Ceriatone Chupacabra effects loop/tone changes?
- Thread starter ledvedder
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FourT6and2
Well-known member
scottosan":d7451z99 said:It is not shown on your pic. It’s further upstream.ledvedder":d7451z99 said:
On a separate note, I noticed Nic ommitted the dropping resistor between the PI filtering and the subsequent stage filtering caps on both the 50 and 100. Doesn’t make sense
These amps don't need it. You could add one in and try it, but your preamp voltages in V1 and V2 will be too low.
FourT6and2
Well-known member
I posted a bunch of videos in one of my build threads comparing different values of dropping resistor. Subtle differences. But they are there. I wired in a 5-watt pot to go from 8K up to 25K for that resistor and I could adjust on the fly. Not a huge difference. Lower voltages = brown sound (fizzy and mushy). Higher voltages = tighter and cleaner. But too high = harsh. 10K for stock Chupa voltages. 18K if you're running a higher-voltage power transformer (like in the Yeti). The Chupa benefits a bit from higher voltages. But changing that resistor isn't how to do it. You need a new power tranny that puts out more juice. Then you can tune the preamp voltages with that first dropper.
If you lost 11v from the loop, don't worry about it. Not a huge difference. But like I told you earlier, you could just get a bunch of replacement 10K resistors and find one with a lower tolerance that measures lower, like 8K. And use that one. Will bring your voltages back up. But again... not noticeable.
If you lost 11v from the loop, don't worry about it. Not a huge difference. But like I told you earlier, you could just get a bunch of replacement 10K resistors and find one with a lower tolerance that measures lower, like 8K. And use that one. Will bring your voltages back up. But again... not noticeable.
FourT6and2
Well-known member
ledvedder":13wc2p6f said:
Yeah I've tried it in various builds. Slightly tighter low-end, but less of it. the 0.1uF are good for that deeper, bouncy low-end. But it's slightly looser. 0.047uF is a good middle ground between that and the stock Marshall value. 0.047uF is what Soldano uses, for example. Easy enough to swap 'em in and try it.
scottosan
Well-known member
It’s not just about voltage drop. The resistors also serve as the bifurcation of the filtering at different stages along the B+. Generally the PI node has dedicated filtering a dropping resistor after the screens and a dropping resistor after the PI and before the preamp. In the current configuration 50uf of the board mounted dual can is paralleled with 50uf of the chassis mounted cap with no standard dropping resistor between the 2 intended filtering stages. I don’t think this was by design because the same could be accomplished with a single 100uf cap. If keeping the B+ Up was a concern then compensate on the plate resistors. Of courseFourT6and2":21b5wt3b said:scottosan":21b5wt3b said:It is not shown on your pic. It’s further upstream.ledvedder":21b5wt3b said:
On a separate note, I noticed Nic ommitted the dropping resistor between the PI filtering and the subsequent stage filtering caps on both the 50 and 100. Doesn’t make sense
These amps don't need it. You could add one in and try it, but your preamp voltages in V1 and V2 will be too low.
The current layout works but I think it was not intentional
ledvedder
Well-known member
FourT6and2":1subdt9u said:
I'm thinking less low end might be a good thing. Although the Chupa has plenty of highs, the low end tends to get woofy. And this is with the bass and/or resonance at 4 or less.
Any particular cap brands you used? Or just the TAD brand like the ones in there now?
psychodave
Well-known member
scottosan":3rnoeolb said:
I’d look at the depth cap too. That .0047uf has lots of sub lows. I think the OP mentioned barely turning up the depth pot. I’d try a .001-.003 ceramic cap. Can be changed in like 30 seconds.
ledvedder
Well-known member
psychodave":sx9rwuzb said:scottosan":sx9rwuzb said:
I’d look at the depth cap too. That .0047uf has lots of sub lows. I think the OP mentioned barely turning up the depth pot. I’d try a .001-.003 ceramic cap. Can be changed in like 30 seconds.
Yep, I realize a tone of these things can be changed quickly. But, I don't have all these components available. I have to order them, then wait a week. Unfortunately, I've always been the type that wants to play around with things to see how they work.
FourT6and2
Well-known member
scottosan":3azdwf2y said:It’s not just about voltage drop. The resistors also serve as the bifurcation of the filtering at different stages along the B+. Generally the PI node has dedicated filtering a dropping resistor after the screens and a dropping resistor after the PI and before the preamp. In the current configuration 50uf of the board mounted dual can is paralleled with 50uf of the chassis mounted cap with no standard dropping resistor between the 2 intended filtering stages. I don’t think this was by design because the same could be accomplished with a single 100uf cap. If keeping the B+ Up was a concern then compensate on the plate resistors. Of courseFourT6and2":3azdwf2y said:scottosan":3azdwf2y said:It is not shown on your pic. It’s further upstream.ledvedder":3azdwf2y said:
On a separate note, I noticed Nic ommitted the dropping resistor between the PI filtering and the subsequent stage filtering caps on both the 50 and 100. Doesn’t make sense
These amps don't need it. You could add one in and try it, but your preamp voltages in V1 and V2 will be too low.
The current layout works but I think it was not intentional
I've asked Nik about this in the past and he said it was by design. Yes, one half of the main cap and one half of the board cap are in parallel with one end at ground and the other at V2b/PI/choke. But the amp doesn't really need it. What would it accomplish in this circuit?
FourT6and2
Well-known member
ledvedder":nsox47o1 said:
Doesn't matter. Just use whatever is already in the rest of the amp (match the voltage handling). If you're building an amp then you can tune some things with component types/brands. But don't worry about it here.
ledvedder":nsox47o1 said:
If you engage a bright switch to the left, reduce the corresponding gain to below 11:00. 10:00 is a sweet spot. Then raise the other gain to compensate for the decreased drive. I use a 4x12 with G12M-25s and I run the Depth up around 2:00 and the bass down around 9:30/10:00. Doesn't sound woofy to me. But depends on your speakers and cab.
scottosan
Well-known member
We know the amp works as is. Let's just say it's just unusual.FourT6and2":24vhel3m said:scottosan":24vhel3m said:It’s not just about voltage drop. The resistors also serve as the bifurcation of the filtering at different stages along the B+. Generally the PI node has dedicated filtering a dropping resistor after the screens and a dropping resistor after the PI and before the preamp. In the current configuration 50uf of the board mounted dual can is paralleled with 50uf of the chassis mounted cap with no standard dropping resistor between the 2 intended filtering stages. I don’t think this was by design because the same could be accomplished with a single 100uf cap. If keeping the B+ Up was a concern then compensate on the plate resistors. Of courseFourT6and2":24vhel3m said:scottosan":24vhel3m said:It is not shown on your pic. It’s further upstream.ledvedder":24vhel3m said:
On a separate note, I noticed Nic ommitted the dropping resistor between the PI filtering and the subsequent stage filtering caps on both the 50 and 100. Doesn’t make sense
These amps don't need it. You could add one in and try it, but your preamp voltages in V1 and V2 will be too low.
The current layout works but I think it was not intentional
I've asked Nik about this in the past and he said it was by design. Yes, one half of the main cap and one half of the board cap are in parallel with one end at ground and the other at V2b/PI/choke. But the amp doesn't really need it. What would it accomplish in this circuit?
Merlin talks about this in his book and the importance of decouple between stages. Because each stage shares the same supply there is always a degree of feedback/feedforward between stages. Keep in mind that signal emits form the anodes. Because the power supply does no have a zero source impedance audio currents will travel across it and appear on a shared power supply. This can lead to excessive LF distortion or oscillation. Decoupling the filtering isolates the signal as well as smoothing and filtering. Even looking at the of the Fortin Cali which this amp is based off or any Marshall schematic for this matter as well as Fenders, all have filter coupling between the PI and preamp.
FourT6and2
Well-known member
scottosan":1kuvb26s said:We know the amp works as is. Let's just say it's just unusual.FourT6and2":1kuvb26s said:scottosan":1kuvb26s said:It’s not just about voltage drop. The resistors also serve as the bifurcation of the filtering at different stages along the B+. Generally the PI node has dedicated filtering a dropping resistor after the screens and a dropping resistor after the PI and before the preamp. In the current configuration 50uf of the board mounted dual can is paralleled with 50uf of the chassis mounted cap with no standard dropping resistor between the 2 intended filtering stages. I don’t think this was by design because the same could be accomplished with a single 100uf cap. If keeping the B+ Up was a concern then compensate on the plate resistors. Of courseFourT6and2":1kuvb26s said:scottosan":1kuvb26s said:It is not shown on your pic. It’s further upstream.ledvedder":1kuvb26s said:
On a separate note, I noticed Nic ommitted the dropping resistor between the PI filtering and the subsequent stage filtering caps on both the 50 and 100. Doesn’t make sense
These amps don't need it. You could add one in and try it, but your preamp voltages in V1 and V2 will be too low.
The current layout works but I think it was not intentional
I've asked Nik about this in the past and he said it was by design. Yes, one half of the main cap and one half of the board cap are in parallel with one end at ground and the other at V2b/PI/choke. But the amp doesn't really need it. What would it accomplish in this circuit?
Merlin talks about this in his book and the importance of decouple between stages. Because each stage shares the same supply there is always a degree of feedback/feedforward between stages. Keep in mind that signal emits form the anodes. Because the power supply does no have a zero source impedance audio currents will travel across it and appear on a shared power supply. This can lead to excessive LF distortion or oscillation. Decoupling the filtering isolates the signal as well as smoothing and filtering. Even looking at the of the Fortin Cali which this amp is based off or any Marshall schematic for this matter as well as Fenders, all have filter coupling between the PI and preamp.
Good info, thanks
ledvedder
Well-known member
The empty hole where to old effects return jack was measures 7/16". Of course, Home Depot only had 3/8" or 1/2", neither of which fit. Grrr!
On a positive note, I replaced the 10K resistor with an 8.2K and the B+ is now 358v. I know this wasn't necessary but I wanted to do it anyway since I'm still learning about all this stuff.
On a positive note, I replaced the 10K resistor with an 8.2K and the B+ is now 358v. I know this wasn't necessary but I wanted to do it anyway since I'm still learning about all this stuff.