Parallel effects loop for Marshall style amps

novosibir · Post by **novosibir** » Tue Oct 02, 2007 1:34 pm

Icarus, when the loop section is after the Master and you crank the master, then "after the laws of physics" ALL after the master gets more juice - also your Send Level pot, also your Send jack!

Why do you wonder about this?

But OTOH I've never recommended, to place the loop section AFTER the Master! That's by your choice, if you like the sound colouration due to the 'afterburner effect' of the loop's recovery stage.

If not, and if you don't want to readjust your Send & Return pots after changing the output level via the Master, simply put the Master AFTER the loop section.

All might be so easy, if you only would imagine the signal flow through an amp. If you can't imagine the signal flow through an amp, better don't touch its inside and bring it to a good tech!

Larry

Icarus · Post by **Icarus** » Wed Oct 03, 2007 1:19 am

Ok thatnks for clearing this up.

I had to ask because the FX loop in my Plexi Reisse seems to distort the Rev/Delays when I turn up my (Standard Non PPIVM Master Volume)
And it sounds crap !

So im looking to put a better loop in my amp, to make the
Rev/delay/Chours FX sound Lush , not as if i am going through the front end of the amp.

Im not a tech , just a musician who has an great interest in amps
more than guitars these days.
So excuse my ignorance

Learning my way through reading through forums.

franc · Post by **franc** » Wed Oct 10, 2007 3:52 am

I'm finally getting there

I had these cute chassis and boards made and I am deciding on where to put the holes to feed the wires into the main chassis.

I have already done the one for the heaters and thought about doing it like in the picture.
The pots are on the back to the left of the speakeroutputs so the wires are coming from there also.

Also, I am not sure whether I should create a grounding point inside the small chassis or feed a ground wire into the main chassis and connect it to the pots at the front or anywhere else.

Any thoughts?

novosibir · Post by **novosibir** » Wed Oct 10, 2007 7:36 am

franc wrote:Also, I am not sure whether I should create a grounding point inside the small chassis or feed a ground wire into the main chassis and connect it to the pots at the front or anywhere else.

Ground the additional chassis ONLY to the amp's chassis simply by mounting it to it and ground the loop's layout inside the amp between the V2's and the PI's ground. Keep in mind, that you took the voltage supply from the PI's node, hence you'd have to ground the device 'in the right order' next to its ground point.

Larry

MacGaden · Post by **MacGaden** » Wed Oct 10, 2007 8:08 am

Nice looking box, Franc. Who made it ?

I have the schematic for the LaLoop, but do anyone have a layout for it ?
Please PM if you do...

franc · Post by **franc** » Wed Oct 10, 2007 9:12 am

Thanks Larry! Will do, I hope to report on the results very soon

Box was custom made by Ceriatone, most of my stuff comes from them (sorry George

importing from US is not very cost effective).
They also made me the boards (I had a batch of 10 made of both box and board).

joshwilson3 · Post by **joshwilson3** » Thu Oct 11, 2007 12:41 am

I'd like a rundown of what caps are needed for this loop w/ voltages.

I'm not a good schematic reader and plan to order some caps for this loop that matches the caps on my board.

Tuco · Post by **Tuco** » Thu Oct 11, 2007 5:16 pm

franc wrote:Thanks Larry! Will do, I hope to report on the results very soon

Box was custom made by Ceriatone, most of my stuff comes from them (sorry George importing from US is not very cost effective).
They also made me the boards (I had a batch of 10 made of both box and board).

franc, it looks great, much better than my project box. Can I ask how much it cost? TIA.

franc · Post by **franc** » Fri Oct 12, 2007 5:08 am

I had 10 of them made so they only cost something like 10USD each.

After drilling the top left hole for all the signal wires, I realised it is too close to the inputs. In fact, when I put in the grommet, there's no room for any wire at all because it touches the input

So I have to put it a bit closer to the hole for the heater wires.

Any problems in that?? Would it have been a good idea at all to have the signal wires that close to the inputs?

franc · Post by **franc** » Fri Oct 12, 2007 7:20 am

This is what it's going to look like on the back of the amp.

Can't wait to hear this thing!

franc · Post by **franc** » Fri Oct 12, 2007 2:42 pm

I really could use some advice on the use of shielded wire.
I hate shielded wire, never really had better results with it

I have a wire from the input of the Send pot to the 820k resistor, which is going from the back of the amp where the controls are, through the top of the chassis, into the small chassis. Should I shield this?

Then there's a wire from the wiper of the Send pot, from the back of the amp, through the chassis, into the small chassis. What about that?

Another one, coming from inside the small chassis (.47u cap), through the top of the chassis, going to the Send input.... Shield?

Finally, a wire from the Return pot's wiper, through the top of the chassis into the small chassis....

Thing is, I can't really 'just try it out' because everything is under the main board, so if I have to change anything....

novosibir · Post by **novosibir** » Fri Oct 12, 2007 5:32 pm

Use RG174/U coax antenna cable as shielded wire, it has less than 100p/m (=30p/ft.) capacity conductor-shield, is flexible and small in diameter.

Larry

franc · Post by **franc** » Sat Oct 13, 2007 2:31 am

Thanks I'll look for that.

So the general idea is: yes, use shielded wire everywhere?
What would be a good place to ground the wire coming from the tube, going into the PI? There's not really anything there to connect it to.

MacGaden · Post by **MacGaden** » Sat Oct 13, 2007 3:43 am

novosibir wrote:Use RG174/U coax antenna cable as shielded wire, it has less than 100p/m (=30p/ft.) capacity conductor-shield, is flexible and small in diameter.

Larry

Is this the right stuff ? :

novosibir · Post by **novosibir** » Sat Oct 13, 2007 7:13 am

Looks right!

When there's printed "RG174/U" anywhere onto the insulation, then it IS correct

Larry