewhat close to this than to be vastly different."

That is, it's a guideline only, not a specification or a rule. Unfortunately, this has little bearing on our DIY designs, other than telling us that Boss thinks guitars put out about 100mV peaks, too. It's neither a minimum, a maximum, nor an average. It's an expected value that may well be violated.

Sorry - not what you're looking for, I know.

[R O Tiree]

There's going to be quite a bit of headroom built in to them, but a hot humbucker can push out in the order of +/-1.2V p-p (total 2.4V) and EMGs etc push out a lot more than that. Makes you wonder why we insist on powering our pedals with 9VDC, doesn't it?

[DDD]

Usually NOMINAL input level (or output level, or ambient temperature, or power supply voltage, etc.) is a characteristic of a device, within which other device properties are guaranteed.

[R.G.]

Makes you wonder why we insist on powering our pedals with 9VDC, doesn't it?

I know that was a rhetorical question. However, we use 9V because we're constrained by history - we use 9V because early portable radios used 9V and that caused 9V batteries to be common, and early pedals picked up 9V batteries because they offered more headroom than one or two single-cell carbon-zinc batteries at the time.

It's kinda like why we cling to high-impedance, single-ended pickups, cables, and jacks; because the first popular ones used that, so everyone jumped on the bandwagon, so the old, highly prized devices use it, so you can't sell anything that doesn't use it.

History is not only something to learn from, it's a straitjacket in many ways.