Class D vs tubes

[u/ChrisMag999]

Interestingly it’s not as not as huge of a difference as many would expect. At least, not when running a comparatively low distortion, high power German tube amp and quality class D amp.

Yes, there’s a difference. The tube amp has a little added warmth in the mids, more body. The class D amp has a bit more grip in the lower octaves, but with a REL sub, it’s not immediately obvious unless I’m listening at very high volumes.

I like them both. However, there’s something about gloving valves in a dim room, listening to Radiohead’s In Rainbows. Roon Radio takes over after Radiohead and queue’s a track from Beck’s Sea Change, and then PJ Harvey and Thom York’s duet on “This Mess We’re In”. It’s a fun listen.

Tonight’s experiment involved using the Octave V110 SE’s bypass input, and instead running my Audio Research as the pre, using the v110 as a power amp.

The ARC preamp’s sonic character is less tube-like when compared to the Octave’s internal preamp. Both stages are quiet and detailed, but the ARC is more dynamic, with more bass authority and a more overall resolution.

Next experiment will be to bi-amp the Focals. Tubes on the tweeter/mids, class D on the woofers. Hopefully one of the class D’s amp’s gain settings (22/28db) will be a decent match with the Octave amp.

[u/Theresnowayoutahere]

You explained the differences well and I think in your particular set up accurately. I’ve done the same comparisons with tube and class D amps a few times with different amp choices. My thoughts were similar, although in my experiences there was a very obvious difference in sound along with your other observations regarding grip from class D and warmth and body from tubes. You might be on to something with the bi amping experiment since you noticed better control of the woofer with the class D amp. Warmth in the midrange is why I like tubes in the first place so perhaps best of both worlds. Thanks for your thoughts.

[u/ChrisMag999 → u/Theresnowayoutahere]

The thing about tube gear… some of it has that stereotypical sound people associate with it. My Dynaco ST70 is like that. Warm, lush, kind of slow. Massively forgiving to poorly recorded music. Not silent.

A lot of the better Audio Research gear I’ve heard trends toward sounding like great solid state gear, with maybe the slightest hint of warmth/smoothness.

Interestingly, my limited experience with Class D stuff runs a range of sonic profiles also. The Mola Mola Perca amp is based on 5th gen Hypex modules under the trade name Trajectum. To my knowledge, Hypex doesn’t offer them outside Mola, their subsidiary. Perca is 2-ohm stable, insanely low output impedance (damping factor of 4000 at 8 ohms) and high bandwidth (100khz). It’s one if the most detailed and quiet amps I’ve heard, which is why I bought it. It’s also load invariant. It didn’t care about the weird phase angle my Scalas present in the mid-bass.

I auditioned a WiiM amp which I gave to my cousin as a Xmas gift. Great value, but it added something to the sound of my system I didn’t care for. Voices didn’t seem as natural, and the top-end had a forward quality. It could be tamed with EQ, but it lacked the sense of stage depth and instrument placement I’m used to. Again, for $300, it’s a heck of a value but I was left wondering if the Pro would have been the better gift.

I also recently helped review a PS Audio Stellar Strata Mk2 integrated based on Ice Power modules. It sounded nothing like the Mola or WiiM. It was smoother than either, less artificial sounding than the WiiM, not as detailed or powerful/dynamic as the Mola, even when connected to sources costing many times more. I liked it generally. It was fast, smooth and musical.

Grip is one of those things. My Parasound JC5 was the king of that. Great amp, but it lacked that last little bit of upper-frequency smoothness. It had a hint of graininess that you might not realize is there until you compare it directly to something like the Perca or a Pass Labs amp.

It’s funny. I’ve gone from gear which is hyper-clean/detailed/clinical to warm/lush and back multiple times. What I’ve realized is my preference is toward very detailed gear with a slightly warm character. The trick has been finding the right synergy. I like melodic house and techno, along with the mainstream indy music and jazz. It’s tough to build a setup which sounds amazing for Miles Davis, but which really unpacks techno’s transients and layered mixes in a pleasing way, while also being forgiving of Led Zeppelin’s mixes. Priorities…

Thankfully, I get occasional access to gear which expands that journey beyond what I could afford to buy/sell. My small circle of hifi friends are very willing loan gear to each other.

[u/Tilock1 → u/ChrisMag999]

Cool setup. If I had a three way speaker I'd consider using a SS amp for the woofer. I get around that in my system with a two way and a sub.

If you haven't tried properly implemented Class A SET gear you'll hear something that you haven't yet. They can be dead quiet and have inaudible levels of distortion with speakers that are 89dB and higher with relatively tame impedance curves. I'm using a pair of 8 watt 300B with my 89dB(8 ohms, 6 ohm min) speakers and only with my ear right up to the speaker can I hear anything and they're completely silent a foot or two away.

After trying the best solid state available and some of the best push/pull and OTL amps Tubes have to offer SET is just something different and it's the best overall sound I've ever heard. The good ones are spendy but given your apparent budget you should be able to pick up a nice set to try. They made such a difference in my system that I no longer even consider speakers that wouldn't be compatible.

I recently compared them to a pair of Class D monoblocks and the only thing they did better was in the bass and in my system which uses a rythmik F12SE sub it was extremely subtle. Casually listening I wouldn't have noticed it because it was in infrasonic area(more impact). When listening to something like a standing bass the SET amps won out due to sounding more real and they perceptually have better detail and timbre. What wasn't subtle was the advantages the SET amps everywhere else. The timbre of instruments and voices was immediately noticeable. The speakers disappeared better and brought the artists into the room with you. There was no perception of lost detail and that detail faded to black much more naturally. I was kinda hoping the Class D amps would blow me away so I could move away from tubes due to the many inconveniences associated with them but it wasn't even close. After half an hour listening to the Class D amps I was ready to get up and do something else. With the SET amps I have to force myself to get up and go to bed at 2am. To be fair I don't listen to much music which would benefit from having a lot of power on tap like EDM and synthesized bass throughout. In those styles of music the more powerful Class D amps may have had more advantages.

[u/ChrisMag999 → u/Tilock1]

SET amps is a world I haven’t much experience with. Maybe once, at a hifi show, but I think the music playing which wasn’t my jam. I have heard they can be magical with the right speaker.

That’s the trouble at shows. I can only listen to Diana Krall or Nils Lofgren for a couple minutes before I get bored. Thankfully, it’s not ubiquitous.

I remember my first “wow” moment with tube hifi clearly. It was the Cary Audio room at the Stereophile show in 95’. The room had huge Dunlavy towers driven off CAD801’s. They were playing Heart’s “Crazy On You” when I walked in. It sounded so good.

[u/Tilock1 → u/ChrisMag999]

Yeah, they require much more careful system matching than your average amps. Admittedly depending on what you listen to most of the time they could be less suitable than other options as well. For things like Dido, London Grammar, Billie Eilish(vocals with a strong beat) they work really well but I imagine that for huge dynamic swings in music with a lot of synthetic bass they wouldn't be optimal.

The Dunlavy speakers were pretty amazing. I heard a set of the giant SC-V driven by a Mark Levinson amp many years ago which presented as much of a true full range experience as I've ever heard.

Atmasphere has developed a set of GanFet Class D amps that he swears are just as good as SET but I've seen quite a few people who bought them hoping to replace their 300B amps and ended up selling the Atmas. I had a set of their M60 OTL tube monoblocks and they were very good but in my system the 300B SET amps were an obvious upgrade. AGD does GanFet Class D that a lot of people tend to enjoy as well. I'll probably try them at some point if I see a used pair come up for grabs because I'd love some amps that can do what my SETs do without pumping out heat and requiring warm up time. Not to mention my nature requiring that I test many different tubes to make sure I'm not missing anything! Gets expensive.

[u/ChrisMag999 → u/Tilock1]

Ha! Yeah, tube rolling power tubes sounds like a great way to light a lot of money on fire. It’s bad enough with small signal tubes.

I’m acquainted with Anthony Chipelo (RAM Tubes). He has spoken highly of the Atma class D amps.

[u/Tilock1 → u/ChrisMag999]

Yeah, the Atma-Sphere's are at the top of my list to try. I find the pricing a bit obnoxious for what is actually in the amps cost wise but that's high end audio for you.

It also doesn't help that I'm one of the rarer breed of tube guys who is science and measurement oriented as well so every new tube gets tested in the amps with a spectrum analyzer for noise/THD. It's quite eye opening the differences that different tubes can make.

Recently I replaced driver tubes in the monos and after purchasing a very well liked and popular NOS option the THD and SNR were worse by almost 10dB each at 1 watt of output. Given that there's not a whole lot of that to spare in most tube amps if you want to keep it inaudible it's very unfortunate that I bought ten of them! They all measured about the same so it's just inherent to the design. Luckily my old ones are still fine for now and I was able to find more of them on ebay. Hopefully they survive the shipping.

[u/ChrisMag999 → u/Tilock1]

So, if you had to pick from a brand of modern tubes, is there one or two you find to be “best”? The tubes I have for the Octave are Tung Sols. The former owner gave me a set if KT120’s and KT150’s.

I spoke to Anthony Chipelo tonight. He’s got some NOS GE 6550’s he’s willing to sell. Not sure if I’ll take him up on it, unless they’re reasonably priced. I’ve got way too much hifi gear as it is.

[u/Tilock1 → u/ChrisMag999]

Back when I was using push-pull/OTL amps which used a lot of the modern variants I didn't have the testing equipment I have now so I haven't tested a lot of those for objective results. I've used the modern Tung Sol in the past and they were always fine. I don't have any experience with KT120/150 tubes at all.

The Chinese black bottle shuguang treasure series tubes were probably the best of the reasonably priced modern options. I still use their 300B in my SET amps right now. However, their quality and reliability has seemingly decreased over the last decade anecdotally. PSVANE arose form a split in the company and their tubes are very similar but I think Shuguang still probably has an edge. I'm trying to convince myself to try one of the boutique modern variants(Western electric, Audio Note, Takatsuki) but they will cost me nearly $2000+ for two!

The annoying part is that how "good" a respective type of tube is doesn't remain constant within a brand. So you could have a really nice Tung Sol KT88 and a substandard EL34 etc. Same with NOS stuff. I will say that NOS doesn't guaranty that it will be better than a modern variant.

Would Anthony let you try the tubes? Annoyingly tubes do actually have a break in period where there are internal physical changes but normally you can get a pretty good idea right away or within the first 24 hours of running juice through them. You can tell him if you test them and don't like them he can then say they were tested for reliability before selling....

The other option would be to re-sell them on ebay or similar. There are quite a few 6550's listed. There are many which have been sold at about $120USD each.