How much millivolts is 'instrument level'?

[RuudNL]

I have to design a box that converts 'instrument level' to balanced line level.
Preferably without a 'gain' knob.
Inputs can be guitar pickups, but also synthesizers etc.
OK, high input impedance for guitar pickups ( 1 M.ohms or more), that is for sure.
But what are the signal levels I can expect?
I have asked around and opinions vary between 'a couple of millivolts' and 250 mV.
Any opinions about this? I found that most manufacturers of digital pianos etc. do not specify output levels.
(I seems musicians live in a different world than we do...)

 

[gyraf]

Isn't this exactly what a DI-box is all about?

I've found "instrument" levels ranging from ca. 20mV to some 5.5V RMS. There is probably no way you can do a "universal".

Jakob E.

 

[RuudNL]

Isn't this exactly what a DI-box is all about?

True, but most DI-boxes deliver microphone level, not line level.
(Apart from some expensive ones.)

 

[sahib]

As Jacob said there is no way of having a  " one fits all " level output.

Build a unity gain amplifier so that if the level is too high for the receiving end (console?) then it can be turned down at the destination.  If you want the player to have a control over the outgoing signal level then stick a volume control.

 

[JohnRoberts]

I have to design a box that converts 'instrument level' to balanced line level.
Preferably without a 'gain' knob.
Inputs can be guitar pickups, but also synthesizers etc.
OK, high input impedance for guitar pickups ( 1 M.ohms or more), that is for sure.
But what are the signal levels I can expect?
I have asked around and opinions vary between 'a couple of millivolts' and 250 mV.
Any opinions about this? I found that most manufacturers of digital pianos etc. do not specify output levels.
(I seems musicians live in a different world than we do...)

Unfortunately "instrument level" does not exist as a simple single number,  I went through this exercise for an active  DI design back in the '80s.  I had the luxury of working at a company that also manufactured such sound sources so I went to the horse's mouth and asked guys like guitar designers who wound their own pick-ups. I did not get useful answers from them, so next I asked the engineers designing guitar amps what kind of input levels they encountered and got slightly better answers. 

My judgement was to take a more practical approach to this, namely how much power supply do the sound sources have to work with. The hottest guitar outputs are generally running from 9V batteries, so do your own math. Keyboards, generally send out singled ended audio from +/-12V to even +.-15V rails. I believe they target something like 500mV (lots of prosumer gear is in that ballpark) no doubt from cheap single supply audio circuitry.

If you are not putting gain trim in your interface make it low noise with lots of headroom so you can trim up/or down after it.

JR

 

[RuudNL]

Just measured the output of a Yamaha CP4 (digital stage piano): 30 mV! (On the jacks and XLR's)

 

[PRR]

Classic guitar amps take at least a half-Volt input without distress; yet can also be turned-up so that 20mV puts you on the edge of distortion.

I've seen all different things from "synths". The Yamahas do tend to be reasonable, though 30mV seems low. OTOH the patch-it-yourself ARP Modular would deliver 10V peak, and really preferred to work high-level. IIRC we had a pad to bring that down to something the recorders would eat.

Stage levels are ALL over the place and I think a no-knob interface won't work in all situations. It helps if the destination has VERY wide input range and the engineer is willing to turn his knob from one end to the other as needed.

 

[analogguru]

Professional Level is at +6 dBm (or +4 dBu) [1,55V)
Semiprofessional (Teac, Fostex, etc) and (japanese) consumer level (HiFi) is at -10dBm [300mV]
German DIN-Level (HiFi) is/was at - 20dBm [100mV]
Instrument level is between -40dBm and -20dBm [10mV - 100mV]
Mic Level is between -60dBm and -40dBm [1mV - 10mV]

 

[JohnRoberts]

Professional Level is at +6 dBm (or +4 dBu) [1,55V)

I'm not familiar with a +6dBm  standard but there is a 0VU=+4 dBu that as I recall was around 1.22V

Semiprofessional (Teac, Fostex, etc) and (japanese) consumer level (HiFi) is at -10dBm [300mV]

Bedroom recording gear used a -10dBV standard. -10dBV = 0.316V

German DIN-Level (HiFi) is/was at - 20dBm [100mV]

I'll have to take your word for this..

Instrument level is between -40dBm and -20dBm [10mV - 100mV]

Many guitars and keyboards put out a lot more than 100 mV, more like several volts,

Mic Level is between -60dBm and -40dBm [1mV - 10mV]

Like i said provide a low noise path, with a lot of headroom...

JR

PS: dBm is a power ratio wrt 1mW, archaic and hard to use accurately with modern gear.

 

[PRR]

> Mic Level is

I recall a mixer which came with a choice of input transformers. 30mV or 100mV.

Modern mike inputs (large condenser, close-micced) have to swallow nearly 2V cleanly.

(I have seen a higher level in a percussion orgy.)

 

[analogguru]

Professional Level is at +6 dBm (or +4 dBu) [1,55V)

I'm not familiar with a +6dBm  standard but there is a 0VU=+4 dBu that as I recall was around 1.22V
.....
PS: dBm is a power ratio wrt 1mW, archaic and hard to use accurately with modern gear.

Yes, probably archaic, but "instrument level" is archaic too.  The same with 100mV for HiFi (DIN 45500).

"dbm" was used by all german broadcast companies suppliers.
Here at the right column:
5. "Ausgang" (Output Level) ........ in dBm
http://www.wsw.cz/04WSW_SUMME_MONO/WSW_SUMME02.JPG

And here you can find more of it:
http://www.wsw.cz/index1.htm
http://audio.kubarth.com/rundfunk/index.cgi

And below you can find the - archaic - use of "mic" and "instrument inputs" on an analog echo from the 70's... including db-values.