How to roll tubes in the BHK
Tube rolling, the practice of swapping stock tubes that we designed the product with for a different variety to change the sound of a preamp or power amplifier is something we not only support but encourage. It’s why we made it super easy on the BHK series to roll your own tubes. In the BHK preamp, you can select either 12V tubes of 6 and 7-volt variety with the simple change of a jumper. Here’s how to do it.
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I’m interested in tube rolling with my BHK preamp, but I haven’t been comfortable with the process as I didn’t entirely understand it. The manual is helpful, but this video really clarified the process and gave me the confidence to open the unit. One thing that confused me at first was that the manual directs the user to move two jumpers to adjust the filament voltage. In the video, only one voltage jumper was adjusted. In opening the preamp, I realized that there is a jumper for each tube. Also, the explanation on adjusting of the bias current was really appreciated and filled in the gaps left by the manual. Good job!!
In the video, he states you don’t NEED to engage the current jumper but you can if you wish to create a change in sonics. What change should I expect by doing this? Tks
Look at the first number on your tube. 12 or 6. The jumper is 12v or 6v.
https://www.electronics-notes.com/articles/electronic_components/valves-tubes/numbering-systems.php
I just replaced my tubes and after warm up and a few minutes of playtime, I’m getting a rhythmic pulsing/popping from the left channel output. I assume I’ve got a bad tube (NOS Tungstram PCC 88). Looking from the back and top of the preamp, which channel is the right tube and which is the left tube? Thanks!
Jay