Using a Metro FX Loop on a VOX ac15c1?

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woodsjl1
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Using a Metro FX Loop on a VOX ac15c1?

Post by woodsjl1 » Sat Oct 30, 2010 9:43 pm

I'm really close to purchasing a Vox ac15c1, which does not have an effects loop. I am wanting to know the best way to adequately use delay and such time effects. Would the Metro FX loop easily be installed in a Vox? Also, is there any other way to use delay besides using a distortion pedal and only running through the clean channel, etc?

Witness
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Re: Using a Metro FX Loop on a VOX ac15c1?

Post by Witness » Sun Sep 04, 2011 9:01 pm

Bump!

I'm about to pick up an AC15C1 and would LOVE to know whether this kit will work on any amp without an effects loop or if it will only work on Metropoulos amps?

SDM
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Re: Using a Metro FX Loop on a VOX ac15c1?

Post by SDM » Sun Sep 11, 2011 5:22 am

This is a tough one as first off I'm not even sure I have a fully correct schematic. Assuming I do, the reverb kinda throws a kink in things, but if a LINE LEVEL version of the loop were placed directly after the divider/reverb mix resistor, directly feeds the PI input cap, I believe it could work.

Only done very rough calcs here, but you'd want to use a line level version of the loop - with pedal level effects in the loop. Reason for that is the divider before the PI (where the reverb mixes in as well) knocks the signal level down too low for the standard pedal level loop. To compensate, would just need to use a line level loop (and with the amp pretty well cranked up), that should give you back the appropriate levels for pedal/instrument level gear in the loop.

Install would go like this: A line level version of the loop (but with pedal/instrument level gear used in it). Loop power should be drawn from the screen node here (thus step 15 of the instructions would be omitted). The loop should be inserted following the 220k/220K divider (which the 1meg from the reverb mix control meets as well), the output of the loop should feed the PI input cap (C11 on the schem I have). One could accomplish this just by lifting/freeing the leg of C11 that heads to the divider/reverb 1meg, leave the other end of the cap as is headed in to feed the PI. The pad where the C11 leg was lifted would then connect to the loop's "in" side, the loop "out" side heads to the lifted C11 leg.

Another thing to keep in mind here is that EL-84s are EXTREMELY easy to overdrive. So (relative to a typical EL-34, 6550,6L6 etc.. Marshall or such anyway ), much more of your (cranked up) distortion typically comes from the EL-84s (and PI). A loop may not be quite as beneficial as it is in amps with more preamp overdrive on tap, relatively cleaner poweramps. Really depends on how the amp is used, how and what effects are used (and personal preferences).

So any way, in the end here I'd really need to do more calcs (which I likely won't have time to do, at least not soon unfortunately), the reverb circuit could throw in something I'm not seeing in a quick/rough analysis. Though I think the above setup would (technically at least) get along well with the loop, just cannot make any guarantees here. If I get the time to analyze the circuit more in depth, try it myself (or hear back from someone who has tried it) in this particular amp, things could well change. In the meantime though, due to some uncertainty (and just the general nature of EL-84 amps), I'd have to say it's not something I could recommend.

Hope that helps,

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