SOLVED GCI N.E.W. Apostle rotary caps.
- Thread starter comradehoser
- Start date
Solution
comradehoser
Well-known member
Yeah, I'm pretty sure it is.
comradehoser
Well-known member
Sorry folks, I keep posting on this in the interest of future builders--I'm trying to determine if this is an inherent problem with arranging the caps in series in this particular circuit, or just something funky in my particular build. It might be a totally stupid answer, let me know. I'm open to being stupid.
With the dpdt switch to the left setting, voltage at Q2 bias point drops from 16v to 12v between the first 5 selector positions and the last CW position. Not ideal, maybe, but you can play it. I should note the overall voltage is slightly lower in this setting than the other.
For the dpdt right setting, I moved everything so it was a 48nf cap in the last position. There is still the same voltage drop between FAC 1-5 and FAC 6, from 18v to 2v. It gates right out with gain at 3:00. So it's not the cap. I'm pretty sure it's either something in the switch or the way I'm wiring it around the last cap and last post. Having less or more caps, different values, leaving the last or first slot open, none of that affects the voltage drop, so it's not a fault in the caps themselves or the amount in series.
Only thing left to do that I can think of is a continuity trace in the switch, see if moving my out-wire to terminal 5 instead of 6 makes a difference. Or, remove c7 and install it inline to the center pole as in Zanshin's FAC schematic. I'd assumed that c7 would take the place of that first cap. Removing C7 seems to make zero difference in any event.
With the dpdt switch to the left setting, voltage at Q2 bias point drops from 16v to 12v between the first 5 selector positions and the last CW position. Not ideal, maybe, but you can play it. I should note the overall voltage is slightly lower in this setting than the other.
For the dpdt right setting, I moved everything so it was a 48nf cap in the last position. There is still the same voltage drop between FAC 1-5 and FAC 6, from 18v to 2v. It gates right out with gain at 3:00. So it's not the cap. I'm pretty sure it's either something in the switch or the way I'm wiring it around the last cap and last post. Having less or more caps, different values, leaving the last or first slot open, none of that affects the voltage drop, so it's not a fault in the caps themselves or the amount in series.
Only thing left to do that I can think of is a continuity trace in the switch, see if moving my out-wire to terminal 5 instead of 6 makes a difference. Or, remove c7 and install it inline to the center pole as in Zanshin's FAC schematic. I'd assumed that c7 would take the place of that first cap. Removing C7 seems to make zero difference in any event.
Stickman393
Well-known member
Hmmm.
No worries about posting brother, just taking me a little time to do some reading and try to apply vague notions of ideas with actual theory.
So, let's talk about that bias point. You're taking that measurement at 2D, right? My thought:
My first idea here is that you might be experiencing an issue with bandwidth. The presence of too much bass in your signal might be overloading Q2 and causing the gating behavior you're talking about.
When measuring the voltage at that point while switching out that cap on a rotary switch, you're not really doing anything that would directly impact your bias. At least not from a DC voltage standpoint.
That switch acts as part of a high-pass filter, and by increasing the capacitance one decreases the cutoff frequency. THis will effect your guitar signal, but it also, importantly, will effect *noise*. EMF, 60 cycle hum, etc.
The increased presence of bass signal will absolutely have an impact on your Q2 Jfet when applied to the gate.
If I have my theory correct here: Increased voltage at the gate of an N-channel Jfet will increase the N-channel width, reducing resistance across the Source and Drain, which will cause the voltage at 2D to drop.
If this is the case, then switching between 68 and 47 nF isn't going to do much to additionally filter out low end. We're talking maybe another 1.5hZ of filtering, while still under 5Hz. At this point, I'd say go lower. Way lower. Like 1/10th the value, 4.7nF or even lower. 4.7nf will get you down to 25hz at least.
But...there's always another option here. If you were to do this:
Leave everything else as is. Wire C7 directly to terminal 1 of the FAC. At that point, your maximum capacitance will be a hair over 0.98nF, and your bass cutoff will be about 140hz.
I dunno too much about filtering before gain stages. Not my area of expertise. But this could very well have been the intent and the guy who put together the schematic briefly mixed up his series and parallel capacitance laws. Or maybe he meant for it to "break" at more extreme settings. Can't say for sure.
No worries about posting brother, just taking me a little time to do some reading and try to apply vague notions of ideas with actual theory.
So, let's talk about that bias point. You're taking that measurement at 2D, right? My thought:
My first idea here is that you might be experiencing an issue with bandwidth. The presence of too much bass in your signal might be overloading Q2 and causing the gating behavior you're talking about.
When measuring the voltage at that point while switching out that cap on a rotary switch, you're not really doing anything that would directly impact your bias. At least not from a DC voltage standpoint.
That switch acts as part of a high-pass filter, and by increasing the capacitance one decreases the cutoff frequency. THis will effect your guitar signal, but it also, importantly, will effect *noise*. EMF, 60 cycle hum, etc.
The increased presence of bass signal will absolutely have an impact on your Q2 Jfet when applied to the gate.
If I have my theory correct here: Increased voltage at the gate of an N-channel Jfet will increase the N-channel width, reducing resistance across the Source and Drain, which will cause the voltage at 2D to drop.
If this is the case, then switching between 68 and 47 nF isn't going to do much to additionally filter out low end. We're talking maybe another 1.5hZ of filtering, while still under 5Hz. At this point, I'd say go lower. Way lower. Like 1/10th the value, 4.7nF or even lower. 4.7nf will get you down to 25hz at least.
But...there's always another option here. If you were to do this:
Leave everything else as is. Wire C7 directly to terminal 1 of the FAC. At that point, your maximum capacitance will be a hair over 0.98nF, and your bass cutoff will be about 140hz.
I dunno too much about filtering before gain stages. Not my area of expertise. But this could very well have been the intent and the guy who put together the schematic briefly mixed up his series and parallel capacitance laws. Or maybe he meant for it to "break" at more extreme settings. Can't say for sure.
comradehoser
Well-known member
My Man!
Now that, my friends, is what we call useful information.
Yes, the measurement is at 2D. All of the other bias points are stable regardless of FAC position. Your diagram would indeed be putting the switch in accordance with the FAC schematic that Zanshin shared: An initial cap (C7) wired in series into the center pole, rather than parallel with one end at the input and the other at the output, which is the way it's laid out currently. I'm noting that the EF120 --virtually the same circuit-- at effects layout uses caps in series with a 1nf cap in parallel across the in and out terminals.
Will try that before I try subbing a 4.8 for the 48nf.
The range of caps I think emulates what was found in the FAC switch of the Orange (TIL that Orange had that) and Matamp 120 models, 68nf looks like the upper limit.
PS: are you a fan of fellow stickperson artist XKCD?
Stickman393
Well-known member
You mean Randall Munroe? That hack stole my s(ch)tick from me when I briefly made myself appear before him in the 3rd dimension when we were both working at NASA.
After a brief and enlightening conversation with the man I asked him to draw me like one of his French girls. He did, but little did I know that he would go on to use my likeness forevermore.
Dude owes me royalties, regardless of how insightful or hilarious or mind-bending his cartoons are.
*shakes fist in the air*
RANDALLLLLLLLLLL!!!!!!!!
After a brief and enlightening conversation with the man I asked him to draw me like one of his French girls. He did, but little did I know that he would go on to use my likeness forevermore.
Dude owes me royalties, regardless of how insightful or hilarious or mind-bending his cartoons are.
*shakes fist in the air*
RANDALLLLLLLLLLL!!!!!!!!
comradehoser
Well-known member
MAN! This pedal.... After a lot of desoldering and excessive monopolization of the troubleshooting forum, we finally have a fully functional and super bitching or/cr120 circuit that sounds pretty amazing.
Changing C7 from parallel to series into the FAC rotary did it. We have stable voltage at Q2 regardless of selection, and it is a GREAT pedal!
In terms of selection, I went with 1nf into the rotary, then 1nf>4nf>10nf>22nf>48nf. I tried 470pf as the lead-in cap, but preferred the 1nf. Leaving the first slot blank doesn't work well in this configuration.
Also, 68nf as the final slot just makes everything after slot 1 sound very similar, 48nf you can hear the changes. I most likely will take stickman's advice and go with an even lower value spread of caps to see the difference, but for the moment, this is good, and what an amazing amp in a box pedal. I don't know if it's the 36v or what, but it is pretty crazy good at what it does.
@Stickman393 gets the nod for the solution, but the FAC serial wiring idea wasn't even on the table until @Zanshin dropped his wisdoms. If you're ever in DC, I'll buy you both a beer.
Thank you so much to both of you for helping me understand this pedal, orange/Matamp circuitry, and general electronics better and hopefully it will help another soul trying to get this thing to work.
And to the future yous looking for help out there, don't forget C2 is a 68nf film cap, not 10uf film. It's a dang annoying mistake I wish Kurt would just go ahead and correct, FFS.
Last edited:
Stickman393
Well-known member
I got my first internet solution bragging right point! Woo!
BrainDrain
Member
comradehoser
Well-known member
Yeah, I had them wired that way (in parallel) first, but found that they did not a lot, to put it mildly.
According to the link in Zanshin's post, series is how it is set up in the original amp heads the pedal is emulating. I don't own a Matamp or Orange 120 to peek into, so I can't confirm or deny, but I really like the way it sounds.
It might be my confirmation bias but I prefer the change to the sound of the pedal. Sounds richer and more amp like. Of course, the real test would be an a/b recording using the same sample, and swapping out the FAC and C7 between series and parallel.
It's worth noting that effects layout ef120 FAC section seems to also be wired in parallel, so I think this is the way Nick Williams intended it. Whether it's better is the question.
According to the link in Zanshin's post, series is how it is set up in the original amp heads the pedal is emulating. I don't own a Matamp or Orange 120 to peek into, so I can't confirm or deny, but I really like the way it sounds.
It might be my confirmation bias but I prefer the change to the sound of the pedal. Sounds richer and more amp like. Of course, the real test would be an a/b recording using the same sample, and swapping out the FAC and C7 between series and parallel.
It's worth noting that effects layout ef120 FAC section seems to also be wired in parallel, so I think this is the way Nick Williams intended it. Whether it's better is the question.
comradehoser
Well-known member
Did some more Internet diggings. All the schematics for the OR120 FAC I can find have the caps in series-- in various interestingly different values, but all in series.
So why Nick Williams decided to put them parallel, I don't know. Anybody know him to ask him?
So why Nick Williams decided to put them parallel, I don't know. Anybody know him to ask him?
Stickman393
Well-known member
It's a perplexing choice, honestly. The difference in cap values when wired in parallel like that make the effect of each position *super* subtle.
Like, shifting a high pass filter's cutoff frequency down 2 Hz when you're already below 10Hz isn't gonna be perceptible. Series makes a lot more sense to me.
Like, shifting a high pass filter's cutoff frequency down 2 Hz when you're already below 10Hz isn't gonna be perceptible. Series makes a lot more sense to me.
eh là bas ma
Well-known member
Nick Williams as in N.E.W ? He is on GCI builders group forum on facebook. His user name is NE williams.
He replied to me once about a question on N.E.W Bass Overdrive.
comradehoser
Well-known member
An HM-2 into the Apostle. Gainy!
comradehoser
Well-known member
Guess my tone in the GCI builder's group was off--too know-it-all and challenging, maybe (but really, I'm just curious and enthusiastic)--no reply and I doubt there's one forthcoming.
Zanshin
Well-known member
eh là bas ma
Well-known member
It's a slow paced group, maybe give it some time. I'm also curious to know if it was a mistake, or a modification to the original schematics with some real purpose.
I find this part unclear : "I can't remember why I decided to wire in parallel, but I'm not the only one and I seem to recall it was a designer directive. So, a) if you did, b) is there a reason you all decided to depart from the amp schematics to go with parallel in the pedal?"
Having C7 in parallel is just GCI circuit's layout, that's probably why you "decided" to have it in parallel in the first place ?
What's your point a) exactly ? Can you rephrase it, please ?
Last edited:
comradehoser
Well-known member
You said it, my dude/etteThe community here puts others to shame
Similar threads
- Question
