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AudioValve RKV Mk II Review

post #1 of 64
Disclaimer: As always, this is purely a subjetive review. The contents herein reflect my opinion alone and do not represent opinions of HeadFi, its sponsors, its moderators, nor do they represent AudioValve or their distributors. Moreover, the opinions were reached by subjective means only without the aid of any measurements. As with any review, please add a grain of salt and assume every statement to mean, “in my system”, “to my ears” and “in my opinion.”

AudioValve RKV Mk II Headphone Amplifier

Associated equipment:
Sony XA777ES sacd/cd player
Sony S7000 cd/dvd player (used as a transport)
ART DI/O DAC
Sennheiser HD600 headphone with Cardas HD600 cable
Etymotic ER-4 headphone with FixUp ER-4S cable, stock ER-4P cable
Grado HP-2 headphone
Audio Technica W2002 headphone
Beyerdynamic DT831 headphone
Ven Haus and JPS Labs Power Cables
Various interconnects including the JPS Superconductor FX

Amplifiers directly compared in repeated AB:
ASL MG Head
Corda HA-1
McCormack Micro Integrated Drive
HeadRoom Maxed Out Home Reference with Stepped Attenuator

A variety of music was used over the past few months to assemble these opinions. Please email me if you'd like to discuss particular music or tracks.

I've had the RKV for a little while now and have only decided to write the review recently. You see, while I consider the amplifier a product worthy of review, it's suffered from one consistent problem. There has not been a good distributor of the amplifier and numerous people have reported problems with dealers in North America who stock AudioValve products. I've also always felt it to be in poor taste to recommend components that are discontined or difficult to acquire--this only seems to frustrate consumers and dealers alike. With the announcement that Meier-Audio will be carrying the RKV, I now feel it is approriate to share my opinions completely with faith that Meier will take care of his customers.



The RKV is undeniably one classy looking piece of hardware. As far as looks go, I like it as much as the EAR HP-4 and Sugden Headmaster. One thing that might disappoint, though, is that the top is not actually glass. I imagine real glass would get very hot and the top is actually made from a dense fiberglass. There is also something that strikes me as “wrong” about not enclosing the amplifier completely. I wonder how much noise is leaking through the ventilation slots beside the tubes and even through the fiberglass top. I'm not an engineer but it's something I wonder about. The amplifier carries a retail price of $1300 in the US, though as I understand it Meier's price may be considerably lower--contact him directly for details about that.

One final note about looks -- my RKV actually looks slightly different than the one pictured here. In mine, the tubes are arranged differently with the quad in a square formation on the right side. I'm not sure what all the revisions are and when they happened but thought it was worth mentioning that they changed.

Some history on my experience:

I originally bought the RKV from Vertigo when I was on the verge of buying the Berning MicroZOTL. The ZOTL was hard to come by used so I was contemplating buying one new at the full price from the manufacturer--something I do fairly infrequently, since I tend to sell things so often.

Some time ago now I was on the verge of buying a Berning MicroZOTL to go with a pair of Audio Technica W2002 which I also reviewed here. By this point I had already decided that I wanted something nice for work and that the Corda HA-1 was doing an admirable job with that but that I wanted to do even more at home. I began a thread asking for reviews of the ZOTL and to my surprise a couple of people chimed in with how good the RKV was. At about this time, Vertigo had placed his RKV for sale and I couldn't resist trying an amplifier that at the time was very hard to come by. Several HeadFi members warned that the RKV may hiss badly enough to not be well suited to the low impedance/high sensitivity W2002 and this was an acceptable risk to me. Vertigo and I worked out the details and my amplifier finally arrived in its original crate a little while later.

The warning was not in vein. The RKV did have a hiss that was, to me, noticable with the HD600, and pronounced with the W2002 enough to be bothersome. I contacted AudioValve and they suggested an Impedencer (an external transformer that would better match the impedance of the headphone) which sold for $250 retail. I decided to wait since I was undecided about the W2002 anyway. Further, the W2002 just didn't sound as good with the RKV as it did with my Corda HA-1 so I pretty much had my systems divided: Corda HA-1/AT W2002 or RKV/HD600. As time went on I found myself returning to the RKV/HD600 pairing more often and decided to part ways with the W2002 despite its many good qualities.

Tragedy struck as my apartment's shoddy electricity sent a power surge and voltage spike to the unprotected amplifier and the RKV became dead. I spoke with Heike at AudioValve via email a few times and she suggested I check the main line fuse. I did and it was indeed blown but replacing it merely blew one after another. Finally the amplifier was beyond my ability to look at. I simply didn't have the talents of Mr. ZZZ who recently serviced his own EAR HP-4 with great success. At Heike's suggestion, I packaged the amplifier and sent it to AudioValve. I'd also mentioned that the top headphone jack was intermitent.. AudioValve's designer, Hemut Becker, repaired the amplifier and fixed the jack. The price? Parts and shipping. Very commendable.

When I received the amplifier back, I discovered that not only was it working--but better than ever. The hiss was gone with the HD600. I plugged in my Etymotic ER-4P which had an impedance of only 25ohm and still, no hiss. I paused the CD and turned the volume up to max and finally there at maximum volume with the ER-4P was the hiss but only there. I'm sure if I had unpaused the CD that the tiny Etymotic drivers would be dead today and that this wasn't a volume level I'd be revisiting. I've since acquired the ER-4S cable from FixUp and again, no hiss, and the pairing is very nice. Finally, I recently got to hear the amplifier with the Grado HP-2 headphone--still, no hiss. Very nice. This isn't to say that the Impedencer won't help the sound further, of course, and my curiosity on that issue remains.

Enough history? On to how it sounds:

If you've ever heard an MG Head, we have the best point of reference. If you haven't, be patient, I'll get to the rest of you in a minute. For MG Head fans, the RKV is the ultimate upgrade. Like that sweet liquid midrange and want more of it? The RKV does it only better. Think the MG Head is maybe a little sluggish? Lacks extension? Fixed. Simply put, anyone who likes the MG Head at all, will absolute adore the AudioValve RKV.

By now those of you who don't like the MG Head have already begun to write this amp off. Not so fast! For me, the MG Head only achieves its sweet spot with the OTL mode engaged and the right set of tubes (I like Nick's recommended tube, the Raytheon 5751). Even then, there were too many flaws for me to stick with the MG Head. The amplifier, to me, sounded confused during complex orchestral movements, it lacked the speed and attack necessary to do make instruments sound real and its lack of bass extension made it not something I could stick with. Still, the vocals were so smooth and natural that the quality was enviable and that beautiful midrange became so elusive in other amps. Even the Melos could not measure up to the MG Head in this one area.

So then, the RKV is like the Melos with the MG Head's midrange? Well, not exactly. The RKV does have a beautiful midrange but the amplifier's stength s in its bass performance. The RKV is without a doubt the best sounding bass I have yet heard in a headphone amplifier. Now I know what you're thinking. You're thinking I'm looking for that “gun toting hiphop gangsta wannabe” bass that you hear thumping from that lowered El Camino that you see when you need one of those weird import foods from a grocery store on the wrong side of town, right? If only it were so easy! Good bass to me is a measure of quality, not just quantity. Sure, it needs to go all the way down and it needs to have impact and it still needs to be there in the proper amount, but that's not all there is to it.

What else is needed for good bass then? For me, cohesion is critical. A lot of amplifiers and even speakers can produce really good bass and really good midrange. But there's something missing there in the middle. I like to refer to this as a “subwoofer” effect because it sounds like what home theater amateurs have--a subwoofer with maladjusted crossfeed that makes the midbass sound thin. What you really want there is a very smooth delineation. No dips, no valleys and no peaks. Just one consistent sound. The RKV does this and it does it like nothing else I have heard. Now the MG Head's midrange is no longer the elusive quality from other amplifiers for me, but the RKV's bass is too--and remember, we got the Head's midrange here already.

Finally, bass should have texture. A lot of people forget that, I think. They hear bass as thumping or powerful but nondistinct. There's even a popular myth that you can't have texture if you have good bass response. This is untrue and the RKV is the proof of that. My guess is that it's this “midbass cohesion” that other amplifiers are missing that force them to have to choose between midbass texture and thunderous bass extension. The RKV gets it all right in this area.

Texture isn't for bass only with the RKV, though. Throughout the entire frequency spectrum the RKV's texture is never sacrificed for smoothness--a trait commonly found in tube amplifiers. The rub of the strings, hit of a hammer in a piano and the unmistakable ambience of a saxaphone are all produced in their full detail, texture and all. For me that makes the RKV a myth destroyer once again--detail and smoothness need not be inversely related.

Another aspect that the RKV excels at is its massive soundstage. I think it is the soundstage by which people say the RKV resembles the Cary SEI. In my brief audition of the Cary SEI, I didn't like the amplifier at all--finding it murky and boomy, but in this way they do have a common trait. I'm sure this is somehow related to the OTL design but I'll leave that for someone more qualified to talk about. In my experience thus far, it is only the Cary SEI that shares this large and natural soundstage. Maybe crossfeed is overrated.

So the RKV is the perfect amplifier? Unfortunately, I stopped believing in perfection a long time ago and now I can't listen to even the most beautiful of music without making a laundry list of complaints. Taking inventory of flaws is virtually the first thing I have to do when I hear a new component and it is ultimately the reason why long term listening is so important to a good audition. Also, I'm always afraid that flaws mentioned in a review drown out the overall sense of the review. Remember that everything is relative. When I say something is a flaw of the RKV is only relative to other similarly priced or more expensive amps. On an absolute scale, everything about the RKV is wonderful.

So what's wrong with it? Compared to other high end amps, the RKV doesn't quite have the high frequency extension. It's not bad mind you and it's not nearly as rolled off as say the MG Head or the HeadRoom Little, but it's not quite as good as the HeadRoom Maxed Out Home and Max. And indeed, I perceive the extension of the Corda HA-1 to be better still than the Max. So, in this area the RKV is only good whereas the other amplifiers are a tad better.

Also, even with my hiss issues resolved, the RKV does not have the blackness of the higher end solid state amps. The Max really reigns supreme in this area and it's very hard for other amplifiers to compete. Still, no one would call the RKV noisy. In this area, it's only very good and the other amplifiers mentioned are just that much better.

In speed and attack the RKV is also not the absolute leader. I was struck immediately when auditioning the EAR HP-4 that the amplifier was faster. Still, the EAR at four times the price of the RKV would require AB comparison and audition for me to choose between them. The differences with regard to speed were there but they were not so great as to overshadow the other qualities of the RKV. Still, I admire the EAR very much and would love to hear more of it. You could probably also surmise that the Corda HA-1 and HeadRoom Max family of amps have slightly better attack and speed.

But the RKV is no slouch. Again, the RKV is very good, I only make the distinction that the other amps are slightly better in this area. In fact, the authoritative nature of the RKV's clean natural bass may compensate for some of this weakness even in the minds of those who value attack so greatly. The real casualty here is that tiny “ting” at the beginning of a cymbal hit in closesly mic'd recordings. With the not quite as good attack and slightly rolled off treble, that touch of the cymbal is given up in an AB comparison. But then you have the most excellent natural decay of the RKV to weigh it against and you have to wonder about opportunity costs.

And that's really the bottom line. Nothing is perfect. Recently I was in a store and saw Natalie Portman in a magazine. I think she's been in nearly all of them since the last Star Wars movie came out. In one of the articles were some close up photographs and I noticed--she had some blemmishes. I almost exclaimed in the store, “She's not perfect after all!” And that's how I feel about the RKV, she's not perfect, but she sure is beautiful.
post #2 of 64
Thread Starter 

AudioValve RKV Mk II Review

Hot damn! What a great review. This should find a home in the review section.

With more members giving thorough reviews of higher end amps, more of us without can make better judgements. I can't audition most high-end amps in my city. I have to purchase based on reviews unless I travel. Those travel costs would be too high for me.

There is a great Cary dealer in town here but auditioning would be tough. There is an ASL dealer here but he is evil and won't get the Twinhead in anytime soon. The only EAR dealer is 500 km away and will never have a demo. Audiovalve stuff is the same. Headroom is Montana only, the Headmaster I could perhaps swing but the closest dealer is 1000 km away. I live in Ottawa for crying out loud!!! Still, no luck with headphone amps outside of grado...

This brings me back to this review. With Jan selling the RKV now, it is an option, but will I like it? Can I take a chance on it? After this review, I just might.

Thanks Kelly.
post #3 of 64
I was seriously considering the RKV before this great review, but now one more step towards ordering. It's better than Stereophile because you compare with much more component than they do!

This is a comment without listening experience of the RKV: It may not be so fast and good at attacks as some other, very good amps. I feel not shure that this is a disadvantage as many recordings are so close mic'd that they overemphasize the attack. Fast attack can sound impessive at first but decay and texture are at least as important for me.

I think the impedancer is intended for 4 and 8 ohm speakers. Of course, it would be interesting to know if it makes any difference for low impedance headphones.
post #4 of 64
I'd like to know the output impedance of the amp, in order to evaluate if that "impedancer" is really necessary or not for low impedance headphones.
post #5 of 64
Great review Kelly! The RKV is the Super MG Head! Unless something displaces it in the future, I'm already convinced that it will be my final headphone amp.
post #6 of 64
Bravo, kelly! Wonderful, in-depth review of what is indeed a beautiful piece of audio gear. Now I have another amp to consider. Thanks.
post #7 of 64
kelly, I thought that when you had the RKV repaired, you had it upgraded to the mark III? Am I mistaken?

Driftwood
post #8 of 64
Quote:
Originally posted by Driftwood
kelly, I thought that when you had the RKV repaired, you had it upgraded to the mark III? Am I mistaken?
Driftwood
Drift
I had been told that the pop filter was the difference between Mk II and Mk III. When AudioValve made the repair, they added the pop filter. According to Jan, there is actually no Mk III and any designation of such on the web is just a typo.

Thanks to everyone else for the feedback.
post #9 of 64
Great review, Kelly!
post #10 of 64
Excellent review! Pray tell: what is the price (in ballpark figure) of the amp?
post #11 of 64
The second solid review posted by you in 24 hours!

Based on some of the comments here, and now this review, I have to admit that I'm very curious about how the RKV sounds.

This has probably been asked before, but I'll ask again anyway in the context of this review:
  • What is the estimated tube life?
  • How hot does it run?
  • Are replacement tubes difficult to find? Expensive?
post #12 of 64
John
Thanks. Did you actually read it all?

Quote:
Originally posted by statistix
Excellent review! Pray tell: what is the price (in ballpark figure) of the amp?
From the review:
Quote:
The amplifier carries a retail price of $1300 in the US, though as I understand it Meier's price may be considerably lower--contact him directly for details about that.


Quote:
Originally posted by jude
The second solid review posted by you in 24 hours!

Based on some of the comments here, and now this review, I have to admit that I'm very curious about how the RKV sounds.

This has probably been asked before, but I'll ask again anyway in the context of this review:
  • What is the estimated tube life?
  • How hot does it run?
  • Are replacement tubes difficult to find? Expensive?
Thanks Jude.
I have no idea how long the tubes last but they've lasted however long I've used them, vertigo used them and whoever vertigo got it from used them. I imagine the tube life is long but nothing like the microZOTL.

The cover gets hot enough that you probably won't want to leave your Snickers bar laying on top of it, but if you touch it you won't burn your hand.

It's been difficult to find a lot of new old stock tubes. I located a few different ones but didn't buy them based on Dusty's opinion. I have some Polamps on the way which are actually still in production. Jan also said he'd be stocking replacement tubes tho I imagine they'll just be the stock ones.

I'd look forward to there being enough RKVs to talk about tube rolling but I wonder if this is another amp in which rolling the tubes won't amout to big differences like the ZOTL and MG Head. None the less, my comparrison to the MG Head was using the best tubes in the Head (as far as I'm concerned) and the stock tubes in the RKV, so I'm not TOO worried about it. I just constantly wonder if there is another tube that could give me slightly better attack and hf extension without losing anything else. Probably too much to ask.
post #13 of 64
Other than the stock tubes has anyone found other tubes for the RKV? I bought a small cache of Sylvania PCL85's and a few other NOS 805's (supposedly the same tube, also labeled as 18GV8's) but haven't any others.
post #14 of 64
Quote:
Originally posted by bearwise
Other than the stock tubes has anyone found other tubes for the RKV? I bought a small cache of Sylvania PCL85's and a few other NOS 805's (supposedly the same tube, also labeled as 18GV8's) but haven't any others.
Care to post your impressions?
post #15 of 64
TO be honest Kelly, I bought the tubes when i got the amp about 8 months ago, and haven't had the time to do much with them. Maybe sometime this summer I'll drag the beat out of its hole, and try the different tubes.
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