Well, time to officially share my impressions of four different tubes in the Lyr. Just so everyone knows where I am coming from:
I listen to most music genres on a regular basis, with those being pop, hard rock, classical (many different genres), hip-hop, reggae, folk, bluegrass, country, etc, etc.
My particular favorites are Willie Nelson, Alison Krauss, Bela Fleck, Chris Thile, Nickel Creek, Bob Dylan, Patty Griffin, Bob Marley, Kid Cudi, Beethoven, Vivaldi, J.S. Bach, Chopin, Pavarotti, Rush, Led Zeppelin, David Bowie, Radiohead, Michael Jackson. I'll call those favorites because they came to mind first; there are many others. Most modern pop music bores me.
The tubes (all costs for a pair unless noted otherwise):
'65 Amperex USA USN-CEP 6922 purchased recently.
'70s National-Mullard Japanese 6922 purchased in '08 from Tubemonger for $60.
'76 Voskhod 6N23P purchased in a lot of 12 from a Ukrainian off Ebay in '07 for $40.
'73 Reflektor 6N23P same lot as above.
1. '65 Amperex 6922 USN-CEP:
I'll call these reference tubes, as they are head and shoulders above the rest.
Pros:
Completely unforced retrieval of detail, I.E. details present but not in your face.
Excellent sense of space, I.E. instrument and vocal separation and the space between; great 'soundstage.'
Accurate tone: I've heard many of the artists listed in the favorites section above live, and these tubes nail tone.
Balanced: No particular portion of the frequency spectrum stands apart from others.
Speed: Not to fast, not too slow. IMHO too fast=quick rise time=loss of decay and harmonics, too slow=lagging rise time=loss of pace, rounded tones and harmonics.
Cons:
Microphonics must be controlled, as they are a little more prone to picking up transformer vibrations than others.
A tad lean, which is attributable to the balanced response and balanced speed. I mention this as a con because many accustomed to romantic tubes would call it so.
2. '70s National-Mullard 6922, '76 Voskhod 6N23P:
These are very different tubes. The National is quick and tonally clean while the '76 Voskhod is slower and tonally rounder. They tied to my ears, as I prefer one or the other for different types of music. Voskhod=Classical, reggae, generally music with pace equal to the tube. National=Rock, pop, bluegrass, hip-hop, same comments on pace matching.
National Detail Retrieval: Equal to the Amperex, but a little too much at times.
'76 Voskhod Detail Retrieval: Slightly opaque compared to the other two, but still very good. Transients are missed in some cases. Definitely never forced or overdone.
National Space: Very good, with separation and delineation not up to the Amperex. Soundstage on par with the Amperex.
'76 Voskhod Space: Largest soundstage of all tubes compared, but the weakest separation, more opaque within the stage between sounds. Very romantic, however.
National Tone: A little dry, lean, harmonics suffer compared to the Amperex. Favors transient shifts.
'76 Voskhod Tone: Round, warm and favors decay of harmonics at the expense of transient shifts.
National Balance: Favors upper mid range and lower treble, can sound a little bright, not kind to compressed recordings, which at times makes its favored rock and pop genres fatiguing.
'76 Voskhod Balance: Favors bass and lower mid range, but still has good extended upper treble, lower treble a little shelved, bass is deep and round, but not bloated. Can sound a little thick, can put one to sleep.
Speed: As mentioned above, National=quick, '76 Voskhod=a few gears slower.
'73 Reflektor 6N23P:
Many give this tube a bad rap, but I like it. First, it's extremely rugged. It exhibits no microphonics. One can tap on the Lyr's case and hear nothing in the 'phones; can't say that for the other three. It's primary fault is too high a rise time, which doesn't allow adequate decay and development of harmonics.
Detail: Very good, but upfront and prominent, glosses over slow cadence in the treble, which is often found in reggae.
Space: Good, but not as convincing as the other three, and a few levels below the Amperex. The speed doesn't allow full stage development.
Tone: Quick, lean, dry, like a faster version of the National. Super clean. Very deep and tight bass, however. Mid range leans towards good solid state style.
Balance: 'V' shaped curve to my ears. Tends to obscure the mid range. Hot in the upper treble.
Speed: I won't be redundant; very fast=too fast, rise time too high.
Conclusions of the Comparison:
1. I think the '73 Reflektor is a bargain.
2. The National is perhaps the best cost-benefit, even at $80 a pair from Tubemonger (they are almost gone).
3. The secret is out on the mid-70's Voskhods, so they are difficult to find at reasonable cost. I wouldn't pay $100 for a pair, but I might buy a mixed batch of 20 - 40 from Russia and pray for rain.
4. As with most things of value, you get what you pay for. The better 6DJ8 variants are costly for good reasons. If you are keen for good tubes, perform careful research and pull the trigger.
