Electret mic preamp - will phono preamp work?

darthmullet · 5th October 2007, 06:41 AM

I have a stereo electret mic that is used on things like DAT and MiniDisc recorders that have "plug in power" (2-12vdc bias). Does anyone know if a phono preamp would allow me to use this with an input that needs line level? Could I plug it into a receiver with a phono input? Or if there is an inexpensive preamp out there instead?

adason · 5th October 2007, 01:38 PM

no, unless you modify RIAA fr response of phono preamp to be flat, see phono preamps do not have flat fr response, they compensate for oposite fr response of record cutting

built your own mic preamp, its easy, its fun, and thats what diy is all about

darthmullet · 5th October 2007, 04:31 PM

so, aside from the RIAA curve, a phono preamp would work with an electret microphone?

adason · 5th October 2007, 05:15 PM

certainly, phono cartridge (mm) and mic provide roughly the same output, few milivolts, need roughly the same amplification to become line level signal,
some old phono preamps actualy came with swith for flat fr response to be used as mic preamps

but before you embark on modying your phono preamp, you should consider building dedicated mic preamp

there is ton of good schematics out there

you might suceed modifying phono preamp, but you might not, might become unstable, oscilate....at the end you just might destroy perfectly working phono preamp

darthmullet · 5th October 2007, 07:28 PM

Quote:

Originally posted by adason

built your own mic preamp, its easy, its fun, and thats what diy is all about

Alright. I'd been hoping it wouldn't come down to this (I'm no stranger to a soldering iron, but I am to audio circuitry...)

Looks like I'll probably be making my own.

One last question before I decide: If I use software equalization to flatten a mic input through a 70dB S/N ratio phono pre-amp, how much audio degradation will I have when compared to a simple DIY pre-amp?

Thanks for all your help!!!

adason · 5th October 2007, 10:27 PM

my guess it will sound horrible, for you will be lifting up all the noise after phono preamp

ricobasso · 12th October 2007, 07:32 AM

I assume your original question was because you had a ready made RIAA preamp that you wished to modify rather than starting from scratch. It should be quite easy to make the frequency response flat and change the gain by removing capacitors and changing resistors in the feedback path. However, no one seems to have mentioned that you will still have to come up with some phantom powering arrangement. You do need to do this. Check out http://www.epanorama.net/circuits/mi..._powering.html or Google "electret"

5th October 2007, 06:41 AM	#1
darthmullet diyAudio Member Join Date: Oct 2007	Electret mic preamp - will phono preamp work? I have a stereo electret mic that is used on things like DAT and MiniDisc recorders that have "plug in power" (2-12vdc bias). Does anyone know if a phono preamp would allow me to use this with an input that needs line level? Could I plug it into a receiver with a phono input? Or if there is an inexpensive preamp out there instead?

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5th October 2007, 01:38 PM	#2
adason diyAudio Member Join Date: Nov 2004 Location: troll in US	no, unless you modify RIAA fr response of phono preamp to be flat, see phono preamps do not have flat fr response, they compensate for oposite fr response of record cutting built your own mic preamp, its easy, its fun, and thats what diy is all about

5th October 2007, 04:31 PM	#3
darthmullet diyAudio Member Join Date: Oct 2007	so, aside from the RIAA curve, a phono preamp would work with an electret microphone?

5th October 2007, 05:15 PM	#4
adason diyAudio Member Join Date: Nov 2004 Location: troll in US	certainly, phono cartridge (mm) and mic provide roughly the same output, few milivolts, need roughly the same amplification to become line level signal, some old phono preamps actualy came with swith for flat fr response to be used as mic preamps but before you embark on modying your phono preamp, you should consider building dedicated mic preamp there is ton of good schematics out there you might suceed modifying phono preamp, but you might not, might become unstable, oscilate....at the end you just might destroy perfectly working phono preamp

5th October 2007, 10:27 PM	#6
adason diyAudio Member Join Date: Nov 2004 Location: troll in US	my guess it will sound horrible, for you will be lifting up all the noise after phono preamp

12th October 2007, 07:32 AM	#7
ricobasso diyAudio Member Join Date: Jul 2007	I assume your original question was because you had a ready made RIAA preamp that you wished to modify rather than starting from scratch. It should be quite easy to make the frequency response flat and change the gain by removing capacitors and changing resistors in the feedback path. However, no one seems to have mentioned that you will still have to come up with some phantom powering arrangement. You do need to do this. Check out http://www.epanorama.net/circuits/mi..._powering.html or Google "electret"