Erik S
Well-known member
- Build Rating
I posted a while back asking about people's experience with quality issues from some "other" PCB brands. I got some great feedback, and @MichaelW blessed me with a care package of some off-brand stuff from his stash to try out including this Sabotage board. GPCB says its a modified version of the Sabbra Cadabra from Catalinbread.
These are currently on sale for $1.95 because they have a silkscreen error. Two of the electrolytics need to be installed reverse of what's indicated.
@Chuck D. Bones also did his own mod of this circuit built on one of these boards if you're interested.
I built this one per the BOM. I got the Five 2N5485 JFET from AES and used a BC550B from Tayda.
I've been trying to read up on JFET selection, biasing, etc. I still have no clue, but I did run some tests on these before I used them.
Test rig I used:
Here's how they went in.
Q2 Vp 3.3v, Idss 6.8mA
Q3 Vp 3.5v, Idss 6.9mA
Q4 Vp 3.1v, Idss 6.0mA
Q5 Vp 2.9v, Idss 5.5mA
Q6 Vp 2.7v, Idss 5.0ma
It looks like I installed them in decreasing order, but that wasn't intentional. I just grabbed them at random and that's how it turned out. I didn't have any extras, and they all were all close to each other, so I just went with it. I'm not sure if these are even in-spec, but I figured I'd post the numbers since I had them. I can at least confirm that the circuit functions with these and sounds pretty good to me. I don't know what the Sabbra Caddabra sounds like, and I've never played a Laney but it is a nice high gain amp sound.
I'm still a little intimidated by all the JFET-based troubleshooting threads, but after one success, I'm interested to try some other JFET amp-in-a-box stuff.
I built this with a dual-color LED since it was set up for it, but it's a little weird. Super-bright green when it's in bypass, red when it's on. Other than that, I like it a lot so far.
These are currently on sale for $1.95 because they have a silkscreen error. Two of the electrolytics need to be installed reverse of what's indicated.
@Chuck D. Bones also did his own mod of this circuit built on one of these boards if you're interested.
The Week on the Breadboard: Sabbra Cadabra
Holy Crap! This thing ROCKS! I built it stock except I put a 250K trimpot in place R22 and connected pin 2 to C16. This is where the Treble pot would go in a Marshall tone stack. More than enough gain on tap. There is no clean setting unless you dial your guitar volume way down. Who wants...
forum.pedalpcb.com
I built this one per the BOM. I got the Five 2N5485 JFET from AES and used a BC550B from Tayda.
I've been trying to read up on JFET selection, biasing, etc. I still have no clue, but I did run some tests on these before I used them.
Test rig I used:
Half my J201s are bad?
Long story short, it looks like half my through-hole J201s are bad. Short story long: I was troubleshooting my in-progress Low Tide build, as it had farty, distorted output, which pointed to one of the JFETs. I assumed I had done a poor job soldering the surface mount 2Sk208, but my audio probe...
forum.pedalpcb.com
Here's how they went in.
Q2 Vp 3.3v, Idss 6.8mA
Q3 Vp 3.5v, Idss 6.9mA
Q4 Vp 3.1v, Idss 6.0mA
Q5 Vp 2.9v, Idss 5.5mA
Q6 Vp 2.7v, Idss 5.0ma
It looks like I installed them in decreasing order, but that wasn't intentional. I just grabbed them at random and that's how it turned out. I didn't have any extras, and they all were all close to each other, so I just went with it. I'm not sure if these are even in-spec, but I figured I'd post the numbers since I had them. I can at least confirm that the circuit functions with these and sounds pretty good to me. I don't know what the Sabbra Caddabra sounds like, and I've never played a Laney but it is a nice high gain amp sound.
I'm still a little intimidated by all the JFET-based troubleshooting threads, but after one success, I'm interested to try some other JFET amp-in-a-box stuff.
I built this with a dual-color LED since it was set up for it, but it's a little weird. Super-bright green when it's in bypass, red when it's on. Other than that, I like it a lot so far.
