Volume loss on bypass (true bypass)

suncrush · May 04, 2015, 09:02:20 AM

I think my issue is that I'm working on a breadboard, and not through soldered connections, but I've never done an audio project before and I want to make sure I understand what's happening before I box it all up.

I'm making a valvecaster, using this schematic, with two modifications. I did not install a tone knob, so C4 and VR2 are nonexistent. I am also running at 18 V.

I am using a DPDT switch to bypass the effect. I have the input jack connected to the common lug of the switch, and the output connected to one of the poles. The input is soldered to a jumper, which runs to the breadboard. A jumper runs from board to common. A soldered jumper runs out of the switch to the board, then a jumper carries the signal to the ouput, also soldered.

With the switch on bypass, the level is about 10-15 dB lower than direct connection to the amp.

Will this resolve itself when I solder input to common, and solder pole to output, or is there something about this that I don't understand?

suncrush · May 04, 2015, 10:41:39 AM

I found this diagram for a footswitch, which grounds out the circuit input when bypassed. Is that important? It doesn't seem to me like it would matter, but.....

canman · May 04, 2015, 10:45:15 AM

I'm not sure I understand how your DPDT wiring is set up, but regardless...I don't think soldering everything in will solve a 10-15dB drop in volume.

Is your switch wired up exactly as shown in that picture, minus the left pole with the LED indication?

Grounding the input can be important, but it's not necessarily required. It probably isn't the cause of your problem. I find grounding the input helps more with signal bleed and switch pop.

bloxstompboxes · May 04, 2015, 10:47:12 AM

Permission to re-post this drawing is denied. oops. lol.

canman · May 04, 2015, 10:48:24 AM

You'll notice it's no longer posted. (It's a common 3PDT wiring method anyways...a quick google search will bring it up for anyone who cares to find it)

Suncrush...is one of your cables bad?

suncrush · May 04, 2015, 10:50:12 AM

That's not my switch. That's one I found. Let me sketch what I did with my switch, and post in a few.

suncrush · May 04, 2015, 10:58:49 AM

Ok, this is what I've done.

suncrush · May 04, 2015, 11:00:14 AM

Quote from: canman on May 04, 2015, 10:48:24 AM
Suncrush...is one of your cables bad?

That's a good question.... I'll have to check tonight when I get home.

canman · May 04, 2015, 11:02:20 AM

So you've only used one pole on the DPDT?

I'm not an expert by any means, but I think in true bypass, the output is supposed to be on a switch as well as the input.

Wire up the input jack wire to the common lug of one of the poles, and the output jack wire to the common lug of the other pole. You'll want the circuit input and circuit output to then connect to those respective poles you just wired the jacks up to. You'll also need to jumper the other two lugs you didn't use.

suncrush · May 04, 2015, 11:05:09 AM

Ok, got it.

canman · May 04, 2015, 11:08:34 AM

Do a quick DPDT true bypass search in google images and you'll find plenty of diagrams that will sort out the mess I just wrote up

I think once you wire up the switch that way, you'll find no drop in volume!

bloxstompboxes · May 04, 2015, 11:28:17 AM

Quote from: canman on May 04, 2015, 10:48:24 AM
You'll notice it's no longer posted. (It's a common 3PDT wiring method anyways...a quick google search will bring it up for anyone who cares to find it)

Suncrush...is one of your cables bad?

Yeah, I know. Just messing with you.

duck_arse · May 04, 2015, 11:30:15 AM

suncrush - in that single pole drawing you showed, you volume pot (or whatever is at the output) will ne always connected to your signal, dragging it down. if you (want to persist with a single pole,) hard wire the input jack to the circuit input, and then switch the circuit output and bypass line, the high input impedance, 1M set by R1, will not load yr signal.

but a double pole true bypass would be 'better'.

suncrush · May 04, 2015, 11:34:29 AM

Quote from: duck_arse on May 04, 2015, 11:30:15 AM
suncrush - in that single pole drawing you showed, you volume pot (or whatever is at the output) will ne always connected to your signal, dragging it down. if you (want to persist with a single pole,) hard wire the input jack to the circuit input, and then switch the circuit output and bypass line, the high input impedance, 1M set by R1, will not load yr signal.

but a double pole true bypass would be 'better'.

Yeah, I'll redo it "right." It's all a learning process.

And I guess I'll need to grab a 3PDT switch to run the indicator LED.

duck_arse · May 04, 2015, 12:27:08 PM

ahh, well, now, you can do a true bypass with led indicator on a dpdt if you search up "the millenium bypass" over at geofex.

suncrush · May 04, 2015, 12:54:13 PM

I could, but I don't own the parts! I'll just order a 3PDT. I plan to make a tester box with the jacks and switches hard wired and jumpers to the bread board. I'll use the DPDT on that, where an LED indicator isn't so important.

canman · May 04, 2015, 02:49:14 PM

Quote from: bloxstompboxes on May 04, 2015, 11:28:17 AM
Quote from: canman on May 04, 2015, 10:48:24 AM
You'll notice it's no longer posted. (It's a common 3PDT wiring method anyways...a quick google search will bring it up for anyone who cares to find it)

Suncrush...is one of your cables bad?

Yeah, I know. Just messing with you.

I'm not very good at picking up jokes online...

My apologies for taking it too seriously!

garcho · May 06, 2015, 09:10:45 AM

Just so you know, soldered connections and breadboard connections are the same in regards to conductivity. Scratchy, intermittent signal could be from the breadboard and loose jumper wire or leads but never a volume drop.

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Volume loss on bypass (true bypass)