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PostPosted: Sun Apr 07, 2013 9:12 pm 
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Can anyone explain how to add phase inversion to Output B of the amp selector? I've been searching the internet for hours trying to find examples but just can't find anything.


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PostPosted: Mon Apr 08, 2013 3:26 am 
There are two ways to do this, unfortunately both seem to involve fairly major surgery on the PCB (to be really picky we are talking about signal inversion - pseudo phase inversion).

1/. Reverse the connections to the ends of either the primary or the secondary winding on the B channel output transformer. It doesn't matter which. This would be most easily done before the kit is built by bending the leads of one winding or the other so they don't go through the holes in the PCB and adding two pieces of hook up wire to them (careful the leads don't twist / rotate while bending, it might snap the internal connections to the windings). The two lengths of hook up wire could then either be permanently soldered reversed into the transformer pads on the PCB or wired to a two pole two way switch wired cross over style to allow switching between in phase or out of phase.

2/. Modify the circuit around IC3a so that it has both a non-inverting and an inverting input using the pin 2 input (you would need to add a couple of resistors to do this). Then again you have the option to either hard wire it as inverted or add a cross over switch.


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PostPosted: Mon Apr 08, 2013 8:20 am 
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Option 1 seems the easiest. So something like this?
Image


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PostPosted: Mon Apr 08, 2013 9:28 am 
You have the phase invert switch right, but the ground lift goes on that output side of the transformer (as it is on the original) not on the input side. To put it another way - the transformer provides isolation (between the two windings) and the output winding can either float or have one end tied to ground through the ground lift switch. The invert switch needs to flip the connections independent of any connection to ground.

So you need a conductor running from the 'bottom' of the phase switch (where you show it going to ground) to the sleeve of the output jack and then the ground lift goes between the sleeve and the pedal ground.

Or you can just wire the phase switch to flip the ends of the input winding of the transformer (one pole of the switch connecting to the output of IC3a , pin1, and the other pole connected to pedal ground, with the cross linked throw tags wired to either end of the transformer input winding) and leave the output winding and ground lift as original.


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PostPosted: Mon Apr 08, 2013 9:41 am 
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Yeah, I just grabbed that off the internet as that is the one image I could find with phase inversion.
I think I have a grasp on it now. Just using a switch to flip the secondary winding will invert it. Sounds pretty simple.
I'm just going to cut a few traces and wire up the new switch and see how it works.
I may ditch the ground lift on that output as I haven't used it and put the inversion switch there.

Thank you.


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PostPosted: Mon Apr 08, 2013 10:23 am 
Sounds like a plan but cutting tracks to get what you want could be tricky because the ground track to the transformers runs past them and provides ground for other parts of the circuit.

I'd say keeping the ground lift if you can is worthwhile because with two amps you can easily form a ground loop and get hum induced into it.


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PostPosted: Mon Apr 08, 2013 10:38 am 
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Yeah, I noticed that. I just need to run a small wire to patch that up. Thanks.
I may keep the ground lift. I don't use it now but I may need it in the future.

So rereading your previous post, swapping the primary side would work the same as swapping the secondary? That may prove a little easier as I don't have to deal with the ground lift switch at all. I may just try that instead.


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PostPosted: Mon Apr 08, 2013 10:50 am 
That's right. It really does not matter if it is the primary or the secondary, as long as you reverse the connections to one of the windings


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PostPosted: Mon Apr 08, 2013 11:43 am 
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I'm going to do that as it seems less to deal with. Thanks.


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PostPosted: Thu Apr 11, 2013 1:16 pm 
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I don't have it bookmarked on this computer, but I found a forum thread explaining that the circuit board already has the connections to do this - they're just not implemented in the normal wiring instructions. If you look at the instructions, there are two clusters 103/104 resistors that aren't connected to anything. You do some wiring with them, add a switch, break a connection somewhere, and apparently you're good to go. I believe it's one of the opamps that inverts, not a transistor.

Does that ring a bell for anyone? If not, I can look up the page when I'm back at home.


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PostPosted: Thu Apr 11, 2013 1:38 pm 
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I'd be interested. I tried to search for it and came up empty.


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PostPosted: Fri Apr 12, 2013 9:10 am 
I'm really sorry, I had forgotten the details on this. The memory of those extra pads on the PCB did float through my mind but I didn't follow up on it.

Here is a link to a thread that discusses the pads (I don't know why BYOC doesn't include this on the build instructions) -

http://www.buildyourownclone.com/board/viewtopic.php?f=12&t=32756&hilit=amp+selector+phase

You need to add 3 resistors, a 10K and two 100K (marked 103 and 104 on the PCB, although the 104s could just as well be 10Ks), a single pole two way switch to flip the phase back and forth (the switch is wired as the centre pole to the pad labelled P on the PCB with the two throw tags to T1 and T2) and cut one PCB track (the track between P and T1 on the top side of the PCB).

This mod wires the unused half of IC2 as an inverting buffer and the extra phase switch switches the signal to the primary of T1 (secondary drives channel OUT A) between its normal configuration and an inverted version from the output of the normally unused op-amp. This is similar to one of my original suggestions except I was saying to modify the circuit of the second op-amp in channel B so that it had an inverting input with a switch between that and the non-inverting input.

The BYOC mod using the 'un-used' op-amp adds the phase inversion to channel A and not to B as you wanted but does it really matter which channel gets flipped?

By the way, following the BYOC circuit diagram is pretty tricky because the IC pin numbers on the diagram do not correspond to those on the PCB layout (sigh!).

I have now added these instructions to the BYOC mods thread.


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PostPosted: Thu Mar 17, 2016 11:07 pm 
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Joined: Mon Mar 16, 2009 9:12 pm
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The link discussing the pads is apparently dead, as I've found it several places on the forum and it keeps failing. I'm very interested in adding the phase reversal mod and hope that someone has the new link. Thanks.

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BYOC Pedals: OD2 (MosFET mod); Large Beaver (Triangle); Armstrong Twin; Leeds Fuzz; Analog Flanger; Analog Chorus; ESV Fuzz


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PostPosted: Fri Mar 18, 2016 10:10 am 
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hamerman wrote:
The link discussing the pads is apparently dead, as I've found it several places on the forum and it keeps failing. I'm very interested in adding the phase reversal mod and hope that someone has the new link. Thanks.



If you change the URL to 'byocelectronics' whenever you see something board related with the URL 'buildyourownclone' there is a good chance it is still live:

viewtopic.php?f=12&t=32756&hilit=amp+selector+phase

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PostPosted: Thu Mar 24, 2016 7:36 pm 
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Nwkenning wrote:
hamerman wrote:
The link discussing the pads is apparently dead, as I've found it several places on the forum and it keeps failing. I'm very interested in adding the phase reversal mod and hope that someone has the new link. Thanks.



If you change the URL to 'byocelectronics' whenever you see something board related with the URL 'buildyourownclone' there is a good chance it is still live:

http://byocelectronics.com/board/viewto ... ctor+phase


Thanks. This is a big help. Your link worked, and I'll remember the tip.

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BYOC Pedals: OD2 (MosFET mod); Large Beaver (Triangle); Armstrong Twin; Leeds Fuzz; Analog Flanger; Analog Chorus; ESV Fuzz


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PostPosted: Fri May 20, 2016 11:54 pm 
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I built the phase inversion mod into my Amp Selector and it worked like a charm. I don't see why this isn't part of standard build.


Sent from my iPad using Tapatalk

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BYOC Pedals: OD2 (MosFET mod); Large Beaver (Triangle); Armstrong Twin; Leeds Fuzz; Analog Flanger; Analog Chorus; ESV Fuzz


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