Moving Master Volume In A Ceriatone Chupacabra For Effects Loop Installation

[ledvedder1972]

Ugh! I'm getting so much conflicting information. I have several people telling me that the return 1meg pot will do just fine, yet others are telling me it will not work so well.

[Gingertube]

For reference the schematic will be VERY close to this:
http://music-electronics-forum.com/t43046/

See sheet 2 for the existing "loop".

Cheers,
Ian

[Chuck H]

For reference the schematic will be VERY close to this:
http://music-electronics-forum.com/t43046/

See sheet 2 for the existing "loop".

Cheers,
Ian

Well, not really. Because the Metro loop is balanced. The loop shown in the link still operates the loop from the tone stack, which I can tell you for certain doesn't work well. "I" understand your reference though. That is, the loop is driven by the TS, the master follows and feeds the PI. Unfortunately the "conceptualized" circuit placements are beyond our patron. I think an actual "connect this point to that point" instruction is necessary. I'll work on it in case no one else does. I have some free time right now

[Chuck H]

Like this:

Note differences in wiring for master and tone stack feed. in/out for Metro loop are somewhat generic.

[Gregg]

Not really. The Chupacabra is a high-gain amp in sthe style of Jose, Friedman and so on. It is designed mainly for preamp distortion, not poweramp crunch.

Yes and no. Yes because unlike a regular Plexi most of the overdrive/distortion is coming from the preamp. No because cranking it up also adds to the tone but considering he will be using it with reverb and delay overdriving the power amp won't be a good idea so we can assume he will be relying on the preamp for most of the tone.

How complicated is option 1? I wouldn't be switching the loop in and out. I basically need a reverb on most of the time, and a delay and boost to turn on and off for solos, etc.

Since you're not switching the entire loop in and out forget about that option. Another way to do that would be to include a place for a relay (that can be bypassed if not used) that will switch only the jacks (the loop circuit in the sound path at all times) but obviously that's not available on Metro's loop.

[pdf64]

Like this:

Note differences in wiring for master and treble pots. in/out for Metro loop are somewhat generic.

It may be beneficial to break the circuit 0V / common connection between the fx loop sockets and the speaker sockets, and give the loop circuit its own connection to the star point.

[ledvedder1972]

Yes and no. Yes because unlike a regular Plexi most of the overdrive/distortion is coming from the preamp. No because cranking it up also adds to the tone but considering he will be using it with reverb and delay overdriving the power amp won't be a good idea so we can assume he will be relying on the preamp for most of the tone.



Since you're not switching the entire loop in and out forget about that option. Another way to do that would be to include a place for a relay (that can be bypassed if not used) that will switch only the jacks (the loop circuit in the sound path at all times) but obviously that's not available on Metro's loop.

Well, the metro loop did come with a switch to turn the loop on and off, so I would like to use it.

[ledvedder1972]

Like this:

Note differences in wiring for master and treble pots. in/out for Metro loop are somewhat generic.

Wow, I really appreciate this! What are the differences in the treble pot?

[ledvedder1972]

It may be beneficial to break the circuit 0V / common connection between the fx loop sockets and the speaker sockets, and give the loop circuit its own connection to the star point.

For what reason? Noise reduction?

[Chuck H]

Wow, I really appreciate this! What are the differences in the treble pot?

Sorry, no difference with the wiring to the treble pot. The difference is the feed to the tone stack.

[Chuck H]

For what reason? Noise reduction?

Yes. Since the Metro loop has it's own little amplifier, and it will be feeding the master volume which is grounded at the buss there may be potential for a ground loop. I'll modify the layout I posted to represent Pete's good advice.

[ledvedder1972]

I sincerely appreciate everyone's help and feedback. I realize I'm a rookie at this and I probably should take the amp to an experience tech for this stuff, but I'm trying to learn on my own. This is extremely interesting to me.

[ledvedder1972]

Yes. Since the Metro loop has it's own little amplifier, and it will be feeding the master volume which is grounded at the buss there may be potential for a ground loop. I'll modify the layout I posted to represent Pete's good advice.

Thank you! Could you also include the switch wiring?

[Chuck H]

Thank you! Could you also include the switch wiring?

No. At the site I looked over the installation instructions and it seems they prefer to fully remove the unit from the circuit AND use an in/out jumper for true bypass. I'm sure they have their reasons, but I couldn't locate a schematic of the Metro loop to confirm why. This being the case, follow the instructions on their site for installation. The "where to install" and necessary amp circuit modification is covered in the layout I posted.

EDIT: It's very likely all you need for a bypass is a shorting switch across the in/out on the Metro loop board. But I'd need to see a schematic to confirm this.

[Gregg]

...I couldn't locate a schematic of the Metro loop...

There's one (rev.3) in another thread here:

http://music-electronics-forum.com/a...-rev-3-sch.jpg

I seriously doubt rev.4 is very different from rev.3.