Parallel effects loop for Marshall style amps

thinlizzy · Post by **thinlizzy** » Fri Feb 08, 2008 8:21 am

Hi

I'm using this loop for somtime now in my 2204.
I use a DD-3, CE-3 and an GE-7 in the loop.
Mostly I have both the send an return on 5, I like to know how others use there loop and what there send/return level is.
I also was wondering how hot the send level is and how much a Boss pedal can handle?

regards Marcel

MRX2099 · Post by **MRX2099** » Wed Feb 20, 2008 11:25 am

Someone riddle me this answer:
If I install this FX loop in my amp, I have already the Larry/Rockstah Maste Vol Mod ok.....What I want the FX loop mainly for is I am getting a Tube Preamp ( Mesa Boogie Recto Recording Preamp) I will run this thru my Fx loop into my Marshall Plexi Clone amp.. Will I still need the Master Volume mod since the Fxloop has controls for send/return I can crank the gain on my preamp and adjust the send return volume so I won't need the main amp turned volume way up, is this correct? I am also getting a G-Major Fx unit to run them both thru the FX loop, so I am wondering if I still wound need to have the Master Volume mod at all with that combination.....ands does anyone have pictures of both the top and bottom of the FX loop ( PTP board) and how exactly its wired into the amp, so I don't screw it up royally?

Jeff

novosibir · Post by **novosibir** » Wed Feb 20, 2008 11:44 am

MRX2099 wrote:Will I still need the Master Volume mod since the Fxloop has controls for send/return I can crank the gain on my preamp and adjust the send return volume so I won't need the main amp turned volume way up, is this correct?

It's a parallel loop, not a serial, so the parallel dry path doesn't care about, how your Send & Return level controls are set to.

So the answer to your first quest is YES!

Larry

MRX2099 · Post by **MRX2099** » Fri Feb 22, 2008 2:25 pm

So actually I need a serial FX loop then correct? I want to use only the power amp section of my amp and let the Tube Preamp (rackmount) be the whole preamp along with the full signal from the G-Majot unit....

Jeff

franc · Post by **franc** » Fri Feb 22, 2008 3:02 pm

The way I installed it is with a DPDT switch so you can switch the loop parallel or serial.
When you switch to serial and nothing is plugged into Send you basically disconnect the preamp.

Ricky Lee · Post by **Ricky Lee** » Fri Mar 07, 2008 8:12 pm

I know this may be putting the cart before the horse, so to speak, but my main board is already complete so installing a board with dimensions (14") to suffice placing a loop between the preamp and PI section was NOT an option at this time. George's BB board would probably make a good candiate for the size of board needed without having to add an external board for a loop. My question is with the loop board placed forward as shown, would PO or other problem be a concern? Also, since ther schematis shows an .022 cap at the beginning of the Phase Inverter, on the main board, I'm assuming the .022 cap on the loop board and PI are one in the same. Therefore, I would need to tie the .022 cap on the PI back to the 100k and 4.7k resistors, as well as connect to pin 6 of the added (4th) preamp tube.

Ricky Lee · Post by **Ricky Lee** » Sat Mar 08, 2008 11:58 am

Larry, the schematic for the loop shows the last cap being a .022uf which is the .022uf that's at the beginning of the PI, and yet has a lead connected to the 100k in the loop. My question is when using an eternal board for the loop where is connection made to join the .022uf that's already on the main board and the 100k resistor that's on the loop board? Do I just run a lead from the .022uf from the main board to the 100k resistor on the loop board?

novosibir · Post by **novosibir** » Sat Mar 08, 2008 3:47 pm

Yes!

Larry

Ricky Lee · Post by **Ricky Lee** » Sat Mar 08, 2008 6:54 pm

Thank you Larry, your worth your weight in gold. Have a nice weekend!

Ricky Lee · Post by **Ricky Lee** » Wed Mar 12, 2008 12:39 am

Loop board all wired but sounds terrible. I've checked all connections and everything appears ok. I may be mis-reading the schematic where the 100k resistor on the loop board connects the .022uf PI cap on the main board. As you can see I have routed most hook-up wires on top of the board until I can figure out the problem. The center wire normally connected between the treble pot center wiper to the PI .022uf is disconnected and the center wiper on the treble pot is now connected to the 820k resistor on the loop board which is connected to the outside wiper on the 1M send pot. The PI .022uf is now connected to the 100k resistor on the loop board. All loop grounds are cooneted to a lug on the stand-off under the loop board. The preamp tube is lit and all wires connecting it appear to be joining the loop board properly. Also, the loop and master volume don't seem to interact well with each other, one's always effecting the other in a negative way. Larry am I missing something here?

Ricky Lee · Post by **Ricky Lee** » Tue Mar 18, 2008 2:48 pm

Is this thread still active?

novosibir · Post by **novosibir** » Tue Mar 18, 2008 11:56 pm

Ricky Lee wrote:Is this thread still active?

Yes, but Larry was off home for a week and doesn't have a notebook, to check emails & forums 'on the road'

The wire to the PI's input runs a long way unshielded, what's not a good thing!

And I can't see an electrolytic after the 4.7K to the loop's voltage supply.

Still more I'd see better, if the photo would have been taken more vertical onto the board.

Larry

Ricky Lee · Post by **Ricky Lee** » Wed Mar 19, 2008 10:34 am

Thanks Larry, maybe this is better view. The red line depicts shielded wire under board connecting between the 4.7k resistor on loop board with B+ Rail on main board - The blue line depicts shielded wire under board connecting between 100k resistor on loop board to .022 PI cap on main board - The pink line depicts wire from center lug on treble pot to 820k resistor on loop board which connects to the loops send pot outer lug. All grounds from loop board, input jacks and pots are coonected to lug under tone board. The loop and PPIMV seem to not co-exist very well with each other.

novosibir · Post by **novosibir** » Wed Mar 19, 2008 3:55 pm

To make it short with my German's English:

The brown from Return Level unshielded across the plate resistors of the first stage might create an oscillator. The pink from Treble such a long way across everything under the board unshielded is an absolute no-go and can't give nothing except bad coupling issues to certain other spots.

I hope (can't see it) that the black electrolytic is connected to the 4.7K and the other end (of the electrolytic) grounded.

The long way of the green grid wire after the SoZo left of the electrolytic also is very critical, since this wire is highly sensitive and catching all crap from around!

Make your cables as short as possible and don't buildt so much transmitter & receiver antennas with it in the amp! Then it will work properly.

Larry

jerrydyer · Post by **jerrydyer** » Wed Mar 19, 2008 6:44 pm

thats killer how you intergrated th eloop onto that board. work of art there Ricky Lee.