Apex HiFi Sangaku Hybrid Amp

Just saw this pop up on TTVJ, today.

Here's the accompanying press release:

Probably a bit too pricey for me, but I'm intrigued nonetheless. Just a layman, but this looks like a promising amp. And I like Todd, for whatever that's worth to anyone.

Edit: Added what @JoshMorr posted in his thread, as I think it has merit.

 

That korg nutube tech seems somewhat interesting. Wonder how this would stack up against a Mjolnir 2.

 

Right? I tend to doubt that it'd be worth the extra $1250 over the Mjolnir, but I'd love to find out! It'd have to bring a hefty chunk of additional performance to the table, cuz that chassis isn't doing it many favors. Although the look does have a certain utilitarian charm, I can't deny. And its footprint is convenient.

I mean, Pete Millett designed the circuit, so I think there's a reasonably good chance that it won't suck. Hopefully.

 

There's finally something using the Korg tube! I've been waiting for those to be available for sale. Anyone know where I can buy one?

 

At Ttvj. A link is provided in the first post...

 

No, @Cspirou is asking about the Korg NuTube, not the amp.

"NuTube." Ugh. What a name.

 

Yeah, it's a crap name, but they still look interesting. I've been keeping my eyes open to find some, but they're just not publicly available from what I can tell.

 

Wonder what a modern tube would sound like, even if NuTube is pretty terrible name. I would think an Apex P Millet designed amp would be pretty good, but apex always seemed a bit overpriced to me. I agree with the comparison to Mjolnir above. Double the price of a T3, Hands whole shootout etc. $2k is a high mark, performance needs to be there.

 

Speaking purely on the basis of relative affordability, I feel like this would be a notably more compelling option if it were $500 cheaper. But the price is what it is, so we'll just have to see how it works out. Assuming that anyone on here winds up buying one, of course. Or gets in on an future loaner tour, as @Ray suggested was likely.

Absolutely. At $2k, the bar must be set quite high. And given the variety of well-regarded options available for considerably less, I'm afraid that might be a tough hurdle for the Sangaku to clear.

Anyone have any knowledge of what this NuTube (bleh) might conceivably bring to the table, in terms of performance? I mean, what's it got going for it on specs that conventional tubes don't? Outside of perhaps longevity, which doesn't seem terribly compelling on its own. I imagine that Korg developed this thing for a reason, not just shits and giggles. Or maybe that is why? I'd have no f**king idea.

 

So the TTVJ loaner showed up today.....


impressions to come.....

 

Looks pretty cool, @JoshMorr. Anticipating your impressions. Especially as compared to the Mjolnir 2, if you've heard that?

 

Ive only heard mjolnir 2 breifly, but this amp would be ahead of that in my mind. I don't want to spill the beans too early, but this is a fantastic amp with dryer / brighter cans. Doing great things with hd800 & he560. HD650 sounded bloomy with bass bleeding into the mids for some reason???

What I will give away is that it runs super cool, had it on for a couple of hours and it still feels as cool as if it were off. I think this may be a great option for people looking for tube amp sound without worrying about tube rolling, heat from tubes, or tube life.

 

Ok, without further procrastination...

As stated above I was fortunate enough to be part of the Sangaku loaner from the very kind Todd from Todd The Vinyl Junkie. Right up front this is a $2,000 amp, my expectations are high. Listened through my usual source, Gungnir Multibit and Mutec MC1.2 DDC.

I've been a Pete Millet and Apex audio fan for a while, building several of project on his DIY site. I was quite excited to try a high end tube amp using a new type of tube, the Korg NuTube



The Korg Nutube runs cool to the touch, lasts 10,000 - 20,000 hours, and cant be rolled with other tubes (yet?), removing the biggest fear of most users new to tube amps. No more kids / cats / nervosa excuses fellas.

My "How to write a audio review for dummies" manual insists that I start talking about the physical characteristics of the amp before I start on how it sounds, so here goes... Sangaku is much smaller and lighter than I anticipated. When it arrived on my doorstep I was pretty convinced it wasn't a top of the line amp, just too light and too small of a package. Well I was wrong, Sangku is in fact a thin and trim amp. I was already getting clues that I haven't experienced a tube amp like this before.

Three inputs on the back 1 bal xlr, and 2 rcas, with a rca pre amp out. On off switch is on the back, but on the front there is a power button that switches between ON and STBY for standby. Next three blue LEDs select the input. Lastly there is an output selector button, UNBAL LOW, UNBAL HI, BAL LOW, BAL HIGH, and PREAMP. No constant pre amp! As you can see in pic in previous post, each tube has 2 square while lights per tube that glow when powered on. High quality build, would expect no less from Apex.



HERE WE GO! GONNA PLUG A HEADPHONE IN I found myself tapping my toes, bobbing my head, getting lost in the music - Now that I got the big three audiophile cliches out of the way- ACTUAL IMPRESSIONS THAT MATTER - SOUND!

I started out listening to Sangaku with HD800 (sdr, cork, and sbaf rug liner - balanced, low gain). WOW. WOW Again. I'm getting a rush. This sounds like a tube amp!?! Not warm wet laid back BH Crack tube amp, and not dry etch of Schiit Valhalla2. This has great neutral sound, tiny bit of edge, but thing that popped out at me was the classic tube imaging and stage that only good tube amps can provide. Stage is forward, tall, and wide. Not unrealistic, not too in your face, feels natural. Serveral times I looked over my shoulder to pinpoint where the sound was coming from. This is good. I thought to myself this might just be HD800. Need to try something else. Natural choice? HD650.

HD650 (sbaf mods -bal, low gain) - Yuk. What happened? This doesn't sound right. Stage, imaging and tube characteristics are still there, but now i have bloated bass that bleeds into the mids. Boomy. Try 4 or 5 more tracks to confirm. Yup. I honestly haven't ever heard a tube amp that doesnt do well with hd650. Next...

HE560 (bal, high gain) - My other newer addition that helps me determine amp characteristics. These sound fan-f'ing-tastic. Best Ive heard these sound to be honest. Speed, clarity, warmth, tight bass. This little amp has power to push harder to drive planars, and push them really well. Well if it can power HE-560 it can power....

HE-6 (bal high gain)- Nope. Nope. Nope. Doesn't sound terrible, kinda sounds similar to how HE6 sounded on the Jot. Headphone can get loud, but it doesn't have the air it should, sounds slow and veiled. Bass is a bit muddied. Something that HE6 owners are familiar with...

Late addition - forgot I have HD580's. Much better. Cleaner bass / mids. Sounds pretty good, but not great. I think these sound better with Black Widow. I think HD600 will be similar case. Bloomy bass is gone, tightened up. Weird. I don't have a good explanation for any of this.

Ok, back to common characteristics. Sangaku has power, enough to drive he-560 well. Should cover most headphones out there. HD800 sounds great, but HD650 doesn't. Conclusion is Sangaku is a a bit of a warm tone that can affect warm cans. Not warm and lush, but slightly leans on warm side. Gungnir Multibit & HD650 was just too much. Again, pairs fantastically with HD800 and HE560, probably due to their dry or brighter nature. Amp is fast and clean, has an edge, but no fatigue. I listened to album after album for hours on hd800, which is not an easy thing to accomplish (as reference Elear's 10k spike killed me). The height and depth of the stage and precise imaging stole the show. I imagine this is what great tube amps have that SS can never replicate. Slightly mid forward, but not overly full, certainly not lean or dry.

There not much for cons, tubes are microphonic. I frequently swapped out cans, and the last click of the XLR pings the tubes just right and you get a bit of high pitch ringing for 4 seconds or so. Not a big deal, just strange and new. If this amp were lacking anything it would be sub-bass, would love a little more punch or thump on the low end. But I would say its full and tight throughout the bass range, just lacking a bit of subbass. I might also be coming from a amp with subtle subbass and its not a fair fight.

Apex has a winner on their hands. Thanks to Todd I can see this amp coming back to me in the near future.

 

Congrats! I also bought one, and I concur with your thoughts although I have been just way too lazy to can-roll. Plugged in my Code-X, and that was it, bliss.

These are tubey smooth; yet fast, clear and clean. I really like its presentation.

I sold my Black Widow after receiving the Sangaku.

 

That would be a good idea. This is an easy amp to send around- it almost looks transportable.
Pasting my other post from HF:

First of all, this is a very different amp from the Peak/Volcano. It really should be considered a successor in terms of price point only. It has more "single-ended triode" sound (mostly second harmonic distortion), for a more tubey presentation than his previous hybrids. This is a result of the way the Nutube's circuit was designed. Nonetheless, bear in mind that most of his tube amps do tend to have broadly similar sonics- in short, there is a "house sound", a certain harmonic mix that he shoots for. He typically does this by moving the operating point of the first tube stage. Some other differences between the Sangaku and the previous Apex hybrids: The new amp has much more output voltage driving capability than any of the previous hybrids; and also the lowest output impedance. Part of this is because of the Nutube- it only uses milliwatts of voltage. At the same time, the power supply voltage on the Sangaku is much higher (+/-18V, vs. 12V or 10V) to provide bigger output swing.

The output stage is also different from the Peak/Volcano. The Peak/Volcano had a discrete MOSFET buffer. In the Sangaku, however, Pete has moved back to using power opamps. According to him the Peak was more of an experiment to see how well he could do without an opamp, but he's since decided that power opamps are better. He knows that some will argue that this is a less 'pure' approach, but he's made his choice- they dissipate less power, are smaller, and simply just perform better. He's implemented these power opamps with CCS loads on them to keep them in class-A operation at low signals. Nonetheless, when driving lots of current, the output still goes into class AB operation. The CCS keeps more bias current flowing, which reduces any crossover distortion, an issue most problematic with small signals. This is what Tyll had said about this approach in the past:

"Class AB op-amps are configured such that the positive side of the amplifier amplifies the positive half of the signal, and the negative side of the amp the negative half of the signal. There is an area around zero where both halves, or neither half, is doing the amplification depending on how the amp is biased.

Using a constant current source/sink to draw current continuously out of an op-amp forces this "cross-over" region to become wider such that both sides of the amp are running for more of the time, or operating in class-A.

The current sink attaches directly to the output of the op-amp.

Read more at http://www.innerfidelity.com/content/butte-headphone-amplifier-apex-hi-fi"

Finally, the Sangaku is not DC coupled, but it's -3dB point is very low (single-digit Hz).

 

I recently got added to the loaner list, so I'll be able to share my impressions in a few weeks. I'll be evaluating with modded HD-650 and the Elear I have incoming and Chord Mojo as a DAC. I don't own any other amps currently to directly compare, but recently owned the Valhalla 2 and Torpedo III. And further back, Trafomatic Head 2, and modded Eddie Current Super 7.

 

I am fascinated by this Korg Nutube 6P1. I got out the tube game because these days most everyone uses mediocre tubes while paying an arm and a leg for them, a situation that grows worse with each passing year. (All this assumes that early 1950s through late 1960s Europe was the height of tube manufacturing - as was my experience with the Earmax Pro.) A new approach to making quality tubes is overdue. I hope that this it it - or at least a step in the right direction.

 

Maybe I'm a sentimentalist and a sucker for visuals.. but if I'm going to have a tube amp I think I'd prefer it to have tubes which I can actually see.

Sounds like a great amp though. And if it runs cool and doesn't eat tubes that's a huge plus, many people forget about that aspect when buying their first tube amp.