Hey Anders, this is verified. I had issues with the down pot cutting out at around 2 o clock. Fixed this by reducing to a 1K pot with no noticeable difference. Its a cracking circuit, way better the DBA and Dwarfcraft Robots.
I built it some years ago, but using TagBoard layout. I noticed just today the same issue about the Down pot: it works just until around 2 o'clock. It's seem a schematic mistake, it isn't?
So, do you used a 1k pot instead of a 100k? Al this difference resistance is ok?
Hi guys! I'm cutting a piece of board right now for this little grunter....I was thinking of adding an extra pot for a blend option What could be the best procedure here? I see a possibility of taping the"clean" at pins 7 of the 386....how bad it can sound?
You could certainly try running pin 7 of the 386 to lug 3 of a clean pot, then lug 2 to pin 2 of the TL072 (and lug 1 to ground somewhere). But since pin 7 of the 386 is the "bypass" pin, I'm not sure you'd actually get any volume from that pin and the clean blend would be overwhelmed by the effected signal. Worth trying, I guess?
The only mention I can find of anyone doing anything with pin 7 of the 386 amp chip involves connecting a capacitor to limit high frequency noise. Not sure if you will be able to get a clean signal blend from here. Also, a review of just about every layout on this blog that uses the 386 shows pin 7 left unconnected - so once again, not sure if this can be used to make a clean blend. You may have to use an additional blend circuit that involves a jfet or bjt to take the unaffected signal from the input and mixes it back again closer to the output. There a quite a few layouts for various clean blends on the Tagboard blog that may or may not do the trick.
Those tabs on the transformer are just physical anchors for better securing it to a PCB. On stripboard builds, I just bend those things up under the body of the transformer to get them out of the way. I wouldn't wire them to any part of the circuit.
Hey Anders, this is verified. I had issues with the down pot cutting out at around 2 o clock. Fixed this by reducing to a 1K pot with no noticeable difference. Its a cracking circuit, way better the DBA and Dwarfcraft Robots.
ReplyDeleteand I used a 42TM022 instead of a 42TM011, similar specs so I can't see it making too much of a difference
DeleteI built it some years ago, but using TagBoard layout. I noticed just today the same issue about the Down pot: it works just until around 2 o'clock.
DeleteIt's seem a schematic mistake, it isn't?
So, do you used a 1k pot instead of a 100k? Al this difference resistance is ok?
I did use the 1K and it works fine, I think I tested a few values before settling with 1K
DeleteThank you. Next time I build it I'll make some test with it.
DeleteI didn't get if the original have this issue, too.
Hi guys!
ReplyDeleteI'm cutting a piece of board right now for this little grunter....I was thinking of adding an extra pot for a blend option
What could be the best procedure here? I see a possibility of taping the"clean" at pins 7 of the 386....how bad it can sound?
You could certainly try running pin 7 of the 386 to lug 3 of a clean pot, then lug 2 to pin 2 of the TL072 (and lug 1 to ground somewhere). But since pin 7 of the 386 is the "bypass" pin, I'm not sure you'd actually get any volume from that pin and the clean blend would be overwhelmed by the effected signal. Worth trying, I guess?
DeleteThe only mention I can find of anyone doing anything with pin 7 of the 386 amp chip involves connecting a capacitor to limit high frequency noise. Not sure if you will be able to get a clean signal blend from here. Also, a review of just about every layout on this blog that uses the 386 shows pin 7 left unconnected - so once again, not sure if this can be used to make a clean blend. You may have to use an additional blend circuit that involves a jfet or bjt to take the unaffected signal from the input and mixes it back again closer to the output. There a quite a few layouts for various clean blends on the Tagboard blog that may or may not do the trick.
ReplyDeleteSorry I confused the pin out.....I meant pin 5....ups!
ReplyDeleteAlso another question: about the transformer.....what to do with those little tongues of the frame, cut them or they should go to ground?
ReplyDeleteThose tabs on the transformer are just physical anchors for better securing it to a PCB. On stripboard builds, I just bend those things up under the body of the transformer to get them out of the way. I wouldn't wire them to any part of the circuit.
DeleteThanks 🙏
ReplyDelete