[CheggStudyTools]

Since I have a similar problem I checked on YouTube and found a video that said to try a USB isolator. These devices plug in in front of the USB cable and aren’t that expensive. Judging from Amazon reviews the results are mixed and only around half the people are happy with them.
Someone else suggested a Ferrite choke. These are inexpensive little devices that clamp on the cable - don’t know if they work.
For the AC power you can buy an isolation transformer but these are more expensive and I don’t know how well they work in very case.
In my case I can reduce the hum to inaudible levels by adjusting the volume controls on both my amp and preamp, but the hum is still there when I turn up the volume to levels that are too high to listen to. And being obsessive it annoys me lol…

I'll definitely be taking a swing at the USB isolator soon when I move into my new apartment. For now, the single thing bothering me the most however is how moving the cable around in front of me will generate a digital type of buzzing/humming- if I raise the cable in front of my face it quite literally sounds like some botched attempt at morse code, with a high frequency buzz and sputtering beeping. I know this probably isn't related to the LD1+ anymore, but could be related to why I had to EMF shield my tubes.

 

[D1N0]

Fosi has a tube pre/headphone amp on kickstarter. They seem to be using the platform as a marketing tool. Not a lot of info yet: https://www.kickstarter.com/projects/fosiaudio/fosi-audio-p3-vacumm-tube-pre-amplifier

 

[CheggStudyTools]

Don’t feel stupid about the hum. There is an audiophile proverb that says:
If they make it, it hums.
Many times it is difficult to pinpoint the source of the hum. Before the cell phones became landlines portable phones were often the culprit.
You can try different electrical outlets and if possible move the amp further away from laptops etc.
Recently I upgraded my PC and now, using the same USB cable, I have much more hum than before - haven’t been able to figure out a fix yet.

I did a bit of testing on a couple of guesses, here's the results on the buzzing (laptop power brick) and humming (usb interference, ground loop, idk)

1) Swapped away from the E10k into my audio interface, a Scarlett 2i2, and tested that as a DAC- humming and buzzing remains. So not a problem with the E10k on its own.
2) Ferrite beads- did nothing.
3) Bought ground loop isolator- removed all of the buzzing and most of the humming.

I want to say this is a ground loop issue then, would that be right?

 

[mordy]

I did a bit of testing on a couple of guesses, here's the results on the buzzing (laptop power brick) and humming (usb interference, ground loop, idk)

1) Swapped away from the E10k into my audio interface, a Scarlett 2i2, and tested that as a DAC- humming and buzzing remains. So not a problem with the E10k on its own.
2) Ferrite beads- did nothing.
3) Bought ground loop isolator- removed all of the buzzing and most of the humming.

I want to say this is a ground loop issue then, would that be right?

Happy to hear that things are improving! I think that I solved my own hum problem. The issue was that a lightning strike a block away fried a couple of things - the power supply in my PC blew out and a12V wallwart for a DAC stopped working.
I replaced the wallwart with a beefier power supply - an old PC PS. However, I now discovered that this 12V rail on the PS is the source of the hum. Changed for another 12V wallwart I had lying around and the hum went away.
What I discovered was that the first 12V alternatives I tried (old power supplies for portable phones) measured 16V although it is printed 12V on them. Don't know if it becomes 12V under load, but I didn't like that the indicator lights on the DAV were glowing too bright. Finally I found a wallwart for a fancy flashlight that put out 12,7V and figured that within 10% it should be OK.
No noise, no hum - all is well.

 

[CheggStudyTools]

Happy to hear that things are improving! I think that I solved my own hum problem. The issue was that a lightning strike a block away fried a couple of things - the power supply in my PC blew out and a12V wallwart for a DAC stopped working.
I replaced the wallwart with a beefier power supply - an old PC PS. However, I now discovered that this 12V rail on the PS is the source of the hum. Changed for another 12V wallwart I had lying around and the hum went away.
What I discovered was that the first 12V alternatives I tried (old power supplies for portable phones) measured 16V although it is printed 12V on them. Don't know if it becomes 12V under load, but I didn't like that the indicator lights on the DAV were glowing too bright. Finally I found a wallwart for a fancy flashlight that put out 12,7V and figured that within 10% it should be OK.
No noise, no hum - all is well.

Glad to hear you got everything sorted out when moving to my new apartment, I'll take that power issue into mind; within the past 15 minutes or so I've had another development- in another post in this thread I complained about the cable possibly picking up EMF- before I went on to return the ferrite beads, I clipped some onto my cable, and voila- a solid 95% of that EMF hum is gone, so I can tick that one off the box! This didn't solve the previous two issues more up the chain, but we're getting closer. Granted, the cable now looks horrendous, but that's a problem for a later date.

to give an update on the ground loop isolator- I definitely won't be keeping that in my chain- it does solve the problems, but sound quality takes a serious hit so I'll only be keeping that thing around for testing purposes in the future, now that's left really, is getting one of those iDefenders.

 

[TrollDragon]

Fosi has a tube pre/headphone amp on kickstarter. They seem to be using the platform as a marketing tool. Not a lot of info yet: https://www.kickstarter.com/projects/fosiaudio/fosi-audio-p3-vacumm-tube-pre-amplifier

I think you posted this in the wrong thread. Why would we care about a gimmicky amp that uses tubes for novelty/marketing purposes...

 

[Cognomen]

Currently enjoying listening to Amperex 6AM5 / EL91 after solving a dumb hum problem. The right channel was humming. The closer I got my hand toward the right tube, the louder. When I touched the metal socket saver, it was very loud. When I touched the amp, it was somewhat quieter. I went through the usual rigamarole of checking for electronic interference from the cell phone, pc, lights, etc including rotating the amp 90degrees which can get rid of noise sometimes. Next I switched the right and left tubes and the right one hummed but not the left one, suggesting the tubes were probably ok. Next I tried turning down the LDIII gain switches. It still hummed. While turning the gain back up I noticed "the kid" had jumped one side for EF95 and the other for EF91/92! I jumped both for EF91/92, and powered up to...silence! A couple of EF91/92 mode tubes had run quietly with this asymmetrical wrong setting. The 6AM5 datasheets indicate one should not connect anything to pin 6. There is nothing connected to it in the Amperex 6AM5 tube. They work well in EF91/92 mode without clipping pin 6. After very briefly listening to Karen Dalton, I have not yet heard a flaw or coloration I dislike in the audio produced by these tubes. Will be interesting to listen more and see how they fare with other genres. They were designed for low power audio. The datasheets include running them as triodes with pin 5, the anode, strapped to pin 7, grid 2, which I believe is what EF91/92 mode is doing. The tubes offered on Ebay seem to be rather European, mostly British, with quite a few Mullard. Perhaps the 6AM5 aka EL91 is a rather British tube. It's warm.

 

[barbazz]

That's quite interesting. Another family of tubes that don't need an adapter.

Thanks for sharing.

 

[jsk ksj]

Recently got a used little dot mk4 & loving it. First tube amp, so know nothing.

I have noticed that the volume was noticeably higher on the left channel.

The centre point of the sound in my head is about 1 inch off centre.

I have cleared and reseated all 4 tubes. The issue seems to follow the big 2 tubes at the back, I swap them over, the issue changes side.
Do they need replacing? Any recommendations

Sound quality is great, nonetheless & I can alter the balance within Uapp, so not the end of the world.


Also 2nd question. I recently swapped the front 2 tubes for a pair of 6HM5 EC900 EI Yugoslavia.

Sounds great but amp seems to run a lot hotter than previously. Normal?

 

[mordy]

Recently got a used little dot mk4 & loving it. First tube amp, so know nothing.

I have noticed that the volume was noticeably higher on the left channel.

The centre point of the sound in my head is about 1 inch off centre.

I have cleared and reseated all 4 tubes. The issue seems to follow the big 2 tubes at the back, I swap them over, the issue changes side.
Do they need replacing? Any recommendations

Sound quality is great, nonetheless & I can alter the balance within Uapp, so not the end of the world.


Also 2nd question. I recently swapped the front 2 tubes for a pair of 6HM5 EC900 EI Yugoslavia.

Sounds great but amp seems to run a lot hotter than previously. Normal?

There is a good probability that the uneven volume levels are connected to the power tubes - changing them (or one of them) should help.

 

[Cognomen]

Recently got a used little dot mk4 & loving it. First tube amp, so know nothing.

I have noticed that the volume was noticeably higher on the left channel.

The centre point of the sound in my head is about 1 inch off centre.

I have cleared and reseated all 4 tubes. The issue seems to follow the big 2 tubes at the back, I swap them over, the issue changes side.
Do they need replacing? Any recommendations

Sound quality is great, nonetheless & I can alter the balance within Uapp, so not the end of the world.


Also 2nd question. I recently swapped the front 2 tubes for a pair of 6HM5 EC900 EI Yugoslavia.

Sounds great but amp seems to run a lot hotter than previously. Normal?

Many here have enjoyed 6HM5s for hours successfully in the MkIII and MkIV. They draw about .2Ah per tube. People have successfully run drivers up to .4Ah each. My LD MKIII functions as a heater in my small offfice.

 

[jsk ksj]

Many here have enjoyed 6HM5s for hours successfully in the MkIII and MkIV. They draw about .2Ah per tube. People have successfully run drivers up to .4Ah each. My LD MKIII functions as a heater in my small offfice.

Great, in winter

 

[barbazz]

With all this conversation about 6HM5 couldn't resist plugging them in. A perfect companion to the Portuguese Summer

 

[TrollDragon]

I've been running the Yugoslavia 6HM5 in my LD MK IV for 9 years, great tubes!

 

[jsk ksj]

I've been running the Yugoslavia 6HM5 in my LD MK IV for 9 years, great tubes!

I have seen them described as "gooey & very warm". I tend to agree but have limited experience of tube rolling.

Would you agree with this description ?

Also, does changing the rear tubes (power tubes?) affect the sound ?