Hi
Can anyone say which of these is most appropriate for a substitute to BC550
- BC560
- BC549c
- BC549b
- 2n3904
or anything else. ive socketed of course so can just test it out..
I would go with the bc549b or bc549c (same thing with higher gain)
anyway, the bc560 might be pnp so definitely not that one.
Probably any of those. I would go for 2n3904 or the 549B. 2n3904 has the opposite pinout.
It's a current mirror. I'm not sure the gain is even relevant. In any case, BC549 and BC550 are identical transistors under most situations. They have the same datasheet.
I'd probably use the 2N3904 because it's cheapest. ;)
cool. thanks
Ill have it finished tommorow.
;D ;D ;D ;D ;D
Looking forward to seeing it.
I've got a few parts to order then I'll start on mine.
As usual it will be weeks before it gets boxed up.
Ive got the box mostly drilled and the board fully populated
need to decide where to put the rotary switch.
Also I am wondering whether to tag a rub-a-dub on, so might leave space for that
aaaah decisions.
Hmmm
Couple issues here.
Delay time is barely anything, certainly not 600ms+
I did use a A50K for the delay knob, because I tend to favour shorter delays and figure id spread that end of the spectrum out...still, something not right here.
Also, there is a noticeable jump in level once you turn the pedal on, even with the mix all the way down.
Also, I managed to label my controls in the wrong order like an idiot!
On the plus side the modulation (when the delay is long enough to hear it) sounds really nice.
What did you sub for the current mirror? The pin out might be different.
Haven't built mine yet, but I'd poke around in that area to start troubleshooting even if your pins are correct.
Josh
Quote from: gtr2 on February 02, 2013, 05:22:10 PM
What did you sub for the current mirror? The pin out might be different.
Haven't built mine yet, but I'd poke around in that area to start troubleshooting even if your pins are correct.
Josh
HI
I used the BC549
I can swap it out.
In the meantime I changed the a50k for a b250k and it sounds pretty awesome.
flipping the transistors gave me shitloads more delay time.
switching back the 50k now hahaha
b100k for the win
now to sort the dry path volume...
Reduce R3 to 470k to lower the dry path. That was a last minute change.
I don't know why flipping your transistors caused more delay time...unless maybe they have a different pinout? That's just strange.
Oops! I see an issue. Remove R45 (the 1M). That should increase your delay time even further. I'll update the doc to omit that from the build (same goes for the DD). I doubled down on the Delay parallel resistors without realizing it.
son of a bitch, ive broken my rotary switch :(
worst build experience in ages!
Quote from: madbean on February 02, 2013, 06:18:36 PM
Reduce R3 to 470k to lower the dry path. That was a last minute change.
I don't know why flipping your transistors caused more delay time...unless maybe they have a different pinout? That's just strange.
Oops! I see an issue. Remove R45 (the 1M). That should increase your delay time even further. I'll update the doc to omit that from the build (same goes for the DD). I doubled down on the Delay parallel resistors without realizing it.
hmm interesting. ill fix the rotary first then get to this,
pedal complete
the 470k at R3 fixed the volume change. I just like delays at unity for the dry path...
not messed with the 1M as Im getting a nice range of delays with the 100kB and that in place, for now at least. Ill wait and see what the next persons build reports say.
just out of pure interest, why are the resistors coming off the BC550's of different values (560R, 620R) ?
Thanks!
Great effect.
The values prevent heterodyning of the two delay clocks controlled by the current mirror. The different values cause a slight mismatch in delay times but also prevent unwanted frequency noise from creeping in the audio path. The mismatch is not really a big deal since the delay are run in series from what I understand.
Quote from: madbean on February 02, 2013, 09:55:22 PM
The values prevent heterodyning of the two delay clocks controlled by the current mirror. The different values cause a slight mismatch in delay times but also prevent unwanted frequency noise from creeping in the audio path. The mismatch is not really a big deal since the delay are run in series from what I understand.
Makes sense, cheers for the explaination.
I'm thinking to experiment a bit more with the transistors to see what's going on there when I get time
Hi!
I've built the circuit and I hear a very faint but constant clicking even when the mod switch is off. I didn't receive a 1uF MLCC yet and I've added a film cap instead. Could that be the reason?
Thanks
Film cap should be fine. Try pulling out IC5. Is the click still there?
Hi Brian,
I didn't box it yet.
I didn't receive a 1M Rev for the Rate pot and I've tried a C500K with 2 jumpers without soldering it.
I've realized that when the Input wire is closed to those jumpers the noise occurs.
As soon as I move them away it stops.
Should it be ok once I solder the proper pot?
About the Tails, instead of the Valvewizard's mod is there a way to add a switch like the Echo Base using the Bypass footswitch instead of having to add an extra one?
Thanks