voice changer into guitar effect

[bonkdav]

i was going to take this circuit apart for the 386 but then i realized that it was already an effect. i hacked off the mic and replaced it with a jack and then traded the speaker for another jack. i got a 3 AA battery back supplying the 4.5 V it asks for and it gives some really fun sounds. there are 3 settings. im guessing one was supposed to be demonic one was robotic and the other just made your voice really low so the las two are very ring modish and the one is octave down. but anyway i was wondering if anybody could recommend a pot to use as a volume pot cuz this sucker is LOUD because it was supposed to push the 3" speaker.  im planning on hooking up a 100k log with output signal to lug one lug 2 to output jack tip and lug three to ground and hoping it works out but ill probably experiment a bit.  if anyone has any advice on what i should do about the volume thing it would be greatly appreciated. 

also would this thing work on 9v?  the caps are rated above that but i dont want to risk frying the little black bubble thing that does the magic. (good electrical terminology. i know)

i think i have the switching figured out i am going to either use a rotary type switch i took off a 3 speed cake mixer or use 2 spdt switches. so it will be stompbox friendly.

any and all advice will be greatly appreciated.
also i reccomend trying this if you ever come across one of these voice changers in a bargain bin or at a garage sale or something. its pretty unique.

[RickL]

Your idea for the volume pot will work but you may find that you have to turn it down quite a bit to get the volume you want. If so you may want to add a resistor between lug 1 and the output. If you use a 100k it will be like having a 200k pot that you can only turn up half way. It will give you a little finer control where you actually use the pot. Choose the resistor to fit how much you have to turn the pot down, the further you have to turn it down, the bigger the resistor.

If you want to use a 9 volt battery one easy, although somewhat wasteful of current, way of doing it is to use a voltage divider. Two equal value resistors (the higher you can go and still have the effect work the less current you will waste - try 470k) between 9v and ground with an electrolytic cap between the junction and ground (10uF or so should do) will give you 4.5v at the junction. If you hook it up and get less than half the battery voltage at the junction keep lowering the value of the resistors until you get about 4.5 volts.

[remmelt]

Great idea! I'll keep this in mind. I love that you took the parts from a toy and a mixer. DIY!

Perhaps you can check if there is a pre-amp and a power amp section and try to use the pre-amp signal as your output. You don't need to drive a speaker so it's probably cool. Seems useless to let the effect beef up the signal for real output, then attenuate it with a pot for fx/amp in use. You could even make the thing use less power that way. Maybe it won't work or you'll need a buffer...

[bonkdav]

Thanks Rick! im gonna try getting the volume pot to work with the resistor across the lugs.  I am also going to  try and make a voltage divider so i can run it off a regular guitar pedal power supply.

i cant really tell where the pre amp and power amp sections are.  Mostly because im quite new to circuits but that little black bubble is quite a mystery to me   im guessing the 386 is doing some kind of powering but i need more knowledge to get your idea into action.  Ill put that part on my "to do when i get more experience" list.  Id try and recreate a schematic but that $#@$%* black bubble would make it really hard.

i understand what your saying and it seems like a really good idea though.

[boyersdad]

I believe I have one of these! It's a megaphone that is called "Voice Mutator" (my friends and I affectionately refer to is as the Voice mutilator) and aside from the voice changing (just as you described) it has an array of changing coloured LEDs, that swirl and flash etc. I'm almost positive it runs on 9v already. I'mma have to open that sucker up and play around. I hope mine doesn't have a "black bubble", lol. I have a feeling it might be a mini 555.

[bonkdav]

i got the volume pot working, i just used a 100kB and it can go from wide open to silence so its good enough for me since it will rarely get turned.

Im having trouble fitting my head around how to make a voltage divider. Basically i want to have a boss style jack and then be able to plug 9v into that and have a voltage divider that will give me 4.5v to put into the circuit. im going to have a battery pack in the enclosure but i decided it would be nice to not have to bring AAs around so i may put a 9v clip and run it into the voltage divider also. this is what i gathered from Rick L. tell me if its wrong or right and any changes i should make to it so it works properly. the top black wire is ground and then the red wire is the 9v + and im hoping that the green wire will give me 4.5 v.

Boyersdad: please let me know how your voice mutator turned to guitar mutilator turns out.  Post some pics if possible. ill be doing the same with mine when its finished.

[RickL]

Not quite right. Right now you've got all the components in parallel. You want the two resistors in series between +9v and ground and the cap in parallel with the resistor that attaches to ground. So the cap goes from the connection of the two resistors to ground. The connection of R1, R2 and the + of the cap is where you get 4.5v.

Check out any schematic that uses a bias voltage or reference voltage or Vref to bias an opamp. That's exactly what you want.

[oskar]

Also, as your cirquit is sucking current it will lower the voltage from your divider/cap net.
you'll probably need lower values or a 10 - 100k trimmer that you can set for proper voltage depending on the current drawn.

oskar

ps. You can use an OP-stage to lower the impedance of the divider!

[Alex C]

[bonkdav]

ok. thanks a lot you guys i knew that something was fishy with my drawing but i get it now, this project is coming along quite well and i cant wait to post some pics when im done.

[runmikeyrun]

where did this toy come from?  how much was it?

[bonkdav]

where did this toy come from?  how much was it?

it was free, i found it in a house that had been abandoned for about 7-9 years, i considered that finders keepers,  dont worry i was 16 when i scavanged it and i had no idea it would actually be useful, im 18 now. older and wiser.

but i did see a few threads like mine when i searched for voice changer. one even had some reccomendations on how to get it. (2nd post, hope it helps)
http://www.diystompboxes.com/smfforum/index.php?topic=55603.0

[bonkdav]

i just ran into a bit of a problem.  i made the voltage divider just as recommended - two 470k resistors and a 10uF cap - and it worked great it gave me 4.6ish v out of a 9.5 ish v wall wart. but when i hooked it up to the ground and the pos in the circuit it doesnt power it. i took a reading and at the junction point it has around 300mV where it used to have 4.6 V. i connected and reconnected and checked and double checked and i cant get it to give me 4.6 V into the circuit like it would on its own.

do i need different resistors or a different cap? it may be pos ground because where the ground hooks into the circuit is what chooses the effect so does the cap need to be reoriented? thats just a stab in the dark, but i am truly flustered and if anyone could shine some light on this i would be tickled.

thanks
davis

[RickL]

I'm not sure exactly how you're hooking it up but unless the circuit has an enormous current draw the voltage divider shouldn't be dropping down to less than a volt.

First let's confirm that you're hooking it up correctly. Hook the ground wire from the voltage divider to the ground of the circuit (where ever the negative of the original batteries connect). Hook the centre (yes centre I'm Canadian  ) of the divider (where you get 4.5 volts when it's not hooked to anything) to where the positive of the original batteries connected. Don't connect the 9 volt battery or wall wart to anywhere else except the voltage divider.

At this point you may get a little less than 4.5 volts at the centre of the divider (remember I did say start with 470k resistors, that they might be too big). If you do, try 220k resistors, or 100k and so on. You may have to go as low as 10k. If you have to go much lower than that the voltage divider idea isn't going to work and you'll have to try something else like a voltage regulator. I'd be surprised if you have to go that low. Anything designed to work off batteries for any length of time is unlikely to draw a huge amount of current.

BTW if you're going to use a wall wart why not just use a 5 volt adaptor instead of a 9 volt? Then you won't have to deal with dropping the voltage.

[bonkdav]

i re-did the whole thing using gator clips and im 90% sure i hooked it up correctly (i put them directly to the battery line ) and this time the voltage read .6 V (im pretty sure it read that last time too but somehow i confused myself) when  i hooked it up to the circuit. it would be 4.6 v until the pos met pos on the circuit board. i then used 2 more 470k resistors and gator clipped both those in parralel with the other resistors to cut the resistances in half but then i was only getting .8 V it was an improvement but not nearly what i needed.
are 3 AA batteries just more powerful than a divided up wall wart?
im really confused at this so any more help would be great.
and what exactly do you mean by 5 V adaptor? like a 5v wall wart?

Davis

p.s. i love Canada, ive gone deer hunting there, but it is a bit cold sometimes, even for a Minnesotan

[oskar]

Also, as your cirquit is sucking current it will lower the voltage from your divider/cap net.
you'll probably need lower values or a 10 - 100k trimmer that you can set for proper voltage depending on the current drawn.
oskar
ps. You can use an OP-stage to lower the impedance of the divider!

Or read this one again... 

[RickL]

Okay, it looks like the circuit is drawing a lot more current than I thought it would. The fact that you got a little more voltage with smaller resistors would seem to confirm this. It looks like you'll have to go with bonkdav's suggestion or hook up a voltage regulator if you want to power it with 9 volts.

I do indeed mean a 5 volt wall wart when I say 5 volt adaptor.

[oskar]

EDIT: Picture changed

If you want to stuff it in a box with 9V-things you can put this in a corner ( it's also a good 4.5V reference which a lot of circuits use... )
I think your machine is going to be worth the job though... sounds fun!

oskar