I believe the 6SN7 would theoretically work in the amp but the height of the tube plus the octal to 9-pin adapter might not fit depending on the height of different kinds of 6SN7 tubes. Ah, but taking the top cover off the amp would fix that. The 12SN7 wont work simply because the heater voltage in the amp is 6.3V. The preamp has the facility for using 12 and 6V tubes because the heater circuitry via jumpers provides for paralleling the two heaters inside the tubes for the 12V tubes.
Windom in the DSD and some Telefunken 6922’s back in the BHK Pre. Also back to running the DSD at 100 and the pre at 40-50+. The sharp edge on the mid high end that sent me back to the 12v tubes seems to be gone. Very nice.
16hrs on a nice pair of Tesla 70’s Ecc802s. Enjoy the Long plate tubes!
P.S. I did monitored the tubes by using a portable battery headphone amp (connected to the output RCA of the BHK/100 of gain) to my in ears with all the gain also at the headphone amp searching for the best pair with lowest SNR.
I was quite surprise to hear the sound of the display from on and off with this pair. I guess that is good SNR for my BHK
Lowering the plate current to 4 mA will increase the distortion a bit over running at 5 mA. The 4 mA was created as a choice for the supplied 12AU7’s.
BTW, even though I have a number of different kinds of12AU7s, I am using the stock 12AU7s with good sound. Bottom line - try the 4 mA and see what you think about the sound.
The gain of the input stage is degenerated to approximately 4X or 12 dB. So the relative gain with the different amplification factors is relatively constant. Don’t be afraid to try the many tubes of the 6922 genre.
My next move will be to try some 6922, just wanted to try a few 12v tubes before moving jumpers around.
Do you think a 6211 tube could work?
6211 is a computer grade tube and close to 12AU7, but NOT exactly. Amplification factor is 27 to 31 vs. 18 to 19 for 12AU7. Click 6211 data and 12AU7 data for comparison. These tubes have a brace or flange that runs the entire length of the plates.
The BHK amp and pre are the first tube gear I’ve owned, very happy with the sound. just curious , are the stock tubes that bad or is everyone just having fun with it.
A FUNNY THING HAPPENED, ON THE WAY “THROUGH THE FORUMS”…The other night I decided to try the new current production Mullard 12 AU7’s I purchased awhile back, replacing the stock Psvanes, trying to tame some of Windom’s upper end. I put them in, and realized I was now getting some of the dreaded “pulsing noise” described earlier in this thread. Oddly, it was just in my right channel. I checked all connections, and even swapped the tubes in the pre-amp from right to left. Still the pulsing noise, right channel only. So I decided to re-read this entire thread, as I seem to remember various theories and possible solutions. One of which I came across that sighted a listener who discovered his router was the source of his pre-amp noise…on one channel only! Sure enough, I relocated my router, and that ended the pulsing noice in the right channel. It’s interesting to note that with the Psvanes, there was no noise, but the Mullards aloud it to come through. BTW, the router was closer to my right channel speaker…when I centered it, the noise disappeared. I remember reading about some of the forum members having a similar experience with some tubes from Kevin Deal. I can’t help but wonder if some tubes just seem to allow more environmental junk to pass through than others? Also, I have Herbies tube dampners, so it was not a microphonic issue. Also, in my case the throbbing/pulsing noise could be heard easily from the listening chair with no music playing…most loudly at volume level 1, progressively getting quieter until i got to level 9 where it became as loud as level 1…and with each 8 clicks going up the volume level, it would do the same…meaning: 8,16,24,32 was quietest! Go figure! Moral of my story…check your environment before you RMA…I was glad I did. And thanks to these forums, and especially the contributor who mention his router as a source for noise. And now, back to our regularly scheduled program.
You might want to take a look at the Select Tungsram’s. I got a pair a couple of weeks ago that were both matched to 2900/3000. Quiet and very good sounding. This is about as good of a match as you will find on 50 year old tubes.
I haven’t tried rolling the tubes just yet. I purchased a few months ago a matched pair of Gold Lions but I’m getting such great sound from the stock tubes I’m in no hurry to roll them.
They are quite good so far plus no clicks and are actually cheaper than the triode matched Gold Lions. I have never listened to the stock tubes in the amp or preamp. I replaced them them with NOS tubes when I un-boxed the two pieces.
