I suggest you email Kevin Deal at Upscale Audio, I recently bought 3 different platinum pairs of 12AU7's for my Unico (I got the Mullards, the Radiotechniques, and the Siemens; I have yet to try them yet, I need to get speakers first to pair with the amp...) and he was very helpful in selecting them. Guessing from what he told me, you would like either the Mullards or the Siemens, but I would email him with what you're looking for and he'll point you in the right direction.
Thanks. I have the Siemens from Upscale Audio, and they're not working out. That was the original problem. When I talked to Kevin, he said either the Mullards or the Radiotechniques would be good, but I don't want to choose randomly, and I'd really rather not throw down the capital for both.
What speakers are you thinking about? It really is a great amp.
I have done some searches on old threads on Audio Asylum where Mullards come up most often as the tubes of choice, a tad relaxed on top and glorious midrange. Similar to your experiences, I still have the Phillips stock tubes in my Unico, and simply haven't been able to convince myself to do tube rolling yet, as it just sounds so good. In my case I'm not sure I would want more relaxed top end... it is just right. I have visited Upscale Audio's website to explore... and really been thinking about the Siemens... interesting that they did not work out for you. How long did you leave them in, and did you leave the Unico turned on all the time? For me the difference in sound was nothing short of breath taking after about 36 hours on... and I haven't turned my Unico off ever since.
The best sound I've achieved with my Unico is with Brimar 13D5 tubes.
I left the Siemens pair in overnight, with the amp on, and listened the next day. So far, they've been very lifeless.
Is there something to be set for letting tubes settle in a piece of equipment for extended periods before passing judgement?
Lousyreeds, when you say lifeless, are you talking about lack of body and midrange jump? If so, Mullards will be a better choice than Siemens. You might also try Raytheon 5814A Windmill Getter or RCA 5814A Blackplates. Both have more body than Siemens, and they are relatively inexpensive at around $50/pair.
By lifeless I mean one-dimensional, kind of flat, and "slow" sounding. I wouldn't say there's a lack of body, but perhaps we're describing the same characteristic in different words. The bass is also not as strong as with the stock Phillips.
My impression is that Mullards would be even more laid back in the mids than the Siemens. No?
Thanks for your input! I'll check those out.
My experience with Siemens E188CC is that the bass is not as strong as with Siemens E88CC, however they are anything but slow, and the image they produce is sensational. Slow is an adjective I'd never ascribe to Siemens tubes. Frankly, something seems off with your tubes if this is what you are hearing.
The Mullards are slightly, and I emphasize slightly, softer in the upper mids and highs than the Siemens, but they are not more laid back in the mids. In fact, the Mullards have more pronounced mids than Siemens or Phillips tubes, IMO. If Siemens are Eva Langoria, then Mullards are Eva Mendez. A little rounder, but equally as sexy.
Don't overlook the Raytheon and RCA tubes simply because there is little buzz on Audiogon about them. They are both excellent tubes, and screaming values. They can certainly hold their own with Amperex, Phillips, Mullard and Siemens.
Well, warming up overnight sounds appropriate, I think Tvad may have a point-maybe something is off with these particular tubes... although I would be hard to believe given that they are tested and all from Uscale Audio. But I think what you are looking for is probably the Mullards... given the description above...
Keep us posted on how this goes...
i use mullard cv4003s in my unico cd and tung sol blackglass in the unico amp. deep base and excelent mid, great for jazz.
i have noticed that many of the current tube designed preamps and cd players are not very tube sensitive.
i can't say the same for amplifiers.
older products are more tube sensitive.
In my unico I've tried several different tubes. In my system, my experiences are:
Radiotechnique: Beautiful airy treble - no bass at all
Mullards: Too Dark and syrupy for my 'modern' taste in music.. fantastic with pre-1970s music recorded on valve equipment though (loves my bossa nova collection!!)
Brimar 13D5: Better balanced than the Mullards I had..still the same house sound, but less so.. lots of missbass punch, high treble could use a bit more refinement
Siemens E88CC: Beautifully liquid, cyrstal clear, well balanced..perfect -EXCEPT they lack dynamics!!!
Amperex/Beckman 7316 Holland: So far, the best I've found.. Slightly drier than the siemens, but WAY more dynamic.. HUGE, precise soundstage (best of the lot), well balanced (perhaps just slightly tilted toward upper/mid, lower treble..but in a good way!).. not cheap though, but worth it!!
Lousyreeds1, did you ever settle on a 12AU7 tube that you liked?
I recently discovered new production Tungsram 12AU7, and I think they're excellent. They compete with NOS Mullard 12AU7, IMO (not quite as good as the Mullard...but darned close).