AWESOME!!!

I think I'll stick this in a box together with the JLSounds DAC. Did you notice any changes for the buffer when you stepped up the power supply?

P.S. This amp embodies what I consider to be the "modern" DIY headamp. It uses obtainable cheap parts that don't need any matching whatsoever, the size is quite desk friendly, there is almost no heat emission as the bias stands at about 10mA. The whole thing draws a max of about 10W so keeping it on all the time is a viable option.

Also it made me to stop worrying and learn to love surface mount soldering. It is faster than through hole. However your hand has to reasonably stable, most of the time I drank wine to dampen mine. Good needle nose tweezers are a must.

Cool. Wonder how it competes with The Wire amps.

Looks great RW!  Awesome work.  What's the plan for boxing it up, or are you just going to keep staring at all the SMD work!? 

yes, you must be organized.  as RW has already said, i spent a few hours organizing the BOM in Excel into an easier to follow format similar to parts lists that AMB and Cavalli have on their websites, double checking against the schematics, and the original parts specified from ELFA.  with the exception of the electrolytics, both through hole and SMD, and the TXs, all components are identical to the stock ELFA BOM and obtained through Mouser or Digikey.  since the PCB is designed for 230V PCB-mount TXs, i had to go with off-board chassis mount from Amveco.  i'm more than happy to send my BOM to DIYers.

i was all rammy to build it, then flaked out on RW, getting caught up in other projects for customers and the Krell Klone for myself.  finally got around to coaxing tunes out of it a couple of weeks ago.

the pitches are easy, even with a 1mm tip.  i couldn't find my 0.8mm tip and was too lazy to source another one for the Hakko.  the SMD electrolytics are a total bitch though, with the pads being each about 0.5mm short.  i would change up my method next time.

three of the four rails came up fine at 16.3V, but i was only getting 10V on one.  the regulator was cooking - short somewhere in the PS.  pin-7 on the AD825 to a nearby ground test pad was the culprit.  a little solderwick and all was well.

the most challenging part of the build was figuring out where the components go and strain on the brain and eyes.  i could maybe chip away an hour or so before i would need to take a break.

sonically, this amp is pretty special, or to quote Per-Anders, "...this headphone amplifier is not mainstream".  i couldn't agree more.

as RW alluded to, it doesn't wow you at first listen.  no screaming bass, mids, or trebles - "look i'm here" kind of stuff.  very coherent sound from bass to treble.   everything is cut from the same cloth, but without bland, chalky tonality and timbre.  excellent details and transparency.  headstage is perfect.  non-fatiguing, and maybe on the "smooth" side.  sounds great with my Don-mod T50RP, AD2000, and K701.

if you think slammin' bass is the definition of "dynamics", then you will be disappointed.  dynamics here are more on the micro-scale.  you can feel the pulse of the musicians.  the QRV08 can carve out the most complex music with ease...with tone.  effortless and no strain.  sounds like a well behaved FR speaker. 

i rate the CK2III highly.  too bad it never got the praise it deserves.  it plays well with everything and sounds fantastic - "synergy" need not apply.  i could easily live with the CK2III and my BM DAC1 and never wish for more.   i think the QRV-08 is in the same company.  subjectivity comes into play here, but this amp is a reference of sorts for me.  i'm glad RW rode my ass to finish this amp - i just need to convince him to build the QRV01 now  . 

huge thanks to Per-Anders for the design, the contribution to the DIY community, not being "mainstream", and to RW for lighting a fire under my ass .                 

here's my QRV08 in a recycled Par-Metal 12x12x3 chassis.  wire is Belden, shielded inputs, and pot is TKD.   smaller form-factor is easily possible.  i already had holes for the TXs and didn't care for a smaller layout.  just needs a proper faceplate.




UPDATE 5/16/14

i hear differences in pots/SAs.  i think these differences can be apparent than rolling cables.  i've had pairs of identical B22,M3,CK2III amps with the only difference being the pot/SA, and line level matched with a DVM.  this actually kind of pisses me off.  i would rather just stick the cheap and cheerful RK27 on everything and call it a day.   

while i didn't have two identical QRV-08 here to compare, i did roll the RK27, TKD, GoldPoint, and Alpha.  i recently rolled the Alpha and it changed the sound enough that i thought my impressions warranted amending. 

the Alpha is nicely detailed but definitely the more "forward" and dynamic sounding of the bunch.  i hate to use "aggressive", but the note attack is a little more incisive and dynamics are more punchy.  i prefer something a little more relaxed with the AD2000 and K701, but this works really well with my Don-modded T50RP.