Kingslayer gain problem

[toddvirgil]

Hey guys,

So I've built two kingslayers now, and they both sound great - BUT - the first I built was the buffered version, it has massive amounts of gain. The second is true bypass. It has hardly any gain -- the volume is at Unity at 12 o'clock and only goes up slightly when cranked.

Any ideas what gives? They are using identical chips -- is it possible my Charge pump is screwball in one? I swappled the TL274s and saw no effect. Haven't had a chance to swap the 1044's.

Anything else I can check?

Thanks for any help!

[toddvirgil]

Oh, and just to be clear -- when I said the buffered version has massive amounts of gain, I meant boost -- it's not distorting differently, its just way louder.

[madbean]

The buffer vs. true bypass will not effect the overall volume output, so that is not the issue. You need to check your "gain setting" resistors. If you used an incorrect value that could lower the output significantly.

Double check these values: R9, R10, R11, R15, R19, R22.

Also, make sure you aren't using 56k or 560k on R24 instead of 560R.

If these all check out, then you may need to audio probe the outputs of the ICs to see where the volume is dropping off. This would be pin8, 14, 7 and 1 in that order (of the quad amp, not the charge pump).

[toddvirgil]

Dude! Now that is service! Thanks for the quick and very thorough reply. I'll see if I can track it down and report back.

[toddvirgil]

Double check these values: R9, R10, R11, R15, R19, R22.
Also, make sure you aren't using 56k or 560k on R24 instead of 560R.

I checked em and they look right!

If these all check out, then you may need to audio probe the outputs of the ICs to see where the volume is dropping off. This would be pin8, 14, 7 and 1 in that order (of the quad amp, not the charge pump).

I probed these pins -- 1 and 7 seem about the same as the final output. 8 and 14 seem like they are about half-volume.

Attached is a photo -- I can pull it out of the box (I didn't notice the gain problem till after I boxed it) if you don't see any obvious problems on this side. So strange...

<EDIT> added photos of the back side. I found a potential bridge on my 9v/G connection so I reflowed it, no avail.



T

[toddvirgil]

ok, in checking signal on the 274 again --

pin 8 -- Loud
pin 14 -- quiet
pin 7 -- medium
pin 1 -- loud (similar to 8, maybe slightly quieter)

So is the problem in between 8 and 14?

T

[toddvirgil]

Bump I'm at a loss at this point... seems like something weird is going on with my gain since it goes really quiet on pin 14. I reflowed all of the components in that end and still nothing, same issue. Help!

[madbean]

I've looked over your resistor values and they seem correct from the parts that are visible. Those BAT41 diodes are a bit different looking than I'm used to. Where did you get them? Have you tried using something else there...say 1n914?

Have you checked to see if you have +/-9v going to the IC?

[toddvirgil]

Hey Brian,

Thanks! I got the bat41's from Tayda -- would that be causing a gain problem?

Yep, I checked the IC -- I'm getting +/- 9v... everything's checking out there...

T

[madbean]

Yup, try different diodes 

[toddvirgil]

That was the trick! Apparently I have a lot more to learn about how these circuits work

So question -- is it just the OD pair of diodes that affect the gain of the opamp, or do the other pairs affect it as well?

[aballen]

Interesting,  I'm going to try some different diodes in my kingslayer,  mine is crazy loud too.