CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

Lobby => DIY => Topic started by: Hroðulf on January 12, 2014, 07:15:34 PM

Title: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 12, 2014, 07:15:34 PM
The tale of the QRV-08 or as its inventor Per-Anders Sjostrom called it -

"DC servo controlled ultra high performance current feedback headphone amplifier with dual mono quadruple super regulated power supply".

I think it was about a year ago when I and Fishski met in the shoutbox to comment on some random stuff and we both pointed to the QRV-08 headamp to be somewhat an enigma of the DIY headamp world. Some posts later we both decided to build one just for the fun of it.

Initially Fishski was ahead of me and had made a handy BOM with corresponding part numbers for Mouser. I was very surprised that the board had to be populated by more than 300 smd parts which meant filling about 800 pads. I took the BOM from Per-Anders (PA) himself as it had also ELFA Distrelec part codes. The board itself, despite containing a large number of parts can be populated for about 250 - 400 dollars, depending on what provider you use. As far as I know almost all of the parts are readily available, with the non-230V on-board EI transformers being the exception. None of the parts used are anything close to audiophile grade.

If you are systematic, populating the board is a breeze. I'd recommend starting ground up with PSU first so you can test it. After all the PSU circuit takes about 2/3 of the pcb. Due to the QRV-08 using a current feedback topology, its PSRR is very low so clean power is a must. I made three mistake while populating the PSU part which comprised of untouched pads and a solder bridge. The design uses self-resetting fuses, so overcurrent can be easily detected by looking at the dimmer PSU LED (the fuse lets through some current when tripped). Populating the amp part was a breeze as I had already mastered the technique by working on the PSU. Dialing the amp in initially seems counterintuitive as you need to jumper either of two pads per each channel. Then set the bias and you're ready to get your jaw dropped on the floor.

As for how it sounds... Excellent. As with many good amps initially it sounded a bit flat and meh, but in a day or so I realized what it has to offer. The resolution is way above my Dynalo, same goes for frequency extension, soundstaging. The amp is as neutral as I've heard. Technicalities wise it's on par with the Beta22, however it is immensely more likeable with zero etch and leading edge emphasis. Transients are lightning fast, as it should be for an amp that theoretically can amplify up to 25Mhz with slew rate being 1200 volts per microsecond. This is why it needs a shitton of ceramic caps - HF decoupling so it doesn't ring.

Power wise - it may not make the HE-6 sing, but it sure can drive the Paradox to almost ear splitting levels at 12'o clock volume.

The THD and IMD plots look pretty much out of this world -

(click to show/hide)

Specs:

Frequency response:   0 Hz - 25 MHz(?), more than 10 MHz. This is valid without input coupling cap. With this cap, 8 or 17 Hz
Frequency response with input filter:   0 Hz - 1.29 MHz, -3 dB. This is valid without input coupling cap. With this cap, 8 or 17 Hz
Power bandwidth at 7 Vrms, 50 ohms:   0 Hz - 25 MHz(?), more than 10 MHz. This is valid without input coupling cap. With this cap, 8 or 17 Hz
Equivalent input noise:   0,6 µV
Signal to noise ratio:   112 dB at 1 V out
Dynamic headroom:   129 dB
Distortion:   0,00046%
Slew rate:   1200 V/us
Step response:   Perfect without overshoot
Gain:   4 (12 dB)
Input impedance:   >1 Mohms, pullup, pulldown resistors not included.
Output impedance:   2.5 ohms (or 125 ohms, switchable by jumpers)
Output current:   1 A peak
Supply voltage:   230 VAC in 115 VAC is also possible.
Dimensions:   203,2 (8,0") x 123,2 (4,85") mm

http://sjostromaudio.com/pages/index.php/hifi-projects/129-qrv08-headphone-amp (http://sjostromaudio.com/pages/index.php/hifi-projects/129-qrv08-headphone-amp)

Transatlantic hi-five to you Fish for all the help you provided, the floor's all yours...
Title: Re: The Par-Anders Sjostrom QRV-08 Appreciation thread
Post by: ultrabike on January 12, 2014, 07:28:10 PM
AWESOME!!! :boom:
Title: Re: The Par-Anders Sjostrom QRV-08 Appreciation thread
Post by: MisterRogers on January 12, 2014, 07:50:18 PM
Thanks for sharing this RudeWolf; I've been contemplating this as a build in the near future. I've build a few of Per-Anders super regulators (using one in my slimline DAC to power a JG Filter), and have been impressed by his design work.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 12, 2014, 08:10:27 PM
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.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: dBel84 on January 12, 2014, 08:24:51 PM
well done to you both. The sheer volume of SMD has always been the deterrent for me. It is good to finally hear some feedback about this design..dB
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: mvwvm on January 12, 2014, 09:07:04 PM
Cool. Wonder how it competes with The Wire amps.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 12, 2014, 09:14:51 PM
I'm wondering that as well. I know QUSP ditched his QRV-08 for a Wire as it supposedly had more bass. That said he did for some reason use the OPA627 for shuntreg and servo opamps. No idea why would anyone do it.

As for the bass, some might like more of it. With the Paradox I find that there is plenty extension and texture. The Vio V200 I had for some time for testing had more bass which I initially loved, but later grew tired of.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: shipsupt on January 12, 2014, 10:52:10 PM
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!?  ;D

Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: MisterRogers on January 13, 2014, 01:44:44 AM
If I get around to building one soon I'll compare with 'Wire' both SE, SE-SE Balanced and Balanced. I've built a few of Owen's latest boards and test them. Haven't decided how to assemble them yet.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: fishski13 on January 13, 2014, 04:52:08 AM
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  :P. 

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 :)p5.                 

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.

(http://i23.photobucket.com/albums/b353/fishski13/IMG_1868_zpsce5f43ec.jpg) (http://s23.photobucket.com/user/fishski13/media/IMG_1868_zpsce5f43ec.jpg.html)


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. 
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: AstralStorm on January 13, 2014, 07:48:24 AM
Considering it has so high frequency response (even with filter), does it amplify the dreaded GPRS signal?
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 13, 2014, 08:04:42 AM
Agree on the small 'lytics - the pads are okay for oven soldering, but for hand soldering you have to be extra careful to not cover up the other pad when sliding on the can. Sjostrom's buffer boards (also highly recommended) are better as the pads are longer.

The board design is sound with some traces being a bit too close for comfort to pads that must not be connected. Some markings are a bit harder to decipher, but all in all it's understandable for such a densely populated board.

As for the QRV-01... TEMPT ME NOT, HEATHEN!

But seriously, I'm not convinced it will be better than the 08. Also it looks like PA isn't too eager to deal with them judging by the price of the board.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 13, 2014, 08:11:06 AM
Quote from: AstralStorm on January 13, 2014, 07:48:24 AM
Considering it has so high frequency response (even with filter), does it amplify the dreaded GPRS signal?

I haven't noticed any audible artifacts and I don't have an oscilloscope at hand to check higher frequencies. I was able, however to make it oscillate by using improper grounding and long cruddy wires.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: AstralStorm on January 13, 2014, 08:19:56 AM
Oh, so it can be made to oscillate by BA IEMs most likely - they have high capacitances in the drivers and crossovers.

(Of course it is too high gain for these anyway.)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 13, 2014, 08:24:18 AM
No dice with my SM3v2. Plays nicely with them.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 22, 2014, 09:08:05 PM
Finally found a dac that's worthy to complement the Swede.

http://www.customworks.cz/dac/dac_1/ (http://www.customworks.cz/dac/dac_1/)

(http://www.customworks.cz/wp-content/gallery/ak4396/ak4396-1k-fs96khz-1dbfs.png)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: funkmeister on January 23, 2014, 04:10:52 AM
You need to start a thread on that DAC if you put one together.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: peranders on January 31, 2014, 06:52:44 PM
RudeWolf, well done. Not many in the world has this amp so it's quite unique and pretty hardcore when it comes to soldering. For those who might don't know, I am the person behind this design.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: shipsupt on January 31, 2014, 07:24:04 PM
Welcome to our little place on the inter web Per.  Seems you've got some fans here, and others really interested in the stuff you're designing.   :)p1

Got anything really cool brewing?

Thanks for stopping in!
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: fishski13 on January 31, 2014, 08:55:26 PM
Welcome PA!
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on January 31, 2014, 11:03:13 PM
Welcome and thanks for the amp design PA! It is a real shame that many are afraid of the SMD soldering, because apart from that the QRV-08 is a terrific deal for the expenses involved to build one.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: anetode on February 01, 2014, 05:27:01 AM
Quote from: RudeWolf on January 22, 2014, 09:08:05 PM
Finally found a dac that's worthy to complement the Swede.

http://www.customworks.cz/dac/dac_1/ (http://www.customworks.cz/dac/dac_1/)

You must really love that AK4396.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on February 01, 2014, 09:57:38 PM
  What is there not to love? The stello siggy sounds lovely and if that DAC achieves the thd stated, then... Well, it doesn't get much transparent than that. Basically what Nwavguy wanted, but with good sound.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on February 17, 2014, 07:38:15 PM
Casing. Casing never changes...

(https://scontent-a-ams.xx.fbcdn.net/hphotos-ash3/t1/1939875_695267433859394_836287568_n.jpg)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: fishski13 on February 17, 2014, 11:10:40 PM
nice.  i've always wanted to try that Hammond chassis.  how's the fit and finish? 
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on February 18, 2014, 07:16:57 AM
The finish is really good, however for the price I was expecting better construction in terms of threaded holes. None of the holes are threaded so I need to use self-tapping screws and rather dinky threaded inserts.

All in all it does look good!
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Mullet on March 04, 2014, 06:25:17 AM
Looks like a cool challenging SMD project. Don't mind the SMD stuff at all. Actually prefer it to through hole. Have The Wire SE-SE as well. Love it. Too bad I'm about to embark on the EHHA Rev A first. Then have way too many ES9023 associated DAC boards/parts to make up another DAC creation. Too many projects! --- no can't stop now! ahoy
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on April 12, 2014, 11:31:54 AM
Finally boxed up the thing.

(https://scontent-b-ams.xx.fbcdn.net/hphotos-frc3/t31.0-8/10264219_722898734429597_7907745878787172285_o.jpg)

(https://scontent-b-ams.xx.fbcdn.net/hphotos-frc3/t31.0-8/10256641_722898771096260_6036403474119826426_o.jpg)

(https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-prn1/t31.0-8/1962469_722898747762929_1534871836771406525_o.jpg)

(https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-ash3/t31.0-8/10003716_722898811096256_2013501525692732275_o.jpg)

Obviously I can't be bothered to do lettering.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: MisterRogers on April 12, 2014, 01:48:26 PM
Nice work! I'm with you - can rarely get myself to do letting, etching, etc. It's only been the last year or so since I've begun to find enjoyment in casework at all.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: firev1 on April 13, 2014, 03:22:07 AM
Very nice, I do not enjoy doing casework at all, seems like an absolute PITA to me.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on April 13, 2014, 09:18:27 AM
Well, I'm sort of getting better so it gets less and less painful. That said most of my amps tend to remain in the guts-on-the-table state for a good while.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: fishski13 on April 13, 2014, 05:29:11 PM
love the form factor with the Stello.  i can't tell from the pic, but did you decide to toggle the output impedance or is the switch for preamp duties?
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on April 13, 2014, 05:39:05 PM
Output impedance. Preamp output is hooked up to the potentiometer.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on April 20, 2014, 06:29:29 AM
Finally heard the full potential of my system!

(http://3.bp.blogspot.com/-8vBzXaWe1es/U1LF1fOfDuI/AAAAAAAAAjM/Vexb6QoFgDY/s1600/NORDOST+012L.jpg)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: funkmeister on April 21, 2014, 04:10:06 AM
Your Nordost stuff is impressive.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on April 21, 2014, 07:11:29 AM
Yeah, finally understood what Patrick82 was going on about. Two 5k EUR power cables and interconnects for about that much was what has been keeping my system to reach total greatness. Also note how Nordost thingies are presented by a genuine viking. I'd too get that ripped by lugging around all that copper.

(http://3.bp.blogspot.com/-Rd2fCAvYZBs/U069FICqBJI/AAAAAAAAAiQ/V8O0LN0GtrQ/s1600/IMG_6743.jpg)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: munch on April 21, 2014, 03:03:12 PM
that guy's facial hair is more like trucker than viking. thinking they can get away with such non-sense... (source: I am from Sweden)
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: PhoenixClaw on May 14, 2014, 09:50:47 AM
Hi all, forgive the "noob" question but how does one begin on assembling this? I understand that you have to order the PCB from the webstore here http://sjostromaudio.net/shop/index.php?id_product=29&controller=product (http://sjostromaudio.net/shop/index.php?id_product=29&controller=product) but what about the rest of the parts required?
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: firev1 on May 14, 2014, 10:29:30 AM
You will have to source them from Mouser/element14 yourself. Its really a build not meant for starters.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: PhoenixClaw on May 14, 2014, 10:43:41 AM
Yeah, but what I meant is that where is the parts list/ BOM?
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on May 14, 2014, 11:22:35 AM
All of the documents are provided upon making the purchase.
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: fishski13 on May 16, 2014, 01:51:28 PM
updated/amended my initial impressions after rolling in the Alpha pot: http://www.changstar.com/index.php/topic,1395.msg36424.html#msg36424
Title: Re: The Per-Anders Sjostrom QRV-08 Appreciation thread
Post by: Hroðulf on May 16, 2014, 02:23:38 PM
Good thing I only have the RK27 at hand...