Merlin's Practical Serial Effects Loop layout

[xtian]

Sorry, no experience.

[angelodp]

No worries…. rock on.

[arcturus]

I've just finished installing this fx loop in a Hot Cat based amp, and it works really well, transparent as glass since the amp is on the bright side of the spectrum.

I found that the input voltage divider is wrong for my preamp values, i'm just tweaking that.

Thank you very much for pulling this out for me!

[arcturus]

After rolling some resitors on the input voltage divider, I still can't get a hot enough signal to drive my Digitech Jamman.
The Digitech Jaman has a "peak" LED that goes bright when the signal from the loop is too hot. I assume this signal to be somewhere arround 1Vpp.

But first, let me introduce myself.
I've been fiddling with electronics since I know myself. Recently I started building a tube amp, to be more precise, based on the BC Hot Cat. The layout is from ceriatone but I've sourced the components locally and made myself a nice 3mm thick aluminium chassis.
The amp has been modded so, now has channel switching, foot controled and this "Merlin FX Loop", soon to be installed a MV pot.

Well, back to the loop. I thought that I would get away without plugging the amp to my scope, but now I feel that is the only route to find out how hot is the signal before the PI. Is there anything I can do before I send the Cat to surgery?

BTW, english is not my first language

[ChrisM]

I might as well ask a question too lol

Regarding the return level control...
You could put it before the recovery stage or after it. What are the pros and cons of both?

[surfsup]

Updated layout attached, error corrected, input voltage divider values updated.

Looks like this was the same one I tried, which introduced a lot of hum. Not sure why the layout was very similar to yours I put the jacks right behind my tubes as well. Glad your's worked well!

[arjepsen]

Updated layout attached, error corrected, input voltage divider values updated.

I just put together an ax84.com october club, and implemented this loop, though with the parallel/seriel - mix pot, as Merlin describes in page 220 in the book.
It works well at the pure serial and parallel settings, but when I dial between those two outer settings, the volume decrease. Any good way to avoid that, so the level would be the same at every setting of the mix pot?

Regards
Anders

[beasleybodyshop]

Thanks for this thread Xtian! Now i want to do this to my 1987X clone.

How would you implement this effects loop into a fender style amp? Still put it right before the PI entrance?

[xtian]

How would you implement this effects loop into a fender style amp? Still put it right before the PI entrance?

Yes, same idea.

[arjepsen]

Updated layout attached, error corrected, input voltage divider values updated.

I just put together an ax84.com october club, and implemented this loop, though with the parallel/seriel - mix pot, as Merlin describes in page 220 in the book.
It works well at the pure serial and parallel settings, but when I dial between those two outer settings, the volume decrease. Any good way to avoid that, so the level would be the same at every setting of the mix pot?

Regards
Anders

Anyone?

[matt h]

(deleted)

[martin manning]

Being that the pot is mixing two out of phase signals, I can't imagine a way to make them not cancel themselves out. That's... kinda what out of phase signals do.

Not true, unless whatever is in the loop is inverting the wet signal. The CF driver is non-inverting, and the mixing occurs before the recover stage.

Haven't thought it through, but maybe try a larger pot? 500k or 1M?

[matt h]

(deleted)

[arjepsen]

Im not at home atm. So I cant show any schematic or layout.
But I remember Merlins book mentioning, that this circuit is the same as used in the Engl Fireball with its balancing pot.

[martin manning]

You could try this solution: http://ampgarage.com/forum/viewtopic.ph ... highlight=