[CoiL]

It would.
Can you not bring rails down though?
Most DAPs use DC-to-DC boost converters that allow to set output voltage, so it’s pretty much 1 resistor replacement affair.

I`m currently talking about my desk gear - Aune T1 It has separate +-15V power brick and uses no USB-power.
I haven`t messed with resistor or other opamp tweaking tricks as I haven`t put my time in it to learn about it.
You make it sound so easy and if You say it is just one resistor-trick, I`m willing to give a try but need some guidance. I`m pretty skilled with soldering tiny stuff, so this is not problem.

 

[Ivan TT]

I`m currently talking about my desk gear - Aune T1 It has separate +-15V power brick and uses no USB-power.
I haven`t messed with resistor or other opamp tweaking tricks as I haven`t put my time in it to learn about it.
You make it sound so easy and if You say it is just one resistor-trick, I`m willing to give a try but need some guidance. I`m pretty skilled with soldering tiny stuff, so this is not problem.

Ah, sorry, I believe power is arranged quite differently on this one compared to those DAPs and amps I had practical experience with.
Feel free to PM me photos of the main PCB under the amp PCB daughter board, we can try brainstorming it (to not to take this thread off-topic).
Or ask in the dedicated thread, I believe there’s one here and the may be some people with specific practical knowledge there too.

 

[CoiL]

Ah, sorry, I believe power is arranged quite differently on this one compared to those DAPs and amps I had practical experience with.
Feel free to PM me photos of the main PCB under the amp PCB daughter board, we can try brainstorming it (to not to take this thread off-topic).
Or ask in the dedicated thread, I believe there’s one here and the may be some people with specific practical knowledge there too.

Will think about it as much as I know about Aune T1 thread - I think I`m actually first one to change its HO opamp and try out different ones (quinea pig)!

Finally had time to solder ADA4084-2ARZ in DIP-8 to SOIC-8 converter PCB and installed it into my modded Aune T1.
Initial impressions after 10min listening - detailed, open and airy sounding (at times "holographic" but at same time with smidge of fowardness in vocals & instruments), well balanced sound, extended but not harsh/sibilant highs (cymbals and crashes sound very detailed and clear).
This is very good opamp and it might top even OPA1612A in this setup/gear but I`m suspecting OPA2228PA still sounds more organic and natural with great details all over spectrum, very open soundstage and tight textured bass.

Will report back after some "burn-in".

Current subjective preference in order (might change):

1) OPA2228PA
2) ADA4084-2ARZ / OPA1612AID (need to compare more)
3) NE5532A / NE5532PA
4) AD8599 (too bright/sibilant in this gear, otherwise detail-monster)

Edit: Did swap as fast as I could and OPA2228PA is just another level compared to ADA4084-2ARZ (at least in this hardware setup).
What I noticed was also slight upper-mid-bass/lower-mids "boom" with 4084 but know that I`m sensitive to any kind of mid-bass boost and prefer "dead-flat" mid-bass with rather slightly raised sub-bass and low extension (not bass-head). I mainly listen prog-rock-metal-jazz.
OPA2228 bass also hits harder and tighter and soundstage is "holographic" and very open/airy with more natural decays/reverbs.

Anyway, 4084 back to "oven" and lets hear if it changes better...

Edit: Hmmm... seems 4084-2 is humming very slightly when no music playing. Idk if it is occillating or I damaged it during soldering or just mismatch with this hardware but I better take it out for now and stay with OPA2228PA.

Edit2: LOL, I totally forgot about EMI/electronics nearby! Since my Aune T1 had open shell and my PC (sound source) was currently laying nearby "naked" without shell too, I was holding T1 too close to it and that`s where from that slight "hum" came. So, 4084-2 back to "burn-in".

Btw, did more listening and opamp lineup has changed for Aune T1:

1) OPA2228PA - most natural, organic, open, airy, balanced (think of Harman target), large soundstage & "holographic", layered, best imaging, sounding out of those.
It is just so coherent and revealing without being "hollow" or "details in Your face" (like AD8599).

2) OPA1612AID - well balanced but doesn`t sound so organic/natural and "misses something" that OPA2228PA has. Nothing bad, nothing really great - which makes it kind of "boring sounding". It just doesn`t grasp You into music like OPA2228PA.

3) NE5532A / NE5532PA - open/airy soundstage and pretty great imaging/layering but misses some mids timbre and bass/percussion tightness/thump (which sound laid-back sometimes). Very good opamp actually but some details/instruments may sound slightly "out of balanced/subdued".

4) AD8599 - this is detail-monster like I said previously. Soundstage is very open/airy and bass/percussion is tight/punchy (beating 5322 & 1612) but highs can sound somewhat sibilant/harsh & "strident" depending on record/genre. I imagine if I had HPs with less highs/details and warm source - this opamp could do wonders.

5) ADA4084-2ARZ - first thing I notice with this opamp is slightly boosted mid-bass / low-mids "glare", which ruins overall "picture". I imagine this opamp would suit source gear with recessed mid-bass/low-mids as otherwise it sounds pretty good in other areas. In my rig - no go.

X) Burson V5i-D - did not work

 

[Headmate]

AD8066 (wider soundstage)
AD8599 (more forward highs)
AD8620 (best transparency and details, most balanced of all)

Thanks, Ivan! Have shortlisted the 8066.

Since OPA1612 has input upto 36V, AD8620 (13V) might be risky. Xduoo XD05 runs from 3.7V 4000mah battery.

How about LME49860MA or 49720MA? they are discontinued though. Any other opamps to consider?

I really dislike colored/warm/bassy sound.

 

[Ivan TT]

Xduoo XD05 runs from 3.7V 4000mah battery.

It has +/-9V rails (i believe), so most opamps should be fine.

How about LME49860MA or 49720MA?

It's pretty much the same opamp (different grades though), I never liked it as I find its highs a bit plasticy/artificial and soundstage lacking precision (even if appears to be wide), but obviously it's my subjective opinion/impressions.

Have shortlisted the 8066.

I'd say AD8620 is the most balanced/natural sounding (or less coloured one). It may come across as a bit boring initially, especially compared to somewhat more "vivid" opamps (I don't mean Bursons here, but there's few out there that act almost like exciters you can find in studios/DAWs).
By the way, if you can find values for C75 and C57 in feedback loop or C60-80 in LPF you can replace them with Panasonic PPS SMD caps, this should clean up highs a bit. But it has AK4490 and its highs are somewhat laid back and lacking resolution (compared to more recent or higher grade AKM DACs), unfortunately.

 

[CoiL]

Panasonic PPS SMD caps, this should clean up highs a bit.

Panasonic POSCAP`s are also very good for cleaning up power filtering and output/coupling/decoupling stages. At least I have very good results with those.

I really dislike colored/warm/bassy sound.

Maybe You should still also try out AD8599? Its pretty cheap to try out anyway. I`m suspecting it would be good option for You but since I haven`t tried other to, can`t give comparisons.

 

[raoultrifan]

[...]
Since OPA1612 has input upto 36V, AD8620 (13V) might be risky.

AD8620 has actually 26V recommended voltage (+/-13V).

I find AD8599 very good in I/V, of course...OPA1612 too, but AD8620 very good in output buffer.

 

[raoultrifan]

Pity I can try only AD8599 in my gear, would like to try those other two, especially AD8620 but it supports only max-dual power supply of 13V. Wonder if +-15V would kill it?

I tried AD8620 at +/-15V for several minutes, but for a long term solution either you add in your circuit a pair of LM7812/7912, either you add 3 diodes per each rail (not quite the best design, of course).

 

[HeyManslowdown97]

I’ll ask this again since the discussion has turned into implementing AD8620 with resistor, etc

What is the difference between the AD8620AR vs AD8620BR besides the price tag sonically. Or is the difference felt in how it’s implementing into the DAC?

There is a census forming in regards to it being the best output buffer op amp in that stage. That’s great to know since I have one just sitting here. Haha

 

[Rroff]

I tried AD8620 at +/-15V for several minutes, but for a long term solution either you add in your circuit a pair of LM7812/7912, either you add 3 diodes per each rail (not quite the best design, of course).

I haven't tried it with the AD8620 but in my experience the AD8xxx series will get warm and die quite quickly much above their rated voltage - usually best results come at +/- 12V with them anyhow. Any attempt to drop voltage near the opamp is going to be extreme sub-optimal without some reasonable sized reservoir caps even with regulators that are stable without an output capacitor and a real risk of upsetting the rest of the circuit depending on how resilient the design used for generating a negative rail is against becoming unbalanced, etc.

2) OPA1612AID - well balanced but doesn`t sound so organic/natural and "misses something" that OPA2228PA has. Nothing bad, nothing really great - which makes it kind of "boring sounding". It just doesn`t grasp You into music like OPA2228PA.

The only opamp I've found that bridges the gap between the 2228 and the 1612 is the OPA2209 (think I got that right) which someone recommended here, sorry forgot who. But I still found I was missing something that the 2228 has.

I find myself coming back time and time again these days to a combination of OPA1692 (sadly not DIY friendly due to form factor) for buffers and either OPA2228 or AD8066 for the gain stage.

 

[HeyManslowdown97]

I haven't tried it with the AD8620 but in my experience the AD8xxx series will get warm and die quite quickly much above their rated voltage - usually best results come at +/- 12V with them anyhow. Any attempt to drop voltage near the opamp is going to be extreme sub-optimal without some reasonable sized reservoir caps even with regulators that are stable without an output capacitor and a real risk of upsetting the rest of the circuit depending on how resilient the design used for generating a negative rail is against becoming unbalanced, etc.

Educated guess but this would explain why the AD8620BR package cost 2x because of burnout. It must have an voltage regulator or resistance baked into the transistors or silicon chip!

Would also remark that I’m sure large manufacturers implementing the cheaper AD8620 chip know how prevent burnout via circuitry and moderating software to control its functionality which is again not privy to the Majority of Diyers.

This said, I’m am only speculating which is no different than one who quotes datasheets that are essentially guidelines and how they relate to a certain dap. My experience sometimes it works and other times like a heart transplant it rejects the implementation or works some of the time like I want it to.

The only true way to get optimum results is to create your own evaluation/development boards and as bonus learn how to write code to get it to operate the way you want.

In many respects that’s why many manufacturers get away using cheaper costing op amps to lower overhead cost and get them to sound great even better when they are using top notch hardware implementations.

The biggest challenge even for them is to prevent background noise from the signal when using highly sensitive IEMs or truly balanced isolated mono channels. Based on my reading film caps work best to offset DC noise allowing the sound frequencies pass through the signal path to the output.

This is very challenging for DIYERS since we don’t have large budget to break crap in experiments like in a controlled laboratories. Unless of course you don’t mind pissing money away with experiment and parasitical living vicariously through others mistakes on forums. But who among us would be brave enough to share such misdeeds to prevent property lost.

 

[Rroff]

One aspect that I've not cracked is the input side of a truly isolated dual mono output - bit beyond my expertise how to split the source ground without adding additional noise to the signal - isolated output is possible using transformers and/or DC-DC POL devices.

Unfortunately I don't have much input on the AD8620 as it is one of the opamps I've not spent a lot of time with.

 

[CoiL]

The only opamp I've found that bridges the gap between the 2228 and the 1612 is the OPA2209 (think I got that right) which someone recommended here, sorry forgot who. But I still found I was missing something that the 2228 has.
I find myself coming back time and time again these days to a combination of OPA1692 (sadly not DIY friendly due to form factor) for buffers and either OPA2228 or AD8066 for the gain stage.

The thing is, I don`t need to "fill that gap" and seems I`m settled with OPA2228 @ gain stage

Now I need to try out something instead OPA2134 as DAC differential opamp. Any recommendations what to pair with OPA2228 and is compatible at that stage? Not sure if OPA1692 fits there?

 

[HeyManslowdown97]

The thing is, I don`t need to "fill that gap" and seems I`m settled with OPA2228 @ gain stage

Now I need to try out something instead OPA2134 as DAC differential opamp. Any recommendations what to pair with OPA2228 and is compatible at that stage? Not sure if OPA1692 fits there?

What if you created more stages op amps and increased the voltage or current so not lose power via creating custom circuitry. Wouldn’t it bridge gaps with the differentiations provided you prioritize the series in which the op amps in the sequence you like best?

Could be fun experiment!

 

[Rroff]

Now I need to try out something instead OPA2134 as DAC differential opamp. Any recommendations what to pair with OPA2228 and is compatible at that stage? Not sure if OPA1692 fits there?

Annoyingly in terms of performance it is hard to beat the LM4562 (or higher end LME variants) in that application especially as they aren't crazy expensive. The actually better options generally cost 20x more.