If you have a Dark Voice 336SE headphone amp you likely had the same thought as many other owners. Why does such a nice little amp come with such poor vacuum tubes? Well most Chinese made amps do come with cheap Chinese tubes because they are readily available. Unlike some Chinese amps that use obscure tubes with limited or no western equivalents to upgrade to, the DV-336SE uses tubes that have many substitution/upgrade options. It’s most common to upgrade the 6SN7 tube. We won’t get into which tube sounds best in this article though. Rather I want to address the common problem folks find when installing their new or NOS 6SN7 tube. With rare exception, there is a noticeable hum in the left channel. This will occur with any 6SN7 tube. But the good news is that after burn-in they will become dead quiet again. Here’s what to do:
1. Power off the amp and remove the 6AS7/6H13C power tube. This will keep the unit from over heating during this burn-in procedure.
2. Install your new 6SN7 tube and power the amp on again.
3. Wait. And keep waiting. We find that approximately 72 hours will do.
4. Power off and re-install the 6AS7 / 6H13C power tube.
5. Connect your favorite headphones and power the amp on.
You should find the hum in the left channel has completely disappeared. At the least you’ll notice it’s much quieter and likely only need one more day to get it completely quiet.
I realize you can modify the amplifier and add a couple capacitors to solve this but the instructions above will “fix” it for free so give it a try.