Arion - SCH-Z Stereo Chorus

Dirk_Hendrik · Post by **Dirk_Hendrik** » 24 May 2010, 11:22

lolbou wrote:THis could have been in the Stuff Seen For Sale section, but considering this thread, my guess is no one will ever buy a modded Arion by EWS...

http://www.leboncoin.fr/instruments_de_ ... tm?ca=11_s

How much for 3 knobs, a 3PDT, one decal and countless bullshit?

How much for a fairly easy modification?

Chakaranda · Post by **Chakaranda** » 14 Nov 2010, 14:29

I have a SCH-1 (so thats the schematic to look at in this case)

I was just thinking about doing this vibe mod without loosing the stereo option, by installing a separate switch for vibe/chorus
But could someone tell me if I'm on the right track here:
the connection we want to break to get the vibe effect is the signalpath going to pin 3 and 5 of IC 2.. right ?
I was thinking about then breaking that connection right before the W5 (the zero-ohm resistance that looks like "wz" in the schematic of the SCH-1 )

Am i on the right track here ? or du you have a better idea ?

bigorangefan79 · Post by **bigorangefan79** » 08 Dec 2010, 05:50

To mod an SCH-Z for true bypass with stereo outputs, you must make it stay on all the time by bypassing q4 and q7 (jumper their outside legs together), use a 3PDT switch to switch the input (pole 1), output 1 (pole 2), and output 2 (pole 3). Output 2 must be ran through an inverting buffer after the switch if you are doing it the right way. You can then use millenium bypass 2 to turn on an LED, I prefer placing the ground and voltage ends of the millenium across the outside lugs of the rate pot so that the LED pulses. And then of course do the vibe mod.

candletears7 · Post by **candletears7** » 16 May 2011, 11:39

I picked up a SCH-Z. Awesome little chorus pedal, and I'm keen to give the EWS mods a crack.
From the above post Dirk, you state to disconnect all connections to the switch, and then rewire the switch to disconnect the dry signal from the wet.
I'm not after a blow by blow account of how to do this, but I can't for the life of me find a decent readable schematic for the SCH-Z. The one mentioned above doesn't show for me.
If anyone can help with one I'll attempt the rest and report back.
Cheers.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 16 May 2011, 14:41

That's odd... Let's fix that omission.

candletears7 · Post by **candletears7** » 17 May 2011, 12:14

Thankyou for posting the schematic, Dirk.
I took the pedal apart and desoldered pins 3 and 5 of U2. Totally no dry signal, but only when I ran out of output 2, nothing out of output 1, unsurprisingly.
I'm going to keep at it, only because I hate not finishing something I start. I'll admit though, that I'm not sure where to make the break to remove the dry signal from the wet. I'll follow the traces on the pcb from the switch tomorrow and work out which components need to be removed from the switch in order to rewire it.
In the meantime I came across across a post from Brian Wampler wherein he noted a resistor that could be changed to a trimpot in order to get rid of the volume boost that happens when the pedal is engaged. I forget which one it was, but that would be handy as the pedal increases volume substantially when it is on.
Apparently the conversion to truebypass is needed for this Chorus/Vibe mod as it means nothing will come through on the dry signal when it's done. This is most complicated mod I've tried to work out, but I'm having fun!

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 May 2011, 13:22

Make R28 switchable. No R28 is wet only for out 1. Same thing for R34 for out 2.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 May 2011, 13:33

Full:
- Isolate the switch by removing C5 and R39.
- Disconnect C28 and R38 at the switch side
- disconnect R40 at the switch side.
- Connect the disconnected side of R40 to the junction of C28 and R38 where they used to be connected to the switch side.
- disconnect R34 and R28 from U1b, pin 7.
- connect one of the outer isolated lugs of the switch to the junction of R28 and R34
- connect the center lug of the switch to U1b, pin 7.

candletears7 · Post by **candletears7** » 17 May 2011, 13:47

Thankyou!

candletears7 · Post by **candletears7** » 18 May 2011, 11:50

The above mods stated by Dirk are verified.
The second point stated above should read ''- Disconnect C28 and R38 at the switch side'', not ''- Disconnect C8 and R38 at the switch side''.
Apart from that tiny typo, it's all gravy, baby!

I simply lifted R28 and R34 out of the pcb and tied them together, then to the switch's outer isolated lug.

Thanks again Dirk!

Dirk_Hendrik · Post by **Dirk_Hendrik** » 18 May 2011, 17:41

My pleasure. Thanks for the verification and the typo correction. What I wrote was purely hypothetical and written from screen. You don't have switch pops when changing over fron chorue to vibrato?

candletears7 · Post by **candletears7** » 19 May 2011, 11:22

Absolutely no switch pop, very quiet. Your hypothesis was 100% correct!

candletears7 · Post by **candletears7** » 22 May 2011, 06:48

Ok, tonight I'm gonna finish this little plastic box off. I'll post up pics when I'm done of the steps along the way.

Here's the plan for it from go to whoa:

1) Chorus/Vibe mod as outlined by Dirk above - verified and done.
2) Mod for truebypass by bypassing Q4 and Q7 as outlined on the previous page by bigorangefan79. If that doesnt work I'll try to work out how to omit the buffers and switch from there.
3) Mod for pulsing LED - I'll work that out, possibly from the aforementioned post, or...
4) Mod for unity gain - according to a thread I found on DIYsb's, R30 is the resistor that governs this. Stock it is 47k. A 100k trimpot should work.

I'll post results.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 23 May 2011, 20:00

When doing that TB and while working on the anti-switchpop matters keep in mind the adapter negative pole is lifted above the pedal's ground through R1 and D1 (or only D1 when using an adaptor).

candletears7 · Post by **candletears7** » 25 May 2011, 12:12

Thanks for that tip, Dirk.
Sorry, just to clarify something. Obviously the pedal's jacks are board mounted. Modifying this pedal for true-bypass is obviously different to a pedal with an isolated pcb and wiring the jacks in through the 3pdt as per usual.
By your above post do you mean I need to make and break the R1/D1 ground connection through the 3dpt in order to switch the circuit in and out?
I'll look at the schematic again to figure out how to true bypass this circuit, keeping the jacks on the board.

candletears7 · Post by **candletears7** » 28 May 2011, 14:02

Ok, quick update.
The unity gain mod is easy peasy. That resistor I mentioned is correct. Just swap it for a trimpot.
Truebypassing it was a snap too. I just ran continuity from the in and out jack tips, lifted the next components on the schematic out to break the connection, then remade either connection via the 3pdt stomp. Voila.
A pulsing LED wants 9v at the power source with ground on the rate pot. But this means that it won't switch off as it nothing to do with the stomp. I'll have to check that out some more.
Dirk, from your post I'm going to try a 1M pulldown resistor in parallel with that diode. Thanks again.

bigorangefan79 · Post by **bigorangefan79** » 02 Jun 2011, 13:32

I used millenium on a seperate little board for the LED pulsing across the rate and the 3PDT stomp to switch the in and both outs. But if you don't care about output 2 then just run the - of LED to one pole of the switch and run that pole's ground wire to the rate pot.

quaternotetriplet · Post by **quaternotetriplet** » 09 Jul 2011, 07:25

i kinda have some hard time understanding..

i figured out how to true bypass it.. my problem is how can i do the vibrato mod.. thanks

Dirk_Hendrik · Post by **Dirk_Hendrik** » 09 Jul 2011, 07:43

Dirk_Hendrik wrote:Full:
- Isolate the switch by removing C5 and R39.
- Disconnect C8 and R38 at the switch side
- disconnect R40 at the switch side.
- Connect the disconnected side of R40 to the junction of C28 and R38 where they used to be connected to the switch side.
- disconnect R34 and R28 from U1b, pin 7.
- connect one of the outer isolated lugs of the switch to the junction of R28 and R34
- connect the center lug of the switch to U1b, pin 7.

Like this?

Adji · Post by **Adji** » 15 Feb 2012, 17:25

Sorry to bump this guys. Does anyone know how to reduce the noise of the SCH-Z? My god is this thing noisy, massive whooshing sound. SCH-1 is quiet as a mouse (more or less) but the SCH-Z, ridiculous.
Surely it isn't 'supposed' to be this noisy?

Arion - SCH-Z Stereo Chorus [schematic]