Little Jem Mark II mini amp where's the gain?

[John Lyons]

I finally got around to building the little Jem MKII version. ( I have not built to regular version, this is the first one i've built.

After getting it together I expected it to be in ovedrive gain mode because I had pins 1 and 8 jumpered with 10uf caps as in the schematic (runoffgroove.com) my little jem is dead clean, a little background noise/hiss but no overdrive. Breaking the connection between pins 1 and 8 lowers the volume a bit... The 386 chips get a bit hot as well. Usually this is a bad thing but I was thinking it was due to it being an amplifier chip / needs to disipate some heat...

Any ideas out there why im not getting any distortion? I've checked against the schematic at least 5 or so times.

I did have a power miswire...maybe this took out the Fet or 386?

Just thought someone out there may have experience with the amp.

Thanks.

John

[petemoore]

Take some voltages from OA pins to ground? Might tell something..
 Maybe try a different, same type chip.

[RDV]

I've not built this one, but I know that polarity is everything on this one, cause it does a push/pull thing. The inverting & non-inverting inputs should be paid attention to, as well as speaker polarity, or those 386s will get quite hot indeed.

RDV

[Ansil]

hmmmm sounds like maybe something is parasiticly coupled  i was messign around and thought i had my 386 ukp on the bread board but hadn't put the output pin to anythign yet i was still getting signal. from a wire that was close but it did somethign that you were describing..  

sometimes too i have had a lm386 that the fifth pin didn't work on it. for some strange reason.

but you can always try pin eight. it is louder anyway.. since there is no 15k resistor before the output.  check the datasheet and you will see what i mean.

[John Lyons]

Ok, got a little stumped last night and just started over on the original little Jem (only one 386). I added the fet buffer as well. It worked like a champ...er...uh actually more of a marshall...

So I don't know what the deal is, was, but I'll order another 386 and see if the one remaining from the first attampt was bad. I soldered the 386 directly in to the circuit for the new Little Jem (No socket) other wise I would just swap 'em out to see if there was anything strange going on.

Thanks for the help folks. I'll look up the data sheet and see if I can get some more info.

JOhn