My 1st rolling round:
Well after getting a feel for my amp I decided to do a little tube rolling. At the moment I’m pretty limited with only 3 sets of tubes, and only one NOS set. However, it’s already evident that this amp really lets the tubes qualities show through, which is to be expected with the OTL and SET design.
+ EH 12ax7
Electro-Harmonix new issue 12ax7
No pic here because I traded them to my uncle for use in his Orange amp.
They EHs had a pretty nice sound. The frequency range was really wide and they threw a nice head stage. Over all they were pretty warm sound but still kept the highs intact. One thing that Fitz noticed and I later did was that on some complex passages the EHs would sound really strained like they were having a hard time keeping all the sound together, when played at very high volumes.
Not much to write here since they are what the other tubes are compared against, so I’ll go on.
JJ electronics ECC83s
These tubes are mainly used as a guitar amp tube but I had read some on AA about them so I figured it was worth the trade for the EH’s since I was getting some NOS tubes soon either way.
Over all these tubes are REALLY warm and dark. Originally after hearing them I though that the sound I was getting was a lot less detailed, however after listening to some of my reference tracks I noticed parts I hadn’t before, what’s going on with that? After some sine sweeps it was actually a lack of highs that made the sound seem less detailed, not less actual detail.
They are a VERY detailed tube, however the frequency range gives a really fluid mid that is intoxicating, but the lack of highs prob puts them below the EHs in the big scheme of things. Paired with a can like the SA5000 or something I could see where they would be nice. But with the already rolled off top of my 501s it was way too much.
1960’s NOS RCA 12ax7
These tubes really are nice. I see why people go for NOS tubes. The dynamics are amazing compared to the others. On the hit of a bongo or the strum of a guitar string you really get a since of how the sound is made, not just a mono tone sound, but a really complex sound. The highs are a little much after listening to the JJs for a week or two, but its like hearing part of the music that was missing before.
The bass is noticeably tighter with them especially over the JJs. The JJs had the habit of making some bass just into a soup of low frequency sound. The bass is tight and also dynamic so bass guitar has an extremely appealing sound.
The mids on the RCAs aren’t as forward as with the JJs, however the response is a lot smoother. The JJs basically are good for acoustic and some just vocal oriented stuff, but that’s about it with my system synergy.
Note that there was no over driving problems with either the JJs or the RCAs.
My second round:
Thanks to the generosity of Steve, Ironbut, I was able to try out a wide variety of diff tubes, some of which are the best around. The list is as follows: Mazda Grey plates, Mullard 4004 box plates, Raytheon 5751 black plates, and what I believe are some new issue Sovteks. I also got some old stock Sylvanias that are included in the following write up.
WARNING: Obliviously I have
way too much time on my hands… and all opinions are based off of my amp and the AKG K501s, which are a real different HP, so what works for me could be completely wrong for another.
Sylvania 12ax7s’
These were gotten on a steal, if you ask me, at $20 for the matched pair shipped, and I am very happy with them. The bass is very neutral in terms of frequency response in these tubes. However, one of their main qualities is highlighting the dynamics of the K501s. I am really floored by the bass attack. I’m not claiming that these tubes turn the K501s into bass monsters, however they really do give a kick to the mid bass I guess you would say. Mids are smooth and clean with a bit of a swing, if that makes any since. The highs are slightly bright compared to neutral, however this helps give the K501s a little bit of lacking sparkle. Over all my fav tube, especially for the money.
Mazda grey plates
These were in a lot of ways the best tubes in the test. They just seem so clean and separated. The sound stage isn’t exactly giant, actually slightly pulled on over the Sylvanias, but the placement and separation is just amazing. I really love these tubes and I have to get a pair, although lacking some punch for rock they really are amazingly smooth for vocal stuff and any acoustic.
Raytheon black plate 5751s’
The bass is nice and bouncy if that makes any since, not a lot of impact, but its quick. A lot of fluid mids, but almost too pronounced when paired with the K501s. The highs were nice, but not above and beyond any other. I could see these tubes really being nice with a pair of cans that lack midrange magic. They were nice, but almost too much of a good thing.
Mullard 4004 box plates
By far the most expensive tubes of the bunch I was slightly let down with them. The bass is nice, and the mids are fantastic, but the highs seem to be lacking. With hind sight in mind I expect that it is the most neutral of the bunch, but when paired with the K501s lack of highs it really kills something. When listening to these for an hour or so I really got into them, but when switching to the Sylvanias, the tubes I’m most familular with, I was gracious for the mid bass kick. Probably in the big picture the Sylvanias just have a brawlin attitude, but it brings out the dynamics a lot.
Sovtek 12ax7s’
These didn’t really get much of a listen as they are by far the dog of the pack. They are decent and pretty balanced, but to my ear they didn’t have much going for them. Deff a much better tube than the JJs that I review before, probably on par with the EHs, but it’s hard to know since I don’t have those to directly compare.
