[L0rdGwyn]

I just tried 3 pairs of drivers. The hum is the strongest around 75% max volume then goes almost silent at full volume.

The hum is not dependent on the tubes actually. It's the same hum and level for those 3 pairs.

Hmmm well you will have to let us know if the issue is fixed with the heater modification. The issue with omitting a center tap is heater-to-cathode leakage, which typically will vary from tube to tube. If there are leakage currents coupled from the primary to the secondary of the mains transformer and the heater supply is not center tapped in any way, they can be coupled to the cathode of the input tube from the heater. If the tube has little-to-no leakage, there may be no hum, even if the heater supply is not center tapped. If someone is going to do a mod I worked on, just wanted to make sure it is done correctly, only reason I chimed in. Hope everyone is enjoying the music.

 

[bpiotrow13]

For me it's hard to detect the hum at full volume in during the day. But at night i can identify the hum better when everything is so silent.
With hd800 ad hd650 it's hard to hear the hum at full volume but if you concentrate you can, plug and unplug the jack.
With lcd3 though i can detect the hum easier due to the lower impedance.
If you say there is no hum then more power to you!
I know i reduce the background noise in mine when I change the capacitors, i had more background hum in my stock 339.
If you don't then fine, you don't need to do anything to your 339!

Just I have not tried extreme situations but I did not hear any hum during normal listening.

 

[telecaster]

Hmmm well you will have to let us know if the issue is fixed with the heater modification. The issue with omitting a center tap is heater-to-cathode leakage, which typically will vary from tube to tube. If there are leakage currents coupled from the primary to the secondary of the mains transformer and the heater supply is not center tapped in any way, they can be coupled to the cathode of the input tube from the heater. If the tube has little-to-no leakage, there may be no hum, even if the heater supply is not center tapped. If someone is going to do a mod I worked on, just wanted to make sure it is done correctly, only reason I chimed in. Hope everyone is enjoying the music.

Thanks again LG. I have understood your mod and i will be careful. Will report here if it cures it.

I enjoy and respect the 339 and i am just searching a way, if any, to improve it gents!

 

[telecaster]

Just I have not tried extreme situations but I did not hear any hum during normal listening.

During normal volume level, say less than 50% you will never hear any kind of hum for sure.

 

[UntilThen]

Does the hum go away with different tubes, telecaster?

That's a good question. I find some adapters introduce hum or noise of some sort... and some tubes of course.

I was aghast when my single NOS 5998 from Langrex was humming loudly and I mean loudly. It's unusable. Fortunately I have my other pair of NOS 5998 that is totally silent and sound great.

 

[L0rdGwyn]

That's a good question. I find some adapters introduce hum or noise of some sort... and some tubes of course.

I was aghast when my single NOS 5998 from Langrex was humming loudly and I mean loudly. It's unusable. Fortunately I have my other pair of NOS 5998 that is totally silent and sound great.

Was this 5998 still making music but humming? And was working in other circuits? The La Figaro 339 appears to have the same heater issue as the DarkVoice which is what the linked mod was made to address. Tubes that were otherwise silent in other circuits were unusable in the DarkVoice until I fixed it. Many new DarkVoice owners think their tubes are defective, but it isn't the tubes.

 

[UntilThen]

Was this 5998 still making music but humming? And was working in other circuits? The La Figaro 339 appears to have the same heater issue as the DarkVoice which is what the linked mod was made to address. Tubes that were otherwise silent in other circuits were unusable in the DarkVoice until I fixed it. Many new DarkVoice owners think their tubes are defective, but it isn't the tubes.

Was definitely that tube because it's humming loudly in my Wa22 as well. You can hardly hear the music due to the loud hum. I took it out immediately.

I'm fortunate to have both Wa22 and LF339i to verify my tubes.

 

[UntilThen]

Was this 5998 still making music but humming? And was working in other circuits? The La Figaro 339 appears to have the same heater issue as the DarkVoice which is what the linked mod was made to address. Tubes that were otherwise silent in other circuits were unusable in the DarkVoice until I fixed it. Many new DarkVoice owners think their tubes are defective, but it isn't the tubes.

I had the DarkVoice 336se before and I know that's more temperamental. With 3 of my LF339 and 339i, I have never had such issues except the 2nd LF339. This incident in question is a pair of NOS brand new Mullard 6SJ7gt. One channel had no sound but when I reverse the tubes, I get stereo again. Switch it back again and I get no sound in one channel again. Repeated this many times and the same behaviour. I'm really puzzled. You can't say it's the tubes because subsequently I use that pair in the newer LF339i and I don't have that problem.

 

[L0rdGwyn]

Was definitely that tube because it's humming loudly in my Wa22 as well. You can hardly hear the music due to the loud hum. I took it out immediately.

I'm fortunate to have both Wa22 and LF339i to verify my tubes.

Well I'm glad it was just the tube and it isn't an issue with the amplifier! Hopefully they gave a refund.

I had the DarkVoice 336se before and I know that's more temperamental. With 3 of my LF339 and 339i, I have never had such issues except the 2nd LF339. This incident in question is a pair of NOS brand new Mullard 6SJ7gt. One channel had no sound but when I reverse the tubes, I get stereo again. Switch it back again and I get no sound in one channel again. Repeated this many times and the same behaviour. I'm really puzzled. You can't say it's the tubes because subsequently I use that pair in the newer LF339i and I don't have that problem.

Maybe a loose socket connection? I have seen it before where the pins of a socket make poor contact in one channel, swapping the tubes and the fit is better in the opposite socket, that is my best guess.

 

[hp4fun]

6922 as a replacement for 6sn7? I have a 6922->6sn7 adapter, and it "works" on my another 6sn7 preamp.

For those who has 6sn7 as driver tube in LF339, have you ever considered this? Any warnings?

 

[UntilThen]

Well I'm glad it was just the tube and it isn't an issue with the amplifier! Hopefully they gave a refund.

No I'm not chasing a refund because I had the tube for 3 years and did not check it out. Problem with my having so many tubes. I lose track of them. Besides I have very high regard for Langrex. Won't make an issue of it. They are one of my favourite supplier.

 

[UntilThen]

6922 as a replacement for 6sn7? I have a 6922->6sn7 adapter, and it "works" on my another 6sn7 preamp.

For those who has 6sn7 as driver tube in LF339, have you ever considered this? Any warnings?

Trying it will cost money. I had Euforia before and I wanted to experiment EF86 in Euforia's 6sn7 sockets because I like the EF86 in La Figario. I got mrsxuling to make EF86 to 6sn7 adapters for me but when I tried EF86 in Euforia, it didn't sound right and had occasionally piercing noise. I stop the experiment then and there. Adapters are still with me.

 

[UntilThen]

Similarly I have c3g to 6sj7 adapters and have use c3g tubes in LF339i but the sound is not tight like EF86. It's not bad but not good too. I gave up using those lovely c3g tubes, which sounded great in Glenn OTL amp.

 

[L0rdGwyn]

No I'm not chasing a refund because I had the tube for 3 years and did not check it out. Problem with my having so many tubes. I lose track of them. Besides I have very high regard for Langrex. Won't make an issue of it. They are one of my favourite supplier.

I like Langrex myself, very consistent, in fact I need to place an order with them...

Unfortunately not all tubes are plug and play due to differing bias requirements. EF86 are nice, very linear triode strapped, I use them in my phono stage, low noise as well.

 

[Galapac]

I know many of you like or are looking for Tung-Sol 7236 tubes. This guy has plenty for a pretty good deal.
https://www.ebay.com/itm/Vintage-Mi...381987?hash=item3ff50fa1a3:g:JOoAAOSwMAhgNTFy
You can even make him an offer.