FX Loop problems

[Valvehead]

I am trying to install a basic passive loop in an Orange amp . The thing is, its got 2 master volumes. Im trying to find the right spot to insert the loop . Please take a gander at the pic, i blocked out most of the circuit because i promised not to share this. But you can see where Im talking about. Where it says Loop Break is where its at now.

When testing the loop, The clean channel works perfect, but the dirty channel is super low on volume (with the fx unit inserted).

Where should I tap into this for a passive loop ?

I thought about the middle treble wiper....but then i wouldnt have fx on the clean channel....or am I wrong ??

[Valvehead]

Has anyone added a basic loop to a 2 master amp ??

[g1]

Not sure about your loop break point. There is a dot connecting R45 and R46. The loop should be in series between that dot and C25. That means you have to cut the trace between the R45/R46 junction and C25. If you have a true series loop between those points, you should get the same relative levels as you do when nothing is plugged into the loop.
A schematic of your exact loop wiring would be helpful, switching jacks and all.

[Valvehead]

Thats exactly where I have the loop g-one . where it says loop break. im just using 2, 1/4" jacks with the switch sides connected .

[g1]

Where your arrow is touching looks like between R45 and R46, not after the junction. And it doesn't sound like the jacks are series connected. I could be wrong but that's how it seems from your drawing and description.
Here is the break I mean:
Point A should go to the tip terminal of the "send" jack, and to the tip switch terminal of the "return" jack. Point B should go to the tip terminal of the "return" jack.
This way when you have nothing plugged into the loop, the signal routes through the return jack.
You said it was working fine for the clean channel so I'll assume this is an ok spot for the loop level wise, I haven't considered that aspect of it.

Edit: Aside from all this, before you started, what was the position of the 2 masters that gave you balanced settings between clean and dirty?
Are you using those same master settings when testing your loop?

[Valvehead]

ok--looks like i have my jacks wired wrong. i will re-do them and post back

[Valvehead]

ok... i corrected the jack wire.... no change !!

i can run the fx unit ( big Boss floorboard unit ) thru the different patches, as long as im on the clean channel on the amp---seems normal, plenty of volume.

if i switch to the dirty ch on the amp i get severe feedback / oscillation , and VERY low amp volume ! Even with a clean fx patch selected.

what am i missing here ????

and, g-one , ive tried all different settings on the amp masters, and settings on the output level of the fx unit.

Im SO close......due to the fact the clean amp channel is fine

Just to mention---the amp works perfect with nothing in the loop.

[Jazz P Bass]

Is it me or does the relay circuit make no sense?
What is Relay 2B doing?

[g1]

Is it me or does the relay circuit make no sense?
What is Relay 2B doing?

Appears to bypass R45 when using dirty channel. Makes no sense to me either. Starting to suspect the drawing has errors or does not match the amp.

Im SO close......due to the fact the clean amp channel is fine...

Just to mention---the amp works perfect with nothing in the loop.

Ok, as I mentioned I'm a little iffy about whether the drawing is correct (if it is the loop should not care which channel you are using).
Here are two more tests to try.
1) Plug your guitar straight in to the FX return jack. You should get sound and it should be the same whether or clean or dirty channel. You shouldn't even hear a click when switching channels and the volume level should stay the same.
2)Play through the amp normally, guitar straight into input jack, nothing in loop. While playing, plug one end of a patch cord into the return jack. The sound should cut out. Try this while playing through clean channel, then try again while playing through dirty channel.

[Valvehead]

the loop is between the 2 resistors junction and the cap. Right where it says loop break.

plugged gtr into the return , both channels have the same vol.

plug gtr into input jack, and one end of a cable into ret jack. = dirty ch. works fine, clean channel has loud buzz from the cable

the fx loop jacks are wired as it says in post 5 above.

[g1]

plug gtr into input jack, and one end of a cable into ret jack. = dirty ch. works fine, clean channel has loud buzz from the cable

the fx loop jacks are wired as it says in post 5 above.

Do you mean the clean channel quits except for the loud buzz from the cable at the return jack? That is what should happen. With the series loop, plugging something in to the return jack breaks the connection between the preamp and power amp. So your guitar signal should cut out when you plug that other cable into the return. Sounds like there is some other path for the dirty channel as you said it kept playing when you broke into the loop. So the schematic does not seem to match the circuit. Pretty tough to add a loop with an incorrect or incomplete schematic. You would have to draw one out yourself from looking at the amp circuit.

[Valvehead]

Yes---on the buzzing cable.

I will do it again and try to be clear so we are on the same page -

Plug guitar into input, and have a cable into the return jack= clean channel gets cable buzz--touch end of cable gets louder buzz, AND you CANT hear the guitar. Thats on the clean channel.

now switch on the dirty channel--it acts normal and you can hear the guitar signal.

step 2 . Now i take out that cable, plug guitar into the Return jack, and i get normal volume on clean AND dirty channels.




ok. i got that scem directly from Orange . I guess i will pull the board again and look, but...i did before and looked at the traces and it looked correct--i will pull it again to be sure and follow all the traces in that area.

[Valvehead]

just pulled the pcb. verified that the only thing r45/46 go to is the relay , and the other end they join to go to the cap.

[Jazz P Bass]

Can you verify that the circuit does match the schematic?
As drawn, the schematic makes no sense!

[Valvehead]

well , it matches the section im putting the loop in. Still dont understand why one channel works and the other wont