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Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 08/09/2008 : 04:00:54
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I love the sound of my PH-1R, but it's often too much... I've always wished I could have a "mix" or "effect level" control for it. So I built one. Still on a breadboard, but it will go onto a circuit board and into a housing no problem.
The incoming signal gets sent out to the pedal (just like an FX loop) and the pedal output is mixed with the incoming signal - the incoming signal and the return from the pedal have individual level controls for infinite blend adjustment.
I will add a 3PDT true-bypass footswitch when I get it into a housing - it will be a "true-bypass loop-mixer".
Think I might build a few of these - it will be good for anything that doesn't have an "effect level" control.
Copyright (C) 2008, Laurie 
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Edited by - Laurie on 08/09/2008 09:06:10 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 08/09/2008 : 04:31:42
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Hi Laurie
Good evening-your end.
Great idea Laurie.
I gather you're using the op-amp as the mixer?
& the FETS for the Hi-Z inputs, or a pair of 458's as the low-Z output buffers?
Nice Rats Nest.
I should one day take a pic or my breadboard, prototype & development platform with built-in test gear.
It has a +/- 15V variable supply, fixed +5VDC & 7.5VAC RMS
a logic probe, 8 logic switches(2 are de-bounced), a 1mS hi-low pulse, an 200mW audio amp, a 8ohm 2.5" speaker, a variable square & triangular oscillator.
Built it back in Collage, during some night classes, at the same time I was building my fist CRO - Scope (Oscilloscope).
Apologies for going off topic.
Regards Dr. Bob
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the-destructor
Silver Member
USA
334 Posts |
Posted - 08/09/2008 : 14:50:39
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Hi Laurie,
Yet another common-sense but very good idea. Let us know how it turns out and post a pic once completed please. I didn't even know there was such a thing as a breadboard. I told ya I'm green on the inner electronics game. I can't get enough of the tech-stuff, as I'll soon be hurting myself trying to figure it all out.
Dr. Bob, please oblige with a pic of your breadboard if you would be so kind.
 T-D |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/09/2008 : 16:36:59
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quote:
Originally posted by the-destructor
Hi Laurie,
Yet another common-sense but very good idea. Let us know how it turns out and post a pic once completed please. I didn't even know there was such a thing as a breadboard. I told ya I'm green on the inner electronics game. I can't get enough of the tech-stuff, as I'll soon be hurting myself trying to figure it all out.
Dr. Bob, please oblige with a pic of your breadboard if you would be so kind.
T-D
Don't be hurting yourself
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/09/2008 : 16:41:16
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quote:
Originally posted by Dr. Bob
Hi Laurie
Good evening-your end.
Great idea Laurie.
I gather you're using the op-amp as the mixer?
& the FETS for the Hi-Z inputs, or a pair of 458's as the low-Z output buffers?
Nice Rats Nest.
I should one day take a pic or my breadboard, prototype & development platform with built-in test gear.
It has a +/- 15V variable supply, fixed +5VDC & 7.5VAC RMS
a logic probe, 8 logic switches(2 are de-bounced), a 1mS hi-low pulse, an 200mW audio amp, a 8ohm 2.5" speaker, a variable square & triangular oscillator.
Built it back in Collage, during some night classes, at the same time I was building my fist CRO - Scope (Oscilloscope).
Apologies for going off topic.
Regards Dr. Bob
Your breadboard sonds a LOT better than mine. But then again, I picked up the breadboard + a shoebox full of assorted cvomponents at a garage sale for $10, so I can't complain
Yep - mixing element is an inverting opamp. NPN BJT's for the input buffers.
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DeFrag
Moderator
USA
3409 Posts |
Posted - 08/10/2008 : 04:40:01
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Can't you use one level knob to mix the two signals?
All the way CW for Dry & all the way CCW for FX with 12:00 50/50. |
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pedals 4 pv
Platinum Member
Canada
1351 Posts |
Posted - 08/10/2008 : 05:27:22
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Nice project Laurie. Couldn't you just use a LS-2? |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/10/2008 : 06:13:00
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quote:
Originally posted by DeFrag
Can't you use one level knob to mix the two signals?
All the way CW for Dry & all the way CCW for FX with 12:00 50/50.
Yeah - it's possible, but one of the pots in the dual pot required for a single control is "reverse log" - hard to find (can be faked, but 2 pots are easier).
Two controls also gives more control - on a dual pot, it's not possible, for example, to have a mix of 100% + 45%
The two mix controls in my design actually give a range of 0%-200% for each signal.
Sooo... even with a single mix control, you might want a separate overall gain control, giving two controls again.
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Edited by - Laurie on 08/10/2008 06:59:45 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/10/2008 : 06:17:05
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quote:
Originally posted by pedals 4 pv
Nice project Laurie. Couldn't you just use a LS-2?
Hmmm... well look at that. I guess you could at that
But... you would need to use a "Y splitter" cable on the input (to jump the input across to "return A" so it would mix with the external pedal return - assuming the pedal was in loop B), plus it wouldn't be true-bypass.
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Edited by - Laurie on 08/10/2008 06:55:37 |
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pedals 4 pv
Platinum Member
Canada
1351 Posts |
Posted - 08/10/2008 : 09:33:02
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LS-2 has a A+b mix setting and separate level controls on each loop. No true by-pass, but FET switching fine for me. To make one myself would be cost prohibitive as I would have to tool up some before I could build my own pedal. The LS-2 isn't too expensive either.
http://www.zzounds.com/item--BOSLS2
Of course they can be had cheaper used. |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 08/10/2008 : 15:19:57
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Thats really cool!!
To make it like a LS2, add a second effects loop
there's a schematic in the manual for it
think its the only one that has a schem in the manual |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/10/2008 : 16:54:17
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OK OK... it's been done before
Still a worthwhile exercise - taught me a lot about buffering and signal management in a pedal (I am now able to design mathematically, not just read it on someone elses schematic). Plus I now have a "mix"/"effect level" circuit I can include in any new pedal design. My version sounds REALLY transparent and has heaps of headroom - I've taken care with the biasing and can run about 7V peak-to-peak through the whole pedal.
I have all the parts... For me at the moment, making these will be WAY cheaper than buying LS-2s. And I do like the true-bypass 
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Edited by - Laurie on 08/10/2008 16:55:31 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/08/2009 : 09:05:38
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The beast so far...
Prototype is complete. Just fiddling with levels (so 12 o'clock on the level controls = unitiy gain) and working through getting rid of some low-level thermal noise (that "bacon frying" sound).
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Edited by - Laurie on 01/08/2009 09:06:08 |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 01/08/2009 : 13:00:14
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| wouldn't a ls-2 do the trick |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/08/2009 : 13:20:51
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Hi Laurie
Once again, nice work.
quote:
working through getting rid of some low-level thermal noise (that "bacon frying" sound).
Once you get it into a properly shielded enclosure, like the Hammond's that you use, A lot of the circuit noise will disappear.
Some of that Bacon Sizzle, is probably induced from the gears on & around your Lab bench, & especially those 40 watt overhead fluro's.
I always mount my proto's onto a slightly larger Hammond box,
with a number of assorted holes drilled in it, for mounting various pots, sockets & switches.
It make a big difference.
I sometime even tape or screw on the back plate/lid to see how much quieter the project will become.
Regards & just my 2 cents worth.
Dr. Bob |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 01/08/2009 : 15:20:52
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Laurie's boutique shop of horrors!
Great project & excellent job.  |
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Looper/mixer
