[newzooreview]

You could just give Acopian a call. They make everything at their facility in Pennsylvania (or Florida, near NASA) and are likely to have the missing part.

https://www.acopian.com/

[bbaker6212]

Tried the SX52 op amps and found that OPA1656 sounded more clear in the mid-range with comparable bass response, at half the cost.
In my experience, the discrete op amps cost too much and don't contribute a proportional improvement in sound quality.
The Douk A5 is a remarkable small amplifier that performs well above its price class and is replacing a high bias class AB amp in my own system.
For under $130 total with upgraded op-amps & 36v power supply, it is hard to beat.

what front-end/DAC and speakers were you using?

[NXSTUDIO-DRUMMER]

Nlitworld,
What's the latest updates on your A5 Mod's?  How's it sounding, versus stock with all the significant upgrades you've added to this point? The AC community would enjoy hearing your feedback.

[nlitworld]

Oh I'm sorry I missed this post last weekend or I would have responded earlier. I guess I was too sidetracked with how freakin amazing my stereo has been sounding.  Everything has really settled in nicely after the 50hr mark, and now it's really opened up to be just gorgeous. Open, airy, dynamic slam, great tone to guitar and drum (especially floor toms!!) but there's no more edginess or artificial loudness effect anymore. Everything is smooth, well layered in its place, and 3d depth for days. Albums like Jazz At The Pawnshop or Alice In Chains MTV Unplugged absolutely put you inside that room with the performance.

I did also find that leaving this amp on 24/7 helps things as well. For some reason, after the 48hr mark it really sounds good. That could be the circuit itself, or the giant psu caps, but I just leave it on nowadays. Also I have the volume knob about 80% as this unit always had a tiny buzz at full volume on my system. My room is super small and sitting 5' away from speakers means alost any noise is audible. 80% on amp makes my preamp around the 12 o'clock mark, maybe a little more on the real fun listening days but still dead silent with ear on speaker.

As hindsight is 20/20, it really feels all the upgrades are a sum of the parts and that one by itself fixed one issue but creates another. Power supply creates more oomph and drive, but doesn't fix detail. Connectors fixed detail but became too much of a good thing, opamps opened soundstage but doubled down on too much detail, then capacitor mod was final piece to set everything in place. Running the Miflex as my high-pass @90hz was just icing on the cake for opening everything up to a gorgeous sound. I guess it's proof that everything matters and need to create balance. All in all, upgrades are worth every penny of the roughly $600 total invested, and I'd bet you'd all be astonished how good this thing sounds. Most people won't dive head first down this upgrading rabbit hole, but it was a hell of a fun project to learn with the end result being pretty rad!

[goggle1824]

I just wonder how it “MEASURES”!!!       

[nlitworld]

Hahahaha

[goggle1824]

“Whuuuut…?” 

[Tyson]

Clearly how it measures dictates how it sounds.  It’s not .000000001 THD like a digital amp, so this amp is definitely trash.  I don’t even need to hear it to know that!!  SCIENCE!

[bbaker6212]

Tried the SX52 op amps and found that OPA1656 sounded more clear in the mid-range with comparable bass response,

super helpful opinion, thanks @cml811.  What about the treble and soundstage/imaging of the 1656 vs SX52?

I'm ready to upgrade the opamps in my A5 now and looking for what is an obvious upgrade from the NE5532 but doesn't add any "warmth", smoothness, etc. as I'd rather tackle that separately with a tube preamp.

My humble low cost system:
PC USB >> SMSL D1 DAC >> FX-Audio Tube-02 Pro >> Douk Audio A5 >> 96db/1w large Open-Baffle 2-way 15" + horn loaded titanium compression tweeter.

I was pleasantly surprised that the FX Tube-02 Pro did help provide some tube-ish warmth/smoothness and maybe a little wider soundstage /presentation. 
I haven't tried tube rolling the original tubes yet.

I also want to upgrade the stock 32V 5A power supply.  Prob will go initially with a 36V (6A to 10A)...
I might try a cheap china SMPS to keep cost low - maybe mod it if needed. 

[bbaker6212]

Clearly how it measures dictates how it sounds.  It’s not .000000001 THD like a digital amp, so this amp is definitely trash.  I don’t even need to hear it to know that!!  SCIENCE!

LOL, for a few seconds I thought you were being serious here. 

This little thing sounds pretty great with my 96db sensitive big OB's.

[bbaker6212]

Nlitworld,
What's the latest updates on your A5 Mod's?  How's it sounding, versus stock with all the significant upgrades you've added to this point? The AC community would enjoy hearing your feedback.

he did post a bit more recently about it at this link.
Notice I posted here about the possibility to simplify this mod changing the value of the coupling caps
from 10uF to 0.68uF to create a high-pass filter around 115Hz and so no need for the expensive big Miflex caps used at the amp inputs.
And these 0.68uF caps can be small enough to fit in the stock case for anyone like me who would prefer to do everything in the factory case/chassis.
https://www.diyaudio.com/community/threads/douk-audio-a5.423344/post-8192397

[jedics]

Hi all, baffled by a problem.
Got a working system, unplugged speakers and input from it to the A5 all working, then the left channel cuts out, I turn it off and on working, then left channel cuts out again, did this a bunch of times and then left channel just stopped working all together. Tried the working right speaker in the left channel and that works fine so it doesnt like my left speaker or cable for some reason. I am just putting the raw wire into the holes of the post and screwing down. Could it have anything to do with me not using banana connectors?
My brain cant compute what is wrong, any suggestions?

[nlitworld]

So when you swapped the left and right channel speaker wires, the right speaker from the left amp channel was working fine? What about the left speaker plugged into the right channel? Did that start to cut out?

There should be no problem with bare wire in the binding posts, provided they do not touch each other and cause a short. That would trip an amp into protection mode, or worse go poof in a bad way. Banana plugs do make that part easier, but ultimately it shouldn't be an issue.

You were right to start at speakers and work backwards. Check that all the wiring is clean and tidy and isn't touching, and see if that solves it. If it doesn't, then move backwards to the rca cables and swap them. Did the problem move? Keep us posted.