A quad of NOS RFT EL-34's installed in PrimaLuna Four.

My amp blew the autobias plate fuse recently, likely due a tube or two going bad. As a replacement, I bought a quad of NOS RFT EL-34's from Germany. Everything is now sorted out, fuse replaced, new tubes installed, so the amp was fired up without problems, and is working fine now. There was an issue with an "upgraded' power cord too, it made the amp sound lifeless, but that's been sorted now as well. So, here are my initial impressions of the amp with the new tubes and no power cord issues:

A) Having installed these tubes, I now understand the lore about tubes needing warm-up time - this is no joke for older tubes. These RFT's need a good hour to start sounding good, and sound their best after about two hours. Upon powering on, if you play it right away, which I did two days in a row, the amp sounds as exciting as cardboard: lifeless, no dynamics, no bass, the sound is recessed and somewhat veiled.

B) With the RFT's in, the amp seems to have lost some gain: I find myself having to turn the volume up anywhere from 4 to 8 dB higher from what I used to with the stock PL tubes, just to get to my normal listening levels: 73-77 dB average, 80-84 dB peaks. After about and hour of listening, the gain gradually returns, and I can lower the volume by about 3 dB. But still, the preamp now has to be at a higher level than it used to: 18-21 on the dial for tuner, as opposed to 14-17 before tube swap, and 25-30 for the DD TT, where it used to be at 21-24;

C) Soundstage width is pretty much unchanged, but the depth is diminished. My listening distance is about 10 feet, I'm on a bed facing the system, my head on the pillow. With the stock tubes, the soundstage felt to extend to about the edge of the bed facing the system, so if I sat on the edge, I felt immersed in it. Now the soundstage is shallower - the music is dead center, so stereo blending is good, but it feels like the music is still out there, like coming from a flat screen. Not that it is flat and 2D, but instead of a fat round bubble of sound, it's more like a flattended oval/elliptical bubble. My jargon may suck, but it's the best I can describe it;

D) Detail is improved - the sound is more defined and subtle, sort of like my SET amp, but it comes at the expense of dynamics/grunt/slam. With the stock PL tubes, the amp was +/- universal, suitable foo any kind of music. With these tubes still needing break-in, it feels the amp is now more suitable for acoustic music, rather than dymanic. Mind you - it's only dynamic music so far that I played on that DD TT: a Belgian band from the 70's called COS, playing a wonderfully psychodelic hybrid of rock and jazz (it may ring a bell for @bever70), mostly with electric instruments. Suffice it to say - I like that band through an SS amp better. at least for now. I have yet to actuallyplay acoustic jazz on the belt-drive table through the amp, but the jazz station of the tuner sounds more natural than COS sounded on the turntable, both through the same amp. COS is capable of sounding super-dynamic, it's basically jazz-rock, but here it sounded very "polite" so to speak, so as not to disturb the neighbors. I know how it sounds in my other system with the SS Parasound, so here I wasn't impressed.

E) Bass is diminished: well-defined, but too "polite", no bite to it.

All in all, it sounds different. Not bad, but not an improvement from stock tubes, either. More of a side-step, a change in overall sound signature. I seem to like the old sound better. This sound is un-involving for now, doesn't make me tap my foot to the music.

I do realize the tubes need break-in, and if I'm to judge by the change that happens after good warm-up, I hope similar overall "blooming" will happen when the tubes are finally broken in. If that doesn't happen, I may install the other SS amp into that system for more dynamic music, the way I have in my main system, as my preamp has two outputs. To see if that would be beneficial, I need to play some acoustic vinyl through it to see how I like that. Will do that tonight and report.

 

Never heard of COS before, but I looked them up and the music looks interesting (I read some of their albums resemble Caravan a bit?) so I definitely will check them out on spotify one of these days .

 

Never heard of Caravan. will check them out!

Actually, I do own a CD by Caravan, but it's an outfit that plays Jazz Manouche, a-la Django Reinhardt. Your Caravan must be something older. Do you have any links where I can check them out? Amazon or YouTube.

 

It's very amp dependent I think. When I ran an Audio Space Galaxy 34, I had RFT's and they sounded better than the stock EL34 tubes - would not be surprising if these are the same as the stock tubes in Primaluna amps, but I'm just speculating there. In that amp, the RFT was a worthwhile upgrade. But in a Cayin CS-55A, I preferred the stock KT88 tubes to the RFT's. I suspect that's an amp where KT88 tubes will generally sound superior. Probably can't make that statement too strongly though, as it also surely depends what the amp is connected to.

 

You mean the speakers? PSB Image T-45's. Same as before the tube change.

 

No, I just mean with my comment that in the Cayin, KT88 tubes are likely to always sound superior. Maybe, or maybe RFT EL34's would sound better than the KT88 tubes if connected to different speakers.

On that same note, maybe with your PL amp, the RFT's would sound superior if you had different speakers.

 

This kind of thinking only widens/deepens the rabbit hole - soon it will fit an elephant. - I gotta buy new speakers to make the new tubes sound better?!

 

Interesting your findings. I've been running NOS RFTs for a while, first in a PL Four, then a Five, and now a Dialogue Premium HP (eight of them!). In all cases the tubes performed noticeably better than the stock EL34s in pretty much every way, particularly in the bass. Some might say the RFTs are less dynamic, but after prolonged listening I think that is because of two things. First, they are less compressed than the stock tubes--that is, a wider bandwidth and breadth of tone. Second, they are smoother on the top end, but not at the expense of detail. Who did you get your tubes from?

JohnK

 

A reputable eBay seller in Germany, with 100% positive feedback.

 

Probably the same guy I use.

 

When you say they were better across the board, was it out of the box, or after a period of break-in? How long was that period, if so?

 

audiotubes_de.

 

I hit submit before I identified. I source from euroklang.

JohnK

 

RFT power tubes or RFT 6SN7 may be good, even outstanding,but I find their ECC83/12AX7 and ECC82/12AU7 to be weird sounding, too much treble shy for my taste among other things.

 

I liked the sound of the stock tubes. Besides, these tubes may sound better after break-in, I hope. If they don't - they should be easy enough to sell, and then I'll just get more PL tubes, or maybe try Gold Lion KT-77's.

On top of that, it is my understanding that KT-88's can also be used - that's another possibility.

 

Stock PrimaLuna, no mysteries, it's in the OP.

 

I've owned an RFT 12ax7 tube very briefly. It sounded really dark and closed in, the bass was really good though. I traded it with a Mullard 12ax7 which I liked much better. I hope they improve with more burn-in time.

 

It's the whole synergy thing. You basically now have an amp that sounds different. Different sounding amps may each sound their best with different speakers.

I guess you can buy new speakers, with no guarantee that you will think the tubes sound better. Or just stick to the stock tubes, if you truly love the sound. Personally, I don't think I would buy new speakers just to try to get the most from one set of tubes.

Oh, and I think what Steve was asking is, what tubes does Primaluna include with their amps? I know they are Chinese, not certain from which company though. PL gets them from somewhere and has the PL logo slapped on them.

I think Kevin Deal likes new issue Mullards with PL amps.

 

I don't know who makes the tubes for PL. As to using them again - I realize that now, but thought tube-rolling was a big part of this hobby.

 

benzion, the small signal tubes you also changed would be affecting the sound significantly.

 

Good point, will try to swap the older tubes back and see what happens.

 

Word on the internet is that Primaluna tubes are made by Shuguang.
I like Shuguang EL34s more than any other new tube and I have tried Tung Sol, Golden Lion KT77, and Mullard reissue.
Shuguang have a very nice sweet midrange and they sound great for jazz and small scale classical.
They can not compare though with the best nos.