1/2 12BH7??
On Tuesday, 19 January 2016 05:52:28 UTC+11, wrote:
Hello!
Which tube is equivalent to 1/2 12BH7?
Thanks!
Quite a few comments on 12BH7.
Its about equal to having two 12AU7 in parallel.
The Ra for 1/2 12BH7 is half the value for 1/2 12AU7, but µ is nearly equal, so BH7 has higher Gm.
This means that for a given B+, RLa and Ea and Ia, BH7 can swing a wider voltage before Ea swing is limited by Ra curve for Eg1 = 0V. The lower Ra means F response extends to higher F. Because it swings wide, its an ideal driver for output stages needing high Ea swing, such as in McIntosh amps.
I've used BH7 often for rebuilds when I found I had them around - its a very good driver, IMHO.
The only equal tube I know is 6BL7, but that's an octal tube, but then a quite fabulous twin triode with fabulous reputation same as 6SN7, or big plate 6CG7 which are 9 pinnie versions of 6SN7s.
When I first built a decent preamp in 1994, I tried SRPP and I could not tell any difference in sound between 12BH7, 12AU7 or 12AT7 in a line stage amp; you can build the SRPP to suit all 3 without changing Rk. IN SRPP, there is no RLa, the tubes are in series with no anode resistor. But signal is less than 1Vrms, so no matter what you use, it works, and you only have to worry about gain.
Patrick Turner
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