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Thanks Antonis, This was an old Topic of mine, hadnt revisited for a while and was pleasantly surprised to find your redraw of the FA-1 Circuit to include Dual supply power. Appreciate it.
Building your own stompbox / Re: What would happen if...
« Last post by GGBB on Today at 07:38:50 PM »
I'm off for my 5th Covid shot in 10 minutes

Painful! Why wouldn't you just get them periodically like most people?  ;D

I have a modified BluesBreaker circuit that has a clipping switch which changes the feedback clippers from 2||2 to 1||3 using the same 4 diodes. Flipping back and forth there is no noticeable difference between the output volume. But they sound different - distinctly but not massively. This is at lowish/amp-on-the-edge-of-breakup gain levels. No post op-amp clipping here though.

The 1||3 setup is "woollier" in texture - less clarity, slightly warmer and grittier, it doesn't really sound like more clipping overall but naturally it would be more clipping on half of the wave. I would assume that at that low gain level I am not clipping the 3 diode side but I can't be certain (I should scope it I suppose). I do know that there is no op-amp clipping - the switch can also disconnect the diodes and when I do that at the same gain level the signal is clean. I'm not sure if this actually asymmetrical clipping, 2nd order harmonics etc, or single-sided "half-wave" clipping, or something else, but there's a definite difference.

Building your own stompbox / Re: Pro Co FATRAT
« Last post by GGBB on Today at 07:14:20 PM »
And and interesting note - looks like they are buying their 3PDT switches for USA production (or at least for that run of FatRATs) from LoveMySwitches:

Building your own stompbox / Re: Pro Co FATRAT
« Last post by GGBB on Today at 07:04:50 PM »
Hard to believe I've been working on it for 12 years. And the latest revision took almost 7!

Here's a family photo:

Building your own stompbox / Re: What would happen if...
« Last post by Rob Strand on Today at 05:46:10 PM »
With the amount of gain in distortion/overdrive pedals, as soon as you remove one diode the opamp clips.   As soon as that happens the sound of opamp clipping enters the picture.

Would this behave or sound any different than what we are used to?  I was reading a thread on another forum, and it occurred to me that I've seen circuits where one pair of diodes is used in the feedback loop, and then another pair is used somewhere after that output, but that simply duplicates clipping on both half-cycles.
It's not duplication, ithe feedback clipper prevents the opamp from clipping and that means the tone becomes independent of the opamp (unlike say the MXR distortion).

There's nothing *wrong* with single ended clipping.  You can do what you want.   What might not be so obvious is single ended clipping will do different things when feedback or stages are DC coupled vs AC coupled.  Asymmetrical waveforms will charge-up caps to meet the new average DC conditions, which varies depending on the amount of clipping, and there will be a time for that new equilibrium to be reached.
Building your own stompbox / Re: I have a cunning plan. HP Filter.
« Last post by Kipper4 on Today at 05:02:15 PM »
I also got to thinking that I really don't know what any dub stuff sounds like.

back of that guy's right hand - ska.

Sad Eyed Beatniks do a track Piper At The Gates Of Dub (and it's not very dubby) - Rich would only need to change an I for a Y and he'd be away.


Thanks Stephen.
Looks like the performance was mostly on the bell setting and the bell knob (rh side) almost cranked then  sounds like he’s cranking the sends to the echo and verb. Controlling the HPF filter to make a build through the track.
Where filters become your instrument . Simple but great.
Love the Melodica recording too.

‘king kipper. Dub it up.

Cheers for making my day. After spending the day in hospital being prodded and poked and electrocuted I needed that.
Building your own stompbox / Re: What would happen if...
« Last post by marcelomd on Today at 04:59:24 PM »
You can cascade gain stages that clip only one side of the signal, like this excerpt from Amptweaker's Tight Metal, from Aion FX.

Note three gain stages with zeners, providing assymetric clipping.

Building your own stompbox / Re: What would happen if...
« Last post by CheapPedalCollector on Today at 04:44:37 PM »
It would be different and have that tubescreamer "clean" thing in the background.

I'll one up you, how about feedback diode in an inverting configuration and one in a non inverting configuration.
Building your own stompbox / Re: DOD FX-90 troubleshooting
« Last post by Rob Strand on Today at 04:39:39 PM »
Sorry if I missed some bit, but what happens if you completely remove Q6 R39 and C31?
Worth trying at this point.  It's actually Q8, hard to read on the schematic.

I guess one thing that's not so clear is how much signal is being lost?  a few dB or 20dB.

R31 might need to be increased.    When you use things like R31 it's not uncommon to have a similar part on compressor section U2A.  Having only R31 sort of acts like a noise gate.  However if the signal isn't strong enough it might end up causing an overall attenuation.

Another thing that caught my eye is C30 is around the wrong way on the schematic.  Probably not the cause of the problem and I'm assuming the PCB is like the schematic- with DOD that might not be the case.

If I got to this point I'd be putting a signal generator into the unit and plotting out Vin at C30 and Vout at U2B pin 10 over a range of input voltages Vin.  That will quantify what's happening at the Expandor and perhaps give a hint of the cause.
Building your own stompbox / Re: DOD FX-90 troubleshooting
« Last post by CheapPedalCollector on Today at 04:31:16 PM »
Same thing, I have full echo signal there. It's the output where it's quiet and muffled.
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