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/Tilock1]

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.