Ram's head too quiet

[Valoosj]

Last week I built myself a Ram's head big muff. Using the layout I had (from a green big muff) I subbed the necessary components and added an ICL7660 with 2 10uF to provide me the -9V. The pedal works just fine, but I need to crank it all the way to get near bypass volume. I've looked at everything (wiring, soldering, etc ...) and it all seems good.

The only difference I just noticed is that with between both versions is that the diode pairs are on the other side of the cap to go to the -9V via a 15K resistor. Could this be causing my low volume?

[StereoKills]

Curious, why use -9V, this is not typically a positive ground circuit?

[Valoosj]

I thought it was. When looking at the schematic



Positive ground, so in order connect it to my daisy chain, I need to supply it with -9V, no?

[jasperoosthoek]

You are right, it's a possitive ground effect.

You can do a negative ground conversion for a positive ground effect. It'll work on a negative ground supply in the daisy chain. I wasn't very satisfied with the noise levels though...

Just wondering, what's so special about the transistors that they need to pnp? Are they perhaps Ge trannies?

[StereoKills]

The schematic you have is for a positive ground. I think every other schematic I've seen for any variant Big Muff has been neg ground before.....

By the way, do NOT connect positive ground circuits to the same power supply as neg. ground circuits, you'll short out your power supply as soon as it's plugged in.

[Valoosj]

2N5087 according to the source site.

http://www.pisotones.com/BigMuffPi/psst/BMP_versions.htm

I don't have any noise, just a lack of volume. I am wondering if I made a mistake in component placement, or the placement of the diodes. If you look at the Green muff schematic, they are on the other side of the capacitors.

Stereokills, I know, that's why I added a voltage converter to have -9V as well. The ground can thus be shared with other pedals.

[jasperoosthoek]

There is no real difference to the way the caps and diodes are connected in the different schematic.

Follow the '' Debugging: What to do when things go wrong'' thread. And post voltaged and some images of your build.

[StereoKills]

Interesting that the Ram's Head is pos. ground and the Violet Ram's Head is neg. ground.....

+1 on posting voltages.

[oliphaunt]

I found this same issue with a different Ram's Head schematic.  I put the cap on the other side of the diodes and it solved my problem!

What transistors did you use?  Got any of the right ones you want to share!?

[quarara]

Interesting that the Ram's Head is pos. ground and the Violet Ram's Head is neg. ground.....

There are Ram's Head Muffs that were built using NPN transistors too. To my knowledge the negative ground Ram's Head Muffs are more popular than positive ground ones, actually.

[jasperoosthoek]

+1 to what quarara said.

I don't see any reason to use pnps. They probably used them because they were cheap and available. And with a battery it doesn't matter.

You could consider converting it to a npn device by swapping the transistors with npns from another BMP and reversing the bipolar caps. But as you say hum and noise is not an issue. But that could be related to the low output. If you fix it the noise might become an issue.

[jaysg]

The pedal works just fine, but I need to crank it all the way to get near bypass volume.

Is the volume pot audio taper or linear?   Are you saying that it doesn't put out more level than when bypassed ?

[blooze_man]

There's a big volume drop if the diodes connect to Base. They need to come off the Collector.

[John Lyons]

I found this same issue with a different Ram's Head schematic.  I put the cap on the other side of the diodes and it solved my problem!

Really?! I have been making BMs with a layout with the cap off the collector
and series diodes to the base and I have full volume. (no loss).
When you have two components in series the order does not matter unless there
is another connection at their junction.

Yorick
Do you have a little volume drop or a lot? Are you using an audio pot? (as mentioned above)
I always use a linear volume pot as the originals did. Unity gain should be around noon or a little
less.

[Valoosj]

I am using a log pot of 100K. As I always do with BM clones. I maybe just make it to unity gain with all the knobs turned all the way to the right. With the knobs at noon I barely have sound.

Voltages: all negative off course

Q1:
C:6,8
B:0,6
E:24mV

Q2:
C:4,43
B:0,6
E:70mV

Q3:
C:3,9
B:0,64
E:64mV

Q4:
C:2,09
B:2,09
E:1,5

This don't seem right ...

[jasperoosthoek]

Must be Q4. The collector and base voltage should not be equal.

Seems like there is a short somewhere. Either a bad component (unlikely), blob of solder connecting two traces or a copper bridge where the copper wasn't completely etched.

[John Lyons]

Oh...I overlooked that. Yes, check there, that's your problem. 

[Valoosj]

Cut some copper that hadn't etched all the way (though I saw nothing) and it works. What a beast! And no extra noise due to the -9V.

Thanks to those that helped me out!

Pics in the appropriate thread.