diy mic preamp help and suggestions

[saheb11123]

Hello ,
i am looking for help regarding a diy mic preamp, this will be for my sister who learns music and will use this as a means for rehearsal (rewaj). need help regarding design schematics easy local component sourcing , overall budget is around 1.5k.





Thank you
Regards
Soumyajyoti

 

[reubensm]

I have built several mic preamps for different types of mics. If you can specify what type of mic you have (dynamic/condenser) or perhaps, provide the make and model number details, that would be of great help.

 

[saheb11123]

The mic is a local dynamic mic...
basically will be used for home karaoke/rehersal by sister.
i will needing something which can be blend the mic inputs to a cd player playing a song...
maybe a summation amp is reqd, i have 2-3 ne5532 chips at hand also if that helps

 

[saheb11123]

@reubensm
bump

 

[reubensm]

@reubensm
bump

sorry, forgot to visit this one.

maybe you can try something like this, its simlar to the microphone preamps on Ahuja amps:

if you are bent on OP amps, then something like this will work:

if you want to do one which can accomodate both condenser and dynamic mics, then here's a design (you can probably add a switch to flip between the 2 types of inputs):

here's a high quality version:

If you are not familiar with electronics DIY, I can help putting one together for you.

 

[saheb11123]

i have bought some mic preamp circuit from local chadni shop which is a replica of the first circuit you have attached.

My biggest problem here is how to mix the inputs from micrphone and cd player so that karaoke tracks can be played from cd and my sister can sing along.

thanks and regards
Soumyajyoti

 

[saheb11123]

Also the opamp schematic you had attached, what supply is reqd , ie, how to obtain supply from 12-0 transformer? bridge rectification?

 

[reubensm]

i have bought some mic preamp circuit from local chadni shop which is a replica of the first circuit you have attached.

My biggest problem here is how to mix the inputs from micrphone and cd player so that karaoke tracks can be played from cd and my sister can sing along.

thanks and regards
Soumyajyoti

well, in that case, what you actually need is not a mic preamp but a audio mixer like this one:

You can connect your mic preamp's output to one of the inputs and your cd player to the other. You can then adjust the levels (R1 and R2) to have your mic's sound superimpose over the cd player's sound.

 

[reubensm]

Also the opamp schematic you had attached, what supply is reqd , ie, how to obtain supply from 12-0 transformer? bridge rectification?

That's very easy. You can try the following rectification types:

1) Half-wave design:

2) Full-wave design:

3) Bridge design:

 

[saheb11123]

@reubensm
Sir I have built the ne5532 opamp circuit that you attached , but there is a problem that i am facing the problem is if i connect a 47k pot at the input and feed it with input from dvd cd or mobile or mic whenever i decrease the pot there is a loud hum which is noticed. Also if i directly give input or pot is turned at full there is not hum. Now how to impose mic line into dvd input after opamp amplification? Like building a passive mixer after mic amplification.

 

[reubensm]

@reubensm
Sir I have built the ne5532 opamp circuit that you attached , but there is a problem that i am facing the problem is if i connect a 47k pot at the input and feed it with input from dvd cd or mobile or mic whenever i decrease the pot there is a loud hum which is noticed. Also if i directly give input or pot is turned at full there is not hum. Now how to impose mic line into dvd input after opamp amplification? Like building a passive mixer after mic amplification.

The NE5532 circuit is a mic preamp hence you should connect the mic directly to its input. Don't attempt to introduce a pot at its input as it will only cause you problems.

The output of the NE5532 preamp should be mixed with your music source (DVD), hence you'd also have to build the single transistor mixer circuit to mix your NE5532 preamp's output and your DVD player's output. If you want to avoid the single transistor stage, you can use a passive mixer with 2 pots at this point as well (but not sure if you will have full control over the gain without a transistor stage).

 

[omishra]

If you could get tape head preamp LA3161 based kit then its one stop solution. Use mixer as Reuben suggested in previous post. I made it for my Guitarist friend who wanted to record acoustics Guitar with mic. PS adapter was kept outside as wallwart.

 

[saheb11123]

Out of my garbage collection I found a mic preamp with echo settings and volume/gain settings.. but the problem is it has one input now how to introduce multiple inputs? I need to somehow control each input..

Ps : Would this topology work: Build two inputs for mic with two channels of ne5532 and control the gain of that circuit's with the pot..
Then where to connect the pot? In place of feedback resistor or the resistor which connects to ground (the design of opamp discussed here has 22k feedback resistor and 1k connected to ground via a 10uf cap).


Thanks
Regards