[L0rdGwyn]

@mordy it can't hurt, but what I said only applies to transformer-coupled amps like Glenn's EL3N and 300B, and any SET amp made by Glenn will not be prone to this, he includes a protection resistor on the output transformer secondary and as I mentioned, Lundahl transformers have very high insulation ratings, so it is really a non-issue in Glenn's SET amps.

 

[mordy]

Personally I did not have problems with the 55998, but I had several different tubes making explosive popping sounds. These tubes were Sylvania 6SN7W and Tung Sol 6/12SN7GT BGRP.
The popping sounds were cured by heating the pins, but I blew out a driver before I understood how to take precautions.

 

[mordy]

@mordy it can't hurt, but what I said only applies to transformer-coupled amps like Glenn's EL3N and 300B, and any SET amp made by Glenn will not be prone to this, he includes a protection resistor on the output transformer secondary and as I mentioned, Lundahl transformers have very high insulation ratings, so it is really a non-issue in Glenn's SET amps.

Thanks for the answer. Do you think that the explosive pops are something different than arcing?

 

[L0rdGwyn]

Thanks for the answer. Do you think that the explosive pops are something different than arcing?

I have experienced the same thing with loose pin connections, most recently on my Mazda AC/HL drivers, tightening the pins fixed the issue. Reheating the tube pins and reestablishing a good solder joint is essentially the same fix, I think it is related to one of the triode elements having a poor connection, so it is intermittently connected / disconnected, causing the pops as voltage is reapplied to the tube rapidly. You'd have to take some measurements to see, but that is my best guess!

 

[mordy]

Thanks

 

[leftside]

A possible alternative to the Tak's for 300B owners:
https://www.europeanaudioteam.com/en/e.a.t.-300b-valve-wp000024.html

I haven't tried them. And I'm not about to start rolling 300B tubes. Best thing I ever did was buy a Glenn 300B - totally curtailed any tube rolling ideas I might have had

 

[mordy]

https://www.moon-audio.com/eat-300b-triode-vacuum-tube.html
Product Warranty
Add product protection:
1 Year
$61.49
2 Year
$98.49
3 Year
$119.99

$1695/pair

 

[Zachik]

Best thing I ever did was buy a Glenn 300B - totally curtailed any tube rolling ideas I might have had

Didn't work for me... When I ordered EL3N amp from Glenn - my plan was exactly the same: no tube rolling!! EL3N tubes only.
Then, when spec'd my EL3N with Glenn, 6J5 drivers were added (in addition to EL3N), and KT66/EL34 power tubes were added (in addition to EL3N). So now, A LOT of tube rolling options, almost as bad (for my wallet) as the GOTL... sigh...

 

[Xcalibur255]

What is the amount of minimum time you'd feel "safe" letting a 5998 warm up before switching to main headphones? Is it fair to assume that most tubes fail during warm up and that after warm up arcing won't/rarely happen? My routine with my bottlehead crack is to let it warm up for 60 seconds without any headphones plugged in. Then I'll connect an old Sony MDR-V6 to play some music on low for 10 minutes, before switching to a ZMF.

30 seconds is all you should need to wait. You're basically waiting for the tube to come on bias. If it's going to misbehave that is when it will happen, the moment it starts conducting as the bias current first ramps up. This process beings about 10-15 seconds after hitting the power button.

 

[Velozity]

We're up to 22 on the possible group buy. I said it half in jest, but we might be able to pull it off. Only problem would be logistics and sending out each individual package to everyone.

I negotiated with the seller to buy 10 of these. 50 was just too many to deal with. So I would assume if any of you also wish to buy smaller quantities from him directly he may do it. I believe the seller has 100 total available. I haven't found any information or pictures on the web so far about Cossor 6C5G tubes. Maybe these are a rare tube that were found buried in a war bunker somewhere in the middle east. If anyone has some history on or insight on this tube I'd love to know.

https://www.ebay.com/itm/50x-6C5G-C...391811?hash=item5489c12e83:g:4GsAAOSwroxfSCFH

 

[L0rdGwyn]

I negotiated with the seller to buy 10 of these. 50 was just too many to deal with. So I would assume if any of you also wish to buy smaller quantities from him directly he may do it. I believe the seller has 100 total available. I haven't found any information or pictures on the web so far about Cossor 6C5G tubes. Maybe these are a rare tube that were found buried in a war bunker somewhere in the middle east. If anyone has some history on or insight on this tube I'd love to know.

https://www.ebay.com/itm/50x-6C5G-C...391811?hash=item5489c12e83:g:4GsAAOSwroxfSCFH

Hard to say from the photos, but Cossor did a fair amount of rebranding, those may be Brimar 6C5G which did come with solid gray shields, here is a pic. Regardless, they are nice tubes.

 

[Velozity]

Hard to say from the photos, but Cossor did a fair amount of rebranding, those may be Brimar 6C5G which did come with solid gray shields, here is a pic. Regardless, they are nice tubes.

That would be awesome. I've been trying to find more Brimar 6C5G and they've all apparently disappeared.

By the way, I don't plan to keep all 10 of these so if anybody wants to share let me know. Hoping they arrive within a month.

 

[L0rdGwyn]

That would be awesome. I've been trying to find more Brimar 6C5G and they've all apparently disappeared.

By the way, I don't plan to keep all 10 of these so if anybody wants to share let me know. Hoping they arrive within a month.

The Brimars are very nice! I have a couple pairs with mesh shields, the Cossor branding is pretty cool too, nice looking tubes.

 

[whirlwind]

Yeah, the Cossor branding is very nice.

 

[gibosi]

I recently made a modest change to my system that really pleases me.

I have the OTL on a shelf and, up until now, if I wanted to adjust the volume I had to stumble out of my comfortable chair. Serendipitously, I recently found a used Schiit Saga with a stepped attenuator (64 steps) and a REMOTE! Life is good! lol