Bellum MK1 Questions

[joelorigo]

I ordered a Bellum MK1 with the weekend sale and I'm looking at past conversations about it, and as usual, I have a few questions before I place a Tayda order. Thanks in advance

Based on another build report I am going to omit the 27K in R24. Does that mean D3 & D4 are out of the circuit and I don't need them either?

It looks like using 100n instead of 680n for C1-6 & C10-12 is the way to go, yeah?

And 100n or 220n for C7? But still use a ceramic?

I saw a report that said matched transistors were used. Is there a way to get 7 matched 2N5088s? Would a random selection from Tayda be ok?

Also, looks like swapping a A1M for the B1M will be smoother for the volume pot so I'm going to do that.

 

[Sturdag Lagernathy]

Seem to remember R27 is replaced with a jumper, not sure.
I think I might be the source of the "100n" advice. At the time, I was breadboarding a lot, and had some incorrect values other places, so 100n seemed closest. After replacing for original values, 680n sounds pretty good to me; I say socket. Experiment. But the original BOM values are good.
C7- Once again, quoted values seem best to me, but again, socket. Experiment. And remember this is a raucous fuzz. You could use about any type of capacitor- it's not gonna make a difference you'd notice.
Matched transistors? Seriously? Death by Audio matching transistors?
No.
Tayda is fine. Use the lowest gain trannies in the bag, call them "matched".
Probably good call on the pot..

 

[Coda]

I ordered a Bellum MK1 with the weekend sale and I'm looking at past conversations about it, and as usual, I have a few questions before I place a Tayda order. Thanks in advance

Based on another build report I am going to omit the 27K in R24. Does that mean D3 & D4 are out of the circuit and I don't need them either?

It looks like using 100n instead of 680n for C1-6 & C10-12 is the way to go, yeah?

And 100n or 220n for C7? But still use a ceramic?

I saw a report that said matched transistors were used. Is there a way to get 7 matched 2N5088s? Would a random selection from Tayda be ok?

Also, looks like swapping a A1M for the B1M will be smoother for the volume pot so I'm going to do that.

I too am working of a V1 Fuzz War. I agree with everything said above, but will add that I have been sorting for 5088’s around 350 hfe. Those seem to work best in the circuit. They also seem to be pretty rare, as most of my 5088’s are well above that…

 

[joelorigo]

Seem to remember R27 is replaced with a jumper, not sure.
I think I might be the source of the "100n" advice. At the time, I was breadboarding a lot, and had some incorrect values other places, so 100n seemed closest. After replacing for original values, 680n sounds pretty good to me; I say socket. Experiment. But the original BOM values are good.
C7- Once again, quoted values seem best to me, but again, socket. Experiment. And remember this is a raucous fuzz. You could use about any type of capacitor- it's not gonna make a difference you'd notice.
Matched transistors? Seriously? Death by Audio matching transistors?
No.
Tayda is fine. Use the lowest gain trannies in the bag, call them "matched".
Probably good call on the pot..

OK, thanks, I'll socket and start with the values listed on the build docs for this caps.

 

[joelorigo]

I too am working of a V1 Fuzz War. I agree with everything said above, but will add that I have been sorting for 5088’s around 350 hfe. Those seem to work best in the circuit. They also seem to be pretty rare, as most of my 5088’s are well above that…

Thanks, looking forward to your build report.

 

[joelorigo]

Oh, that does leave me the question of if I omit the R24, do I need to jumper, and not use D3-4?

 

[GizzWizzKing]

I just built one of these a bit back. I will need to look at my notes. If I left out R24 I definitely did not jumper it (and i kept the diodes for sure so maybe I kept R24). I will check my change notes and see what I did.
I did take the time to sort through 100 transistors to find 7 that were "matched" (within 25ish hfe on my Amazon multimeter) and they worked. When I first started it up there was a very noticable blossom to the sound. Not in a good way though. It was like your signal had to fill up a cup before it actually started to come through. I expected to have to roll the transistors around a lot and maybe order more to match more closely but I just flipped them around and it sounds ace. More to come tonight when i have access to my build notes.

 

[joelorigo]

I just built one of these a bit back. I will need to look at my notes. If I left out R24 I definitely did not jumper it (and i kept the diodes for sure so maybe I kept R24). I will check my change notes and see what I did.
I did take the time to sort through 100 transistors to find 7 that were "matched" (within 25ish hfe on my Amazon multimeter) and they worked. When I first started it up there was a very noticable blossom to the sound. Not in a good way though. It was like your signal had to fill up a cup before it actually started to come through. I expected to have to roll the transistors around a lot and maybe order more to match more closely but I just flipped them around and it sounds ace. More to come tonight when i have access to my build notes.

Thank you. The reason I am asking is that I saw a post on here that implied that if you don't use R24, then D3 & D4 are out of the circuit, so not necessary. And another post said they compared with and without R24, and with there was a noticeable volume drop and no discernible change in the character, so I was thinking to omit.

 

[GizzWizzKing]

I opted to omit R24 and did not use a jumper but kept all of the diodes even though it may not have been necessary.
Other things included using a 220nF film cap in C7 to adjust the tone sweep, transistors were all matched within 20hFE reading 268,269,270,272,287,288. I would for sure use sockets for those. I also had to flop C8 to 22nF because of a shortage in my inventory. Also it is a good idea to try and tame the volume knob. Mine is sitting under 9o'clock currently.

 

[joelorigo]

I opted to omit R24 and did not use a jumper but kept all of the diodes even though it may not have been necessary.
Other things included using a 220nF film cap in C7 to adjust the tone sweep, transistors were all matched within 20hFE reading 268,269,270,272,287,288. I would for sure use sockets for those. I also had to flop C8 to 22nF because of a shortage in my inventory. Also it is a good idea to try and tame the volume knob. Mine is sitting under 9o'clock currently.

Ok, thanks for looking into that!

Did you use 680n for C1-6 & C10-12, as listed on the BOM?

 

[GizzWizzKing]

Ok, thanks for looking into that!

Did you use 680n for C1-6 & C10-12, as listed on the BOM?

I believe so. I use blue tac and it took the label off of most my caps for this build. The ones I can see are 680n.

 

[joelorigo]

Great, thanks!