Arion - SCH-1 Stereo Chorus

bacaruda · Post by **bacaruda** » 17 Sep 2007, 21:02

Hi all,

I recently rehoused an SCH-1 chorus, and made it true-bypass. It ticked terribly at first, so I shielded the input wires, shortened the pot wires, and decoupled power to the LFO. This solved the ticking problem.

Anyway, it worked perfectly for about 3 weeks, then suddenly started making noises again, only this time the ticks are more siren-like. Short "beo-whoops" over and over, in time with the LFO. At fast speeds it still sounds like a "tick-tick-tick . . ."

Unlike before, moving the PCB or wires around makes no difference in the noise. The chorus still sounds great, it just has the annoying noise problem.

I'm at a loss - I've tried everything I know to do with my limited knowledge/experience. Any ideas? I could really use some help.

Thank you.

analogguru · Post by **analogguru** » 17 Sep 2007, 21:17

Seems to be a grounding problem - ground loop/double earth.

analogguru

bacaruda · Post by **bacaruda** » 17 Sep 2007, 21:29

Thanks very much for the reply AG.

I didn't think it would be something so simple since it was working fine, then suddenly started freaking out, but I will certainly try hunting down ground loops tonight. I could have easily made a mistake with the shielded wire.

Thanks again.

Sorry, I posted this is the wrong section.

Feel free to move it mods.

grolschie · Post by **grolschie** » 18 Sep 2007, 01:59

Why did you convert to true bypass? One can change one resistor (R4, from 470k to 1M) and swap the input buffer transistor Q1 for a JFET (i.e. from a C1815/2SC1825 to a MPF102, J201, 2SK117, etc). One has to swap the Drain and Source pins around on the JFET though (i.e. Drain=Collector, Source=Emitter, Gate=Base). It has much less tone suckage.

bacaruda · Post by **bacaruda** » 18 Sep 2007, 02:41

Grolschie - because I never thought of it . . . and also because I would need clear directions like the ones you just gave me!

I did figure out (from Clay's schem) how to bypass the FET switching to make it true-bypass, but I'm still a beginner at this electronics stuff. I'm learning, though . . . slowly!

That is a really great idea though, and if I ever get another SCH-1, I will definitely try it. Rehousing this one has been a major headache, but I love how it sounds.

grolschie · Post by **grolschie** » 18 Sep 2007, 03:47

If you have quite a few pedals on your board, then a decent buffered bypass will serve you well. True bypass is great when only using a couple of pedals. I too am a beginner. I now look at the schematics for my pedals and try to see if there are any components that can be upgraded. Buffers and ICs are a good place to start. I live near Bajaman , and he has been an excellent tutor for me.

bacaruda · Post by **bacaruda** » 18 Sep 2007, 15:19

Thanks Grolschie. I usually just bring a good boost or two, a delay, and sometimes the SCH-1, with 20-25 feet total cable into my homebrew 5E3. With this setup at least, I always prefer not having any buffered pedals in the loop (at least the ones I've tried). I put the only buffered pedal I bring, a TU2, on a switch.

AG - I found a ground loop, and what do you know, it fixed the problem!

Thanks guys.

grolschie · Post by **grolschie** » 18 Sep 2007, 22:52

Hehehe.... time to upgrade the buffers in those pedals perhaps.

I am glad you solved your ground loop problem. AG really knows his stuff.

bacaruda · Post by **bacaruda** » 28 Sep 2007, 15:19

okay . . . well the "ticking" has returned, but only when I'm using the Arion with other pedals on the same 1Spot daisy chain.

Otherwise, it works just fine. I assume it's a grounding problem, but I've been over the pedal a thousand times and can't find any loops; am I missing something obvious? I have been known to do that from time to time.

I'm playing out tonight, and really want to bring it - but I'll only have about 2 hours to work on it after I get off work. I would be grateful for any suggestions. btw, there is no room in the enclosure for a battery.

Thanks.

pz · Post by pz » 28 Sep 2007, 17:03

well, this looks like the ticking is coupled to another pedals via the power and ground line.
Solutions:
- use separate power supply for this pedal, when it's not possible (pedalboard too small etc):
- use separate power cable for this pedal, split the cables just after the PS, although it may not help to solve the problem. When this is also impossible:
- try to power Arion as the first pedal in daisy chain
hope that helps
regards
pz

bacaruda · Post by **bacaruda** » 28 Sep 2007, 17:39

pz - thanks for your reply.

I tried powering it first in the daisy chain, but it didn't help much. I think I'm going to try making a standard power filter between the DC jack and the Arion, and if that doesn't work - then I'll just have to use a separate power supply, like you said.

I just think I'm missing something because I didn't have this problem before modifying it. Thanks again.

grolschie · Post by **grolschie** » 28 Sep 2007, 21:55

Why not join a battery connector to a 2.1mm plug and power it temporarily that way?

polifemo · Post by **polifemo** » 14 Mar 2008, 05:40

Those that have played an Arion SCH-1 chorus knows that there is a volume boost when the effect is engaged.
This has never been a problem for me personally, but a friend of mine wants his chorus to be modified for "unity gain".

Any ideas what to do?

analogguru · Post by **analogguru** » 14 Mar 2008, 07:04

If this is true, then you can try to look out for R58 (51k) and reduce it to a lower value or install a trim-poti there.

It is a bit complicated since it is not clearwhich and how much volume increase occurs.

analogguru

polifemo · Post by **polifemo** » 14 Mar 2008, 07:23

Thanks!

I really can´t tell how many dB´s the boost is, but it´s quite a lot.
A trimpot sounds like the best way to go.

toneking1969 · Post by **toneking1969** » 19 Dec 2008, 14:52

grolschie wrote: One can change one resistor (R4, from 470k to 1M) and swap the input buffer transistor Q1 for a JFET (i.e. from a C1815/2SC1825 to a MPF102, J201, 2SK117, etc). One has to swap the Drain and Source pins around on the JFET though (i.e. Drain=Collector, Source=Emitter, Gate=Base). It has much less tone suckage.

Thanx grolshie, I took your word for it and changed R4 and Q1 to a 2SK117... And now there's no need for true bypass. Sounds great!!!

grolschie · Post by **grolschie** » 19 Dec 2008, 19:49

Although mine has improved, recently I was sure that I could hear the effect slightly when the pedal was off, when I was playing through headphones. So some might still need true bypass on this pedal...

moltenmetalburn · Post by **moltenmetalburn** » 10 Jan 2009, 23:44

Does anyone have a PCB layout or want to contribute one for this one? I had one as a kid and loved it, it disappeared after many years and Ive never been happy with a chorus since.
The thought of being able to make a clone of the circuit out of top notch parts and true bypass gets me almost giddy. I am surprised no one is selling a clone of this one that I know of.

schematic here:
https://img.photobucket.com/albums/v474 ... Chorus.gif

destro · Post by **destro** » 11 Jan 2009, 02:41

That was the first pedal I ever owned. Bought for 20 bucks at a pawn shop over ten years ago. I always thought that the tone control was rad. Unfortunately it fell to pieces over the years and before I got into diy it died and I tossed it. I've never rean across a clone project, but please post back if you find one!

Dirk_Hendrik · Post by **Dirk_Hendrik** » 11 Jan 2009, 17:20

moltenmetalburn wrote:I am surprised no one is selling a clone of this one that I know of.

Chorusses are too difficult for most wannabee boohteekers. For setting them up they would need an ocilloscope and far worse, knowledge.!

More than 15 components

. Therefore they stick to Fuzzes and treble boosters.

Arion - SCH-1 Stereo Chorus [schematic]