@brd
Forum Replies Created
-
Posts
-
Barry is putting together some awesome boards. The Bass OverThruster is essentially what I built to sound like the Mike Scheidt Yob pedal in a much cleaner package. Don’t dismiss this as just a bass pedal, it can do Doom guitar as well, try it with low A tuning. This one can really melt your face.
I have built a few special request combo pedals for a bass player. They were for Muse (Hysteria) and YOB (Heavy Doom) sounds. They might not be a good fit but I can pass along the formulas if you’re interested.
After following Barry’s advice you will most likely have found your problem. If not, do a visual inspection around LDR2. In your picture there looks like a small strand of wire at the base of that component lying across a visa or pad. A stray strand of wire can throw a wrench in the works.
One other thing that I think might be off is the voltage readings on pin 8 of IC1 and pin 4 of IC2. I would expect them to be closer to 9v. I could be wrong, I don’t have one of these boards built to verify. Check your voltage on both sides of D2, R2 and R25 with IC1 removed and see if they change with the IC installed. That could be another indication of a bad IC.
I hope that helps.
Jason,
I recommend using some sockets. Your rig will determine what sounds good. I also added an option to switch to 3 BAT41’s for asynchronous clipping on that same pedal but never liked it in the mix.
I took a quick look at the rectifier bridge diodes you asked about. They have some extra leads to take 2 AC currents and make them DC. I may not have thought of every way you could wire them into a circuit, but the way I see it, you would need 2 of them to make a typical clipping circuit and you would end up with 4 redundant diodes. I’m not saying that is bad, you never know what kind of mojo is hiding behind the science.
Big O
I used a set of BAT41’s in one of Barry’s older Blues Buster boards which is very similar to the new NT 60’s Overdrive. I did an extensive diode shootout before deciding the BAT41’s sounded better with my rig that the usual 1N914’s or 1N4148″s. Thanks for mentioning those.
The Ge Si combo should work well, it could be very amp like, Have you tried it? I’m sure there are some more great asymmetrical clipping combos, that’s why I went fishing for ideas.
I know you have a nice collection of pedals. Do you have any favorite stock or mod clipping setups?
That article is a great read, It suggests that the 1N5817 Schottky diode is a compromise between hard clipping silicon and soft clipping germanium diodes. The curve traces show that the 1N5817 does have a medium knee and a low threshold, so it could work well as a substitute for a 1N34A.
Another take away that I wasn’t aware of is the stated effect of the knee on harmonic content. To quote the article “Spectral analysis revealed that soft clipping generates predominantly odd harmonics with rapid high-order rolloff, whilst hard clipping produces richer harmonic content extending to the eighth harmonic and beyond.” I had thought that the majority of guitar distortion effects produce symmetrical clipping and that they generally produced mostly second order harmonics. I also believed that softer germanium clipping just made the sound warmer or less edgy. I guess I learned something today.
Time to break out my GuitarPCB Roto-Tone Deluxe diode test rig and check this out. I wonder what some 1N5817’s will do for a Klon circuit…
I didn’t expect to break the internet with my post, but it’s here and it’s searchable, and I just hope it might help somebody someday.
My short answer is, yes, I would expect there to be a difference that would be noticeable. With that said, it’s worth noting that 1N34A’s can have considerably different curve traces. You can find some graphs done by Analog.man showing variations they have found in Klon knockoffs. There is also an excellent post on this forum here that shows in a graph how much of a difference there can be between several kinds of diodes.
There could also be other factors that affect the sonic characteristics of any component that is used for clipping and it’s perceived effect. I believed for years that Mosfets had a nice soft clip because that’s what my ears were telling me. I found out later that they actually have a very abrupt cut-off. I still like them, even though science tells me I’m not hearing what I thought I was.
Nice work Barry, your new Tone Shaping guide is excellent; it takes an easy dive into a broad range of electronic circuit topics. I would say it’s a must read if your new to pedal building or if you want to jump into the rabbit hole of modifying pedals. There are answers to some questions that are often asked on the forum and explanations to topics and terms that are sometimes misunderstood. This is the kind of content that separates GuitarPCB from the rest.
Glad you got it fixed! Testing components in a circuit is generally not the best approach, but you made it work.
-Best
I’m not an expert, but I would always suggest starting at the beginning. In this case it is the power supply jack, assuming the wiring is correct, you want to check continuity between the posts, however, because a short anywhere in the circuit would show continuity between the + and – posts you’ll need to disconnect the ground wire from the jack, then with the power disconnected, check continuity between positive and negative posts. if you you have continuity there then the jack is shorted. I would also try removing the charge pump to see if you get normal voltage readings without it in the circuit.
I hope that helps
Let’s try some voltage measurements while you work on replacing the ribbon cable for the reverb switch. You don’t need the IC’s installed yet. With power supplied to the jack. Meter set to DC voltage, ground lead on a known good ground, preferably on a GND pad or jack.
First check is at the DC pad. expect a little over 9v. We don’t want to see -9V.
next check the voltage after D5. that would be on the cathode side or the stripe. Voltage should be slightly lower. This is your VC voltage as labeled in the schematic. No voltage means D5 died saving your project. stop here and replace it.
Now check IC1,IC3 IC4, and IC6 (the 8 pin IC’s) you want to check pin 8 which will be to the right of the index notch. You should have the same voltage as VC
Let us know what you find.
Don’t give up on it. You put a lot of work into that build. When the power jack wiring is confirmed, be sure you have voltage through D5 then try each section of the build with a guitar. If one or more of the effects still isn’t working report back. If your LED’s work it’s a good sign.
An audio probe is still highly recommended.
I’m not Barry, but I did stay at a Holiday Inn Express last night (bad American humor)
Sorry, I couldn’t edit my previous post. I want to add that, if the power jack wiring was not the problem, an audio probe might be the best next step.
If you look at the schematic for the Reverb in the build doc, the center lug for the Darken pot goes to ground. Your observation just confirms that is as expected.
The previous picture of the power jack and wiring looked like you had the DC (white) and ground (red) on the wrong posts of the jack. Did you fix that? The large terminal is for the ground. (unless you are using a non standard power supply)
Problems if power jack wired backwards:
D5 is your reverse polarity protection, it should hold up to 9V reversed (briefly) but damage is possible. you should avoid bypassing that or subjecting it to prolonged reverse current. It could fail as an open or short.
Other circuit damage could occur if that diode fails or reverse current is applied to the rest of the circuit. i.e. LED damage.
I hope that helps
Wire color doesn’t matter, but I noticed it looks like you have a white wire going to the ground of one jack and a black wire going to the ground of the other. Can’t see where they go under the board. Maybe a shot of the other side of the board might help too.
I’m glad you mentioned the switch, you’ll want to use an on-off-on switch, that will give you a third option of no clipping in the middle position.
You will need an enclosure for the PD to keep it insulated. You don’t want it shorting to the enclosure (or anything). no worries about heat.
The blue and purple wire would be interchangeable for your application.
It does not matter which row you use as long as the leads for each diode are on opposite sides of the line printed on the board
since there are two identical diodes, it doesn’t matter which goes on any row. Use the flat spot on the rim of the LED’s to be sure they are set in opposite polarity. <span style=”text-decoration: underline;”>teaching moment</span> – For D7 and D8, each diode clips half of the AC signal, when both halves are clipped with the same diodes (and number of diodes) the signal is clipped equally or symmetrically. The PD apparently clips symmetrically on it’s own, that’s why you don’t need 2 of them.
connect the blue and purple wires to a round and square pad for either D7 or D8. The other diode pads on the BE board will be empty. Since those diodes are in parallel, using a jumper would create a path of no resistance to ground and you would lose all signal.
You can measure the Vf of your PD using a meter that has a diode check option with the diode out of the circuit. The meter will supply a small current to the diode and give you a Vf reading, That is what Waylon is demonstrating at 1:12 in the video. Any difference in Vf won’t matter unless you switch while you are playing.
I hope that helps
