Monday, May 31, 2010

12BH7 Listening Test!

The 12BH7 shares many similarities to the 6SN7 (also a favorite tube around these parts), but is characterized by a darker sound.  In the past, this tube was known simply as a favorite driver for the old Macintosh amps, or as an inexpensive alternative to the 5687 and the 12AU7.   Lately, however, the 12BH7 has experienced a resurgence in popularity as audiophiles have been discovering its remarkable musicality.

Although they are no longer manufactured, there are still significant numbers to be found due to their original use in audio amplification for television as well as in stereo systems.But some of the brands in this category are becoming very collectable… and, as a result, much more difficult to acquire.

Our 12BH7 stock comes from old tube collectors and aficionados who stocked up decades ago. We tested several nearly identical types of Sylvania and RCAs as the metal used in the plates, the type and position of the getter, and the manufacturing process itself can vary and significantly affect the sound.The differences in quality and texture are often more than variances in the individual tubes and so we tried to create a helpful purchasing guide for our customer’s use.

Here are my notes (in listening order) from a recent 12BH7 tube comparison binge.  We listened to Hilary Hahn’s “Barber and Meyer Violin Concertos”.  The asterisks indicate the tubes deemed (with pretty much unanimous agreement) to be the best of the night.  Enjoy!

Amperex 12BH7A (Orange World): Still, unadorned quality. Seems to be a good level of detail throughout the low, mid, and high ranges. Appealing sound, immediate and bright, but slightly thin. 

Sylvania 12BH7 pinched plate from the 60s: Sound is a little richer than the Amperex. A more musical tube as well –rounder and more full. Both hushed and urgent moments are fleshed out and equally affecting.

Sylvania 12BH7 black oval plate from the 50s with U-getter: Lovely. Very musical. More detailed than the Amperex. Very rare. Soft, lush sensuality to the sound. Velvety.

Sylvania 12BH7 black oval plate from the 50s with D-getter:  Slightly bolder, slightly less lush sound but with even higher level of detail. Maybe a little more musical than the previous – first of this selection I would describe as having a “live” sound.

Sylvania 12BH7 grey oval plate with D-getter from 60s: Tested three, all with yellow lettering.  Two were slightly muted. Still detailed in the low and high ranges but the sound didn’t blossom as fully as the previous tube. (Suffering a little, I think, in comparison.) The third had a nice sound but more noise in the high range and still a loss of detail in the big moments through the mid range. Absolutely a nice tube, but doesn’t stand out against the other Sylvanias. 

Sylvania 12BH7 dark grey oval plate with O-getter from 60s and no copper grid posts (red lettering):  Much clearer and more musical. Pleasant, well-modulated detail. Possibly a little noisy in the mid-range, but still one of my favorites so far.

*Sylvania 12BH7 dark grey oval plate with thick O-getter from 60s and no copper grid posts (marked with red top - possibly a factory rating for audio): Very full, rich sound. Can really hear Hillary Hahn’s bowing technique instead of just the grating buzzing that one usually hears with recorded violin (an artifact, I think, of placing the microphones too close and not allowing the sound to expand before being captured). If life sounded this good more people would probably like classical music. Incredibly rich detail. Nicely developed mid range. High notes really sing. Very beautiful.   What stands out upon re-listening to this tube after the RCAs is the comparative delicacy of the sound. Sort of like fresh poached salmon as compared to a juicy steak. Both are good, and the difference in enjoyment is going to depend on personal taste.
RCA 12BH7A square black plate winged plates, U-getter, late 50s: very nice tube. Close second to the last one we listened to. Very melodic and detailed. Some buzz in the larger string sections. Can still hear bowing technique. Tube really does sing.

RCA 12BH7A square black plate with double wings , U-getter, late 50s (white lettering):  Back to the Amperex stillness, which doesn’t compare well with the previous 2 tubes. Still very a good level of detail, almost comparable to the sound of an old phonograph.

RCA 12BH7A oval black plate with double wings, bent D-getter, late 50s (red lettering, green paint?):  Very clear, rich sound. Sings. Something very honest and straightforward about the sound of this tube – you can hear everything that was heard in the better tubes, but the detail seems less modulated. I can see this tube being a lot of fun to listen to on a regular basis. Glorious in the larger sections.

*RCA 12BH7A long black plate with double wings, dimpled square-getter, late 50s (white lettering):  Similar to the last tube, but with many more dynamic levels. Softer details perhaps, but a very high level of detail all the same. Never thought I’d see the day that an RCA blew an Amperex out of the water.

*RCA 12BH7A square black plate with double wings, O-getter, late 50s (red lettering):  Crystal clear sound but still completely filled out. Solid dynamic range. High level of detail. Beguiling musicality.

RCA 12BH7A square grey plate with double wings, O-getter, 60s (red lettering):  Really not quite as detailed, a little noisy. Some real sweetness at the top. A warm tone. Balance is a little off, some parts pop too much and others are too muted.

RCA 12BH7A grey square plate w/ double wings, halo-getter, early 70s (red lettering):  Clear consistent forward sound, good detail, perfectly decent tube. Not at the very top of the list, but stands up well to some of my favorites tonight.

Sunday, February 7, 2010

12AU7 / 12BH7 / 6CG7: What's best?

The 12AU7, 12BH7, and 6CG7 have very similar electrical characteristics and can usually be substituted for each other. When deciding what's best for you, the following notes may be helpful:
(1) A 12AU7 is identical to a 6CG7 electrically and in the circuit it will function identically. However, there is a different heater pin out. So if you are substituting you need to make a change. In addition, the 6CG7 draws twice as much heater current so be sure that this will work in your circuit. (This may be one reason it is not as popular as it should be.) If you need help write me via
(2) The 12BH7 requires no circuit modification to substitute for a 12AU7, but the plate resistance is a little lower (5300 vs 7700). Thus, even though it has a lower u (or amplification factor), the gain may be slightly higher depending on the circuit design. [This is mainly true for circuits that use an anode resistor load.] It will also draw a little more current, but the 12BH7 is a beefier tube and can handle it. For most circuits this should be well within the tolerances of the design, but you can ask the manufacturer to be sure.
With respect to audio reproduction there is a fairly large difference between these three tubes. The 6CG7 (or 6FQ7 which is the same exact tube) is identical in internal construction to the 6SN7. The 6SN7 has the reputation of being the most linear of the medium mu triodes and the 6CG7 follows suit. Also, the 6CG7 line is remarkably similar in audio performance across various manufacturers of the same vintage or age.  It is a good tube for early or middle stage amplification and has the added bonus of a grounded shield between sections, which reduces hum and increases channel separation.
The 12BH7 can lend a wonderful life to the tone that sounds great for jazz or vocals. For audio listening,  this tube can temper the harshness of CD's. There is, however, a wider variation in the sound of 12BH7s than 6CG7s, so some tube selection or rolling is in order. You can find very neutral 12BH7s (watch for a coming blog comparing them) . If you don't want to modify the circuit and are unhappy with your 12AU7--this is a good choice. 
The 12AU7 family has the widest variety of tonal characteristics which is probably why this tube is rolled so often by audiophiles. I personally find most 12AU7s a little tinny in comparison with the 12BH7 and 6CG7, but there are exceptions. The RCA clear plates from the 60s are more like 6CG7s in their sound, for example. There are lots of blogs and posts about the difference between 12AU7's so I won't waste your time repeating everything. My favorites are Mullard and Siemens, with RCA clear tops and Tung Sol a close second. A lot of people like Amperex, but they work best in a system that is not forward or bright as they add life to the midrange. My Lowthers are already bright in the mid-range, so I stay away from Amperex 12AU7s.
Part of the fun and magic of tubes is rolling them when listening to different types of music.  When you do, we hope you will consider our vintage tube offerings at .

Sunday, January 31, 2010

Testing the New Phono Amp

Congratulations! Burning the midnight oil in preparation for T.H.E. Show (The Home Entertainment Show, Las Vegas 2010) has certainly paid off for you. I've never before heard recorded music sound better than it would in most seats of a concert hall.

 As both a classical musician and budding audiophile, I was very surprised. (The difference, of course, comes from how sound waves move in each individual acoustic space, and how close you are to the sweet spot. I recently missed a lot of the nuance of a Bartok piano concerto because I was sitting too close to the stage and at that proximity the grand piano overpowered everything but the violin section, which was right in front of me. It sounded like the pianist was banging away a' la Rachmaninoff at a college-level competition, which he wasn't.)

 I do wish we'd listened to more than high-quality classical recordings, as amazing as they were (thank you very much for introducing me to Gary Karr's Adagio d'Albinoni, a purely analog-to-vinyl recording using restored vintage equipment).

When we test the amp again I'd like to expand our listening selections - the purity of Kerr's base and the clarity of the strings on Guaneri del Jesu (with Paganini's original violin!) both argue for a high fidelity to any original live sound. (Was it the Albinoni that we could tell was recorded in a studio and not a concert hall? So much fun to be able to hear the actual acoustics of the original "performance" space!) I'm thinking I want to hear some middle eastern folk, Indian classical or a Piazzolla tango. This is, of course, pure personal greed - this is the most detailed and live sounding audio set-up I've encountered, and I want to hear some of MY favorite music played like that.

12AX7 Tube-Rolling Notes

Last night, while hosting a big blind listening test, we decided to compare a few 12AX7 tubes.

We'd started our evening with old-stock 60's black plate RCA and Raytheon pair. Just for fun I put in a pair of Sylvania Gold Label, Gold Pin tubes with low noise testing from the manufacturer. These tubes are really not available from any dealer, anywhere -they are ultra rare, I just happen to have a few quads. (The lettering is real gold leaf! I think they may have originally been made for Amperex.)  Anyway, we put in the pair and oh my, oh my!! I put on a record of J. Heiftz and Brooks Smith doing a recital at the Dorthy Chandler pavilion and you would swear that the Steinway Grand was sitting in your living room! Wow!

The Mullard 12AX7 long plates have long been my favorite for phono stage, but these Sylvania Gold were definitely their equal.

For phono stages, the GE 5751 receives high recommends as well. It is a sleeper tube equal to the Mullard, but often at a better price.