jbucla2005
Active Member
What is the best 12AU7 or equivalent? NOS or new production. I like brighter sonics with good treble air. Thanks!
Best 12AU7?
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vinylkid58
Super Member
In what, amp, preamp? There is no best, but if we knew what your piece of equipment was, then maybe someone would have a recommendation.
jeff
jbucla2005
Active Member
It’s a Hagerman Baritone Tube Buffer. It came with a Mullard reissue 12AU7. I’ve also been using a Tung Sol re-issue 12AU7W. I tried a RCA clear top (grey plates) and it sounded too warm/fuzzy.
hey, as they say, the best 12AU7 is a 12BH7, but they’re not know for bright and air.
jbucla2005
Active Member
That won’t work in this circuit
You can read up on all the 12au7 variants here. Brent also describes the sound, but I not put much credence in that.
Lavane
Lunatic Member
Why? Not enough heater current? Too tall to fit?
jbucla2005
Active Member
that tube draws too much heater current
Lavane
Lunatic Member
Too bad. The RCA clear tops aren't too expensive, they may be worth a try.
I used them in my VTA ST-70 until I tried a new old stock 12BH7.
I still use two clear tops in that amp along with the 12BH7.
Attachments
That unit is supposed to sound warm and fuzzy. That's why it uses a 12AU7 in common cathode configuration. A real tube buffer - which by definition will exhibit little or no gain - uses a cathode follower or transformer output stage.
Jack
jbucla2005
Active Member
Can you provide an example? What about the Musical Fidelity X-Can 10D?
Its an audiophile saying.
For the record, I do not in any way encourage blind substitutions of one tube type for another.
not sure best is a great descriptor. If you want brighter sonics you may want to consider the RCA clear tops, or for more brightness on top the PSVANE 12AU7-T II. Another option you can consider is adding film bypasses to the main power supply caps. As an example a .1uf + a 0.01uf film cap will add a lot of air and openness to a unit.
I haven't researched the market for these products, but that wouldn't be my choice. Two common-cathode gain stages in cascade is an unnecessary amount of signal processing. The unusable level of gain created by this approach and less than optimum output impedance is controlled in this particular design by a substantial amount of NFB between the two stages. It's similar in this regard to the Blue Velvet preamp of years ago. If we're really discussing a buffer - not a preamp - all that's really needed is a simple, low-loss cathode follower with an input attenuator. This approach creates the shortest possible signal path, no inversion, and it maintains both transparency and speed.
Jack
