ampsandsound Arch Power Amps (Part 2)

 

Part-Time Audio

Images & Words By Graig Neville

Perfection. Such an elusive concept, but perhaps rightly applied to the flagship ampsandsound Arch monoblocks. Sam Rosen did a thorough dive into the ampsandsound Arch monoblocks here. But Justin Weber asked me if I wanted to do a follow-up/second opinion. An opportunity to listen to the $38k ampsandsound top-of-the-line monoblocks? Yes, please!

 

Defining perfection can be impossible, outside of the trite “ya know it when ya see it” response. The Arch is a force to be appreciated and marveled at, but first, we need historical context. In the late 1950s, Harmon Kardon gave Chief Engineer Stu Hegeman and his team a mission: create the best-sounding electronics possible. Hence, the Citation project was born, a no-holds-barred, open-ended blank check to make the best gear that could be made. Stu Hegeman and his team released several Citation products over the years. Many are still sought after today, and there is a substantial support community with DIY upgrades, restoration projects, and system tweaks.

 

This led to the Citation I and Citation II. The Citation I was a preamp, while the Citation II was a KT88-based push-pull amplifier that redefined what a tube amp could be – wide-bandwidth, linear, stable into difficult loads, and all with 0.5% or less distortion, a crazy low number at that time. Putting out 60 watts into 8Ω (and 120 watts if ran as monoblocks), the Citation II was an amazing amplifier for its day. With 30dB of negative feedback to help stabilize the circuit, it was a beast and could drive just about any speaker on the market. It was difficult to bias and it ran hot, cooking tubes frequently.

 

Fast forward to Justin Weber, the owner and brain trust to ampsandsound. I had the opportunity to visit Justin at his home in California and had time to ask questions while listening to the Arches.

 

PTA: Where do you get your inspiration to build your amps?

Justin: I don’t think anything over 60 watts makes any sense for the kind of audiophile I am. The moment you need more power you are going after a drier sound. I’m ok with warts or failings as long as it’s honest. I couldn’t afford expensive equipment. I grew up with a wonderful room and pretty good speaker and terrible electronics. I had a set of AR-3s … that sat on end tables … with a Yahama or Pioneer integrated. I grew up listening to R&B, Abba, and classical. I often went to the Wilshire Elbel Theater for concerts. There was a man like a godfather to me that had a set of Maggies he got from Shelly’s. I remember going into Shelly’s and listening to Maggies and I couldn’t afford that sound, but I wanted that sound. I bought a set of MMGs when I started working and built a Dynaco MkIII. I had been building Dynaco clones. Maggies and tube electronics is a failed enterprise. In hi-fi as a young professional, the market was one you’re barely able to participate in unless you row your own boat. I got into building single-driver speakers, full-range drivers and single-ended amps. Then I got turned onto horns for scale. Horns and tubes also had speed.

PTA: How did this turn into ampsandsound?

Justin: I used to buy lots of drivers and horns and building filter networks and Dynaco amps. My spirit animal is the Dynaco ST35. I started working with my current technician and started making small changes to parts to see what changes made an improvement. The very best circuits are already designed, except for the power supplies. The RCA handbook has everything already done. I’m not an electrical engineer, but I’m willing to try the execution and do the math calculations and go through the trial and error to find what works and sounds best.

My experience with transformers were folks were buying the cheapest and least powerful, which had limitations. I asked politely and nicely and these manufacturers would wind custom transformers for me.

Why do I make an Arch if I like single-ended amps? Single-ended amps give you everything you ever wanted, but not enough of it. To not cheat physics you need a large cabinet or listen at low volumes. Where my other designs are thick and rounded in their tonal weight the Zion and Arches are fast and accurate. They are meant to be total demonstration of our capacity as a company that we are capable doing different and single-ended choices are not for everybody.

 

PTA: What attracted you to the Citation II and V designs?

 

Justin: Turrets. Ampsandsound wires their boards with a two pin configuration similar to ham radios. One set of pins holds the part in place and the second set of pins holds the wire in place.

 

PTA: So that reduces noise and vibration?

 

Justin: Ding, ding, ding! The Citation II and Citation V have things that you can copy. The reason we went with HK is you can basically take off the shelf transformers and put them in HK circuits. The magic is in the circuit. If you are going with something that you can copy or duplicate in a modern production the Harmon Kardon was the easiest to duplicate.

PTA: What are you doing differently than what Harmon did back in the day?

Justin: Some and none. Harmon didn’t have access to the same high-tolerance components that we do. Some of what makes ampandsounds special is we don’t change the circuits from long ago but we bring in modern material science. In the 1960s for example resistors had 10% tolerance while modern tolerance is 0.5%. This makes it so we can avoid servos and other nannies to fix problems they had back then.

I broke the Citation II and V (Zion) apart. The old design just got too hot, so I broke it into two chassis’ and made a much thicker chassis that can handle heat soak. The Arch is basically the same amp as a monoblock, with a more robust power transformer, oversized output transformer of the same impedance and higher tolerance components in the circuit. The Arches we did one or two things differently, we changed the ability to dial the bias, we have significantly more bias voltage than the Citation II. We additionally changed the operating points to not sacrifice tubes. We are running at about 70% plate dissipation since we are not trying to kill tubes. There is also lower distortion than a Citation II.

I love the Arches as they are a neutral tool.

 

PTA: There’s a lot of DIY kits, upgrade information, and restorations out there. What did you do differently with the Arch to make it better than all those other options?

 

Justin: Though the Arch is based on the Citation II circuit we’ve made many design changes to increase reliability and usability. The Citation II is a very different amp is many respects. Regarding DIY choices or upgrades, we sell a finished product that has been thoroughly vetted for performance and reliability and our workmanship is bar none. The McShane upgrades are a great choice if you have an original Citation II you want to keep running and improve upon but the upgrades are wedded to the Cit chassis and transformers. The Arches are a clean slate idea and as such we were able to take into consideration significant limitations of the original.

 

PTA: The Citation II could run 120W as a mono. Any thoughts on making a 120W version?

 

Justin: The Arch is cable of more power when paired with KT120, KT150s or KT170s. The headroom differences this would provided for in practical terms is insignificant. The Arch is designed to run KT120/150s via bias fixed bias selection at the rear of the amp. KT150s continue to be difficult to source reliably where their test results do not appear to indicate grey market tubes. I find the KT88s more holographic and the KT120s/KT150s more linear. I have yet to try a set of the KT170s though I have a validated pair. Power ranges from 85watts to 105watts have been recorded with KT88s through KT120s. The Arch as an amplifier choice feels more about choosing an analog amp that has vanishingly low distortion, not huge power per se. With KT170s, the Arch is capable of 120+ watts and will do so without cooking tubes. The original Citation II was famous for its sacrificing nature toward tubes. We realize predictable power, low distortion and do so without killing the tubes or the amp.

 

PTA: 30db of feedback seems like a lot. It makes the amplifier super low in distortion and linear, but what are the detriments of that much feedback and did you do anything to address that? Is so, what? 

 

Justin: The Citation design uses lots of feedback but has huge amounts of gain via its multi-pentode front end. I don’t see many downsides to this approach. It’s difficult to make adjustments to it without new compromises being found and agreed on. The Arch utilizes the same front end and feedback but runs the output tubes less strenuously. Though I would generally describe myself a single-ended fan first and foremost, I find the true-to-source nature very compelling and more honest than using voltage regulators or JFETs to obtain such low distortion.

 

 

 

PTA: Do you feel there is an optimum efficiency range for speakers paired with the Arch? Is there a lowest impedance that they don’t really like. For example, certain Wilson’s are known to have impedance as low as 1ohm. Would the Arch be able to handle that?

 

Justin: I don’t see significant issues with low-impedance loads as long as they are truly dynamic and not fixed. The Arch is not a wise choice to any planer but complex crossovers and difficult loads have not compressed the amp in our testing.

PTA: Biasing the Citation II was a process to say the least. How stable is the bias of the Arch and is that something customers will need to tackle at some point?

Justin: The Bias of the arch is fixed… i.e. it’s selectable between settings, but the dialing in of the distortion is a total pain in the ass and could not be simplified further… we tried a lot. That being said, the AC and DC Balance is best served with a oscilloscope, a distortion analyzer or sending it back to us for service. Given the extreme performance of the amps, we have seen about 50% of our customers getting the distortion analyzer which makes quick work of it or a desire to send it to us once every 2 years or so.  The Analyzer is ~$900 purcharce, but given the investment in these amps and their long-term nature, it’s a wise choice. 

 

PTA:  I know you have super secret transformers, were there any other major upgrades you put into the Arch that deviate from the original Citation II? Did you make any circuit modifications?

 

Justin: The transformers have some significant differences in the both the power and output…allowing for greater tube choices with reduced stress on the tubes and increased bandwidth which was already a strong suit of the amps. 

Circuit-wise, operating point changes were made in addition to general clean-up and massaging to shape performance to being more consistent with ampsandsound’s house sound/behavior. 

 

PTA: Back when the Citation II was sold it was $240, which in today’s money is $2600. Not only is this kinda crazy to think about as the cost of tubes has increased dramatically compared to inflation, but what else has led to the price increases? In short, what do you get at $38k in the Arch that you can’t get in a refurbished Citation II today?

 

Justin: ampsandsound had tried for 3 years to get productive dealers for its 2 channel portfolio without success. Our prices were designed to account for dealer margins. We have moved away from this strategy and squarely focused our engagements and pricing at a direct-to-consumer model. [The Arch used to retail for $50,000 MSRP]

That being said, these are very expensive amps that are hugely labor-intensive to build. Currently, there is no other company attempting to build anything similar in both circuit or build style. As we are a very limited production company, we can not find value in out pricing per se, we attempt to show our value in our craftsmanship/build quality, parts selection, style, and performance. I do feel confident that the Arch is designed in such a manner that it has the ability to be at least as reliable as the Citation has been.

 

Inside the Arch Monoblocks

So, now that you know a bit more about Justin and his design philosophy, how did ampsandsound make it perfect?

 

First off, the fit and finish are robust. Thick chassis work, powder coating, and the connections and plugs are all top-notch and excellent in their execution. The Arch accepts both single-ended and balanced connections. It does have speaker taps for 4, 8, and 16Ω, a switch to select bias for KT-88 or KT-150, and a power outlet. The front has an on/off switch. The tube area has ports for bias access and adjustments for the KT-88 and the 12BY7 tubes. Overall, the design is well laid out and traditional-looking for a tube amplifier. The Arch is heavy at nearly 100 lbs each, as there’s a lot of iron in both the transformers and the chassis work.

 

I had the Arches in the system through several other reviews and had the opportunity to use it on a variety of gear. This included my Rega P3 with several different cartridges, the Michell Gyro SE turntable, LampizatOr Golden Tube Atlantic TRP DAC, a tube TotalDAC, Backert Rhumba Extreme 1.4 preamp, Parasound jc3 jr phono, Triangle Quatuor and Treehaus National Treasure speakers, and a variety of cables and accessories including AudioQuest Black Beauty and Pegasus single-ended cables, and a DS Audio Ion-001.

 

Arches came in as the TAD C1000 preamp and associated TAD equipment were going out. I think it makes some sense to discuss how these products are both similar and dramatically different. Folks talk about how tubes try to sound like solid-state and solid-state tries to sound like tubes. I think this is a mistake; the goal is true sound. The Arch is clean, powerful, and has many characteristics of very good solid-state amp. There is no stereotypical tube warmth, gooeyness, or rolled-off bass or treble. The TAD approach was similarly neutral in many ways, albeit with a lightning quickness that the Arch did not have.

In my system, I did have a hint of tube noise in one channel when no music was playing. I haven’t noticed this at other venues when I heard the Arch, and it wasn’t evident when music was playing, so I’m guessing that this was specific to my set of tubes.

 

ampsandsound Arch Sound

Once the volume was turned up a bit the Arch had great bass with weight and authority and perhaps a hint of bloom and body. Imaging was holographic with rock-solid and pinpoint instrument placements and a huge room-filling soundstage. The sound was definitely not your father’s “warm and tubey sound”, but it wasn’t dry either, it was very clean … dare I say it … perfect.

 

What the Arches are capable of is so good that I’m not sure the rest of my system could keep up. With the TAD gear, I felt the system was elevated to the peak of what it was capable of and that perhaps a more heavily damped speaker would perform better. But with the Arches, I kept getting the impression that there was more to unlock in the amp than my system could resolve. It didn’t matter much which gear I used, the Arch played well with it and sounded great on all the genres of music I threw at it. It wasn’t so much that any flaws were evident in the associated gear. It felt more that there was hidden treasure that was waiting to be discovered – I just didn’t have the right key.

 

As you’d expect, the bass isn’t as tight as the best solid-state. I blame the low damping factor. But that said, the bass has this weight and presence, or almost bloom, to it, that was so very appealing on so many genres of music. And that was, in part, because the Arch is extremely linear. There is no roll-off on the treble, and (aside from the bloom I mentioned) the bass extends deep and linearly.

 

The word that keeps coming to mind is clean, almost squeakily so, but still has many stereotypical tube qualities. Holographic imaging in spades. Weight and body. A heft to the music. Pace and rhythm and timing. Maybe not as lightning-fast as say the TAD electronics I had in the house earlier this year, but I’ve never heard anything that fast before or since.

 

Is the Arch perhaps one of the best tube amps I’ve heard? Yes? No? As an amplifier, I found no faults. It did everything asked of it. However, I’m pretty sure that tube diehards, like those 300B lovers I work with (I’m looking at you, Brian, Marc, and Scot), I’m not sure this amp is “the one” for you. The push-pull configuration doesn’t give you a dripping midrange that oozes vibe. Look to the Bryce, Black Pearl, or Red October if you want vibe. The Arch is a different amp for a different application. If you want to avoid colorations, no matter how pleasant or desirable, then the Arch is what you want.

 

Switching to vinyl was transformative. There was a sweetness on delicate passages that I hadn’t noticed with digital. Instruments had a weight and timbre more akin to real instruments. But perhaps most importantly there was an emotional connection with the music that I was missing with the digital portion of my review. Decay became more natural and the effect was especially pronounced on piano keystrokes.

I’ve heard the Arches drive open baffle and box speakers superbly. At shows, I’ve heard them on more traditional speakers with horn midranges and a big bass driver and they have been fantastic as well. Being able to tame some of the bass of a large driver while avoiding the honkinesss that some horns can exhibit is a trick most amplifiers can’t do – I’ve heard the Arches do that. Music extended beyond the speaker limits, with music just emerging and hanging in space. I felt the Arches can help your system transcend the gear and just get into the purity of the music.

 

No matter how complex or layered the music got the Arch navigated it all effortlessly, never collapsing into a mush or indistinct wall of sound.

 

 

 

Conclusions

Are there bigger more powerful tube amps on the market? Sure, but I bet you can’t beat the linearity, neutrality, and cleanliness of the Arch – perhaps at any price. At $38k/pair it’s a phenomenal deal.

 

The Arch is an amp that won’t pull punches, so electronics pairing can be important. It’s powerful enough to run somewhat inefficient speakers, but be careful with very high-efficiency horns and the like as the Arches are super clean and a powerful amp. They sound wonderful with ampsandsounds speakers, but I’ve heard them with other brands, like Acora and it was clean with clean, which was perhaps too much ‘clean’, even for my taste.

And this gets back to perfection. The Arch is an exercise in minutiae with meticulous attention to every detail. There is no doubt the Arch is an amazing implementation of the Citation II circuit. Maybe even perfect. With distortion measurements that would put most solid-state amplifiers to shame (0.051% at full power), the Arch is powerful, linear, and clean, and will drive a variety of speakers with authority. If you are looking for something vintage, but modern sounding, heirloom quality with traditional looks, and amongst the best amplification to be found on the market, then definitely check out the ampsandsound Arch monoblocks. It might just be the perfect amp for you.

 

https://pt.audio/2024/10/25/ampsandsound-arch-power-amplifiers-part-2-review/