need a tiny blending preamp

[lathamuse]

Hi, I am hoping somebody can help me I am after a preamp to blend passive humbucker pickups with a transducer or mic, I want to hide it under the scratchplate on an archtop guitar I'm building, thus as small as feasible, I would prefer lithium battery power( size constraints), can anyone help me/point me in the right direction Please? Thankyou, paul

 

[ronsimpson]

https://www.amazon.com/Alto-Profess...&qid=1441112625&sr=8-47&keywords=mixers+music
Like this?

 

[audioguru]

You "blend" foods, not audio. You "mix" audio signals.
A geetar pickup has a high level signal at a very high impedance but a transducer or microphone has a low level signal at a low impedance. Because they are so different then they cannot be directly mixed together.
The mixer circuit must either attenuate and reduce the impedance from the pickup, mix it with the signal from the mic then amplify the result, or amplify the mic signal and mix it with the signal from the pickup.

 

[Nigel Goodwin]

As already mentioned, you need an audio mixer, but we need far more details of EXACTLY what you're trying to do, and particularly what microphone you're wanting to use.

 

[lathamuse]

You "blend" foods, not audio. You "mix" audio signals.
A geetar pickup has a high level signal at a very high impedance but a transducer or microphone has a low level signal at a low impedance. Because they are so different then they cannot be directly mixed together.
The mixer circuit must either attenuate and reduce the impedance from the pickup, mix it with the signal from the mic then amplify the result, or amplify the mic signal and mix it with the signal from the pickup.

Indeed, mix is the correct terminology, my apologies, I do know better! I am building an archtop with two passive humbuckers with coil splitting capability, I was hoping to have either a transducer or small mike inside the body with all wired to a small preamp that could amplify the mic signal( if that is what I need to do) and provide mixing capability all onboard the guitar, attached to the underside of the scratchplate, one output jack straight to my amp, or DI when necessary, a lot of the gigs I do are in very tight situations, mostly Jazz, so I need to keep equiptment and leads to a minimum. I have a depth clearance of 17mm and 75x45mm area to house circuit and battery, am I dreaming or is this possible? I have basic kit skills with electronics and a reasonable solder technique, I am happy (would prefer) to pay for a prefab board that I can just fit. I'm a professional musician so most of my ability lies in that field I am hoping to have a guitar that offers me a very broad and varied palate. Thanks for replying, cheers Paul

 

[lathamuse]

https://www.amazon.com/Alto-Profess...&qid=1441112625&sr=8-47&keywords=mixers+music
Like this?

Thanks Ron but I really need to have it all on board and coming out of one output jack, otherwise its just too fiddly, I don't even use fx pedals for that reason, unless I'm doing a show,thanks anyway, cheers mate

 

[alec_t]

Presumably you'll need one or more pots as volume/balance controls? Does that space have to include them, or are they elsewhere?

 

[lathamuse]

Presumably you'll need one or more pots as volume/balance controls? Does that space have to include them, or are they elsewhere?

they are going to be housed elsewhere, so I have 17mm depth 75x45mm for preamp and battery, yes I will (Hopefully!) put a single mixing pot through the scratchplate, all other controls housed elsewhere, thanks so much for your replies, cheers paul

 

[audioguru]

If you mix the guitar pickup outputs with an internal acoustical signal then you will have all kinds of phase problems which create frequency peaks and nulls. Also, if the microphone can hear the speakers then you will have acoustical feedback howling.

 

[lathamuse]

If you mix the guitar pickup outputs with an internal acoustical signal then you will have all kinds of phase problems which create frequency peaks and nulls. Also, if the microphone can hear the speakers then you will have acoustical feedback howling.

Yes well, I guess I would need to reverse the phase if thats possible to fit on unit, my pre-amped classical has this option, as for feedback, I don't play at loud volume on stage, I'm miked if house volume is needed, I am pretty accustomed to working within the constraints of feedback, I may have found part solution, the GFS EAP-100 endpin preamp, so maybe all I need now is a mixer with phase switching capability, is that right, I apologise for my ignorance, I'm am trying to come up to speed quickly, so much to learn! makes music theory look easy!, cheers Paul

 

[tomizett]

The ability to flip the polarity (phase) of the pickup relative to the mic probably won't matter too much in a gig situation; it will affect the sound when your mix pot is between pickup and mic, and I'd just suggest experimenting with the polarity when you build the thing and then leaving it in the configuration you prefer. Whatever you do, you'll never get perfect phase alignment between pickup and mic - the best you can do is find the sound you like best.

I'd suggest starting by deciding what mic or pickup you're going to use - that will have a large bearing on the design of your circuit, and on how resistant the instrument is to feedback.

If you possibly can, I'd recommend using a standard PP3 size battery, as it'll be easy to source, change, carry spares, etc.

 

[tomizett]

Oh, and NOTHING makes music theory look easy! Give me electronics any day...

 

[lathamuse]

The ability to flip the polarity (phase) of the pickup relative to the mic probably won't matter too much in a gig situation; it will affect the sound when your mix pot is between pickup and mic, and I'd just suggest experimenting with the polarity when you build the thing and then leaving it in the configuration you prefer. Whatever you do, you'll never get perfect phase alignment between pickup and mic - the best you can do is find the sound you like best.

I'd suggest starting by deciding what mic or pickup you're going to use - that will have a large bearing on the design of your circuit, and on how resistant the instrument is to feedback.

I'd recommend using a standard PP3 size battery, as it'll be easy to source, change, carry spares, etc.

Small bear offered two suggestions, If someone who knows would give their opinion I'd be really grateful, I could go with either a battery powered preamp and mic the GFS EAP-100 , or a passive one, and again thanks so much for the help http://diy.smallbearelec.com/HowTos/BreadboardBareAss/BreadboardBareAss.htm or this **broken link removed**

 

[audioguru]

If you flip the mic wires to reverse its phase then you will simply change the frequencies where peaks ands nulls occur.
The old Velleman preamp uses the LM358 dual opamp that has a lot of noise (hiss), no high audio frequency output and has crossover distortion. An audio opamp should be used instead. The circuit has an input impedance too high for a dynamic mic and needs to be modified to use an electret mic.
You did not show a mixer circuit.