Impedance ?

  • Thread starter Thread starter Fancy
  • Start date Start date
Is this 10X impedance rule per channel?
For example, a mic with 200ohm output
impedance would be okay going into
a pre with 2000 ohms input impedance,
but could I use two of the 200ohm mics into
that same pre?
 
Fancy said:
So my overheads can be at the drummer's perspective, with little phase issue if I reverse the phase of my kick?
Click to expand...

If you can hack it, try to respect polarity throughout the signal chain from mike to speaker. The others should be reversed. Leave the kick alone.

Cheers,

Otto
 
I still don't understand why the attention should be given to the snare, when the kick is the downbeat?
 
Fancy said:
I still don't understand why the attention should be given to the snare, when the kick is the downbeat?
Click to expand...
Leave the kick alone.


But, I can't.
 
huh????

I don't think the mics know what the beat is...Or the time signature.....Or the tempo either....Or was that a joke???

Phase cancellation has nothing to do with that. It's about how long one signal takes to reach 2 (or more) mics. I find it affects the snare more because the snare leaks into the overhaeds alot more than the kik does.
 
RAMI said:
huh????

I don't think the mics know what the beat is...Or the time signature.....Or the tempo either....Or was that a joke???

Phase cancellation has nothing to do with that. It's about how long one signal takes to reach 2 (or more) mics. I find it affects the snare more because the snare leaks into the overhaeds alot more than the kik does.
Click to expand...
But doesn't the kick have a lot more to do with the downbeat, and the overall drum sound?
 
Farview said:
Remember, the kick mic is the only one on the kit that sees the head moving towards it when it is struck, all the other mics see the head moving away.
Click to expand...
Actually, all bottom head mics (i.e. toms, snare) see the heads moving towards the mic.

All mics placed on the top side of the drum see a negative going pulse and all mics on the bottom side see a positive going pulse. If micing both sides, one should consider polarity switching one mic if the two are to be mixed.
 
Brackish said:
Is this 10X impedance rule per channel?
For example, a mic with 200ohm output
impedance would be okay going into
a pre with 2000 ohms input impedance,
but could I use two of the 200ohm mics into
that same pre?
Click to expand...

Yes, each channel has the stated input impedance, so you are fine.
 
"Impedance Matching" for small signal (line level) and power (amp->speaker) are not the same.

For small signal, generally do not concern yourself with matching impedance levels. Matching the types of interfaces is of importance (e.g. -10dbv +4dbu ...).

When transferring power, matching source and load correctly is very important.

The 10X guide should be taken very loosely.

The mic/preamp 10X guide seldom applies. Refer to the manufacturers suggested interface. For instance a 57 likes a load of 300ohms. Different loading will affect the signal in different ways. Try different loading and use what sounds best.

Transformers load differently than active input loads. Transformers are purely inductive whereas active inputs are mainly RC or only resistive.

Also one needs to know whether active or passive circuits are being interfaced.

Summary, there's a lot more to this than matching impedances.
 
Keiffer said:
Actually, all bottom head mics (i.e. toms, snare) see the heads moving towards the mic.

All mics placed on the top side of the drum see a negative going pulse and all mics on the bottom side see a positive going pulse. If micing both sides, one should consider polarity switching one mic if the two are to be mixed.
Click to expand...
OK, I forgot to type "in his situation" before I typed the rest of it. It was 1:30 am, sue me.
 
Keiffer said:
"Impedance Matching" for small signal (line level) and power (amp->speaker) are not the same.

For small signal, generally do not concern yourself with matching impedance levels. Matching the types of interfaces is of importance (e.g. -10dbv +4dbu ...).

When transferring power, matching source and load correctly is very important.

The 10X guide should be taken very loosely.

The mic/preamp 10X guide seldom applies. Refer to the manufacturers suggested interface. For instance a 57 likes a load of 300ohms. Different loading will affect the signal in different ways. Try different loading and use what sounds best.

Transformers load differently than active input loads. Transformers are purely inductive whereas active inputs are mainly RC or only resistive.

Also one needs to know whether active or passive circuits are being interfaced.

Summary, there's a lot more to this than matching impedances.
Click to expand...
His original question was about interfacing his outboard mic preamp with the line input of his mixer. He was wondering if he needed to use his matching transformer. The answer is no.
 
Farview said:
OK, I forgot to type "in his situation" before I typed the rest of it. It was 1:30 am, sue me.
Click to expand...
Wow... not have our Cheerios this morning :rolleyes:
 
Farview said:
His original question was about interfacing his outboard mic preamp with the line input of his mixer. He was wondering if he needed to use his matching transformer. The answer is no.
Click to expand...
Initally I was directing the comment to Brackish...

Brackish said:
Is this 10X impedance rule per channel?
For example, a mic with 200ohm output
impedance would be okay going into
a pre with 2000 ohms input impedance,
but could I use two of the 200ohm mics into
that same pre?
Click to expand...

I guess I covered more than I had initially intended.
 
Keiffer said:
Wow... not have our Cheerios this morning :rolleyes:
Click to expand...
...and ran out of coffee and stepped in cat puke coming out of the shower.
 
Farview said:
...and ran out of coffee and stepped in cat puke coming out of the shower.
Click to expand...
Damn.....and then find out in the morning that Fancy's a girl?! :eek:
 
what if you have a 30k unbalanced, -10 tape recorder input, and a 600 ohm, balanced +4 mic pre output. what kind of transformer would you use?

say you have a 150 ohm -10 unbalanced tape recorder output, and a 40k balanced mixer input. what kind of transformer would you use?
 
FALKEN said:
what if you have a 30k unbalanced, -10 tape recorder input, and a 600 ohm, balanced +4 mic pre output. what kind of transformer would you use?

say you have a 150 ohm -10 unbalanced tape recorder output, and a 40k balanced mixer input. what kind of transformer would you use?
Click to expand...
None and none. Impedance isn't the issue in these instances, gain structure is. In the first instance it won't be much of a problem because going from balanced to unbalanced, you will lose 6db so you will only be 5db hot. Just turn down the mic pre.

In the second instance, you will just need to turn up the gain on the mixer input. The impedances are good all the way around.
 
Fancy said:
10x 600ohms would be 6K. I'm at a loss, it seems it should be a more precise science.

Thanks, much!
Click to expand...

Hi:

I think what Mr. Farview talking about is:

Input should be something abt 10x of a device which is going into it.


e.g.
Think about a guitar pick up going into a standard input of your mixer, u know how it sounds like - Like a chicken, little sound even if u crank things up. that's just because it didn't follow the rule above.

The guitar's pick have a high impedance (resistance) itself, only little current is generated from the vibration of strings on top of the magnetic coil. If this weak signal's impedance is something higher than 10x than the input that it's going into, well, no sound.

However, if the guitar sound were coming from a guitar preamp, the preamp-ed signal is going into the input which have higher impedance, good sound.
 
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