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.


11 comments:

  1. Thanks for the detail review of 12BH7. I recently replaced a 12AU7 in my amp with 12BH7 and am very happy with that move. My 12BH7 is CBS black plate D getter (or horse shoe). Do you know if that tube was made by RCA, Sylvania, or?

    ReplyDelete
  2. CBS both made their own tubes and they contracted other manufacturers. With respect to the 12BH7 they did manufacturer, through Hytron, their own label. I have noted that the CBS/Hytron 12BH7s seem to have their own distinctive sound, so I expect it is not an OEM.

    Way to go on trying out the 12BH7!

    ReplyDelete
  3. how can you tell the diff in shape between a U getter and a D getter? They look so similar.

    ReplyDelete
  4. My experience with getter shapes is like this: Horseshoe looks like a horseshoe, the occaisional Harp looks like a harp. The "D" getters vary from more sharply cornered outer angles to more rounded outter angles. In my book, the "U" getter looks almost exactly like a stirrup. There is no "outer angles" of a square, it's almost a semi-circle. Just like this: "U" , with a bar accross the top. But hey, the terms are tossed around a lot.

    ReplyDelete
  5. thanks for the excellent review! very helpful. -ad

    ReplyDelete
  6. I'm a big fan of the 12BH7. I'm currently running a current production "electro-harmonix" 12BH7, although my favorite tube for musicality is actually the 12FV7. Its easy to find NOS RCA tubes cheap, but buy a few as some of them suffer from microphonics. They are basically a BH7 but made for computer use, as such, they have extended life but you need to buy a few to make sure you find one that doesn't suffer from microphonics...but hey, at the price point, they are a complete bargain. Be warned though, they use quite a bit of current for their heaters.

    ReplyDelete
  7. Dear OldStockAudio:
    Would you post photos of your favorite Sylvania & RCA 12BH7/12BH7A tubes from the description above? That will help in our pursuit of these!

    ReplyDelete
  8. I second the above request - that would help a lot! There are so many different versions.

    I think I managed to track down the Sylvania thick halo getters

    https://dl.dropboxusercontent.com/u/5794104/www/Sylvania-12BH7A-darkgreyovalplates-thick0.JPG

    I've only seen these in a single listing on eBay. They do sound good - but personally I prefer the mid 50s RCA single wing black plate with D-getter.

    https://dl.dropboxusercontent.com/u/5794104/www/RCA-12BH7-bp-d-halfwing.jpg

    In my setup the RCA has a deeper soundstage with better separation and a lot more body. The Sylvania does sound a little thin with my setup (APPJ PA1502A headphone amp with Hifiman HE400i HP).

    ReplyDelete
    Replies
    1. Small addition: RCA made a lot of these under different brands like Westinghouse.

      Delete
  9. The CBS black plate is a winner. Better bottom end and extended highs. Another great tube is the Brimar 12BH7- best for mids- even better is the variant CV5042 a military tube made for the airforce. There are some fake ones around though.
    I have all of the above top rated RCA and Sylvannia tubes and prefer the Sylvania thick O getter over the any of the RCA's.

    ReplyDelete
  10. My favorite 12BH7s are the Brimar 13D6 and 12BH7. I need to try some of the Sylvanias you mentioned.

    ReplyDelete