Appendix – Modding the ImAmp
I don’t normally mod my amplifiers, but this time, I just happen to have all the right parts at the right time. After using the Burson HD op-amps, I find it hard to go back to the regular chip op-amps. The music is more open, instruments have more distinct positioning and better overall fidelity with the Burson op-amp.
Problem is, the Burson op-amp doesn’t fit in the enclosure, and I really don’t want to use the amplifier in a naked open situation without any top cover. I looked at the battery, and noticed that if I removed the battery, it would provide enough space for the Burson op-amp. That means re-wiring the op-amp so it can be placed remotely.
The Burson opamp still a little too high inside the tiny casing, when I place it at where the battery was. So I heated the pins that hold the two op-amp PCBs together, and narrowed down the distance between the PCBs. Be careful and double check things to make sure that you don’t cause a short between one PCB to the other.
Initially I used a 18AWG copper wire that I use on nearly all my DIY amplifiers and interconnects. It’s a very high quality wire, with a typical copper sound: Warm, full bodied. After finishing the rewiring, I noticed that the transparency is not as good as when I directly plugged in the Burson op-amp on top of the socket (with pins, no wires). So I looked around for a better alternative, and I found a spare SCAG wire only about ~20cm in length. Not long enough, but it would work if I only rewire the input and the output lines while leaving the power line on the 18AWG copper wire. So, I did that.
Now the Burson Op-Amp fits perfectly on the ImAmp. I lay some a very thin tack-it material between the op-amp and the casing, and on top of the op-amp socket, just to make sure that they stay in place.
Everything fits almost perfectly, perhaps still around 0.5mm too tall, which leaves a slight bulge on the top of the case.
The sound is great, although now I’m stuck on having to use the ImAmp with an external power. The mod can always be reversed if I want to have battery power, as I can remove the Burson op-amp, install the battery, and use a regular chip op-amp.
A few weeks ago I had a multi-purpose power supply built with an oversized toroidal that has a 12V, 24V, and 48V DC out. I figure I’d use this oversized power supply instead of the included wallwart. So I hooked the 12V out to the ImAmp. (The 24V powers my Doobooloo TPA6120 amp, and the 48V powers my Millett Starving Student aka SSMH amp). The sound improvements is totally worth it. If you want to build a dedicated power supply like this, you can build one with a much smaller toroidal and keep things fairly compact. I just happen to have a big one laying around.
So, it was quite a simple mod, but I’m loving the sound out of it. The slightly warm sound signature is still there, but all the technicalities have been improved, and the amplifier sounds much “bigger” now.