VFE Choral Reef Chorus (w/o switching board)

[MAO]

I had a couple of MN3008s so I thought I'd give this one a go...and it's awesome!

Does not include the VFE switching circuit.

The volume trimmer can be omitted and replaced with an external 100k pot.

Also, I added an optional 4th in-between range switch setting for use with a 2P4T mini rotary rather than the 3-position on/off/on toggle.

Sounds great with a 9v adapter, even better with 12v.

For a smaller footprint, madbean pcbs are available.

Not the cleanest layout, but verified.

[Addy Bart]

Great work! Definitely like to try this once I've sourced where to find the chips. Thank you.

[GrooveChampion]

Hey MAO, I build the VFE pcb and I have a question. For some reason the board requires a 5V supply through the negative jack. Well I did make a 9 to 5 volt converter using a couple of caps and a L7805 and I do get chorus, but its seriously distorted regardless of the position of the bias trimmer

[MAO]

Hmm, I'll check it out tonight but 5v seems way to low for this chorus.

I'll get back to you in a few hours.

[GrooveChampion]

As in a seperate 5 volt rail and another 9 volt

[MAO]

Ok, I do see that referenced in the switching board doc.

A little confusing, but the switching board creates the 5v (instead of the usual -9v) for the Choral Reef and is applied to the (-) connection on the Choral pcb...which is tied to the VB on the Choral schematic.

Looks like I did the same thing in my layout.

So are you supplying 9v and 5v to the VFE Choral pcb rather than using the switching board?

What voltages do you have at pin 4 and pin 5 of the TLE2074?

[GrooveChampion]

I am using a TL074, if that matters

[MAO]

i dont think so, the 2074 does have better noise specs, but the 1074 should
fine.

Distortion could be low voltage or bad component.

Where did you purchase the MN3008?

[GrooveChampion]

Smallbear

[Sphere80]

 GrooveChampion , did you built THIS stripboard layout,  or the real PCB, but without without the switching board?

[GrooveChampion]

The real pcb without the board

[Sphere80]

Madbean's  switching board PDF shows the powering layouts for the different pedals. Some use charge pumps, some are simpler. The Choral Reef has its own, which I tried to layout. Please try this out, but look for the switching board schematics to compare.

[MAO]

Sphere80's power bd should work for the 5v, but you are going to want to filter the 9v supply too. The PCB doesnt have 9v filtering other than the 3 100n. The filtering is done on thr switching pxb.

What Vs do you have at pin 4 and pin 5 of your TL074? That will probably give us a clue to what might be going on.  

[MAO]

For my stripboard layout I essentially used Neil McNasty's Huminator II to filter the 9v and Sphere80's to create and filter the 5vs.

If you feed the 9v output from Neil's Huminator to the 9v input on Sphere80's layout you have well filtered 9v and 5v lines.

I did bump up the 2nd 47u in Neils layout to 220uf x 2. I also lowered the 100R to 10R.

Overkill, but mine is dead quiet.

But again, I would check your voltages 1st at the ICs, see if they are close to the Madbean Choral Reef doc.

[GrooveChampion]

8.47 on pin 5 and 9.10 on pin 4, from the build docs I should get 4.88 and 8.9 respectively

[MAO]

Pin 4 looks fine, the issue is pin 5. That should be around 5v.

Pin 5 is tied directly to the (-) power supply input pad, the orange wire on page 5 of the Choral Reef doc.

See what voltage you have at the negative pad. It should be the same voltage as pin 5, if it is and if you can, disconnect that wire and check voltage at the wire itelf.

If you're getting the incorrect 8.47v at the wire when connected and 5v with the wire disconnected, you probably have a solder bridge somewhere.

If the disconnected wire is around 8.47v, the 5v supply itelf is the issue.

Hope that makes sense.

Just be real careful if/when disoldering from pcbs, I have damaged a few pads doing this.

In this case, you'd just be pulling the wire out so heat it up, pull it out and if there is a bunch of solder left in the pad itself, or if your solder sucker doesnt get the solder out, heat the pad again and use a toothpick to clear out the solder. But again, if you heat it to much or push the toothpick in to tight, you can damage the pad.

If you can check the disconnected 5v supply line without pulling the wire, better yet.

[GrooveChampion]

Guys I am terribly sorry. I decided to check if the converter supplied 5V to the board...turns out I didnt put the converter the right way around and it was outputting 9V to the board. Turned it around and BAM, crazy ass fantastic chorus sounds

I am so terribly sorry guys for wasting your time.

[MAO]

No worried here, glad you got it sorted out.

[GrooveChampion]

Still dude, you guys did so much for me and yet it was my own incompetence that was the issue. I am starting to work on my own layouts as a way of giving back to the community.

[Sphere80]

I also built this on the real pcb and it's one of the best choruses I've heard. I still have another MN3008 left over though so I'll eventually give this a try, thanks for the layout!