Bellum MK1

[joelorigo]

I've wanted to do a copperplate enclosure for a while so here it is. My first without any art work / labels. Sounds raunchy! I currently have BAT41 diodes in it because I saw in another thread that they would work when the build doc called for "GE diodes." I do have D9E sides to try also. And I don't like the black knobs on this enclosure so I'm going to get cream ones on my next Tayda order. Just a nit picky personal thing.

A couple questions to those who have built this. Does the following sound correct?

1. Mine is noisy, just activating it even with the Gain low adds lots of "hiss." Could be because even with the Gain pot full CCW, there is a lot of gain.

2. is the Gain more of a bias control? It doesn't act like a traditional gian control. As mentioned above, with the pot low there is a lot of gain, and turning it up it doesn't add a lot more gain, but it does get "splatty."

3. If I play, then stop and mute the strings, it is dead quiet for a sec and then the hiss fades in. Huh??

I should also note I omitted R24 and D3 & D4 base on researching this forum. I know this is supposed to be a wild fuzz so all that night be normal, just wondering if I have anything wrong I guess.

 

[Coda]

Sounds like your transistors are high gain. I had the same results when I built mine with 5088/5089. I ended up using 2n3904 in mine, and it works much more smoothly. You could try 2n2222 as well. Even with that it’s still pretty noisy, and the gain control kinda peaks early…

 

[Erik S]

I just finished one of these too. I built it out per the BOM/ silkscreen with 2n5088s, and installed 1n34a for both diode sets.

https://forum.pedalpcb.com/threads/what%E2%80%99s-on-your-workbench.13146/post-211704

Your results sound like they're right on par with what I got from mine. I agree with 1, 2, and 3 above. There's a thread here somewhere where someone suggests a matched set of 2n5088s at around 350 hfe, so I ordered a TC1 tester and went through the ones I had on hand - the best I could do was a set close to 470, but matched much tighter than my original random set. I plan to add a bunch to my next tayda order and see if I can get a set at a lower value. The spec sheet just lists a minimum gain of 300, and no max, and most of the ones I tested were over 500, so 350 is probably a tough ask. @Coda - I'll grab some 2n3904 too for good measure - Thanks!

On my first assembly, adjusting the gain knob would kill the signal for a second, then it would swell back in. There's still some of that with the second transistor set, but much less so. It does seem to gate more at higher gain settings, but not that much more gain like you said.

I will say, for a pedal that kinda sounds like it's broken, I've spent a lot of time playing through it. It makes some awesome noise.

You might be on to something with the gain control being more of a bias. I think the original pedal was a two knobber with an internal trim, so that might make sense.

 

[GizzWizzKing]

When I first finished mine there was some odd blossom to the notes and it felt a bit gated. I began rotating all of my transistors around trying to determine if High gain transistors played more nicely or later (I did match mine as low HFE as possible but there was still a range to them) and eventually it worked much more nicely. So maybe play with the transistor order. I don't remember mine having an unbearably high noise floor.

I also remember there being some debate as to the C7 cap being so small. I believe I changed that to 220n in my build based on a few recommendations.

 

[joelorigo]

Sounds like your transistors are high gain. I had the same results when I built mine with 5088/5089. I ended up using 2n3904 in mine, and it works much more smoothly. You could try 2n2222 as well. Even with that it’s still pretty noisy, and the gain control kinda peaks early…

I will add some of those transistors to my next Tayda order and try them, thanks!

 

[joelorigo]

I just finished one of these too. I built it out per the BOM/ silkscreen with 2n5088s, and installed 1n34a for both diode sets.

https://forum.pedalpcb.com/threads/what%E2%80%99s-on-your-workbench.13146/post-211704

Your results sound like they're right on par with what I got from mine. I agree with 1, 2, and 3 above. There's a thread here somewhere where someone suggests a matched set of 2n5088s at around 350 hfe, so I ordered a TC1 tester and went through the ones I had on hand - the best I could do was a set close to 470, but matched much tighter than my original random set. I plan to add a bunch to my next tayda order and see if I can get a set at a lower value. The spec sheet just lists a minimum gain of 300, and no max, and most of the ones I tested were over 500, so 350 is probably a tough ask. @Coda - I'll grab some 2n3904 too for good measure - Thanks!

On my first assembly, adjusting the gain knob would kill the signal for a second, then it would swell back in. There's still some of that with the second transistor set, but much less so. It does seem to gate more at higher gain settings, but not that much more gain like you said.

I will say, for a pedal that kinda sounds like it's broken, I've spent a lot of time playing through it. It makes some awesome noise.

You might be on to something with the gain control being more of a bias. I think the original pedal was a two knobber with an internal trim, so that might make sense.

Thanks, I guess I should invest in the TC1! I recently got a new DMM and it has a transistor setting but it was giving me strange readings.

 

[joelorigo]

When I first finished mine there was some odd blossom to the notes and it felt a bit gated. I began rotating all of my transistors around trying to determine if High gain transistors played more nicely or later (I did match mine as low HFE as possible but there was still a range to them) and eventually it worked much more nicely. So maybe play with the transistor order. I don't remember mine having an unbearably high noise floor.

I also remember there being some debate as to the C7 cap being so small. I believe I changed that to 220n in my build based on a few recommendations.

I saw some discussion about C7. Isn't it related to the tone stack? What difference would higher value do to the pedal?

 

[GizzWizzKing]

I saw some discussion about C7. Isn't it related to the tone stack? What difference would higher value do to the pedal?

ope. just checked the schematic and yes that cap should just effect the sweep of the tone pot and making it more usable.

 

[joelorigo]

ope. just checked the schematic and yes that cap should just effect the sweep of the tone pot and making it more usable.

One thing I forgot to mention above is that the Tone sweep is a little funny. Full CW it is the brightest, and gets more woolly going CCW, until it gets to the last part of the rotation where it changes again. Going from about 8 / 8:30 o'clock to full CCW, it gets a little brighter and louder. I wonder how a higher value C7 would effect that.

 

[Erik S]

One thing I forgot to mention above is that the Tone sweep is a little funny. Full CW it is the brightest, and gets more woolly going CCW, until it gets to the last part of the rotation where it changes again. Going from about 8 / 8:30 o'clock to full CCW, it gets a little brighter and louder. I wonder how a higher value C7 would effect that.

Same here.

 

[Erik S]

I put in some 2n3904 (all tested between 250-260 hfe). The gating and weirdness went away except for a little at max gain, but I had to pretty much max the volume to get unity, and it wasn’t as much fun. I think I’m going to keep hunting for something closer to 350.

 

[joelorigo]

I put in some 2n3904 (all tested between 250-260 hfe). The gating and weirdness went away except for a little at max gain, but I had to pretty much max the volume to get unity, and it wasn’t as much fun. I think I’m going to keep hunting for something closer to 350.

Did you get them from Tayda?

 

[Erik S]

Did you get them from Tayda?

Yes sir.

 

[joelorigo]

I tried some 2N3904 transistors. It made it a really unique raunchy nasty fuzz! Unlike anything I've ever tried. Using my DMM they measured between 270-286. Don't know how precise my DMM is. For reference the 2N5088 ones I had in above measured between 501-529, with one coming in at 597! With these 2N3904s, the volume needed to be higher for unity, about 2 o'clock, and the tone behaves the like before but has less of a "dark" range, getting brighter around 11 o'clock and keeps going! It's quirky, probably won't use it all the time, but I like it for something different. I have some PN2222 ones to try next but they measure around 200. I definitely would like to see what something in the 350 range mentioned above would do.

 

[Erik S]

I got 40 more 2n5088 in my last tayda order and went through them. Almost all were over 500, so I decided to stick with the last set I installed that were around 470 and call it finished.

You might have got lucky with your 2n3904s. Yours are a little hotter than any of the ones I tested.

 

[joelorigo]

I this a thing? I've got 2n5088s that measure higher than I want and 2n3904s that measure lower than I want, can you mix and match them??

I'm also curious about raising the value for C7 which is apparently makes the sweep more usable.

 

[Erik S]

Mix and match makes sense to me! The circuit doesn't know what part numbers are in there!

 

[joelorigo]

I put 3 in of the 2n5088s and 4 of the 2n3904s. It kind of sits in between having all of either of them. The gain isn’t as gate-y as all 2n5088s and the tone is better than all 2n3904s. There’s a lot of different sounds using the tone knob and gain. The volume is not an issue and it’s still unique and gnarly. I’m done messing with it.