[Claritas]

I can confirm that removing the back tube and leaving the unit on for 48 hours (no signal, just turned on) will make the 6SN7 (front tube) go totally silent. Kind of a pain but the way to go.
This amp is an outstanding bargain so it's well worth taking the time.
Silence is golden as they say.

 
Thanks. I tried it overnight that way and the input tube was silent in the morning--but not the next time I tried that tube! I'll give it longer burn in when I have time.

 

[spacequeen7]

So far my experience is the same - some 6SN7's hum, some don't. And tubes that do NOT hum in other amps do hum in the 336SE. But I have some nice 6SN7GTB's that are completely quiet, including the very nice tall-bottle Tung Sols (vintage NOT re-issue), so I use that.

^^ this  ,same here 

 

[hifihead]

I want to also confirm that leaving the amp on for 48 hours with just the 6sn7 front tube installed with no signal, no music playing will make the hum go away. My tube had a slight hum but is now silent. It is well worth the trouble to make a humming tube quiet. I noticed when burning-in the 6sn7 that the amp stayed relatively cool. It's the back power tube that creates all the heat. I love my Darkvoice 336se and is an awesome value. Thanks ksan for posting the instructions on how to burn-in a humming tube.

 

[Baldeagle58]

Yep, it's definitely just an issue (the hum that is) of "ageing the 6sn7" and everything goes totally silent. I bought a pair of Sylvania Chrome Tops that are most definitely used and they are both totally silent. All others can be made to go silent by leaving them in and the unit on for 48 hours. It's a bit tedious because you want to be listening to music not burning in tubes, but it does work and to me it is worth the trouble.

 

[muckyfingers]

Just wanted to say thanks. I did the Fitz mod with the 220uf 16v capacitors on my new Massdrop Darkvoice 336SE. It eliminated the hum I was experiencing with a new Electro Harmonix 6SN7 tube.

 

[Morrian]

Have to Neco a bit too.

Had bad humm on the left channel and on other tubes both channels..

220uf 50V caps on the same places like in the pictures in this thread. No hum anymore. So nice^^ But with low ohm headphones there will be less bass. But used as a preamp feeding another headphoneamp -> NICE NICE NICE

 

[sennfan83261]

I did the Fitz mod with 220uf 25v Nichicon FG Muse capacitors. It eliminated the hum I was experiencing on a few 6SN7, 6F8G, and 6C8G tubes. The gain increase is real, especially with the 6C8G's (these having an amplification factor of 36 vs the 6F8G/6SN7's having amplification factors of 20 according to this post). As a result, the higher gain from the Fitz Mod coupled with the gain of the 6C8G's pushes listening volumes down to pretty close to the channel imbalance threshold. I use my musicplayer (Musicbee) to 1) drop the volume of my dac and 2) adjust the EQ's pre-amp setting to -10db for all tubes. Next is probably swapping out the 250K volume pot with a 100K alps pot.

 

[JKDJedi]

Hey guys, since you seem to be in the know more than the average Darkvoice consumer here, whats the total amp output of the amp? My understanding is the 6as7 slot or the 6as7 tube itself draws 2.5 amps, I'm asking because I'm thinking of using a dual adapter to roll two tubes that draw 1.5 amps each, (3 amp draw total) will this blow the fuse or melt the amp with the half amp extra pull?

 

[Cyberthingy]

I did the Fitz mod with 220uf 25v Nichicon FG Muse capacitors. It eliminated the hum I was experiencing on a few 6SN7, 6F8G, and 6C8G tubes. The gain increase is real, especially with the 6C8G's (these having an amplification factor of 36 vs the 6F8G/6SN7's having amplification factors of 20 according to this post). As a result, the higher gain from the Fitz Mod coupled with the gain of the 6C8G's pushes listening volumes down to pretty close to the channel imbalance threshold. I use my musicplayer (Musicbee) to 1) drop the volume of my dac and 2) adjust the EQ's pre-amp setting to -10db for all tubes. Next is probably swapping out the 250K volume pot with a 100K alps pot.

I just installed those same caps and I got the desired results. I bought my Darkvoice second hand and it came with about 8 6sn7 tubes and the first few I tried all had humming ranging from slight to moderate. Since I knew I would be rolling tubes to see which I liked best I did not want to have to wait the required break-in process for each tube. No more hum with 2 tubes so far. I'm also using MusicBee Player which I like a lot.

 

[JKDJedi]

I used 220uf caps on mine, worked great - now craiglester has it after I upgraded to WA6 and I won an EF1. My 336i was very special with HD600...

Quote:

Originally Posted by aryntha /img/forum/go_quote.gif Wow. That worked. Like, really worked. Two Nichicon 220uF caps (I used axial vs radial) - and now, ALL hum on ANY 68FG or 6SN7 is GONE from my 336se. The only things I really have to ask are 1) Is this going to cause the amp to become less reliable down the line? 2) In other words -- why in the WORLD isn't this done at the factory? I can't see it being a cost saving issue. There must be a reason?? Anyways, so that folks may be assisted in doing this in the future, here are pics of my mod... The electrical tape, don't mind it, just burnt the insulation there a bit while soldering so a slight precaution... I tried to get some angles that show the connections well. This along with the previous images in this thread hopefully will be a help to people.

Quote:

Originally Posted by aryntha /img/forum/go_quote.gif I'm not sure; the 220uF nichicons seem to be very effective. From what I understand, increasing the capacitance (100uF -> 220uF) increases hum rejection but also increases gain. Having a gain increase may be undesireable in some circumstances; For me, though, on my HD600s, it sounds rather good. You may want to try again with better caps.

I used the 220uf Nichicon when I did mine and it worked beautifully, and I was told if you used too small of a capacitance that you'd also get some bass roll-off and that 220uf was as low as you should go. I was told about gain changes by going higher, so I'm glad I didn't go higher as gain was enough as it was.

I don't see there being any long term harm with this mod.

I did the mod a couple of weeks ago using 220uF/25V Elna Silmic II caps. The amp still sounds good and is perfectly hum-free now. To tell the truth, I didn't have serious problems with hum even before the mod, except with one tube which had other noise issues as well. This faulty tube still hums slightly in the left channel, and naturally still has its other issues.

The faint hum that the amp had with some 6SN7GTs was a blessing in one way. It is now evident that one of my 6AS7Gs makes a tiny whistling sound in the right channel. This was effectively masked by the hum. The whistle is now more annoying during quiet passages than the hum ever was. A quiet 6AS7G solves this problem, of course.

I would like to be able to say something about how the actual sound quality of the amp changed with the caps installled, but I can't. I would need two amps for an adequate comparison. Anyway, if there is somebody who would like to try these Elna caps and report back, I'm ready to send you a pair, especially if you are willing to compare with something else like the Nichicon Muse KZ caps. (This supply is very limited.)

Too all of the above.. the Nichicon Aluminum Electrolytic Capacitors - Radial leaded 25 volts 220uF are spot on for this use. No added gain, no bass roll off and HUM...GONE.

Mouser part number: 647-UKZ1E221MHM

 

[sennfan83261]

Too all of the above.. the Nichicon Aluminum Electrolytic Capacitors - Radial leaded 25 volts 220uF are spot on for this use. No added gain, no bass roll off and HUM...GONE.

Mouser part number: 647-UKZ1E221MHM

What took you so long?

 

[JKDJedi]

What took you so long?

lol... LED mod.. @therremans gave me the push. it was a fun project that I had been putting off for three months. Happy camper.

 

[sennfan83261]

lol... LED mod.. @therremans gave me the push. it was a fun project that I had been putting off for three months. Happy camper.

Any differences with the amp between the LED mod and the Fitz mod?

 

[JKDJedi]

Any differences with the amp between the LED mod and the Fitz mod?

Cleaner. A lot cleaner.