I noticed the poll button the other day and saw a request for this poll.

Vote early, vote often (Illinois style)

What Ghostship said.

Cryotone full bundle, specifically:
     Main Input Stage: 12AU7-WCL Long Plate with Matched Sections;
     Input Driver Stage: ECC88-WC Matched Pair;
     Voltage Regulators: OC2-WC (3) Matched;
     Rectifier: 5AR4-WC;
     Output Stage: 300B Matched pair.

Same bundle as Ghostship, with the exception of the rectifier- I use their 5U4G.  As of late, I’ve been using the Stradi 5U4G rectifier, which is as quiet (if not quieter) as the Cryotone.

I agree, while tubes probably contribute to the lions share of reducing hum, there are other factors as well. By the way, my speakers are also 8 ohm with a sensitivity of 96db.

My hum is not tube related. I have Serial #006, purchased used from a forum member, who purchased it from the original owner (forum member).

Neither of the former owners ever mentioned hum once, and the original owner gave the most glowing reviews...not even sure how it went up for sale.

I have almost 2 sets of Cryotone's which came with the amp, as well as other tubes I have purchased trying to rule out the tubes. I feel confident it is not them.

I have three (3) other tube amps (Torii MarkV, SE84CKCS, and a Denis Had Type 45) none of these hum using all of the same equipment. I have even disconnected all but one source and Sarah still hum's. Tried different rooms/outlets/power cords/cables etc. No effect/improvement.

Speaker efficiency does not impact the hum. KEF LS50's at 84DB hum, as well as every other speaker connected (HRv2, Klipsh Heresy I, and LiiSong Z15L).

The hum is not volume dependent (does not change at all). Just a steady drone once powered up (no volume). Loud enough in a 35XllX7 foot room at 7' from the speakers it is annoying. Smaller room is unbearable. In the larger room I can listen, however soft passages definitely irritate me as the hum is noticeable.

I do like the sound it produces, really wish I had one of the one's that does not have hum or could at least figure out why it does for me and not the prior owners.

I spend most of my time with the Torii in a smaller room. Worst problems in life to have so I am blessed with what I do have.

For what it is worth…I have a push/pull tube amp that had a hum at startup that was slowing getting worse with time.  I sent it in to the manufacturer for diagnosis.  They replaced the power tube sockets, checked resistors and made the repair under warranty.  Dead silent for over 2 years now👍. Good luck resolving your hum!

I have had two meetings with Steve, one lengthy one where we went through different tube combinations in the 300B that might cause or eliminate a hum. At the end of that session, he said that the hum may improve over time, and if not, I could send it back to him for further investigation. After careful consideration, I concluded that the hum from my amp was typical. I decided to look for solutions outside of Decware, and that's where I found Vera-Fi.

Steve wrote in his "development thread" that he had heard a hum in the 300B but did not think it would be a problem. The goal was not to eliminate it, Steve said at one point, elimination would jeopardize fidelity. His goal was to minimize the amps' hum so it was unheard at the listening position.

When I spoke with Don at Wathen, he told me that even with a complete set of Wathen tubes, it would most likely not remove the hum.

Those of us who have installed several products from Vera-Fi have reported improvements with hum for the most part. For me, a softening of the hum has helped take the edge off.

Lon's suggestion to the Other Lon to return the amp to Decware for a checkup sounds logical. If you are not the original owner, however, there are additional costs that I assume Other Lon is aware of. Still, it's a possibility.

That knob certainly works for me to find the right position where the hum is least present for a particular tube.

I now have two different pairs of 300B that I use, two very different types from two different manufacturers. I adjust the hum knob for each type of tube, the knob position is slightly different for the least hum sound for eachy tube type.