aion OD855 & OD820

[jfk1063]

Hi,
Just finished building an OD855 and OD820, but.....

The OD820 has very little gain

Any thoughts?

Thanks!

[jfk1063]

Now with pics, sorry guys 

Anyway, the od820 seems to have less gain then the stock one, also less highs. I checked all the values and everything seems to be right.
Maybe I'll try a 500k pot for the drive/blend pot.
For the led I allways use the anti-plop formula , 390r plus 4,7k plus 47uf cap in the middle to ground (underneath the switchboard)

If there are any thoughts on the gain-issue please share.

Thanks!

[murdog47]

Exactly how low is the gain? It's not a very high gain circuit. Similarly to the Klon, the gain knob does double duty of adjusting the gain level and the ratio of clean to overdriven signal.

[jfk1063]

It sounds like a very lowgain pedal now.
My klons have way more gain.
Will a 500k pot work, since it also adjusts the cleanblend?

[flanagan0718]

Great job! Love the simplicity of the art!

[Kinki fuzz]

I have those 2 pedals about to go into boxes, great sounding pair.

About the gain issue, I can't think of the reason, but I confirm that mine sound OK with a gain range close to the Klon to give you a reference...

[aion]

This is one of the prototypes (green PCB), so there was a kink in the circuit. The pads are reversed on the dual pot's bottom set of lugs (the "balance" half). As you turn up the gain, it actually blends away from the drive part of the circuit instead of blending into it, which is a bit of a problem.

To fix it, you just have to flip around the wires so that lug 1 goes to pad 3 and lug 3 goes to pad 1. (only on the bottom row of the dual pot lugs - the top is fine)

[jfk1063]

This is one of the prototypes (green PCB), so there was a kink in the circuit. The pads are reversed on the dual pot's bottom set of lugs (the "balance" half). As you turn up the gain, it actually blends away from the drive part of the circuit instead of blending into it, which is a bit of a problem.

To fix it, you just have to flip around the wires so that lug 1 goes to pad 3 and lug 3 goes to pad 1. (only on the bottom row of the dual pot lugs - the top is fine)

OH!

Thanks, I am going to try it!

I also have a problem with the OD855 board: clippingdiodes in the section with trimmer work fine, but any kind of diodes in the other section don't work (volume drops very much)

[aion]

I'm assuming the 855 is a green prototype as well. The first lug of the Volume pot (the far right pad, looking at the PCB from the top) was mistakenly connected to VR instead of ground in the PCB layout. To fix it, you'll need to disconnect that lug from the pad and then run a wire to the nearest ground point (probably C12 or C13). If it's a PCB mount pot, you'll want to clip the lug and solder a wire to it. (Unfortunately you can't just cut the trace since the VR signal passes through that pad and continues on.)

Apologies for the inconvenience - I tried to emphasize these errors when I was selling the prototype boards, but it's been a good six months so most of that info is gone now. I had to dig for awhile myself to remember what the issues were!

The good news is, both of your issues are exact symptoms of the layout errors in those two PCBs, so they'll work just fine once you get the pots switched around.

[jfk1063]

I'm assuming the 855 is a green prototype as well. The first lug of the Volume pot (the far right pad, looking at the PCB from the top) was mistakenly connected to VR instead of ground in the PCB layout. To fix it, you'll need to disconnect that lug from the pad and then run a wire to the nearest ground point (probably C12 or C13). If it's a PCB mount pot, you'll want to clip the lug and solder a wire to it. (Unfortunately you can't just cut the trace since the VR signal passes through that pad and continues on.)

Apologies for the inconvenience - I tried to emphasize these errors when I was selling the prototype boards, but it's been a good six months so most of that info is gone now. I had to dig for awhile myself to remember what the issues were!

The good news is, both of your issues are exact symptoms of the layout errors in those two PCBs, so they'll work just fine once you get the pots switched around.

Yes, also a green board.  (OD820 is working now)

Thanks, I thought I was doing stuff wrong all of a sudden.

You're right, I had these here for a good 6 months, but never got the corrections from you. But now all's good.

Cheers from Amsterdam!

[murdog47]

I love happy endings 

[jfk1063]

OD855 is fine too now! 

[aion]

Awesome! Glad to hear

[atreidesheir]

Those look great.
Aion boards are world class.