Ceriatone Chupacabra effects loop/tone changes?

[peckhart]

Bringing this one back up. Curious if OP resolved the loop issues and if so how.

 

[ledvedder]

Bringing this one back up. Curious if OP resolved the loop issues and if so how.

See about 8 or 9 posts up. I installed a metro zero loss loop.

 

[scottosan]

Is there room to put a 16mm 1m pot where the unused whole is? I think I would try that first using the out of the metro board to a pot then to PI. It makes for a global master volume and works great in that location

 

[FourT6and2]

33k on the slope will have better mids, 47k sounds a bit scooped to me. A nice compromise is 39k.

Yeah, "better" is subjective. 47K is a bit scooped. But I think it sounds good in this amp. 33K is a bit honky. 39K or 36K are both good compromises. I prefer 47K or 39K myself.

And I agree on the PPIMV thing. Not a useful mod in this amp. It's got a master volume already and two gain pots. In Plexi mode, just play with the gains and you'll get great cranked sounds at low volumes. A PPIMV is gonna mess with the PI topology of this amp and limit the usefulness of the tone stack when you turn it down. But hey, play around with it, OP.

For the unused hole in the rear of the chassis now, you could throw either a switch or a mini pot in there to have a variable slope resistor. And to see how you like one slope vs another, just wire in a pot in place of the resistor and you can just turn it until it sounds good. Then measure the pot to see what value resistor to use.

After doing it blind for a week or two, I measured the pot. Guess what the value was lol 39K and/or 47K the majority of the time.

 

[ledvedder]

33k on the slope will have better mids, 47k sounds a bit scooped to me. A nice compromise is 39k.

Yeah, "better" is subjective. 47K is a bit scooped. But I think it sounds good in this amp. 33K is a bit honky. 39K or 36K are both good compromises. I prefer 47K or 39K myself.

And I agree on the PPIMV thing. Not a useful mod in this amp. It's got a master volume already and two gain pots. In Plexi mode, just play with the gains and you'll get great cranked sounds at low volumes. A PPIMV is gonna mess with the PI topology of this amp and limit the usefulness of the tone stack when you turn it down. But hey, play around with it, OP.

For the unused hole in the rear of the chassis now, you could throw either a switch or a mini pot in there to have a variable slope resistor. And to see how you like one slope vs another, just wire in a pot in place of the resistor and you can just turn it until it sounds good. Then measure the pot to see what value resistor to use.

After doing it blind for a week or two, I measured the pot. Guess what the value was lol 39K and/or 47K the majority of the time.

How do you get any overdrive when in 60s mode? The manual says to crank the master, then use gain 1 as the volume. But, this gets way to loud before it starts to get any overdrive.

That's interesting about the slope value. Thanks!

 

[ledvedder]

Unfortunately, it doesn't look like there's room for a pot in the unused hole. The level component of the metro board is too close.

 

[peckhart]

Bringing this one back up. Curious if OP resolved the loop issues and if so how.

See about 8 or 9 posts up. I installed a metro zero loss loop.

I don't know how i missed that. How do you like it?

 

[ledvedder]

Bringing this one back up. Curious if OP resolved the loop issues and if so how.

See about 8 or 9 posts up. I installed a metro zero loss loop.

I don't know how i missed that. How do you like it?

It works great. I'm not hearing any difference when I have pedals plugged into the loop vs nothing plugged in. Unlike the original insert loop, which sucked all kinds of highs and some volume when I plugged anything into it.

 

[CrazyNutz]

After looking at the board layout, I'm a bit confused about the ppimv install. The Chupa has 110k instead of 220k resistors. Plus, there are 5.6k resistors at pin 5 of both power tubes. So, with the dual 250k pot, Nik from Ceriatone told me to use 330k resistors on the pot instead of 2.2meg resistors. But, besides the 110k resistors, do I also remove the 5.6k resistors?

He also told me not to put the small jumper wire on the pot.

You keep the 5.6k resistors in place. Those are there to prevent oscillation, and they also affect the tone, so removing them will change the tone. (contrary to some)

This is how you would wire it up on the chupa.

 

[ledvedder]

After looking at the board layout, I'm a bit confused about the ppimv install. The Chupa has 110k instead of 220k resistors. Plus, there are 5.6k resistors at pin 5 of both power tubes. So, with the dual 250k pot, Nik from Ceriatone told me to use 330k resistors on the pot instead of 2.2meg resistors. But, besides the 110k resistors, do I also remove the 5.6k resistors?

He also told me not to put the small jumper wire on the pot.

You keep the 5.6k resistors in place. Those are there to prevent oscillation, and they also affect the tone, so removing them will change the tone. (contrary to some)

This is how you would wire it up on the chupa.

Thanks. Someone also mentioned 2M2 safety resistors? Where would they go, if needed?

 

[CrazyNutz]

Thanks. Someone also mentioned 2M2 safety resistors? Where would they go, if needed?

The 2m2 (2.2m) are being replace with the 330k's on the pots.

They are considered "safety resistors" because if the pot wiper fails, you'll still have bias current going to the tube via these resistors. Keeping the tube from going into thermonuclear meltdown

 

[ledvedder]

Thanks. Someone also mentioned 2M2 safety resistors? Where would they go, if needed?

The 2m2 (2.2m) are being replace with the 330k's on the pots.

They are considered "safety resistors" because if the pot wiper fails, you'll still have bias current going to the tube via these resistors. Keeping the tube from going into thermonuclear meltdown

OK thanks. I guess I should tell the guy on the metro forums who's telling me I still need the 2M2 resistors.

 

[ledvedder]

Which one of these 10K resistors is the PI dropping resistor?

 

[scottosan]

Which one of these 10K resistors is the PI dropping resistor?

It is not shown on your pic. It’s further upstream.


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

 

[ledvedder]

Which one of these 10K resistors is the PI dropping resistor?

It is not shown on your pic. It’s further upstream.


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

Hmm, OK. Here is the full layout.

 

[scottosan]

Which one of these 10K resistors is the PI dropping resistor?

It is not shown on your pic. It’s further upstream.


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

Hmm, OK. Here is the full layout.

it the 10k 2w between the positive terminals of the dual can cap with the letter “P”.

May I ask what this is for?

 

[ledvedder]

Which one of these 10K resistors is the PI dropping resistor?

It is not shown on your pic. It’s further upstream.


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

Hmm, OK. Here is the full layout.

it the 10k 2w between the positive terminals of the dual can cap with the letter “P”.

May I ask what this is for?

This is to bring the B+ voltage back up after installing the metro loop.

 

[scottosan]

Which one of these 10K resistors is the PI dropping resistor?

It is not shown on your pic. It’s further upstream.


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

Hmm, OK. Here is the full layout.

it the 10k 2w between the positive terminals of the dual can cap with the letter “P”.

May I ask what this is for?

This is to bring the B+ voltage back up after installing the metro loop.

how much of a drop did you take. Are you noticing any detrimental? I assume the drop is minimal

 

[ledvedder]

It dropped about 11v. I'm really not sure if I'm noticing anything bad, but something seemed different last night. Maybe it was just ear fatigue. It seemed a bit bassy and mushy, and that was with the bass and resonance both at only 2 or so. Could just be me.

 

[scottosan]

It dropped about 11v. I'm really not sure if I'm noticing anything bad, but something seemed different last night. Maybe it was just ear fatigue. It seemed a bit bassy and mushy, and that was with the bass and resonance both at only 2 or so. Could just be me.

11v is not worth changing it. A few volts variation in wall power can swing B+