Parallel effects loop for Marshall style amps

[novosibir]

Marcel, it's up to you, where you place the loop section. It's working before and after the Master.
But when you've the Master before the loop and increase its level, then the loop section of course will get higher Eff. Send & Dry Return levels, what requires readjusting.

So better place the Master after the loop section, then you can even use it as a booster just w/ a guitar cord plugged in from Send to Return - adjusting the boost then w/ the Send & Return level controls.

Larry

[thinlizzy]

Hi Larry,

I'm using it now in a 2204 after the master.
When I put the loop before the master do I need a extra coupling cap (22n) between the v3b and the master pot? (refering to youre schematic)

regards Marcel

[novosibir]

When I put the loop before the master do I need a extra coupling cap (22n) between the v3b and the master pot? (refering to youre schematic)

Yes! Otherwise you'd have DC on the pot!

But keep in mind, that the 22n AFTER the Master, the PI's input cap has to be kept, to decouple the PI input.

Larry

[thinlizzy]

Thanks Larry,

I'm using a boss DD3 in the loop, any idea what this pedal can take for input level, there must be a max that this pedal can take.
In the preamp section of the 2204 how much will the send level be when the send level is max? Any idea?

Regards

Marcel

[novosibir]

I'm using a boss DD3 in the loop, any idea what this pedal can take for input level...

No! But I think not more than +4...+6dB, but that's a guess.

In the preamp section of the 2204 how much will the send level be when the send level is max? Any idea?

With the Preamp Volume dimed, the Master after the loop - depending on your guitar's output and the tone stack settings +12...+18dB

Larry

[franc]

Has anyone tried to make a separate powersupply for it?

I am considering building the loop into its own enclosure (incl. power supply etc.).
This way, the only mod you would have to do to the amp is make a break between Treble and PI input and keep the rest stock...
I'm not sure what would be needed for tranny and rectification.
6,3V obviously, what else?

I have seen this:
===
Pri: 230 V
Sec1: 200 V @ 0,015 A
Sec2: 6,3 V @ 0,6 A
Leistung / Power: 7 VA
===

But would 200V@ 0.015A be enough to get the one 12AX7 going?

[robbangitarr]

First of all Thank you novosobir for a great circuit!

I used this transformer http://www.tube-town.net/ttstore/produc ... reamp.html" onclick="window.open(this.href);return false;

I have a slight hum that could be the transformer but I can live with it, here a sloppy clip nothing fancy just som reverb and delay and the loop working as a MV http://www.robertgren.se/1.wmv" onclick="window.open(this.href);return false;

I have no pics of the inside but the ps is pretty straight forward. 10k/100uf 4k7/22uf If i remember right, made it last summer

I also have the kleinulator from ceriatone but the tubeloop sounds better even though at a gig no one would know the difference probably

Regards

[yobdab68]

I'm a new user from Italy and first of all I would like to thanks evrybody here for all the info and effort around.

I come from Triaxis - 20/20 - mesa but trying a 2204 master volume model from a friend ( with some pedal in front of it ) was an unforgivable experience ...damn it ..

I already spent some time modding old tube ( and cheap ) hifi amp ..and now this friend told me if I want to play again his amp I have to build a decent loop for him

I already asked Larry for his project ( hoping fron an answer ) .. anyway I 'm happy to be here with this community ...You rock!! ( I listened to sample from rockstah and some other...WOW...'goin to sell my triaxis ... )

[erigm]

Right! Simply place a break/make switch anywhere in the line of the 820K resistor, then in the 'break' position it's a serial loop!

Still 'more' correct would be, to use a DPDT switch and bypass the resistor after the Return Level's wiper with an additional 220p with one half of the switch, while the other half is breaking the line of the 820K.

The reason is, because every resistor network is damping especially highs, therefore the 220p is in the diagram as a 'bright switch' for the parallel path. But switched to serial, the path after the CF is the only remaining path - and now needs this bright switch too

Larry

Larry, I'm confused on the best way to make this a serial loop. The text above seems to contradict the text below.

You can switch the 820K/180K conjunction to ground as well as break the line of the 820K - but an additional 220p you don't need to recover lost highs, because there's no large resistance in front of the Return Level.

Could you please explain this again? Do we need the 220p to bypass the 220k after the fx return wiper if we break the parallel path (I'd break the 820k connection on the send pot side and then ground it)? Thanks!!!

[novosibir]

Larry, I'm confused on the best way to make this a serial loop. The text above seems to contradict the text below.

Could you please explain this again? Do we need the 220p to bypass the 220k after the fx return wiper if we break the parallel path (I'd break the 820k connection on the send pot side and then ground it)? Thanks!!!

Yes, that's confusing
Must have been late in the night (or early in the morning), as I've wrote this.

When you break the dry path (820K), to make the loop serial, all your amp's signal is going through semiconductors* in the effects device, so it depends on the sound coloration of the device, whether you need the 220p across the other 220K from the Return Level or not.

But when you make the loop serial by shunting the 820K/180K conjunction to ground, then the 220p also is grounded at one end and definitely will pull out highs - not a good thing! So in this case use a DPDT, so that you can switch the 220p across the other 220K with the 2-nd switch section.

But also in the first serial example the 220p slightly is pulling out highs - the 220p/180K series construct to ground. So in any case by tweaking the loop to serial, check for high losses and decide about the 220p, whether switchable or not!

Hope all's clear now and the sun is shining again

Larry


(*) except you have bridged the loop jacks with a cable, to make the loop to a booster

[erigm]

But when you make the loop serial by shunting the 820K/180K conjunction to ground, then the 220p also is grounded at one end and definitely will pull out highs - not a good thing! So in this case use a DPDT, so that you can switch the 220p across the other 220K with the 2-nd switch section.

Larry

I wouldn't break the loop there. I would break the connection of the 820k at the top of the send pot, and then put that end of the 820k to ground. So the 220k/220p combo still has to go through 820k before it see ground. I would think the highs being pulled out would be negligible in this case, no?

[novosibir]

No! The 820K then is in parallel to the 180K, both to ground, resulting in 147.6K
Not too much, though well audible - but as I've already said above, it depends on the sound coloration of your solid state stuff.

Larry

[erigm]

No! The 820K then is in parallel to the 180K, both to ground, resulting in 147.6K
Not too much, though well audible - but as I've already said above, it depends on the sound coloration of your solid state stuff.

Larry

Oh, ok. Good point about the paralleling. I didn't even see that. I guess I'm prone to approaching it this way because of the Kevin O'Connor loop, which uses a feedback controlled virtual earth mixer. Thanks for the input!

[novosibir]

Thanks for the input!

No output w/o input

Larry

[catalin gramada]

Hi Larry,

I'm very interested about your FX project. I tested in time some op-amp fx loops but doesn't work 100% quite well. So I want to try your true FX.
Please if it possible to send the documentation at : catalin_gramada@yahoo.com ,I put a request in your PM too.
Thanks

Best regards
Catalin