[mathesar]

I recently bought a Douk U3 Mini headphone amp from Amazon, was only $30 with decent reviews so figured i'd give it a shot, My trusty 15 yr old Go-Vibe v4 amp needs repair due to broken DC port(center pin came out).

The Douk comes with a USB power cord to supply power but some reviews mention you should use a higher volt DC adapter for better sound quality?

I currently have 3 ways to power it but not sure which is ideal: USB cable it comes with which would be 5V, I also have the SPC9707 12V 400mA Regulated power brick from my GoVibe V4 and a GPE603-140400W 14V 4,000mA Switching mode power brick but haven't tried this one yet.

The Douk manual says it accepts "5 - 20V" DC input but doesn't mention anything about amp ratings etc.

headphone amp is being used on PC if that helps

Any ideas appreciated! (couple photos attached)


EDIT: I figured everything out just needed to do more googlin' the 14V GPE 12V SPC9707 adapter is working great actually surprised how good this amp sounds but will have to try other op amps since it has a pluggable socket.

UPDATE: After a more careful comparison I now realize the 14V GPE switching adapter was not the right call, with the amp powered on and no audio playing there was a subtle but noticeable hiss and when comparing the same movie scene & music several times also realized the switching adapter had slightly reduced highs so things were more muffled on the upper end, so the 12V SPC9707 Regulated adapter is superior in this application, also there's zero hiss with no audio playing.

I shouldn't of questioned it in the first place considering the SPC regulated adapter was recommended by the person who built & sold me the Go Vibe v4 I believe his username was tigger on this forum also known as Norm but looks like he hasn't been active for a long time.

Also I recently bought a Muses8920D op amp from digikey and installed it yesterday, this opamp sounds great and was a definite upgrade over the stock NE5532, sound stage is probably the biggest improvement with the 8920.

anyhow I just wanted to update in case anyone happens to stumble upon this thread in the future lol.





8920 op amp installed & digikey part# info, wasn't sure if barcode revealed any personal info so marked it out but guessing its just product info.

 

[Slipmyster]

Thanks for posting this I have the U3 and am very happy with it. I'm going to give the op-amp rolling a go.
I have mine connected to a Sony CD player and it really drags out some detail

 

[mathesar]

Thanks for posting this I have the U3 and am very happy with it. I'm going to give the op-amp rolling a go.
I have mine connected to a Sony CD player and it really drags out some detail

Right on, how do you like the tube amp in your pic?

If possible order from a reputable source like Digikey or Mouser, Before buying the 8920 I made the mistake of ordering an AD8397 opamp from eBay and I'm pretty sure it was counterfeit, It came on a SOIC to DIP8 adapter as AD8397 doesn't have a DIP8 variant.

After a couple days I went to remove the opamp and noticed flux on the adapter which wasn't visible on day 1 so if anything maybe not the best solder job

the ebay seller in question has over 35k / 99.8% feedback but when looking at the few negative feedbacks now theres a couple claiming fake chips (oops).

My other (Go-Vibe) headphone amp has an AD8397 soldered to the board and it sounds way different than whatever I got from ebay lol.

Ebay AD8397 w/ Flux mess:

For reference here's my go-vibe amp with an AD8397 but notice the print is nice & bold and all lined up properly, with the ebay opamp I had to shine a light at a specific angle just to make the print visible:

 

[Slipmyster]

Thanks for the advice I will have a look round.
The valve amp is the Nobsound NS-08e with Russian long life valve's and it's pretty good. It's got Very big slightly smooth sound. I was surprised just how good it is witch is the only reason I bought the U3 and I think that the douk is slightly better but that could be down to the power supply. It doesn't seem to be very easy to find a decent quality 6v supply. For less than £30 the U3 was a massive bargain.

 

[numon]

any one know the max volt given to opamp ?i have discrete opamp 994 that need min 7.5 volt.

 

[6Channel]

In my searches on 5532 OpAmps, for which I've acquired a very soft spot, I rolled some cheap dice on this product and took a chance for $40 based on Amazon reviews. Didn't expect a lot, and out of the box, I found unacceptable SQ & figured I'd either return it or dump it ($40?). Based on others' findings, I elected to pursue a quality 3A dedicated 5V converter. Holy Cow. This puppy is now nothing short of stunning! I'm comparing this to Four-Figure headphone amps. Did I say "stunning"? The only glitches are (1) the wobbly detent pot that jumps too far with each click & crowds my HP plug on the front panel and (2) it chokes when tasked on material with demanding dynamics: e.g., Joe Morello's tom & bass drum hits in HQ versions of "Take Five" and stepping on some demanding orchestral crescendos. I can contend with the detents, but this $40 amp basically sounds so incredible that I wonder if any techies out there can suggest possible solutions to its challenged dynamics issue, such as an even higher-amperage 5V supply or a couple of larger strategically-inserted capacitors in the circuit. I'm convinced from others' experiences that this guy is really optimized for 5V, which with my 3A converter translates into oodles of reserve output for my 600Ω'ers. BTW, this amp responds ever-so-well to guilding with an NJM5532. I know this post may sound crazy, but the transparency in this amp's audio on 90% of source is so spooky that I'm already planning to swap out the pot & put the HP jack on the back so's I can get a better grip on the durn'd knob.

 

[Magic77]

Just got one of these amps yesterday. I’m using a USB port from my power strip to power it up. Sounds pretty amazing. So far I’m really impressed with this little amp. I also swapped out the 5532 with a LM4562. So far, so good.

 

[6Channel]

As I exclaimed above, I'm really impressed. I've got a fresh LM4562 that I've been reluctant to swap in until I had confidence it would match well with the rest of the board interface. Still awaiting a new non-detented pot, but am ready to take the 4562 plunge. I solicit your impression of compared SQ between the chips. [you might also achieve a yet cleaner sound with a good USB wart]

 

[Magic77]

When I first turned on the amp with the 5532, I only listened for a couple of minutes. It sounded really good with the 5532, but I knew I wanted to put in the 4562 right away. The 4562 is great, very detailed overall. I have 2 opa627’s on a brown dog adapter and would like to try those as well. The 4562 is a bipolar chip like the 5532. But, I would like to see how it sounds with a FET chip.

 

[Slipmyster]

When I first turned on the amp with the 5532, I only listened for a couple of minutes. It sounded really good with the 5532, but I knew I wanted to put in the 4562 right away. The 4562 is great, very detailed overall. I have 2 opa627’s on a brown dog adapter and would like to try those as well. The 4562 is a bipolar chip like the 5532. But, I would like to see how it sounds with a FET chip.

I settled on a muses 8920 j fet in mine. It put the detail level up I good bit and is very open

 

[Magic77]

Tried the opa627’s. Sounded really good, but I was still wanting to try the opa1642. I have these chips on brown dog adapters. I had got them from Cimarron Technology online, their soldering of components is excellent. I felt that the 1642 sounded better than the 627. It was much brighter and overall better detail than the 627. The 627 is also great, but the 1642 is designed specifically for Audio applications. I also have to say the LM4562 is also excellent for audio, and is designed just for audio. I’ll probably swap them again to hear the differences with different recordings. I’m so impressed with this little amp. How can you go wrong for just $42 and be able to use chips like the opa627.
Update: I’m now getting a hissing sound when powering on and off the amp with the opa1642. I’m not liking that, so I’m back to the opa 627. Maybe the amp doesn’t like that chip, not sure about the hissing.

Update 2: I’m now staying with the LM4562. Very quiet, and sounds great, especially that this is a chip designed for audio only.

 

[Magic77]

As I exclaimed above, I'm really impressed. I've got a fresh LM4562 that I've been reluctant to swap in until I had confidence it would match well with the rest of the board interface. Still awaiting a new non-detented pot, but am ready to take the 4562 plunge. I solicit your impression of compared SQ between the chips. [you might also achieve a yet cleaner sound with a good USB wart]

I may be interested in the non-detented pot as well. Could you tell me the resistance value of the pot and where you ordered it from? Thanks

 

[barrygee]

Any Amazon links for an inexpensive robust DC power adapter that will plug right into the U3?

 

[shaolin95]

Tried the opa627’s. Sounded really good, but I was still wanting to try the opa1642. I have these chips on brown dog adapters. I had got them from Cimarron Technology online, their soldering of components is excellent. I felt that the 1642 sounded better than the 627. It was much brighter and overall better detail than the 627. The 627 is also great, but the 1642 is designed specifically for Audio applications. I also have to say the LM4562 is also excellent for audio, and is designed just for audio. I’ll probably swap them again to hear the differences with different recordings. I’m so impressed with this little amp. How can you go wrong for just $42 and be able to use chips like the opa627.
Update: I’m now getting a hissing sound when powering on and off the amp with the opa1642. I’m not liking that, so I’m back to the opa 627. Maybe the amp doesn’t like that chip, not sure about the hissing.

Update 2: I’m now staying with the LM4562. Very quiet, and sounds great, especially that this is a chip designed for audio only.

Is this the one?
https://www.digikey.com/en/products/detail/texas-instruments/LM4562NA-NOPB/1217793
Would it be a good match for the HD 560s and maybe Edition XS?

 

[Magic77]

Is this the one?
https://www.digikey.com/en/products/detail/texas-instruments/LM4562NA-NOPB/1217793
Would it be a good match for the HD 560s and maybe Edition XS?

Yes, it’s the right one. Don’t know the HD560s, but should sound good.