Baja MDR Overdrive on breadboard and vero

[micmac]

Build Rating

5.00 star(s)

Hi all!

Recently I was taunted to try the Baja AFD, which I liked very much. So I said to myself that I would try a few more of Bajaman's preamps - on the breadboard at least. The first one was the EVH Overdrive, but althoug it worked fine and was well-behaved noise-wise (like the AFD), it didn't really do it for me. Also tried the "High Gain" Mod from MTK, but with that it turned too hissy for my ears.

Next, I put the Baja MDR Overdrive on the board:



This one I like again! Also not noisy. Bone-dry distortion. I never played an MDR amp, but the "pedal" sounds awesome.

I'm wondering if any of you have any idea about a mod or two to try while the thing is on the breadboard?

So far I've tried a little bit:

The vero layout for the AFD was a bit of a pain, because everything goes to VREF. The MDR does the same. So on the breadboard I tied all the cap legs that go to VREF together and put them on an SPDT on-on switch (pin 2). The other pins of the switch go to ground and VREF. Switching between the two didn't cause any difference in sound. So when I do the vero I'll use that tidbit for an easier layout.

Other things I want to try:

- change the TL062s for other oamps like LM833
- pull the hard clippers to see if the MDR clips without them

Any other ideas welcome!

 

[micmac]

I wrapped it up. Some more things I tested on the breadboard:

- Tried both TL062 & TL072, but I couldn't tell a difference. Both sounded good to me. If only one could easily put two opamps on a switch, so we could flick between the two of them...
- I put the diodes (well, the 1N4148 and the BJT) on a switch and flicked them between ground and VREF. Again, no difference in sound whatsoever.
- Pulled the diodes out and yes, opamps are indeed clipping the signal here and there. Edit: Or maybe the output buffer started to clip the signal because I removed the hardclippers in front of it. Oh well, should've checked with the scope where the clipping really occurs...

When I made the vero layout I put all the caps that went to VREF to ground instead. Same for the diodes. And I used a log pot for volume. Now unity is a pretty much at lunch time 12:00 o'clock (with a lin pot unity was at 9 o'clock already). I used MLCCs for the 1uF caps. There's 11 of them if I counted right, so it really is a space saver. Also, I'm pretty sure Bajaman also used MLCCs in his build, so it's more historically correct I reckon ;-)





The MDR's got quite a bit of lowend. So it's a little woolly down there. Not unlike the real amp, I hear. So I tried an OD-1 clone in front of it. The MDR really takes the overdrive well. It doesn't get much noisier (I put OD-1 Volume to 10 and Gain to 0). It gives the MDR an extra kick in the pants and sorts out the low end, making it tight. Brilliant, I like it.