When a boost is a bust :(

[moid]

>I want a boost, but also one that I could adjust the potentiometer on and lower the volume to 0 if I wanted to.

This circuit won't do that. At minimum, you get unity gain.

Damn, I didn't realise this

He could jumper R5, no?

What does that mean please? I know a jumper is a length of metal wire, but would that mean remove R5 and replace with a cable?

[samhay]

Yes - to jumper something is to replace it with a piece of wire (e.g a resistor leg).

Your voltages look ok. Op-amp pin 4 is connected to ground.

If your circuit is passing sound, then you can check it is mostly working by unplugging the power/battery. If it stops working, it is amplifying.
If your potentiometer isn't working, then you have likely shorted it out - connected lugs 1 and 2 together, perhaps where the wires are connected to the board. Alternatively, R6 is not connected (e.g. cold solder joint).

[GibsonGM]

Don't worry about the very small mV readings, Moid - that's just spurious junk, so small your meter has trouble figuring it out. For practical purposes, that is "Zero".   Voltages look good, like Sam says!   

Do you get sound out of it yet? 

-- yes, he'll have gain 2, maybe the 'junk' in the path will draw signal down so it seems nearly 'off'.  Or he can add a vol. pot to the output later.

Don't worry about 'jumpering' now, Moid - we have to get it working!   

[moid]

Yes - to jumper something is to replace it with a piece of wire (e.g a resistor leg).

Your voltages look ok. Op-amp pin 4 is connected to ground.

If your circuit is passing sound, then you can check it is mostly working by unplugging the power/battery. If it stops working, it is amplifying.
If your potentiometer isn't working, then you have likely shorted it out - connected lugs 1 and 2 together, perhaps where the wires are connected to the board. Alternatively, R6 is not connected (e.g. cold solder joint).

squinting at the build photo, it looks to me as tho pin 8 is bent in/under. perhaps lever the IC out and check for leg straights, then refit, and push down firmly until it seats properly.

OK strange things are afoot at the Circle K... I took Duck's advice and took the IC out and his eagle (or duck eyes?) did indeed notice a bent pin, so I adjusted that and slotted it back in. I also reflowed the solder on R6 as samhay mentioned as being a cold solder joint. I now have audio that goes through and the pot appeared to be working (turn one way audio is audible, but quiet, turn the other and it gets loud so I was about to celebrate when I thought I'd check what samhay said about pulling the power plug out while the audio was running - and when I do that the audio is louder than the power plus the pot at one end of the pot's sweep, but not as loud as the power plus the pot at the other end of the sweep... so is this a success or not? It doesn't sound right to me... I think at the quiet end of the pot I should hear the sound at unity and this should be the same volume as if the power is unplugged, yes?

Would these issues depart if I soldered everything together / and boxed it? (power and the audio jacks are held on by crocodile clips at present)

Thanks everyone for the suggestions, I really appreciate the help.

[moid]

Don't worry about the very small mV readings, Moid - that's just spurious junk, so small your meter has trouble figuring it out. For practical purposes, that is "Zero".   Voltages look good, like Sam says!   

Do you get sound out of it yet? 

-- yes, he'll have gain 2, maybe the 'junk' in the path will draw signal down so it seems nearly 'off'.  Or he can add a vol. pot to the output later.

Don't worry about 'jumpering' now, Moid - we have to get it working! 

Thanks I didn't know what the tiny readings meant, so I'll class those as zero in future. D'oh I never thought about adding a volume pot later - I could throw everything into a 100K lin pot on lug 3, connect lug 2 to audio output and leave lug 1 empty and that would presumably allow the volume to go from zero to the maximum volume coming through the circuit - is that right?

I think I'm going to get some sleep now, my eyes are fuzzy and I'm back to work tomorrow

[GibsonGM]

At the very output of the circuit board, you'd put the signal into one side of the pot, take the wiper to the output jack, and tie the other outer lug to ground.   If it works backwards, switch the outside wires!   

With power applied, and gain pot all the way to one side (the side presenting the highest resistance in the feedback loop), you should have much louder signal than when you pull the power out.   

Put another way...with no power, set level pot to loudest position.  Apply power - should be pretty LOUD!! 

[moid]

Thanks GibsonGM I think I worked out why the volume wasn't as impressive as I thought it would be... I wasn't playing a guitar through the pedal I was using a Buddha Machine to play one of its samples through without realising that this is at line level, not guitar level.... I switched to guitar today and there is indeed a huge volume difference, from almost completely off at one end of the pot's sweep to ouch I shouldn't do this wearing headphones at the other end of the sweep. The bypass signal is louder than the minimum signal, but that's fine, I'm just happy this works now. Thankyou very much everyone for their helpful tips.

I might be starting a new thread soon, I've got a Noise Ensemble that doesn't want to work

[GibsonGM]

Great! Yeah, the min. setting being lower than bypass is probably ok, things dont behave ideally - there are parts in the pathway, which eat up signal.  Not looking at it right now to confirm, but it sounds like you got it!