Audiovox Stereo Graphic Equaliser Booster becomes a Two channel Mic Preamp

  • Thread starter Thread starter Tremaine
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Tremaine

Tremaine

Chancellor of the EOPA
Ok maybe im a fool, but im not the only one.
i got a Audiovox Stereo Graphic Equaliser Booster Amp 760 20W+20W, and i want to try to turn it into a mic preamp. i have no idea if this will work but audio is audio, i think?!?
so my plan: I got an old laptop supply thats 12v and 3 amps, 40w devided by 12 volts is about 4. <?this right?> so i know my power supply is weak, should be about 14v 5amp? but i just want to test one channel for now.
theres 4 wires that go to the car tape deck, im gunna wire these to 1/4" TS inputs and the 6 wires comming out im gunna wire to 4 rca jacks, so i got stereo outs.
great idea eh? probably sound like hell, but only time, or someone elses logic, will tell.
So, the Eq dont say what ohms it outputs, but i assume it must be 4ohms. is this gunna be a problem, i plan on pluging it into stereo inputs on my mixer.
I want to add a volume to each channel, should i add them after the eq, on the way out, i think thats how a mixer is wired. do i need caps and resistors for this <i got lots of junk lying around.>
the eq is worth about 60bucks and its older, so it must be half good...
Also i would like to add a third output so i can send both channels into one stereo input on the mixer, can i just wire it straight, or do i need to add diodes or something to regulate the smooth joining of the channels.
As you can tell, i am new to this. but so were you once!
I hope this is a good idea, it was mine, but now it is ours. im probably not the first to think of it, but i spent time looking for info online, and found none.
OK thanks for your time World, Peace.
Tremaine

BTW: there are alot of old metal tape decks out there, these could make a decent effect box, imh unexperenced opinion.
 
additional information

I just reread that, and realised i did not mention, that the EQ is question, is built for a car stereo system.
i thought it might be important to mention.
Later World, Peace.
Tremaine
 
I don"t know how you can make this into a Mic preamp unless it was a Mic preamp allready, Mic preamps are very low impedance (2200 ohms typicly) and has a huge ammout of Gain , like 10,000x, a mic input preamp is a Toally differeant animal than a Line input amp ......

You plug a 20w signal into your Mixer and say good buy to your mixer and Possibly everything plugged into your mixer , Bad Idea .....

If you actually want to build a couple Mic preamps it can be done easilly enough for pretty cheap , If you sold your EQ amp then you would probably have enough money to build a couple mic preamps .... I have a 4 channel transformer Ballanced preamp that I built for under $20 and some time .....


Cheers
 
I tryed it!

So i black taped the power wires to the power supply, then made sure none of the 10 loose wires were touching, flicked on the power, it was a go.
Then i wire a intrument cable into one side of the tapedeck, i used instrument cable because i didnt have any old hacked mic cables.
the i wired the outs to some four ohm speakers, had you going didnt eye.
there was little noise and lots of static. then i thought i need an amp like in a tape deck, so i got my boss ds1 and hooked it up just after the guitar. good thing eh.
there was more noise, but not enuff. maybe the 4" speaker is to big, its heavy and dont say how many watts it is, until i read the Minions' post that is.
So is there any way i can run this into my home studio, could i put an amp or op amps before it, or a mic mixer?
or hook it up to a guitar.
i assume now, that it has to be the last thing in the chain,just before the speaker or it will kill something, eh?

and Minion im wondering, is this mic pramp you speak of, good enuff? if i new that i would try to built one, i saved a couple pdf's i found, but i dont know what i want, you know....and Thanks for saving my mixer dude.
It was still a good idea!
Peace World
Tremaine
 
Actually the Mic preamps I was talking about were actually premade Modules that I got on e-bay for $1 each (got 6 of them) and I replaced the Input connections with XLR"s (they were screw terminals b4) then Connected a simple 30v DC power supply and some RCA outs and Put it all in a Wooden Box ... They sound great , dead Quiet with plenty of gain and a nice distinctive sound , sound especially good on Drums and Miced Guitar .....

There are also Mic preamp chips out there that are very good and can be built for maybe $20 a channel but you need a pretty good understanding of electronics, there are also Mic preamp Kits that can be bought with PSU for maybe $50 a channel ....

I actuallu have built every preamp in my studio pluss most of my other equipment ......

Cheers
 
free idea, no copyright infringments

Well it was my brillant idea, and a gift to the diy community. but now i guess its a joke. at least i didnt break anything.
Minion, any chance you could give me a lead <name> of the premade Modules, i could use a drum mixer, and a good beginner project, but i want something usable, stuff on the net is so unreliable, i read alot, here and there about misdrawn scamatics.
im still wondering why this EQ amp, wont power my speakers, its 20w. does it have to have a preamp hooked up, can i filter the watts down some aand use it with a guitar amp? or set it up on the effects loop? just looking for some perspective.
Thanks for your words and time.
Peace World
Tremaine
 
credit

Minion: thats awsome, builting your own gear. you must have went to school eh? you ever try to patent something?
i just had a random thought, i wonder how much you guys battle on ebay for parts and gear, maybe we should make a law that only one person from this site is allowed to bid on a given item at a time. im i song righter eh, and i think therefore i am.
Tremaine
 
Hey Thanx , but No , I didn"t go to school , literally I got my grade 8 , I just learned the basics and went from there reading a lot of stuff on line...

If you just learn the basics on how to use an opamp and Look at a lot of Schematics and datasheets you can learn how to build a lot of fairly simple but usefull stuff ....

mic preamps are easy as there are chips which are Mic preamp chips and are easy to use , there are also chips which are Power amps in a Chip and EQ"s in a chip and by reading the schematics in the Chips datasheet you can learn how to build the circuit .....

A chip Power amp is a good first project and there are a Lot of cheap kits on e-bay...... You can probably find Mic preamp kits there also ....

The Mic preamp modules I was talking about were from a 70"s PA system and were on e-bay and I was the only bidder so I don"t think they will come up often .....
I also design my own PCB"s and Make my ow ciruit boards so it really brings the price down when you do it like that .....


Cheers
 
Op Amp's, hiding in junk.

right on, thanks for the direction, im looking into the 'power amp' i've been reading up on op amps, im gunna buy some tl071 IC's and sockets off ebay <from tiawan 11.00 for 20 of each> then i can upgrade later. buying a proper pencil soldering iron too. <6$>
im wonder what i can rob decent op amps out of, are they only used for mic's or might i find them in new dvd players? <with newer chips> i assume anything with mic inputs got them, like tape decks, i got 3 older broken tape decks lying around that im going to gut. i got an old karaoke too, it must have op amps.
one must recycle!
Thanks for your time, Peace World.
Tremaine
 
TL071 Ic"s are perfectly fine , they are old but are reliable and perform fairly well ... basicly if you can"t make a curcuit sound good with TL071"s it aint gonna sound good with Newer/better opamps .....

I do suggest that if you are going to get TL071"s you might as well just get the TL072 or TL074 which are 2 opamps and 4 opamps in a single IC , If you are makeing a Circuit that needs more than one Opamp getting Dual or Quad opamps makes layout a lot smaller and easier to do .......

Generally speaking all that I use out of Old equipment that is even worth your time slavageing are Power Transformers (they are expensive to buy) Power Transistors , Power Amp IC"s , Power Resistors , Heatsinks (are expensive and sometimes hard to find) , Large Capacitors, Potentiometers and the Chassis ....

Opamps are really to hard and time consumeing to desolder and many times are ruined by the desoldering process ......

There are some great IC"s out there that are really easy to use that I use all the time ....

Power Amps IC"s:
LM3875 (50w)
LM3886 (50W)
TDA7293 (100w)
TDA7294 (same as TDA7293)
TDA2030 (14w)
TDA2040 (20w)
TDA2050 (36w)
LM1875 (20w)
LM386 (1w)

Mic Preamp IC"s:
INA217
INA103
THAT 1512
SSM2017
SSM2019

There are also many other IC"s out there that can do pretty much anything audio , not all are easy to use though ....


Good luck
 
Thank you.

Thats just what i needed to hear, you know, your not such a bad lifeform, for a minion. i cant turn down high end junk, even if its broken, so i probably got something good enuff lying around.
Im sure you'll see me pop up on another forum soon. and i think i will buy at least tl072's.
i susceeded in my first challange, fixing a broken mixer i got off ebay, so theres nothing stoping me now, /me closes his eyes and runs...
Peace, World.
Tremaine.
 
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