MIXER/AMP issue.

[deadastronaut]

hi guys, been tinkering again...

this time ive made a mono amp with speaker which can record and playback on my tablet via a trrs cable..and set the record level going into the tablet.

im using a trrs cable so i dont have to unplug and replug in etc....so i have just 1 trrs  coming out of amp to my tablet
for recording and playback of that recording ....

it all works as planned....however.

if i put the trrs playback into inputs 1 ,2 ,3,...its a very low volume compared to 4...which is exactly the same, all mono inputs.

ive tried trs cable from my tablet too, which also plays fine on input 4, but quiet on inputs 1,2,3...

very strange.  thoughts?

heres a crude diagram of what it is....

[antonis]

What about 2 rings wiring..??

[deadastronaut]

ive mono'd the sockets...joined the TR's.

and mono'd the TRRS too...

[antonis]

(what a lazy guy..)

Rob, plz, post a schematic of jacks-plugs wiring..

[deadastronaut]

i am lazy ...the best is what ive drawn really..

basically ive connected the TR of the 3 trs together...to be mono

and the audio that comes back from the TRRS to the input is wired mono too.

all grounds joined together.

so i can have record mono, and playback mono...(the trrs was a pain to sort out as i need the tablet to cut off its internal mic so i only playback whats recorded...no external noise, traffic, dogs barking, etc...and it works fine)

its just the level difference thats bugging me now...hmmmmmmm

[antonis]

its just the level difference thats bugging me now...hmmmmmmm

Make TRS MONO 1, 2 &3 100k resistors 47k or so and walk in peace (of mind)..

[deadastronaut]

Cheers antonis...i was pondering lowering them...nice one. 

[deadastronaut]

hi guys, back again....

made a nice simple electret mic preamp...works great...

made a 2 channel version of the 4 in 1 out mixer circuit. one channel of which has a electret mic preamp added.

all works.

however, i cant seem to get them to play nicely with each other simultaneously.

my needs. :

guitar in. and electret mic in at the same time, with vol for both.

single mono out. 

this is for live jamming / vocal use. straight out into multifx. headphones....


the mic works, but is scratchy as hell on the volume.. (im guessing a dc cap on the input)

but the guitar signal is very tame compared to a straight bypassed signal....loses all top end, and gain etc..especially when using a dirt.

so basically im looking for a circuit that can handle a mic and guitar simultaneously without messing with either inputs output signal...

this is what i have at the moment.....thoughts?

[antonis]

Maybe I'm tired a bit but for what reason you feed MIC pot with +9V (via 10k resistor)..?? 

P.S.
Q1 BJT CE amp puzzles me enough..

[deadastronaut]

hi antonis....yeah after drawing it out like this as it is i see the issue with the mic preamp now.



so the mic volume needs to be after the preamp, instead of before,  at the right side of the mixer in 100k. ?

and guitar side of things is ok?...or?

[deadastronaut]

so like this? makes more sense....

will this then make the guitar and mic behave...e.g the guitar is back to normal?

[antonis]

I'd make R2 470k (although I don't like Q1 input impedance in conjunction with MIC's output one)..

P.S.
I'd delete Q1 circuitry and implement a dual op-amp for two buffers , each of them placed between  inputs and 10k pots..
Or better, delete 10k pots and make buffers of variable gain..

[duck_arse]

what happens to the signal when the upper 10k pot is wound to ground?

[deadastronaut]

cheers guys...

antonis, so a full on rebuild then lol...

the R2 i made 56k as when it is 100k its ludicrously sensitive, you could hear a squirrel on mars ha ha..

so standard buffers on both inputs, meaning a buffer that goes before the preamp?  but then wouldnt the 10k to 9v at the electret mic be an issue?

.....
ducky, haven't tried that config yet as i have the top vero built so far...so need to adapt it...

ahh do you mean wire the top pot as rheostat.... 3/21..to opamp?

[duck_arse]

no sir. with wiper to ground, (-) input is hard to ground, carrying all signal from all sources to ground. fffftttTT! probably you would put the 100nF to pot hot, and that 100k from wiper to inverting in.

[deadastronaut]

so no ground on the top pot....i see..

[deadastronaut]

like this?

[antonis]

 

Are you kidding, Ron..??

You don't have a mixing pot but a variable resistor..

Move the pot (with lug 1 grounded) between Q1 Collector and 100nF cap..

[deadastronaut]

im lost lol.....

[duck_arse]

and stop kidding Ron. you want a voltage divider pot, with cap at top and 100k at wiper. ground at cold. that's if you was going to use that circuit, otherwise, doesn't matter.