[ItsAllInMyHead]

Y'all are terrible influences... Every Thursday cannot be new tube day.... or can it? See below for new stuff I brought home after work. I admit I'm having fun.

Spoiler: Why I'm stoooopid, but still learning - Long Version

Good news! I have new tubes to play with.
Bad news! The area where I have my Lyr3 is an EMI/RFI danger zone, maybe, kinda, sorta, I think, who knows.... More troubleshooting and reading to come. I've never seen anything quite like it.

The first tube I tried was the 6F8G with the adapter. Because it's KEWL. I was excited. Then hummmmmmmmmmmm. Not the very slight amount I was describing the other day. This was/is a disturbing level of audible hum at my perfect volume setting. No way, I could deal with it. I was distraught. It had no hum when the volume was at 0. Hummed most at 10 to 3 and decreased to no hum and started to hiss (normal) at highest volume. Same on high and low gain, but with varied levels. So, it sounded just fine on low gain at max volume... Anyway, that's not so practical. Nothing I did seemed to improve it. I resigned myself to returning the tube. I yanked it out and started putting in the other tubes.

All the tubes did the same thing to varying degrees with the PSVane and the Full Music being the least "hummy". The RCA and Zenith were comparable to all the other standard short bottle tubes I had previously purchased (and the stock tube). LISST - still no hum. After checking to see that all tubes worked, I thought I'd put the 6F8G back in and make sure everything was fully seated etc. etc. I WANTED it to work. As I was gently rocking the tube and pressing the wire on the top to ensure good contact and seating, the hum changed amplitude. I thought... OK grounding or seating/contact issue. Nope... When my hand got near the tube, from the back side ONLY, the hum reduced. If I cupped my full hand behind the top of the tube - NO HUM. Hand in front of the tube hummmmm. Hand behind - no hum. So, I'm assuming RFI and/or EMI. Also, I'm assuming that the 6F8G whether it's its size, something inherent to its design, and/or the wire from the adapter that make it more susceptible. Now, I have to figure out the source and eliminate it or shield against it... The hand trick also works with the other tubes. Total silence and hum free. Even the slight amount I was describing in previous posts - GONE with all tubes. So, I was chasing power issues for days, when I think it's Schiit flying through the air and interfering with my precious tubes.

tl;dr version - I have a potential EMI / RFI issue I learned of when using the 6F8G with an adapter. It seems some tubes may be more susceptible to interference. I am learning, so any help or experience is appreciated. I'm trying to find the source and/or shield properly and move things. Good news is that if I get it right, all hum is gone.

See below for the new fun stuff...

Also happy to report that sibilance with the Ken-Rad did reduce to tolerable levels after ~20 hours burn-in, and all previously purchased tubes are just lovely. Not sure why all the hate for the GE tube. Maybe after they're all fully burnt in, I'll notice more of a difference, or the others will just beat it up at night and leave it for dead.

 

[Zachik]

tl;dr version - I have a potential EMI / RFI issue I learned of when using the 6F8G with an adapter. It seems some tubes may be more susceptible to interference. I am learning, so any help or experience is appreciated. I'm trying to find the source and/or shield properly and move things. Good news is that if I get it right, all hum is gone.

Never tried the Lyr3 with any adapters, but been playing with the Massdrop CTH and 6C8G tubes (with adapter). TONS of hum
I wonder if RF / EMI is my root cause (no hum with stock 6922 tube on CTH)... I did try different wall outlets in different rooms - no change. Did you try different locations and AC outlets?
I am still debugging my hum issue on CTH, so no conclusion to share (yet).

 

[bcowen]

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[ItsAllInMyHead]

Perhaps you should make a hat for the Lyr.

That is Awesome! Thanks for the laugh.

Seriously, that's very strange. Do you have the Lyr sitting near any large electric motor or near a large transformer? A lamp with a fluorescent bulb?

RFI usually manifests itself as a whine/whistle, buzz, or high frequency squeal rather than a proximity-altered hum. Sounds more like an EMI issue, and if so there has to be something nearby generating that field. Or maybe something not nearby that's generating one hell of a field....

I found the culprit! As I mentioned, I am learning... so if others laugh at my expense while others learn... then I'm cool with that. I moved the Lyr around everywhere, thinking it was my laser printer or fluorescent bulbs or the wall-mount AC units etc. etc. What always moves with it.... DUH!!!!

Takeaways - some tubes are in-fact more susceptible to EMI. I would have never learned that I had an EMI "issue" were it not for the fun with the 6F8G. I thought the hum I was hearing was just inherent to the tubes and "normal". It was tolerable with the other tubes, but not normal. Another foot between the Lyr and the culprit... solved.

Never tried the Lyr3 with any adapters, but been playing with the Massdrop CTH and 6C8G tubes (with adapter). TONS of hum
I wonder if RF / EMI is my root cause (no hum with stock 6922 tube on CTH)... I did try different wall outlets in different rooms - no change. Did you try different locations and AC outlets?

I am still debugging my hum issue on CTH, so no conclusion to share (yet).

It may very well be EMI. I hope you get it solved. I was pulling my hair out. I'll never forget to check for these things in the future though.

Spoiler: My Culprit

I chose a 115V Lyr 3 version b/c I'll be back in the US eventually and I have a ton of transformers. Live and learn.

Total side note - Got my e-mail issue of Cary magazine last night... I do miss the Carolinas.

 

[bcowen]

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[bcowen]

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[Zachik]

I found the culprit! As I mentioned, I am learning... so if others laugh at my expense while others learn... then I'm cool with that. I moved the Lyr around everywhere, thinking it was my laser printer or fluorescent bulbs or the wall-mount AC units etc. etc. What always moves with it.... DUH!!!!

I got another 6C8G to 6922 adapter on the way from fellow Head-Fi-er who experiences no hum. If that won't resolve the issue - I will get another CTH and power adapter from Massdrop (CEE TEE) to try if one of them is the culprit. Will report back when I have news... I realize it is the Lyr3 tube rolling thread, but info could still be useful to Lyr3 tube rollers!

 

[Currawong]

I was browsing the site of the local second-hand hi-fi stores -- they are full of old JBL horn-tweeter speakers and Luxkit amps, and I came across a listing for a Sylvania 6SN7GTA chrome-top. They are normally $50/pop, but this was $17! I didn't hesitate to nab that, and it now has pride of place in the Lyr 3, where its slight smoothness, at least for me, nails it sonically.

Oh, btw, never, ever "hot-swap" tubes. You WILL fry the amp or your headphones. Power-off, unplug your headphones and wait a couple of minutes at least before swapping. Make absolutely sure you don't put the tube in the wrong way. You will destroy things.

 

[Ripper2860]

The Sylvania Chrome Dome is a wonderfully smooth tube in Lyr 3. Very nice sound-stage, nicely balanced, and silky smooth mids. Truly a treat.

 

[bcowen]

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[Zachik]

Sound advice.

And as an addendum, if you decide to play with different tube types via adapters always, always double-check that the adapter is wired correctly. I've purchased quite a few with no issues, but had one a few months back with the first triode's plate wired to one of the heater pins. Have no idea what that would do to the Lyr (or the tube), but I'm pretty sure it wouldn't have been happy and glad I didn't find out about it via smoke signals from the Lyr.

Very timely advice! Since I have a 7N7-to-6SN7 adapter on its way (guess whose fault that is...) - how do I check it for being wired correctly?

 

[Ripper2860]

Wussie. Just throw it in there like I did!!

BTW -- I did just throw it in given my experience with a tube saver from the same seller and after checking seller reviews. No surprises -- worked like a champ.

To check it, you'll need a voltmeter and the 'TDSL Tube Data' Windows app. Pull up the pinout specs for each tube type (launch twice and put side-by-side on your monitor) and using the continuity setting on the meter, make sure the correct input-side pins on the 7N7-side map to the correct output-side pins on the 6SN7 side.



Ex:
7n7 pin #1 (h) goes to 6SN7 pin 7 (h)
7n7 pin #2 (k) goes to 6SN7 pin 3 (k)
and so on ...

Letter designator to letter designator. Watchout for the same letters with a " suffix. They are treated as their own unique designator. ex: 7n7 pin k" goes to 6sn7 pin k", etc.

 

[earnmyturns]

Very timely advice! Since I have a 7N7-to-6SN7 adapter on its way (guess whose fault that is...) - how do I check it for being wired correctly?

Here's what I'd do if I were in your shoes. First, get clear pinout diagrams for 6SN7 and for 7N7. Then, using an multimeter, I'd check continuity between corresponding pins in the adapter. Check my work, please, but going from the 6SN7 (male) side to the 7N7 (female) side of the adapter, you should have 7 -> 1, 3 -> 2, 1 -> 4, 2 -> 3, 5 -> 6, 4 -> 5, 6 -> 7, 8 -> 8. Again, don't just trust what I wrote here, check the diagrams I linked to for yourself, as I know well from my DYI days that distractedly exchanging left with right, in with out, or + with - does happen

 

[Zachik]

Wussie. Just throw it in there like I did!!

BTW -- I did just throw it in given my experience with a tube saver from the same seller and after checking seller reviews. No surprises -- worked like a champ.

To check it, you'll need a voltmeter and the 'TDSL Tube Data' Windows app. Pull up the pinout specs for each tube type (launch twice and put side-by-side on your monitor) and using the continuity setting on the meter, make sure the correct input-side pins on the 7N7-side map to the correct output-side pins on the 6SN7 side.

Thanks! Since I bought it from same seller as you - I might just throw it in too!

 

[Zachik]

Here's what I'd do if I were in your shoes. First, get clear pinout diagrams for 6SN7 and for 7N7. Then, using an multimeter, I'd check continuity between corresponding pins in the adapter. Check my work, please, but going from the 6SN7 (male) side to the 7N7 (female) side of the adapter, you should have 7 -> 1, 3 -> 2, 1 -> 4, 2 -> 3, 5 -> 6, 4 -> 5, 6 -> 7, 8 -> 8. Again, don't just trust what I wrote here, check the diagrams I linked to for yourself, as I know well from my DYI days that distractedly exchanging left with right, in with out, or + with - does happen

I might... I do have a multimeter, and this sounds like a 5 minute effort. Thanks!