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 HD Op-amp, next to standard 8-pin DIP package op-amp. (I've cut down the long pins on this one)
The Burson HD op-amp sitting on the op-amp socket.
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.
The original configuration has some space between the PCBs.
After modification, perhaps ~1mm more compact.
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.
Rewired using 18AWG copper.
Changed to a mix of 18AWG copper and SCAG wire.
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.
Add some tack-it on the bottom..
And on top of the opamp, and the opamp socket.
Everything fits almost perfectly, perhaps still around 0.5mm too tall, which leaves a slight bulge on the top of the case.
Slight bulge in 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.
You can always put the battery back into the ImAmp.
With the Burson op-amp, no batteries.
With the batteries, regular IC opamp.
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.
Oversize toroidal power supply with 12V, 24V, and 48V output.
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.
Earfonia
Did you try to change the OPA2134 opamp with AD8066? Would be interesting to know the changes in the sound signature 🙂 Tx!
Mike
Bram,
Somehow the AD8066 doesn't work on the ImAmp, as well as the AD797. Perhaps you can explain why?
Earfonia
That's strange, as long as the op-amp power supply voltage is not higher than +/- 12 VDC, AD8066 should be compatible with OPA2134.
AD797 is single channel op-amp, so not compatible with OPA2134 which is dual channel.
Mike
Ah! I didn't check the spec sheet on the AD797. It is single channel.
jrko
Hi Mike. Which version of the Burson discreet opamp did you use?
Anonymous
Last time I check, there was only one version. Did they make a new one?
jrko
My bad. I saw the list of opamps theirs can replace and assumed it was a different model for each replacement!!
Anonymous
No probs!
AndroidVageta
I have NO IDEA if you will get this but can you tell me exactly what “AD825 (single channel SOIC package, with an adaptor)” is? I want to replace the opamp in this but don’t know what you’re talking about with that. Have a link that I can purchase at or something? Thanks!
deion
Hai , Mike . Can I connect the gears in this way ?
Laptop >> Audinst MX1 >> ImAmp >> PRO900
if yes , which option is best way to go ?
1)Laptop >> Audinst MX1 >> ImAmp >> PRO900
2)Laptop >> Dr.Dac2 DX >> PRO900
Currently , my budget is quite tight and I'm only able to get either Dr.Dac2 DX or Audinst + ImAmp . And I wont looking for an upgrade for next 2 3 years . So I need need to get best options . Can you do me the favor ? Thanks
Mike
I would go with the Dr. DAC2 DX. Having the superior DAC would benefit you more in this case.
deion
thanks for the reply =D
deion
please do let me know if you have better suggestion than MX1+ImAmp and Dr.dac2 … thanks
Mike
Nothing at the moment Deion…
Ozone3
How about HRT MS2 with Imamp? This combo is in the same price range and it also works off the grid. From the reviews I read, it seems that the HRT MS2 would best the HUD-MX1 DAC portion. The slightly warm presentation of the Imamp should pair well with the HRT MS2 and smooth away some of its "harshness".
Mike
Yes, the MS2 with the ImAmp should be a good combination.
Pat M
I picked up an Imamp a couple months ago and I have to say it's pretty darn good when using the external power source and merely OK using the internal battery with HD600s. This is why I primarily use it as a stationary desktop rather than portable. The external power boost presents what I perceive as a stronger, clearer sound than with the battery pack. A big difference was also had when I went from a standard LOD iPod out to 3.5 to an iPod out to RCA (silver wiring). Very nice. I like to call it semi-portable as I can use the external power with extension cord and walk around my garage with it, ha.
Mike
I know. I love the fact that you can use it with a battery and with a wall adapter for instant power boost!
Waterloo
Hi currently I'm deciding between getting the ImAmp or the Audinst as my first amplifier.. will be using with a pair of AD700s. Which would you say is a better choice? What about pairing either with DT770s? Will the ImAmp be sufficient to power them
Mike
I've used the Imamp with the HE5 Orthodynamic, so it's probably enough for the DT770 or the AD700. Cheers.
Waterloo
okay thanks, will the audinst or imamp be more suited for dt770s? if I want a greater improvement on bass?
Mike
Mmmmm… both units really won't give you that much improvements in bass.
Waterloo
alrite thanks…
Mattering
Nice review! Tempted to buy an imAmp but I'm currently saving for JH16 Pros 😀
Mike
Lol you should be eyeing the Pico Slim with your JH16Pros. 😀 I find it to be my favorite amp with the JHs, especially the 16s, as it is the only portable with enough bass control for the JH16s. 🙂
Jldiablo
Hi mike,
I am currently looking for an amp to pair with my HD600 and Shure SE535.. stuck on getting fiio E11, fiio E7, JDSLabs Cmoy or this Audiotrak ImAmp.. in one of your review you said that E11 is preferable than E7 if DAC function is not needed, and JDSLabs Cmoy has better sounding than the E11. However you did not compare the ImAmp with any of the other three amps above directly.. would like to see your option on these three amps (E11, the Cmoy and the Audiotrak)..
thanks!
Anonymous
Yes, I didn’t compare them to the ImAmp because I no longer have the
ImAmp. 🙂
Randius
I have the opportunity of getting the ImAmp or the Fiio E7 + E9 pretty good price. Which one will you recommend? I will be pairing them with either the iPhone 4 or laptop as source and the 1964-Q. Thanks.
Albert
Hi Mike,
May I know where to buy Burson Op-amp in Jakarta?
Thanks for any info.
Mike
Albert,
You have to go direct to Burson.