Balance on amp (Nigel...?)

[grrr_arrghh]

Hi

i'm trying to add a balance function to an amp (u've prob seen the posts). Nigel told me to add this to the output of the amps, so that the pot would control balance (shown below, but without all the extra bits around the op-amp). it looks good on paper, but doesn't work in real life...

why not? (i can't see any faults in my circuit)

Tim

 

[Nigel Goodwin]

Hi

i'm trying to add a balance function to an amp (u've prob seen the posts). Nigel told me to add this to the output of the amps, so that the pot would control balance (shown below, but without all the extra bits around the op-amp). it looks good on paper, but doesn't work in real life...

why not? (i can't see any faults in my circuit)

Neither can I - because it's not there :lol:

When you say you've added it to the output of your amps, what exactly do you mean? - from what I remember, this was to do with a simple mixer.

 

[grrr_arrghh]

lol

very funny

sorry, here is it

by amps, i meant op-amps

 

[Nigel Goodwin]

lol

very funny

sorry, here is it

by amps, i meant op-amps

These are for the individual input channels to the mixer aren't they?, the output resistors cound be the mixing resistors into the mixer op-amps.

What doesn't work about the circuit?.

One possibility I've just thought of - are you using a split supply?, if not you will probably require DC blocking capacitors.

 

[grrr_arrghh]

hi

what doesn't work - the circuit works in general - it mixes, amplifies, and the volume control pots work, but when I tried to add your balance control, it did something a bit strange. instead of making one speaker louder and the other quieter (when the pot was turned) it just made BOTH speakers quiter... which is a bit strange

as for the split supply - i'm using a single 9v PP3, and a a 'Midpoint HT Rail' (diagram below - I hope)

 

[Nigel Goodwin]

You need to make sure that there's no DC fed to the balance control, otherwise it will upset the DC conditions. On the circuit above, where exactly are you connecting the balance circuit?.

 

[grrr_arrghh]

ah, well

you see the first circuit I posted - where the resistors are connected to the op-amps, there is actually a capacitor between them. Soooooo... on the circuit above - the balance circuit is simply inserted between the cap, and the pot (the pot with 'output' written next to it)

Does that make any sense?

 

[Nigel Goodwin]

ah, well

you see the first circuit I posted - where the resistors are connected to the op-amps, there is actually a capacitor between them. Soooooo... on the circuit above - the balance circuit is simply inserted between the cap, and the pot (the pot with 'output' written next to it)

Does that make any sense?

The values you have chosen are too low to go there. You could try your existing values on the input to the pots, depending what it's been fed from. Or use higher values.