So I bought the Willsenton R-800i

Hi,

I have two of VEB Rohrenwerk Neuhaus GDR NOS ECC83s, very similar to the RFTs, same collective ownership as RFT back in the day of communist East Germany. They are noisy in my Willsenton, with higher hum coming from the Forte's which are 99dB.  I believe the Cornwall's are 102 dB so I'd think you'd get even higher noise with RFTs.  They sound a lot like the stock JJ 12AX7, a bit "hard," not as warm or engaging as some of the other NOS 9 pins, e.g., Tele, Amperex, Mullard, RCA, etc.  I also have a set of VEB and RFT EL34s for another small SET amp, and they sound excellent, as good as Tesla's but not as sweet as St. Pete Svetlana EL34s. 

Don't know if you've experienced the hum issue with your Willsenton.  It's not a ground loop, I've troubleshot that, not the issue.  The hum is volume independent (adjusting up or down doesn't impact hum level).  I've played with the hum adjuster, put a DC filter on the power cord (to avoid DC looping back to the power transformer), experimented with lifting the ground, etc, etc and still have a bit of hum at idle regardless of the tube compliment.  It's basically the mechanical transformer noise making its way to the speakers.  China-hifi said it is normal with the amp.  Some 12AX7s are louder than others, and the 12AT7s are quieter overall.

My Dennis Had Inspire KT88 Firebottle has zero hum coming from the Klipsch, so I know it's possible to build a dead quite amp (requires much higher quality transformers, i.e., more expensive).  The Inspire is a different build than the Willsenton (completely by hand, no PCB board, custom wound transformers and highest quality caps and resistors) and only has 10 wpc.  I've read numerous places that the bigger, stronger the amp, the more mechanical noise it will generate. 

Anyway, I found the VEBs humming too much for my taste.  The 12AT7's hum less across the board due to lower gain, 60 mu vs 100 with 12AX7;'s.  That being said, the Telefunken smooth plate AX7 is very quite, as is the Amperex BB, the Mullard and the Russian Gold Lion 12AX7 (which BTW can act as a great reference tube, I've found the entire Gold Lion series to be very clear, clean and crisp, and linear with excellent bass that is tight.  I have a set of KT88s, KT77s for the Inspire, and 300b's and the 12AX7 for the Willsenton).

The RFTs are cheaper, but I would encourage you to save up and go for the Amperex Bugle Boy 12AX7 or 12AT7 (make sure you get Holland build, not France or GB), you'll get low noise (hum), very clear, clean and crisp highs with extended soundstage (more height), AND good bass with warm mids.  The BB is just a bit "brighter" up top than the Tele smooth plate, meaning more detail, cleaner treble extension.  Subtle but distinctive.  

And yes my Svet 5U4C  BP "pops" a little purple blue color/light on top when fired up, looks really cool and I've read it is normal, nothing to worry about, doesn't mean tube is on it's way out or anything.  I also have the gray plate version of the Svet, and it doesn't "pop" on turn on.  I also have a set of Svet 6550s for the Inspire that glow blue when warmed up for 30 mins or so...very cool look.  Also normal and doesn't mean anything.  None of the Gold Lions or any other tube for that matter glow blue in the Willsenton, but boy do the 845s get hot!  I added a slim, quite fan that sits nicely on top of the transformer and tube cage to keep my AC bill down!

Regards

I do experience the hum issue as well and I don´t know if it´s been there from the beginning or not, at least I noticed only after quite a while. After checking all possible component, cables, tubes etc. I also blame it on the tranformer. When I listen closely that´s also the place where it seems to come from. Unfortunately it´s louder with the Elrog 300Bs I´ve been using. Great tubes, but the hum is, well, it´s there. And it´s bothering me to the point where I found it difficult to listen to music. Well, having said that it´s still in the range where my girlfriend just shrugs, it´s basically not noticeable when music place (except for very quiet parts). There was some other issue with them and I´m waiting for a replacement pair, maybe that will change something.
I guess with that hum issue we´re entering real high end territory. If all parts are high qualtiy it just costs more. Considering value for money the R800i is hard to beat.

The RFTs would be really cheap, like under 10€ a piece, so I´d be ok with them not being a revelation.

Thanks for the info on the blue light in the 5U4C, that´s very helpful!

I’m sorry to hear folks have significant audible hum.  That’s frustrating. 
 

I have almost zero hum. I have to put my ear right above the transformer and it’s barely audible still. I think the transformer is potted. 
 

Have you sent a video of the hum to China Hifi?  I’d do that. They may be able to help.  I’d ask them if the transformer is potted too. 
 

I’ll look inside at the transformer when I open the unit up. 

Have already contacted China HiFi, here’s their response, “ Vacuum tube power amplifier and transistor power amplifier are different.  It's normal thatr hear the huming within 1-1.5m.”   So…I believe it is a function of quality of parts, particularly the transformers, and implementation, i.e., the build.  I’ve read the transformers are potted so not viable to upgrade with a mod.  

I have about 700 hours on my 300i, and it’s gotten slightly worse with time on the amp.  It’s much more noticeable with the 99 dB Klipsch Forte’s than the 92 dB Focal’s.  I think it would be unacceptable with LaScalas.  Yes, we’re beginning to migrate from really good mid-fi to more resolving, and expensive hi-fi!  That being said, I’m happy with the Willsenton with its noise floor vs price.  A high end build with much better parts would likely run $10k-$20k, depending on manufacturer.  It comes down to system synergy, the 300i has enough headroom to push 85-90 dB speakers with ease, that would be one solution.  Also with lower gain 12AT7s, I’ve found the hum isn’t noticeable at my seating position even between tracks.  Roll in a noisy high gain 12AX7 and the hum returns.  

As much as I hate to admit, Klipsch Heritage series may not be the best match for the Willsenton 300i.  My Inspire KT88 is a match with the Klipsch , dead silent! Problem is Dennis only builds a dozen or less amps a year. At the moment he has a 300b SET on ebay for $4,250, it won’t last long, maybe 48 hours. 

Anyway, glad I bought the Willsenton, great soundstage, deep bass, warm mids and crystal clear treble with the right pre stage tubes.  Sitting here right now listening with low level volume, a touch of boost at certain frequencies with a Klark Teknik DN360 studio equalizer and loving the mellow yet articulate sound emanating from the Focals.  

Cheers
 

I run Klipsch Heritage Cornwall IVs with the 800i 805 and it's near dead silent. Plus, if it were a transformer hum, the efficiency of your speakers may not matter--it would put that noise into the room without the speakers. 

Since you are running super efficient speakers, you could try going down from the 12ax7 to a 12au7 (that's the lowest gain in that 12 volt tube variety).