Low-impedance microphones to high-impedance

[oran.outan]

Hi

Does Someone will have a schematic/circuit that making low-impedance microphones to high-impedance !?
like something like this : BOOSTMATE MICROPHONE TO PEDAL EFFECTS CONVERTER — TONECRAFT AUDIO

maybe just using a transformer !?
does this one will do the job: OEP A262A2E (primary in parrallel / secondary in serie !?)

Thanks !
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[kingkorg]

Hm, i am not really sure what you're trying to do. I not sure either if that box is doing what it's claiming to do.

What mic? Something like sm57? I don't think it's the impedance that's the issue. Sm57 doesn't have enough "juice" to drive a pedal.

Really simplest way that comes to mind would be mic>mic pre>reamp box>pedal.

I guess you can make something like the famous 5$ pre plus output transformer that would drop the signal level/rise impedance to something a pedal can take.

 

[mhelin]

I think OEP A262A3E would give you similar gain like the inline Shure A85F if connected like proposed. It does not make a guitar pedal an ideal mic pre but might work for some lo-fi purposes if the pedal has enough gain and the cable between transformer and pedal is very short.

 

[Newmarket]

I guess you can make something like the famous 5$ pre plus output transformer that would drop the signal level/rise impedance to something a pedal can take.

If trying to get a typical "guitar level" then you probably need to boost the mic signal (hence the "Boostmate" I guess. Doing that with a passive transformer solution will increase the impedance.
If you "drop the signal level" with a transformer then the impedance of the output is lower.

 

[Newmarket]

The impedance is not really an issue. You can put a "low Z" signal into a pedal (that has a high impedance input) with no problem. Although a microphone may have a different frequency and dynamic response compared to using a typical mic input (say 2K2 Input-Z). Indeed it has been advocated to use higher input impedances to improve consistent results with different microphones).
When you feed one pedal into another you are often putting a signal that is low or medium Z into the pedal.
Signal level is the thing. If you want to boost the mic signal then you can do this with a mic pre solution - and you keep the output Z low. Or with a transformer used to increased level output with higher Z. Input Z seen by the mic depends on the pedal input level and the transformer ratio.

Note that "Fuzz Face" type pedals are an exception - they have a lowish input impedance and require a high-Z source eg a passive guitar pickup - in order to sound as you expect.

 

[oran.outan]

Thank for your return...
I'm not planning to plug a Dynamic Microphone into pedals...

On an 'experimental' instrument with a specific electronic circuit that reproduce e-bow, I have 4 pick-up Mic that I have to isolate each other, so I used 4x CAPI HI-Z plug-in which is a Hi-z to mic impedance... that next is ending to a combined output (the 4x plug-in Output into 1 output)...

Same if the Capi Hi-z plug-in output is Out+/Out-, I don't think/not sure it will be able to drive long distance cable like from stage to control room... and run into a Preamp !? but Maybe I'm Wrong ???
So I was thinking to come back on a Hi-z level and 1st run on a DI, and then going on a Mic Preamp...
But Yes, kind of stupid to move form Hi-z to Low-Z and comeback to Hi-z ! but I don't see other Way for now°°°

Any suggestion is welcome...

I hope I'm clear !?

Best
F

 

[Newmarket]

Thank for your return...
I'm not planning to plug a Dynamic Microphone into pedals...

On an 'experimental' instrument with a specific electronic circuit that reproduce e-bow, I have 4 pick-up Mic that I have to isolate each other, so I used 4x CAPI HI-Z plug-in which is a Hi-z to mic impedance... that next is ending to a combined output (the 4x plug-in Output into 1 output)...

Same if the Hi-z output is Out+/Out-, I don't think/not sure it will be able to drive long distance cable like from stage to control room... and run into a Preamp !? but Maybe I'm Wrong ???
So I was thinking to come back on a Hi-z level and 1st run on a DI, and then going on a Mic Preamp...
But Yes, kind of stupid to move form Hi-z to Low-Z and comeback to Hi-z ! but I don't see other Way for now°°°

Any suggestion is welcome...

I hope I'm clear !?

Best
F

Mmmm...I'm failing to see why there is '@Hi-Z' involved at all. I'm assuming that your "4 pick up Mic" are low -Z mics so you don't really need the CAPI Hi-Z ???.
I think I may be missing something here so will wait to see if others have more understanding. Good luck in any case.

 

[oran.outan]

Mmmm...I'm failing to see why there is '@Hi-Z' involved at all. I'm assuming that your "4 pick up Mic" are low -Z mics so you don't really need the CAPI Hi-Z ???.

The 4 pick-up Mic are coil microphone like 'guitar Mic', so on Hi-z impedance...
the use of the Capi Plug-in is I have to 'isolate' them each others before going on a combine output... otherwise the e-bow feedback loop is 'corrupt' as the 4 pick-up signal are mixing together and the e-bow thing is not working properly...

In link is a diagram of the 'circuit', that will probably help undertsnading...

 

[Newmarket]

The 4 pick-up Mic are coil microphone like 'guitar Mic', so on Hi-z impedance...
the use of the Capi Plug-in is I have to 'isolate' them each others before going on a combine output... otherwise the e-bow feedback loop is 'corrupt' as the 4 pick-up signal are mixing together and the e-bow thing is not working properly...

In link is a diagram of the 'circuit', that will probably help undertsnading...

I see better now. When I see 'Mic' I assume low-Z.
So the issue is that you think there might be an issue with the CAPI units driving the line to the control; room etc.
I would guess that they would be fine although signal is not balanced I think.
Try it - nothing will break.

 

[oran.outan]

The Capi plug-in output is Out+ AND Out- so It supposed to be a symetric output !
will that be enought to go thru the control room and Mic Preamp ?!

 

[Newmarket]

The Capi plug-in output is Out+ AND Out- so It supposed to be a symetric output !
will that be enought to go thru the control room and Mic Preamp ?!

Yes. It should be imo although I don't have detailed knowledge of the CAPI product itself.
Really any issue should be in the high frequencies if cable capacitance is an issue. And with Hi-Z pickup coils you don't really get those frequencies anyway. So all looks good to me but let us know how it works out.

 

[oran.outan]

I will try soon...
@Newmarket , thanks a lot for your time and help !!!

best

 

[kingkorg]

If trying to get a typical "guitar level" then you probably need to boost the mic signal (hence the "Boostmate" I guess. Doing that with a passive transformer solution will increase the impedance.
If you "drop the signal level" with a transformer then the impedance of the output is lower.

I'm sorry, you got something wrong there. Transformer doesn't boost anything, it transforms.

If trying to get a typical "guitar level" then you probably need to boost the mic signal (hence the "Boostmate" I guess. Doing that with a passive transformer solution will increase the impedance.
If you "drop the signal level" with a transformer then the impedance of the output is lower.

I think you got something wrong there. Transformer doesn't boost anything it transforms. No free lunch. I wrote drop signal/slash/increase impedance. Which is exactly what this unit, for example, does. There should be a free schematic there somewhere.

https://www.diyrecordingequipment.com/products/l2a

 

[abbey road d enfer]

I'm sorry, you got something wrong there. Transformer doesn't boost anything, it transforms.

We may end up having endless discussions if a step-up transformer does boost level (while dropping current) and probably fail to agree on anything. The OP has a specific question; he polluted it from the start by assuming impedance was an essentiel ingredient in the receipe.
I must say I don't understand what the issue is...

 

[kingkorg]

Anyways, here's the reamp box schematic. My idea was the famous 5$ pre + this thingy. But now that i think about it, probably the famous 5$ would do the job on it's own. Maybe modify the output to increase impedance if that is an absolute must.

 

[Newmarket]

I think you got something wrong there. Transformer doesn't boost anything it transforms. No free lunch. I wrote drop signal/slash/increase impedance. Which is exactly what this unit, for example, does. There should be a free schematic there somewhere.

https://www.diyrecordingequipment.com/products/l2a

I know very well how and why a transformer works thanks. Of course it 'Transforms' hence "Transformer" but the term "Boost" is commonly used to describe the resulting voltage gain if the turns ratio is such that it provides voltage gain. Voltage Gain (turns ratio) is associated with a rise in output Z (square of the turns ratio). and vice-versa. So if you 'drop signal' (negative voltage gain) you get a lower output impedance - just as in a simple transformer only DI box.
eg a signal from a guitar pickup is attenuated but the output has a lower impedance.
As for the 'Re-amp' box that both reduces level and increases impedance. That involves additional circuitry. See schematics from Jensen and others.
The above points do, of course, ignore the losses within a transformer but are the basics of its operation.
Anyway turns out the OP has high Z transducers more like a passive guitar pickup than a low Z mic.

 

[kingkorg]

Clearly misunderstanding, all clear now.

 

[abbey road d enfer]

The 4 pick-up Mic are coil microphone like 'guitar Mic', so on Hi-z impedance...
the use of the Capi Plug-in is I have to 'isolate' them each others before going on a combine output... otherwise the e-bow feedback loop is 'corrupt' as the 4 pick-up signal are mixing together and the e-bow thing is not working properly...

In link is a diagram of the 'circuit', that will probably help undertsnading...

We need more information about the signal that is delivered by the e-bow box. Is it a direct connection to the pickup or is it buffered?
The CAPI thingy is probably not the most adequate thing also. IIUC, it's a DI add-on that takes an instrument signal and feeds it at low impedance to a mic input.
This is not really what you want. You want to mix the signals that come from the e-bow box, and distribute the resulting signal to...where? Another mic preamp? If so, you must first mix the signals and then convert the result just once with a CAPI thingy.

 

[oran.outan]

Hi all

thanks for all that question !
So I will give more detail... a bit more complicated and expiremental than it seems...
I have a circuit that work as a 10w amplifier where on a side I have a pick-up input and on the other a coil output. all of that reproduce the e-bow things but 10 times stronger...
My circuit is based around a TDA2003. Side to used a regular pot for controlling the level between the IN/OUT i'm controlling digital Pot (MCP42050) from a micro controller (a teensy)...
Since the input pick-up act as a 'guitar mic' I want to used it for get the sound to the speakers, amplify the string sound... So I made a simple In/Thru of the input...

The pick-up coil is home made, rated at 1.85k ohm resistance.

An e-bow is producing a feedback/larsen and one of the coil act as an input microphone and the second coil act as a 'speaker': the input signal is amplified and stabilize on the resonant frequency...
but It appears that if the signal coming from several circuit are mixing the feedback is mixed and the feedback is corrupt and not work. so I need to 'isolate', used them separately, before to mix them...

yes, I think about a buffer which will be the best but I'm only using a +12v DC... I only know IC that used +/- power.
I also was having that Capi plug-in at home which can work on +12v (same if it's made for +16v) it's why I go for it...

and Yes the final step is to go on a Mic pre for get more gain... and be loud on speakers

I hope I'm clear...
thanks for your return...
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[abbey road d enfer]

Opamps can be powered from single rail supplies, as thousands of pedals ascertain.
If I understand correctly, you need to mix the signals coming from these lowish-impedance pickups (compared to standard guitar pickups that range from 6 to 1k usually).
I would suggest you amplify these signals first; for that, anything that produces gain and has a high enough input impedance will work. Could be a single transistor, an opamp or a single FET. The latter would be my first choice, because the input impedance can be very high.
Then for mixing these signals, there is also a vast choice of solutions; I would use either "passive mixing" to a single-FET stage or Virtual Earth with an opamp.