Background
What to do during day five of a power outage after a tropical storm? Hack pedals! My little house in the woods has a generator hookup for backup power. How expensive is it to run for days on end? I could be renting an apartment in the city instead. That expensive. Also, even with backup power, I have no connectivity. I was getting antsy... stir crazy (cue film noir soundtrack).
Since I happened to have some new Burr Brown OPA2134PA op-amps, and since my brand new Oh See Demon featured a TI NE5532P op-amp, and since the sound of the generator was making me nuts, I decided to try swapping an OPA2134PA into my OSD.
Disclaimer
Don't try this at home, folks. Don't try it anywhere. If you do try it in your OSD, it's all you: I am completely not responsible for anything related to your OSD.
Hack
First I tried de-soldering the stock chip from the OSD. But lacking the proper skill and tools, I just could not do it. So I added solder where I had wicked it away, then re-sealed the OSD.
photo of the stock OSD
But I am very stubborn and more than a bit obsessive. I couldn't let it be. As an alternative, then, I chose to snip the stock chip's pins at their base and solder a socket to the part of the pins still in the PCB... on the component side of the PCB! (Not a great idea, but I was desperate.)
It worked.
It was a mess and not pretty, but
it worked. And now my OSD was socketed. So since I also own some TI NE5532AP, eventually I'll do an A/B comparison between the NE5532AP and the OPA2134PA in my OSD.
photo of the hacked OSD
Sound
But for then, I trusted to memory and just wanted to hear my bass through the Burr Brown-ed OSD already. In my test, I played through my pedalboard and bass amp, set as they were before the OSD hack. There were no scopes, meters or careful recordings for before-and-after comparison. There were just my impressions of playing and listening.
What did I think of the hack? I thought the net differences in the sound and feel were not radical, but they were an improvement. Specifically, I believed the following:
- sweet or cold? sweeter.
- warm or bright? no change.
- bass response? stronger, truer.
- nuanced harmonic content? better.
- dynamic or compressed? more dynamic, natural.
- noise? no change.*
* When someday I do an A/B comparison between the TI and Burr Brown chips, I will use headphones and study their respective noise levels in the OSD.
Conclusions
I thought the Burr Brown OPA2134PA retained the OSD's basic voice and feel, but improved the pedal's
- responsiveness to playing inputs
- net audio quality
- usefulness for bass guitar.
If true, I think that's about what you would expect given the reputation of Burr Brown op-amps.
Was it worth the risk, the expense (an OPA2134PA costs about 4x an NE5532AP) and marring the beautiful Fuzzrocious circuit? Offhand, I think it was worth it for the audio, though I regret that my poor skills did not do justice to Ryan's workmanship. (Sorry, Ryan!)
I've heard it said that good components cannot make a good audio device; that first you need a good circuit design. In my opinion, given the good circuit design of the OSD, more of its strength is revealed by the Burr Brown op-amp.
closeup photo of the hacked OSD
Sidebar
While testing the hack and playing the OSD into the DD, I discovered a feedback threshold for sustained, vibrato single notes. DD alone? Lovely sustain and decay. OSD into DD? Raspy bowed cello, baby. Yeah!!
Best,
Snaxster
