norburybrook wrote: ↑Sat Nov 16, 2019 6:01 pm...can you tell me what order the gain controls are?
We have input volume...then a loop send volume and loop return volume and a master volume. there's so many possibilities to add gain in this chain I'm not 100% sure what's driving what.
I don't have a bypass switch so don't have a ball park level setting.
The Clean and OD masters determine the input level to the send buffer, and they are independent. You can set those low or high depending upon how hard you want to drive the CF, and differentially to balance clean and OD. Assuming 10% taper master pots, I'd start with both around noon, and lower one of them to balance the Clean and OD.
Then you have loop send level, which should be set for the desired signal level out to the FX. The CF buffer's gain is always near unity, so the FX send level will also vary with the MV settings.
The FX return level wiper goes straight into the PI, so it is a pre-PI MV, same as the front panel global master on an ODS.
Ok, that makes sense, It was the master volumes I was unsure of. The loop definitely adds gain, I can have everything on 12 O 'clock and the clean channel is breaking up when played hard. That's unusual in an ODS for me unless the input is up and the amp dimed.
If I wanted to fit a bypass how would I wire that in? It might be useful for just A/B what regular levels are.
If I wanted to fit a bypass how would I wire that in? It might be useful for just A/B what regular levels are
.
Page 2 of your/this thread. Third post down.
With respect, 10thtx
thanks I've been looking at that and am confused by the in and out connections to the loop as mine goes via the relay.
Also pin 4 of the DPDT switch is going to a 100k resistor then to the 0.05uF cap I don't have a 100k resistor there, there' no resistors there, does that mean I have to insert one?
the 0.1uF at the 10M -100k node goes top the return pot pin 1 with the bright cap on my build, so not like the schematic.
this is why I'm struggling to work this out , apologies for being a bit thick with this
Ok, So I spent the morning moving pots and wiring to fit a bypass switch.Drilled the chassis wire it all in, very tight between the send and return pots.
But...........NOISY...........really ,unusable noisy , especially when bypassed The long runs that now go from the relay all the way to the switch and back the chassis that was just a 2 inch jumper is how probably 10 inches and the cause of a lot of interference as I can here the sound changing as I move the wires. The background hum doesn't change though and this is a big problem on bypass.
So..perhaps that's what tony experienced when he said his loop was noisy....don't know but it's unusable as it is. My only thought is I'l swap the wire with shielded and see, otherwise its back to how it was with a hole in the chassis bit frustrating really..
I wondered about that Marcus, and almost drew in a shield on the schematic I posted. I would try shielding the long run from the switch to the relay and the loop buffer input cap. Maybe a two-conductor cable would work, otherwise two coax cables, with the shield(s) grounded at the loop ground.
Last edited by martin manning on Tue Nov 19, 2019 1:21 pm, edited 1 time in total.
martin manning wrote: ↑Tue Nov 19, 2019 1:18 pm
I wondered about that Marcus, and almost drew in a shield on the schematic I posted. I would try shielding the long run from the switch to the relay and the loop buffer input cap. Maybe a two-conductor cable would work, with the shield grounded at the loop ground.
just tried that and flew the cables over directly to the switch. The interference noises are gone from the wires being close to others but the ground hum is unusable in bypass mode its better in loop mode now.
what was interesting though is to hear how much the master volume is OD'ing the loop input when everything is at 12 O'clock, the clean channel is OD ing with these settings , i would have thought perhaps that everything at noon would be a sort of parity but no, I have to set the master volume to about 3 for the it to be clean in the loop.
it's now back to how it was. I wonder how many others have tried using a bypass from the get get only to blame the loop for being noisy? shame as I liked the bypass sound. Which leads me to the next question:
How can i reduce the gain being added from the loop? between the send and the master volume there's a lot of gain being added. As i said with them both at mid day the clean amp is very overdriven, its a nice overdrive but not when its supposed to be clean. I can never get either the master or the send to 12 O' clock without it over driving. That might be useful now and again if it were at the end of the scale but not halfway. I seem to be short of clean headroom when compared to bypassing the loop.
is the 10k-1.5k-1M a voltage divider for reducing gain? would that be the place to adjust? .....pot values?
had a 25k so put that in...Didn't like what it to the amp..sort of sounded a bit anaemic with that in. I tried a different (alpha) master volume pot from the original NOS CTS J taper that was in there, perhaps helped a bit so that's stayed but otherwise Back to stock again...
The long runs that now go from the relay all the way to the switch and back the chassis that was just a 2 inch jumper is how probably 10 inches and the cause of a lot of interference as I can here the sound changing as I move the wires. The background hum doesn't change though and this is a big problem on bypass.