Behringer BDI21 - £20 surprise star pedal!

[Bigwan]

I've been building a little headphone practice/IEM rig and was investigating an always on amp sim pedal. Having blown most of my initial budget on a 3Leaf Enabler and having ridiculous GAS for a 3Leaf PWNZOR I opted for the obvious budget option of the Behringer Sansamp clone. Being well aware of the "mid shy" reputation of the design, and being handy with a soldering iron, I thought I'd give it a little tweak.

I removed one resistor in the 1st stage notch/high pass filter section to kill the midrange notch and removed the bridge-T voicing filter altogether, reintroducing more midrange, and now it sounds mighty good! It's a little on the quiet side when blended all the way to the effected side, which I'll have to look into but as a first attempt I'm extremely pleased. Dropping the blend to 80% brings back the volume with just the right amount of hair on the note and still retains enough of the cab sim tone to please. I suspect the volume issue might be down to the way I negated the notch at the first stage so I'll look at changing how I've done that. The well known YouTube video on modding this pedal does it differently so I'll give that a try before settling, but overall I'm over the moon.

And the best bit? £20 off Amazon... delivered!

If anyone is interested in my mods, which I made with the intention of keeping the high and low pass filtering in place but keeping the midrange as unaffected as possible, let me know.

Edited February 13, 2016 by Bigwan

[Sabs4001]

Interesting mod. I've just ordered this pedal but want to mod it to adjust the midrange. Is your mod similar to the FrankenP mod on youtube? Can your mod be done by adding a pot to control the midrange?

I've never done a pedal mod before but at £20 for this pedal I'm thinking it'll be a good place to start.

[Bigwan]

Added a comment to your question on the other thread so read that too, but I'll add more detail here about my mod.

Be aware that this is a surface mount circuit, so if you haven't used a soldering iron before I suggest you give all of this a miss or find somebody who can do it for you. It was easy for me as I have ready access to an electronics lab and regularly solder components similar in size to a grain of sugar. I sh*t you not...

First I put back the resistor I removed to start with (see original post) and placed a 10k resistor across C19 on the board instead (the 22n cap labelled C5 on the attached schematic). This is the notch mod from the youtube video, but I didn't want it switchable.

Secondly I wanted to remove the midrange cut inherent in the design, but leave the low pass filtering (cab sim) around IC2A and IC2D in the schematic. R18, C15, C16 and R21 form an alternative version of a bridged-T notch filter (a bit about it at the bottom of this page: [url="http://www.geofex.com/article_folders/eqs/paramet.htm"]http://www.geofex.co...eqs/paramet.htm[/url]), so that's what I wanted to eliminate. I removed those 2 resistors and 2 caps. To save having to worry about biasing opamp IC2D I then connected the output from IC2A to the input of C14.

I like this pedal much more now, but I'm considering buying another to do the youtube midrange mod on and perhaps a few other little tweaks (maybe the blend you're talking about!). Or maybe not - I have about a dozen pedal projects swirling around in my head at the minute!

It's actually much more than the midrange you're fixing with that youtube mod. It's taking most of the cab simulated high end roll off out of the equation too.

By the way you'll need to change the file extension of the attached schematic to .pdf to open it. An oddity with the forum software apparently!

Edited March 2, 2016 by Bigwan

[Sabs4001]

Thanks Bigwan. I'll probably have a go at modding this when I get the chance.

Edited March 2, 2016 by Sabs4001