Understanding Mic level vs Instrument Line level vs HiZ???

[dang]

Looking at mixers right now, and the Allen and Heath ZED-10 that is my current front runner has 4 mic channels, and below the first 2 XLR inputs the 1/4" input is labeled "line" and the last 2 the 1/4" are labeled guitar 1 and guitar 2 with Hi-Z underneath each.

What is the difference in signal that each of these 3 inputs is made for? Obviously the XLR is a different connector, but there seems to be a lot of obfuscation around these concepts in my mind. And I thought I was just beginning to understand hi impedance and ultrahigh impedance.

I found this reference I think cleared it up a little for me, but not entirely:

"Some common levels you'll see:
+4 dBu is "professional" line level, common in modern pro recording gear, and it is about 1.25 V.
0 dBv is an average line level, typical output from rackmount guitar/bass preamps.
-10 dBv is "consumer" line level, common with older and cheaper recording gear.
-20 dBu is roughly in the neighborhood of a typical instrument's output.
-30 dBu is again in the neighborhood of a typical microphone or DI box's output.
However, instruments and microphones can have a very wide range of output levels in reality, so it is most practical to think of instrument-level and mic-level in/outputs as just "a lot lower than line level", rather than calculating specific dB amounts."

General picture shaping up in my head... but where do the ultra high impedance piezo pickups and Hi-Z fit in? Isn't Z impedance, so... high impedance? Isn't that line?.

Are active pickups and electric guitar pickups both in the -20 dBu range?

Where does the Schertler Dyn-M fit in this? In the technical specs it says "sensitivity (on instrument) ca.-30dBu." So that is why everyone says to treat it like a mic?

Condensor mics? Where do they fall?

THANKS in advance (again)! This site rocks...
Dan G.

P.S. thanks to "foldedpath" for starting this inquiry for me - a "quick tip" raised some questions in my mind

[Toni Schula]

I try a brief summary here:

MIC inputs:
Connector: XLR (balanced)
Typical gain in the range of 10 to 60dB.
Typical input impedance is in the range of a few kilo ohms, e.g. 2kOhm.
Can provide phantom power. 48V is typical.
Most Condensor MICs require Phantom Power. Dynamic MICs do not need phantom power but easily handle it. (Ribbon MICs usually do not need phantom power and might be damaged by phantom power, especially with faulty cables/connections. Ribbon MICs typically need higher gain of up to 80dB. But ribbon MICs are not the common use case.)
On some mixers the XLR MIC inputs also serve as line in. Meaning that the bottom end of the gain range is extended to start from e.g. -10dB (attenuation) or max 0 dB. On other mixers there are separate line in connectors.

Line In:
Connector: quarter inch jack
Can be balanced (using TRS connectors) or un-balanced. In all cases I know balanced inputs can be used with un-balanced sources.
Also XLR connectors can be used for balanced line inputs (which also might be useable with un balanced sources with adaptor cables).
Typical input gain: -10 dB .. + 10 dB.
Input Impedance typically 600 Ohm.
0 dB is usually "+4 dB" = 1,228 V RMS

Line in consumer equipment:
Connector: RCA connectors (called "Chinch" in EUrope).
In some cases also 3,5 mm stereo jacks (same as for walkman headphones) are available.
Level is "-10dB".
Typically used for playback sources on many (even professional grade) mixers.

Guitar In, HiZ
Connector: 1/4" jack (unbalanced)
Is meant for the magnetic pickup of an electric guitar.
Typical input Impedance is 500 kOhms.

Piezo PU:
Connector: 1/4" jack (unbalanced)
Needs an input impedance in the range of several Mega Ohms. 10 to 20 MOhms can be found in contemporary equipment. With lower Impedance (such as HiZ) piezo PUs can sound quacky.
Usually not available on mixing consoles. Typically available on acoustic amps and acoustic preamps.

Schertler DynM:
Is effectively a dynamic microphone.
-> can be directly connected to the mic in XLR.
-> does not need but can accept phantom power.

AKG C411:
Is effectively a condensor mic (or rather a electret mic ?):
Depending on cabling:
- Mini XLR: needs a phantom power supply. This can be switched from mic level output to line level output.
- XLR: needs phantom power. Connect to XLR mic input.

DPA 4099 with XLR barrel (DAD 4099):
Is effectively a condensor mic (really an electret mic).
Connect to XLR mic input, needs phantom power.

Condensor Mics:
-> connect to Mic in XLR
-> usually need phantom power
There are some esotheric tube condensor microphones in the market which ship with their own power supply.
There are condensor mics in the market which can be battery powered if no pantom power is available.
There are condensor mics which require full 48 V and there are some which are happy with lower voltage phantom power.

cheers
Bauzl

[foldedpath]

Bauzl has it, above.

One small correction: when an input on a mixer or preamp is labled "High-Z", it usually means an impedance much higher than 500 kOhm. It's designed for things like passive piezo pickups, or magnetic pickups on acoustic instruments where you want full frequency range and no capacitance loading. Typical impedance would be in the 1 to 10 MegOhm range.

On the Zed-10 mixer, for example, the two "GTR High-Z" jacks on channel 3 and 4 have a 10 MegaOhm impedance. As an added feature, there are also two switches on the back of the mixer that can add a 26db boost for weak pickup signals on those inputs. Without those switches enabled, the inputs act as normal line inputs with a high impedance that won't affect most things you'd connect to a mixer line input, like an electronic keyboard. High-Z inputs on any gear like this is basically a convenience so you don't need an additional DI box for instruments with passive pickups.

With an "active" pickup (built-in preamp), or if you're using an external preamp/DI, then you're already impedance matched, and it's just a question of whether you're taking a 1/4" cable into the mixer's line input (if the signal is hot enough), or if the preamp has a balanced XLR output running at mic level, so you go into the mixer's XLR mic input. Generally speaking, you want the balanced cable if it's a long cable run to the mixer, or you're using a house snake on stage. The "balanced" design uses phase rejection to eliminate any electrical interference the cable picks up. But anything 50 feet or less usually isn't a problem on an unbalanced 1/4" cable unless you're in a really active EM environment.

[almeriastrings]

AKG C411:
Is effectively a condensor mic (or rather a electret mic ?):
Depending on cabling:
- Mini XLR: needs a phantom power supply. This can be switched from mic level output to line level output.
- XLR: needs phantom power. Connect to XLR mic input.

Minor point... the XLR requires phantom power.

However, the mini-XLR as seen on "wireless" versions designed to plug into a transmitter body pack, actually uses a version of A-B power in the 5-10v range. This is similar (but not identical to) the "plug in power" seen on consumer recorder mics, e.g., many Sony devices. Main difference is that "PiP" uses a reduced voltage of 3-5V and the connection wiring is different.

[Toni Schula]

Minor point... the XLR requires phantom power.

However, the mini-XLR as seen on "wireless" versions designed to plug into a transmitter body pack, actually uses a version of A-B power in the 5-10v range. This is similar (but not identical to) the "plug in power" seen on consumer recorder mics, e.g., many Sony devices. Main difference is that "PiP" uses a reduced voltage of 3-5V and the connection wiring is different.

Thank you Almeriastrings for correcting my sloppiness. Of course the power supply for the mini XLR provides A-B power rather than phantom power. I had the B29L battery power supply in mind but did not remember the type when writing this during lunch break.

best regards
Bauzl


By the way (in reference to an awkward other thread) I have seen a Flamenco show in semana santa in Granada (Tablas Flamenco Granada) and can confirm that they needed very little amplification for an audience of 60. Probably they would have done without any amplification at all (but then I guess they would have problems to run 3 shows per day). Maybe because we were no soccer hooligans.
The entire trip through Andalusia was very impressive, unfortunately Granada was as close as I would get to Almeria.

[dang]

Thanks for all the replies, lots of great info here!

Just to clarify...

Guitar In, HiZ
Connector: 1/4" jack (unbalanced)
Is meant for the magnetic pickup of an electric guitar.
Typical input Impedance is 500 kOhms.

Piezo PU:
Connector: 1/4" jack (unbalanced)
Needs an input impedance in the range of several Mega Ohms. 10 to 20 MOhms can be found in contemporary equipment. With lower Impedance (such as HiZ) piezo PUs can sound quacky.
Usually not available on mixing consoles. Typically available on acoustic amps and acoustic preamps.

One small correction: when an input on a mixer or preamp is labled "High-Z", it usually means an impedance much higher than 500 kOhm. It's designed for things like passive piezo pickups, or magnetic pickups on acoustic instruments where you want full frequency range and no capacitance loading. Typical impedance would be in the 1 to 10 MegOhm range.

On the Zed-10 mixer, for example, the two "GTR High-Z" jacks on channel 3 and 4 have a 10 MegaOhm impedance. As an added feature, there are also two switches on the back of the mixer that can add a 26db boost for weak pickup signals on those inputs. Without those switches enabled, the inputs act as normal line inputs with a high impedance that won't affect most things you'd connect to a mixer line input, like an electronic keyboard. High-Z inputs on any gear like this is basically a convenience so you don't need an additional DI box for instruments with passive pickups.

I think I get it, but in the last line you say additional DI box - would that be to run it into the XLR input? Wouldn't you still have the impedance mismatch?

And it's funny how you can just throw something out there like capacitance loading and I realize how little I understand of this subject...

Thanks!

[Toni Schula]

Thanks for all the replies, lots of great info here!

Just to clarify...
I think I get it, but in the last line you say additional DI box - would that be to run it into the XLR input? Wouldn't you still have the impedance mismatch?

Thanks!

A DI box output would run into an XLR input. So you can use it with a long cable between the DI box and the mixer.
On the input side a DI box accepts an instrument's unbalanced output such as keyboard, electric guitar, piezo PU, etc.
So basically a DI box converts an instrument's output to a balanced (microphone like) signal. It takes care for impedance matching. So you can directly plug in an instrument into the desk via the DI box. That's where the name comes from: direct in. The in-direct alternative with e.g. electric guitars is to use a microphone in front of the guitar amp.
Some DI boxes are passive (need no power supply), some are active. Some of the active ones can be powered from the desk by phantom power. Some offer special features for acoustic instruments such as input impedance in the 10 Mega Ohm range for piezo PUs, notch filters and phase reverse for feedback fighting.

[almeriastrings]

Bauzi,

If you ever pass this way again, look me up. We can pick some mandolin and talk microphones and soldering irons

Dang,

The ZED 10 is a very good sounding small mixer. The FX version is a bit more, but the FX provided (reverbs especially) are very good (unlike some small mixers where they are often very poor). Of all the small mixers I have used, the Allen & Heath ZED series and the Soundcraft EFX series are by far the nicest.

The Hi-Z inputs on the ZED 10 really qualify as being called "Hi-Z+" as they are higher than many specialized acoustic preamp and DI units. They are the same as you get on a Tonebone or Headway... 10 Meg. You can even plug a passive piezo in there, for example. So no external box needed at all (unless you need some other feature they happen to offer). They are also happy with the output from active transducers, those with a built-in preamp or active endpin jack, for example.

To clarify all this. If you have an ACTIVE piezo-based transducer installation in your instrument (i.e., if it need batteries or some other power source to work) then you already have a preamp taking care of impedance matching on the input side. You can plug the 1/4" cable from one of these into any normal DI box then into the Mixer XLR. No problems at all.

If you are using a totally passive transducer, then impedance is much more of an issue. Here you do need a very Hi-Z input and you should keep cables as short as possible. All cables have some capacitance. This acts a bit like a very old fashioned 'tone control' as seen on grannie's radio... the more capacitance there is, the more higher frequencies get cut off... it creates a low-pass filter. This is especially obvious with weak signals (from passive pickups) flowing into Hi-Z inputs. The best thing is to keep cables from passive pickups to the initial preamp stage as short as possible, and use high quality low-capacitance cable (but this does not have to be ridiculously over-hyped, over-priced stuff - ordinary good quality pro cable is fine).

[dang]

The Hi-Z inputs on the ZED 10 really qualify as being called "Hi-Z+" as they are higher than many specialized acoustic preamp and DI units. They are the same as you get on a Tonebone or Headway... 10 Meg. You can even plug a passive piezo in there, for example. So no external box needed at all (unless you need some other feature they happen to offer). They are also happy with the output from active transducers, those with a built-in preamp or active endpin jack, for example.

Thanks (again), exactly what I was wondering!

[mandroid]

Where does the Schertler Dyn-M fit in this?

I have one .. I plug it in to a Mic channel .. and use the Mic Preamp and the channel EQ controls. XLR, TRS combo jack


I only use a Roland AC 60 .. there is a Instrument channel too .
they switch between a Piezo or magnetic coil Pickup , 1/4" TR Jack.