[jsk ksj]

That's good to hear. I have the Ei 6H5M, tall bottles installed and a pair of 6N6P's on their way

Replacement 6N30Pi fitted , all is good again

 

[Cognomen]

Not neccessarily

I use them mainly for the good grip they give but also for the protection they give. When I remove octal tubes I always use a screwdriver to pry them loose. This protects both the tube and the sockets, also ad

Thin leather gives a good grip! And protection. Protects the tubes from skin oil too.

Thin leather gives a good grip! And protection. Protects the tubes from skin oil too.

Avoiding overheating and keeping things clean is the best practice. There are two schools of thought, though, on skin oil. The other perspective is that it's bunkum and that the no skin oil rule for halogen light bulbs does not apply to the vast majority of vacuum tubes: skin oil and household dust are likely to have a negligible effect; after purchasing NOS tubes that have in all likelihood been touched by hands, perhaps a lot, there is no need to de-oil them.

 

[jsk ksj]

I have seen 5k -10k hours quoted as life of tubes. Is this reasonably accurate estimate? If I use for 2 hours per day, can I expect 7 - 14 years of use? Is this all at the same level of performance or is that degrading?

Also, do they degrade with use or with time?

 

[mordy]

I have seen 5k -10k hours quoted as life of tubes. Is this reasonably accurate estimate? If I use for 2 hours per day, can I expect 7 - 14 years of use? Is this all at the same level of performance or is that degrading?

Also, do they degrade with use or with time?

Tubes have different ratings re how long they last - anywhere from 500 hours to 10,000 hours. However, the operating conditions in a tank, fighter jet, ballistic missile or old radio or TV are very different from the light operating conditions in our headphone amps.
Don't worry about how long the tubes will last - many people use the same tubes for many years (sometimes 20+) and they are still good. It is more likely that a tube will die from being dropped than from wear.
- There are unscrupulous sellers that claim that you need new tubes after 1000 hours - don't believe them!
Most tubes are rated for at least 3000 hours and many older tubes for 10,000 hours; just use them as much as you want!

 

[jsk ksj]

I guess I was just unlucky having a power tube die on me after 1 month. I bought the amp used, so I have no idea how old it is.

Anyhow, all good now

 

[triod750]

Avoiding overheating and keeping things clean is the best practice. There are two schools of thought, though, on skin oil. The other perspective is that it's bunkum and that the no skin oil rule for halogen light bulbs does not apply to the vast majority of vacuum tubes: skin oil and household dust are likely to have a negligible effect; after purchasing NOS tubes that have in all likelihood been touched by hands, perhaps a lot, there is no need to de-oil them.

I don't think skin oil matters to a tube's performance at all. It's when i put a sticker with identification/information on a tube that I get problems. It won't stick!

 

[jsk ksj]

Final question for today, I have noticed that the amp is much, much cooler since swapping out the failing tube.

Is this a thing ? Do failing tubes cause excess heat?

 

[triod750]

The only tube that has failed for me was one 6C5G from the thirties (?) where the heater died. The resulting silence made the amp cooler.

 

[mordy]

Final question for today, I have noticed that the amp is much, much cooler since swapping out the failing tube.

Is this a thing ? Do failing tubes cause excess heat?

I don't know the answer to your question, but it could be that you gave the answer...

 

[GotNoRice]

I'm having an odd issue with some Sylvania 6DT6A tubes that I got recently, using them on my Little-Dot I+ (v2.0), EF95 setting.

I was REALLY enjoying them. In most cases when I get a new set of tubes, I listen for an hour or two, find them mostly unimpressive, and switch back to one of my favorites. But this was one of those rare cases where I really loved how they sounded, and just wanted to keep listening and listening, and ended up going through most of my favorite songs. These were on-track to replace the 6HM5/6HA5 tubes as my new favorites.

But after about 6-8 hours, I began to notice a somewhat faint, but clearly audible 60Hz hum in the left channel. This hum was NOT present at first (odd noises were the very first thing I checked for after installing the tubes).

Things that I have tried:
-Swapped the left and right tubes- The hum remained, but is still only in the left channel. This would seem to suggest that the tubes themselves are okay, and it's not a case of one tube beginning to fail.
-Swapped in different tubes (tried 6AK5W and 6HM5, since I'm using EF95 setting). No hum present with these other tubes. Hum is ONLY present when using the 6DT6A tubes.
-If I put my hand in-between the tubes and the transformer, the hum becomes slightly weaker. This seems to suggest that it's picking up EMI from the transformer?
-I tried swapping the left and right inputs, and tried running the amp with no inputs connected. The hum remained the same in all cases (faint on left channel only).
-I turned the amp off for a few hours to let everything cool down, but when I turned it back on, the hum came back as soon as the tubes warmed up (~5 seconds).

I'm not sure exactly what the issue is. My best guess, especially being that the hum is at exactly 60Hz, is that it's picking up EMI from the transformer. As to why it's only occurring in the left channel (even when I swap the left and right tubes) is that the left and right tube sockets in the Little-Dot I+ are opposite orientation. Possibly one side of the 6DT6A is more susceptible to EMI, and in the left socket, this is the side that is facing the transformer? It also seems odd that this issue was not present at first but only began after 6-8 hours.

I'm really not sure how to proceed. I'd like to figure out a way to keep using these 6DT6A tubes without the hum.

The only other thing I can think of that I havn't tried yet is to try the tubes in my FX Audio TUBE-01, which also uses EF95-type tubes. I'm currently using it as a tube-buffer with a pair of 6HM5 tubes in my main stereo (I use my headphone amps at my main computer, which is where I actually spend more time).

 

[barbazz]

I'm having an odd issue with some Sylvania 6DT6A tubes that I got recently, using them on my Little-Dot I+ (v2.0), EF95 setting.

I was REALLY enjoying them. In most cases when I get a new set of tubes, I listen for an hour or two, find them mostly unimpressive, and switch back to one of my favorites. But this was one of those rare cases where I really loved how they sounded, and just wanted to keep listening and listening, and ended up going through most of my favorite songs. These were on-track to replace the 6HM5/6HA5 tubes as my new favorites.

But after about 6-8 hours, I began to notice a somewhat faint, but clearly audible 60Hz hum in the left channel. This hum was NOT present at first (odd noises were the very first thing I checked for after installing the tubes).

Things that I have tried:
-Swapped the left and right tubes- The hum remained, but is still only in the left channel. This would seem to suggest that the tubes themselves are okay, and it's not a case of one tube beginning to fail.
-Swapped in different tubes (tried 6AK5W and 6HM5, since I'm using EF95 setting). No hum present with these other tubes. Hum is ONLY present when using the 6DT6A tubes.
-If I put my hand in-between the tubes and the transformer, the hum becomes slightly weaker. This seems to suggest that it's picking up EMI from the transformer?
-I tried swapping the left and right inputs, and tried running the amp with no inputs connected. The hum remained the same in all cases (faint on left channel only).
-I turned the amp off for a few hours to let everything cool down, but when I turned it back on, the hum came back as soon as the tubes warmed up (~5 seconds).

I'm not sure exactly what the issue is. My best guess, especially being that the hum is at exactly 60Hz, is that it's picking up EMI from the transformer. As to why it's only occurring in the left channel (even when I swap the left and right tubes) is that the left and right tube sockets in the Little-Dot I+ are opposite orientation. Possibly one side of the 6DT6A is more susceptible to EMI, and in the left socket, this is the side that is facing the transformer? It also seems odd that this issue was not present at first but only began after 6-8 hours.

I'm really not sure how to proceed. I'd like to figure out a way to keep using these 6DT6A tubes without the hum.

The only other thing I can think of that I havn't tried yet is to try the tubes in my FX Audio TUBE-01, which also uses EF95-type tubes. I'm currently using it as a tube-buffer with a pair of 6HM5 tubes in my main stereo (I use my headphone amps at my main computer, which is where I actually spend more time).

Just tried my RCAs 6DT6A (thanks for remembering me how great these tubes are) with EF95 and I got a hum, just like you.

But.... I usually use them with EF92 settings. No hum and great sound.

 

[GotNoRice]

Just tried my RCAs 6DT6A (thanks for remembering me how great these tubes are) with EF95 and I got a hum, just like you.

But.... I usually use them with EF92 settings. No hum and great sound.

I appreciate the confirmation. Was your hum also isolated to the left channel?

Prior to getting the hum, I did try them on the EF92 setting for a while. The main difference I noticed between the EF95 and EF92 settings is that gain was increased (lower volume needed for same output). After about an hour of listening, my impression of the EF92 setting was somewhat negative. On the EF95 setting the mids are well balanced. On the EF92 setting they are more in-your-face and fatiguing. On the EF95 setting the bass hits hard and is well-controlled. On the EF92 setting the bass becomes borderline bloated. But a longer listening session is certainly warranted, especially if it eliminates the hum issue. I know that these 6DT6A tubes also work with various strapping options which I've never bothered with before.

 

[mordy]

I appreciate the confirmation. Was your hum also isolated to the left channel?

Prior to getting the hum, I did try them on the EF92 setting for a while. The main difference I noticed between the EF95 and EF92 settings is that gain was increased (lower volume needed for same output). After about an hour of listening, my impression of the EF92 setting was somewhat negative. On the EF95 setting the mids are well balanced. On the EF92 setting they are more in-your-face and fatiguing. On the EF95 setting the bass hits hard and is well-controlled. On the EF92 setting the bass becomes borderline bloated. But a longer listening session is certainly warranted, especially if it eliminates the hum issue. I know that these 6DT6A tubes also work with various strapping options which I've never bothered with before.

I encountered similar hum situations with a Little Dot MKIII and was never able to totally get rid of the hum in one channel with certain tubes. My solution is to play loud so that you don't hear the hum...

 

[barbazz]

I appreciate the confirmation. Was your hum also isolated to the left channel?

Prior to getting the hum, I did try them on the EF92 setting for a while. The main difference I noticed between the EF95 and EF92 settings is that gain was increased (lower volume needed for same output). After about an hour of listening, my impression of the EF92 setting was somewhat negative. On the EF95 setting the mids are well balanced. On the EF92 setting they are more in-your-face and fatiguing. On the EF95 setting the bass hits hard and is well-controlled. On the EF92 setting the bass becomes borderline bloated. But a longer listening session is certainly warranted, especially if it eliminates the hum issue. I know that these 6DT6A tubes also work with various strapping options which I've never bothered with before.

I was about to say right channel but I swapped the tubes and the hum followed one particular tube...

 

[GotNoRice]

I was able to confirm that the EF92 setting with the 6DT6A tubes gets rid of the 60hz hum. I still wish I knew what was causing it in the first place.