SOLVED GCI N.E.W. Apostle rotary caps.
- Thread starter comradehoser
- Start date
Solution
Stickman393
Well-known member
How do you have it wired right now?
The build doc doesn't give explicit instructions, but it's clear the intention there is to slap in a single pole (multi) throw rotary switch in there that one can use to throw another cap in parallel with C7. You're only limited by your number of throws.
You'd need to accomplish this by running a wire from one of the FAC pads to the common on your rotary. From there you would connect one lead from each cap to a throw's terminal, connect all the remaining cap leads together, and run a wire from that bundle of leads to the remaining FAC pad.
Pics?
The build doc doesn't give explicit instructions, but it's clear the intention there is to slap in a single pole (multi) throw rotary switch in there that one can use to throw another cap in parallel with C7. You're only limited by your number of throws.
You'd need to accomplish this by running a wire from one of the FAC pads to the common on your rotary. From there you would connect one lead from each cap to a throw's terminal, connect all the remaining cap leads together, and run a wire from that bundle of leads to the remaining FAC pad.
Pics?
comradehoser
Well-known member
That's what I've got. To me, the caps just don't appreciably change much, if anything in the sound. I'm wondering if y'all who have built it hear the same and maybe how to change it so it's more substantive. Apparently the Matamp cap switch also wasn't that noticeable, so maybe it's another case of "that's just the way it sounds".
Will provide pics, but please keep in mind this was one of my first builds, back when I was still building kits from musikding. It was wired totally crazy and one of my dual pots actually broke in two, so replaced it and rewired everything.
Will provide pics, but please keep in mind this was one of my first builds, back when I was still building kits from musikding. It was wired totally crazy and one of my dual pots actually broke in two, so replaced it and rewired everything.
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Stickman393
Well-known member
Looking at the schematic there: it's gonna depend on a couple of things.
Keep in mind, I'm just exercising some very rudimentary knowledge about filters and such so I could be way off here.
The biggest impact will be in mode A, especially if you use one of your throws to make an open circuit. That might get ya in an area where you start to hear a difference.
Keep in mind, I'm just exercising some very rudimentary knowledge about filters and such so I could be way off here.
The biggest impact will be in mode A, especially if you use one of your throws to make an open circuit. That might get ya in an area where you start to hear a difference.
comradehoser
Well-known member
[Edit: trying to wrap my head around the schematic and making too many conclusions too quickly]
I will try no cap/jumper and see what happens.
BTW, I did not choose any of the components nor the rotary, they were all supplied by Musikding.
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Stickman393
Well-known member
I'd leave the connection open, no jumper. That 1nf cap in parallel is there to carry the signal through and block any DC from the previous stage.
It's difficult for me to make heads or tails of how that rotary switch will impact mode B: lots going on there. It's still going to do *something*, but I couldn't tell you if it'll be audible or not.
comradehoser
Well-known member
Ah, okay--sorry for the the OG comment edits, I contemplated the schematic and had an AHA! and I was trying to save you the work of correcting my misunderstanding--but the AHA! turned into another WHU?
Guess I should slow down my posting.
What I really don't understand is why Mode A or Mode B? I assume that the signal will pass through the top of the loop if the bottom is not grounded, but what does that accomplish seeing as they are copies of each other?
Guess I should slow down my posting.
What I really don't understand is why Mode A or Mode B? I assume that the signal will pass through the top of the loop if the bottom is not grounded, but what does that accomplish seeing as they are copies of each other?
Stickman393
Well-known member
Ya caught me 
.
It's an assumption on my part. A slightly informed opinion that is probably somewhere near the peak of mount stupid on tie dunning-kruger graph. I'm assuming that by doing away with the ground on mode A's switch, in addition to all the additional resistances that the signal needs to pass through before it has an opportunity to pass to ground, that the effect of the high pass filter created in conjunction with the bass pot in the tone stack is significantly reduced.
I base this idea on vague notions of circuit functionality that I don't really have the knowledge based to back up 100%. I also disavow any consequences for my advice up to and including electrocution.
.It's an assumption on my part. A slightly informed opinion that is probably somewhere near the peak of mount stupid on tie dunning-kruger graph. I'm assuming that by doing away with the ground on mode A's switch, in addition to all the additional resistances that the signal needs to pass through before it has an opportunity to pass to ground, that the effect of the high pass filter created in conjunction with the bass pot in the tone stack is significantly reduced.
I base this idea on vague notions of circuit functionality that I don't really have the knowledge based to back up 100%. I also disavow any consequences for my advice up to and including electrocution.
comradehoser
Well-known member
Hahaha!
No, dude, what you're saying makes sense. The circuit doesn't make sense!
Anyways, I appreciate you (and your time and your mental effort) for helping puzzle this out together, for sure!
Let me go lift a cap in the switch and see if it does anything at all.
No, dude, what you're saying makes sense. The circuit doesn't make sense!
Anyways, I appreciate you (and your time and your mental effort) for helping puzzle this out together, for sure!
Let me go lift a cap in the switch and see if it does anything at all.
comradehoser
Well-known member
So with the first cap lifted, the rotary does make somewhat of an audible difference in the bass frequencies (dimed bass and then treble pot to test), but not that much cap to cap, with the A/B selector switch to the left, which I assume (maybe incorrectly) is "switch A". In switch B mode, it makes much less of a difference. It's basically only audible in the distortion harmonics/"tails" when you let the note ring out. Like a very subtle filter.
Other than putting in a greater range of capacitors (I was thinking of just making a row of sockets and stock it from none>10nf>50nf>100nf>220nf>400nf>1u and see what happens), is there a way I can boost the effect of the capacitors or make their effect more pronounced in some way, do you think?
Stickman393
Well-known member
From looking at the schematic and doing some high pass filter calcs, honestly, I think you should be looking *lower*.
The reason being...well, I'm not sure I'm doing this entirely correctly because there's more to the tone stack than just this, but if you leave the rotatry switch open and just rely on that 1NF cap, your frequency cutoff will be about 141hz.
Which is definitely within the audible range for bass. You'll feel it at the very least.
Throwing another 1nf in parallel will yeild a cutoff of 70hz. That'll be a noticable shift from 141hz, you'll feel more bass...but as you go down lower you'll definitely have diminishing returns.
At 68nf, you're at 2hz. 1uF? Like 1.4hz. nah. That's not gonna be audible at all.
Now, if you swap that 1nf in C7 for a 470pF, then your cutoff frequency with the FAC pads open will be about 300hz. Thats a significant bass roll off. Then you could use the rotary to switch between open, another 470pF, an 810pf, a 1nF, etc. That would tend to make for a much more usable range (as long as I'm not missing anything with those caps in parallel with the resistances around the bass knob - not sure how those will impact the signal truth told)
Honestly, anything below 90hz is going to be increasingly difficult to hear on the guitar (total of about 1.6nf). Below 40hz (3.5nF) it's gonna be near inaudible.
The larger the cap, the more bass will seep through. Fun little platform for mods you've got there.
Here's the calculator that I've been using:
www.digikey.com
The reason being...well, I'm not sure I'm doing this entirely correctly because there's more to the tone stack than just this, but if you leave the rotatry switch open and just rely on that 1NF cap, your frequency cutoff will be about 141hz.
Which is definitely within the audible range for bass. You'll feel it at the very least.
Throwing another 1nf in parallel will yeild a cutoff of 70hz. That'll be a noticable shift from 141hz, you'll feel more bass...but as you go down lower you'll definitely have diminishing returns.
At 68nf, you're at 2hz. 1uF? Like 1.4hz. nah. That's not gonna be audible at all.
Now, if you swap that 1nf in C7 for a 470pF, then your cutoff frequency with the FAC pads open will be about 300hz. Thats a significant bass roll off. Then you could use the rotary to switch between open, another 470pF, an 810pf, a 1nF, etc. That would tend to make for a much more usable range (as long as I'm not missing anything with those caps in parallel with the resistances around the bass knob - not sure how those will impact the signal truth told)
Honestly, anything below 90hz is going to be increasingly difficult to hear on the guitar (total of about 1.6nf). Below 40hz (3.5nF) it's gonna be near inaudible.
The larger the cap, the more bass will seep through. Fun little platform for mods you've got there.
Here's the calculator that I've been using:
RC and RL Passive Filter Calculator | DigiKey Electronics
Calculate the -3dB cutoff frequency of RC and RL circuits for both Low and High Pass filters using DigiKey’s passive filter calculator.
www.digikey.com
Hal Harvey
Well-known member
Orange OR120 is Gain Stage > Tone Stack > Gain Stage > FAC > Gain Stage.
Matamp GT120 is Gain Stage > FAC > Gain Stage > Tone Stack > Gain Stage.
The Tone Stack and FAC positions are swapped in the two amps and the pedal mode switch emulates this by disconnecting ground in one of the tone stacks.
The pedals FAC position doesn’t change based on mode (like in the actual amps) but, arguably, having it in the GT120 position has a bigger impact. @Stickman393 is correct, it lets more bass into the gain stages. Do you have a bass-heavy guitar or a bass to try?
Edit… More on the FAC here:
Matamp GT120 is Gain Stage > FAC > Gain Stage > Tone Stack > Gain Stage.
The Tone Stack and FAC positions are swapped in the two amps and the pedal mode switch emulates this by disconnecting ground in one of the tone stacks.
The pedals FAC position doesn’t change based on mode (like in the actual amps) but, arguably, having it in the GT120 position has a bigger impact. @Stickman393 is correct, it lets more bass into the gain stages. Do you have a bass-heavy guitar or a bass to try?
Edit… More on the FAC here:
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Stickman393
Well-known member
*Wipes sweat from brow*
Ahem. Yes, quite. Never doubted myself for a second. Jolly good.
comradehoser
Well-known member
Took out C7 and socketed a 470pf, and started rebuilding the rotary along stickman's suggestions, but....
According to this, where I assume C7 is the equivalent to C15 (? Doesn't seem like it to me, but ok),
Looks like I wired the switch wrong and that might be the problem. I soldered one cap leg to the throw terminal and the other to a connector.
The reasons I decided to do it that way have been lost in the mists of time.
Looks the FAC discussion schematic has the cap legs bridging the terminals.
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Stickman393
Well-known member
Yeah, that schematic certainly is different.
In that case, c15 is in series with the switch. With the switch all the way at the top, you get your lowest capacitance value (caps in series always equals less than the smallest value).
It's [1/uF(total)] = [1/uF(1)]+[1/uF(2)]+etc
So as you turn the switch clockwise towards c20, you're taking caps out of the series path, and therefore increasing the capacitance, therefore decreasing the cutoff frequency, therefore increasing bass.
This pedal uses a different means to achieve a similar result. Instead of running in series, you have a base capacitance and add an additional cap in parallel.
Caps in parallel go like this: uF(total)=uF(1)+uF(2)+etc.
Though it could very well be that the intention here is to wire the rotary as drawn on that schematic: it might make the control a bit more useful.
In that case, c15 is in series with the switch. With the switch all the way at the top, you get your lowest capacitance value (caps in series always equals less than the smallest value).
It's [1/uF(total)] = [1/uF(1)]+[1/uF(2)]+etc
So as you turn the switch clockwise towards c20, you're taking caps out of the series path, and therefore increasing the capacitance, therefore decreasing the cutoff frequency, therefore increasing bass.
This pedal uses a different means to achieve a similar result. Instead of running in series, you have a base capacitance and add an additional cap in parallel.
Caps in parallel go like this: uF(total)=uF(1)+uF(2)+etc.
Though it could very well be that the intention here is to wire the rotary as drawn on that schematic: it might make the control a bit more useful.
comradehoser
Well-known member
I do vaguely recall some instructions to wire it up this way (in parallel--and notably c7 is wired in parallel to the whole FAC), but now I'm curious to see what happens with the stock caps in series.
Will report forthwith!
Will report forthwith!
comradehoser
Well-known member
Well, folks, it wasn't even close.
Serial caps is indeed what is needed. Makes a BIG noticeable difference between the selections in bass and amplitude. I left the 470p in at C7 and the 1st rotary slot open per Stickman advice. I might sub the 1n back in later to see what difference it makes, but it is really pretty sweet as is. It sounds maybe more Marshally than Orangey at the open setting, but the FAC changes that in a jiff. You can get thick, sludgy gain really quickly.
I'm not sure what possessed me to wire the caps in parallel to begin with. I'm pretty sure it was some build instructions or advice in the GCI community, as I don't think it would have come to me naturally. The parallel wiring FAC is just super weak sauce.
I might also play around with the cap selection. Right now I have (details for future builders): socketed R7, the cap to the right of the FAC pads, to remove the 1n and put in 470p. I recommend you put in sockets before you put in the trim pot, because it's not fun to get around that. From the FAC round pad on the board to center terminal A on my 2p 12t rotary (It's 6 per pole--I think 1p 12t would have been better just for more options) terminal 1-2 open > terminals 2-3 1n > terminals 3-4 10n > terminals 4-5 47n > terminals 5-6 63n and 6 out to the square pad on the board.
100% thank you so very much to @Stickman393 and @Zanshin , who were very kind and patient in sharing their knowledge and time so generously --you just advanced my knowledge forward a lot and made my pedal 100% more fun to play, and hopefully anyone else looking to build this.
Cheers!
Serial caps is indeed what is needed. Makes a BIG noticeable difference between the selections in bass and amplitude. I left the 470p in at C7 and the 1st rotary slot open per Stickman advice. I might sub the 1n back in later to see what difference it makes, but it is really pretty sweet as is. It sounds maybe more Marshally than Orangey at the open setting, but the FAC changes that in a jiff. You can get thick, sludgy gain really quickly.
I'm not sure what possessed me to wire the caps in parallel to begin with. I'm pretty sure it was some build instructions or advice in the GCI community, as I don't think it would have come to me naturally. The parallel wiring FAC is just super weak sauce.
I might also play around with the cap selection. Right now I have (details for future builders): socketed R7, the cap to the right of the FAC pads, to remove the 1n and put in 470p. I recommend you put in sockets before you put in the trim pot, because it's not fun to get around that. From the FAC round pad on the board to center terminal A on my 2p 12t rotary (It's 6 per pole--I think 1p 12t would have been better just for more options) terminal 1-2 open > terminals 2-3 1n > terminals 3-4 10n > terminals 4-5 47n > terminals 5-6 63n and 6 out to the square pad on the board.
100% thank you so very much to @Stickman393 and @Zanshin , who were very kind and patient in sharing their knowledge and time so generously --you just advanced my knowledge forward a lot and made my pedal 100% more fun to play, and hopefully anyone else looking to build this.
Cheers!
Stickman393
Well-known member
Hey, you're not the only one who was thinking "ah, they want this in parallel". That was my initial thought as well.
Seems obvious in retrospect. Glad you got it figured out brother!
Seems obvious in retrospect. Glad you got it figured out brother!
comradehoser
Well-known member
Wait a minute, wait a minute. As with many things in this discussion, and pedal I think I may have jumped too fast.
After wiring everything in series, with the DPDT switch to the right (matamp setting?), the last CW position in the FAC is gating out. Checked the bias points and rebiased to 17v (middle of recommended 16-18v), point 2 read 2v. Rebiased Q2 to 16v, but the rest of the FAC settings are reading around 32-36v, also sounds a bit craptastic. Swapping C7 from 470p back to 1n doesn't affect it at all, nor does shifting the caps to "close" the open terminals at position 1-2.
My original caps are pretty beat up, I will check to see if a replacement does the trick. But maybe there is something I'm missing--like do I need to extend the connection of the last cap to the next leg or something, or I'm not omitting something(?)
After wiring everything in series, with the DPDT switch to the right (matamp setting?), the last CW position in the FAC is gating out. Checked the bias points and rebiased to 17v (middle of recommended 16-18v), point 2 read 2v. Rebiased Q2 to 16v, but the rest of the FAC settings are reading around 32-36v, also sounds a bit craptastic. Swapping C7 from 470p back to 1n doesn't affect it at all, nor does shifting the caps to "close" the open terminals at position 1-2.
My original caps are pretty beat up, I will check to see if a replacement does the trick. But maybe there is something I'm missing--like do I need to extend the connection of the last cap to the next leg or something, or I'm not omitting something(?)
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