This is a tricky one to nail, but I've just finished one and I've managed to get it very close to my BG Harding Baby Zonk so I thought i'd share the details.
I changed the 2nd 1M from the left (R2) to 1.5m and the 3.3k next to it (R7) to 47k. These and the 15k at R8 are key to tuning it.
I also put the input cap on a DPDT with stock in the centre, 2.2nf on the one side and 10nf on the other. Makes it much more useable with three levels of bass.
It's also worth noting that I'm not getting anywhere near the biasing spec of the well known RG Keen paper on the subject, but neither is the BG Harding version. To get into the -3v to 5v on the emitter of Q1 and -7v on the collector of Q3 would require crazy leakage on those parts. I don't have anything that bad, but it would be interesting to try it at some point.
Really useful info here, thank you! I'm just starting down the zonk rabbit hole, and the bg is one of the best I've heard in demos, so great to see this got you similar results
Hi Ben, I know it's been a while but wondered if you could explain why such a big jump from 3.3k to 47k for r7?i haven't had chance to try out your values yet but just wanted to understand a bit further. Cheers
Sorry for the late reply on this. I wish I could give a scientific explanation, but I was just changing things to see how it effected the sound compared to the Baby Zonk. I can't actually remember why I used 47k, because that 3.3k here isn't actually R7, which I think must have been a mistake on my part. Having said that when I finished it was so close to the Baby Zonk you almost couldn't tell them apart.
No worries and thanks for the reply. I think the schematic shows that resistor as 33k anyway, not 3.3k,so it's nowhere near as big of a jump as I thought at first. I'll give it a go with the 47k,as the bg zonks are definitely the gold standard
This is a tricky one to nail, but I've just finished one and I've managed to get it very close to my BG Harding Baby Zonk so I thought i'd share the details.
ReplyDeleteQ1 = AC128 102 hfe 131uA
Q2 = ACY20 90 hfe 360uA
Q3 = CV 7355 189 hfe 120uA
I changed the 2nd 1M from the left (R2) to 1.5m and the 3.3k next to it (R7) to 47k. These and the 15k at R8 are key to tuning it.
I also put the input cap on a DPDT with stock in the centre, 2.2nf on the one side and 10nf on the other. Makes it much more useable with three levels of bass.
It's also worth noting that I'm not getting anywhere near the biasing spec of the well known RG Keen paper on the subject, but neither is the BG Harding version. To get into the -3v to 5v on the emitter of Q1 and -7v on the collector of Q3 would require crazy leakage on those parts. I don't have anything that bad, but it would be interesting to try it at some point.
I also used a 50kB on the Fuzz pot.
Really useful info here, thank you! I'm just starting down the zonk rabbit hole, and the bg is one of the best I've heard in demos, so great to see this got you similar results
DeleteHi Ben, I know it's been a while but wondered if you could explain why such a big jump from 3.3k to 47k for r7?i haven't had chance to try out your values yet but just wanted to understand a bit further. Cheers
DeleteSorry for the late reply on this. I wish I could give a scientific explanation, but I was just changing things to see how it effected the sound compared to the Baby Zonk. I can't actually remember why I used 47k, because that 3.3k here isn't actually R7, which I think must have been a mistake on my part. Having said that when I finished it was so close to the Baby Zonk you almost couldn't tell them apart.
DeleteNo worries and thanks for the reply. I think the schematic shows that resistor as 33k anyway, not 3.3k,so it's nowhere near as big of a jump as I thought at first. I'll give it a go with the 47k,as the bg zonks are definitely the gold standard
Deletedoes anyone knows what are the voltages? just to have an starting point.
ReplyDeleteGreetings!