The ones I bought are green. I have not see the yellow label ones. May be manufactured in a different time period.
1 Like
I have green ones coming according to photo. Will let you know later this week when they arrive.
1 Like
Yellow is commercial. Green is military (Jan).
1 Like
Can someone tell me which tube socket is left and which one is right? I just got a set of Radiotechnique tubes from Upscale Audio and one of them is making a crackling sound, although it’s much lower in level than when I first inserted them, before I cleaned the pins. Upscale wants to know which tube it is. I guess i can swap in a third known good tube to isolate the bad one, but it would just be more convenient to know the left right layout in the preamp. Please reference from viewing the front of the preamp. Or tell me which side is the one closest to the red light. Thanks.
When viewed from the front the left hand tube is for the left channel.
Thank very much!
I have some old 12AX7 tubes. They have a higher gain that our 12AU7s in the BHK line. Is there any harm in my trying them in my amps or pre?
If you have BHK amplifiers they only accept 6 or 7 volt tubes. The preamp can use 12 or 6 volt tubes but the 12ax7 is not going to be acceptable in the BHK preamp. The gain is too high.
3 Likes
Stupid question since I’m getting ready to replace stock tubes. Are their NEW 12AU7 tubes being made that will allow one to get a more “tubey” McIntosh sound? I am running a FirstWatt J2. Just a little more warmth. I prefer to buy new vs NOS if possible.
Why would you want to buy new versus NOS???
1 Like
Have you tried any other 12A_7 family tubes? Such as 12AV7 or 12AY7. Agreed that 12AX7 would be way to much amplification. I don’t have a BHK…just curious.
No I have not tried any other variation of the 12 volt tube in my preamp. I have tried various NOS 12au7 tubes and ne manufacture as well as 6 volt tubes.
1 Like
I really like the 12bh7 family of tubes.
According to my Tube Lore book, 12BH7 has the same general construction as 12AU7. Used for TV vertical sweep amps.
Substitution book doesn’t cross reference the two tubes.
The 12BH7 is a buffer tube that I used in a previously owned Consonance preamp. I think it has lower output impedance but not sure how the transconductance (Gain) compares with a 12AU7. Not nearly the selection with these buffer tubes so not sure of the advantages.
1 Like
Hi kclevland123,
I’m running telfunken 7dj8’s at the moment and am liking the idea of ‘new’ tubes. These Telefunken ECC82-TK (12AU7) that you are using - what are your jumper settings for these?
Thanks
Kevin
@KevinA I’m back to using my NOS Citfe 12AU7’s because the newly manufactured Tele’s were not as well gain matched and caused some soft pops when changing volume. However, any of the 12V tubes nominally use the 4mA setting (and the 12V jumper of course). Never tried the 12V tubes with the 5mA jumper selected as I think BHK does not recommend this. The BHK preamp manual should have some guidance as well.
Typically,
12AU7: 12v/4mA
6DJ8/7DJ8/6922: 6v/5mA - can play with 4mA
6SN7/CV-181: 6v/4mA
These are tubes recommended in this thread that I have tried, with BHK’s blessing.
2 Likes
so many good options out there for this preamp for both 6v/12v-The challenge is finding those NOS tubes that are tightly matched to avoid that volume pop. My Shaguang are starting to encounter it after about 200 hrs.
1 Like
200 hours? NOS Small signal tubes should be good for 5000 hours. I take it you don’t have access to a tester. You’ll pay a premium, but reputable Tube sellers (with documented ratings) usually are pretty honest with their data. Too many hobbyists have tube testers these days.
Are the Shaguang new production?