Totally Tubular: The Tube Thread

Slimwhit33 said:
I replaced all 14 tubes upon delivery…. Not cheap for sure but yes I know what I’m getting into.
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I’ll feel differently about this if I start getting multiple failures. No doubt. My usage isn’t excessive so I think under the low strain that the EVO places on tubes, I should go years without having to change them. Only one way to find out!
 
Slimwhit33 said:
I’ll feel differently about this if I start getting multiple failures. No doubt. My usage isn’t excessive so I think under the low strain that the EVO places on tubes, I should go years without having to change them. Only one way to find out!
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Because of the adaptive autobias you only really need a couple at a time though to swap out the failed tube, no need to ever swap out all 8 power tubes unless you fancy a tube type change.

I’m thinking KT170 at some stage in the future, apparently the PL can go on and on with those because it runs them so softly.
 
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Joe Mac said:
Because of the adaptive autobias you only really need a couple at a time though to swap out the failed tube, no need to ever swap out all 14 unless you fancy a tube type change.

I’m thinking KT170 at some stage in the future, apparently the PL can go on and on with those because it runs them so softly.
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Good point about not needing a full octet upon failure. I should grab a couple spares shortly.

I considered the 150’s, but the cage doesn’t fit and I have a couple cats, one who is more of a PIA than the other, so the cage is needed just in case. I’ve seen some risers so always an option I suppose.

I don’t think Ive even seen 170’s! The 120’s look so huge, I can’t imagine the others.
 
Slimwhit33 said:
I considered the 150’s, but the cage doesn’t fit and I have a couple cats, one who is more of a PIA than the other, so the cage is needed just in case. I’ve seen some risers so always an option I suppose.

I don’t think Ive even seen 170’s! The 120’s look so huge, I can’t imagine the others.
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You can’t actually use the 170s in the 400, only the 300. They fit across the way but they’re so fat that there isn’t enough space between the two rows for them!

They are both huge and you can’t use the cage but I’ve been running without it for a while now so that doesn’t bother me so much. It will be a few years away though because I’ve a pile of KT88s to work my way through first!

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Joe Mac said:
You can’t actually use the 170s in the 400, only the 300. They fit across the way but they’re so fat that there isn’t enough space between the two rows for them!

They are both huge and you can’t use the cage but I’ve been running without it for a while now so that doesn’t bother me so much. It will be a few years away though because I’ve a pile of KT88s to work my way through first!

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Those are enormous! Geez!
 
Slimwhit33 said:
I replaced all 14 tubes upon delivery…. Not cheap for sure but yes I know what I’m getting into.
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I asked as your purchase reminded me of my first and last tube power amp experience back in 1990. I was able to home demo a Conrad Johnson MV50 and thoroughly enjoyed it matched with my CJ PV8 preamp and Spica Angelus speakers. Looking to the future, I asked the dealer about tube replacement cost and was agog at the $200 expense for four EL34s and four small signal tubes. It scared me away and I bought an Adcom GFSA 555 which never satisfied but it had 200 watts. A learning experience.
Enjoy your new amp!
 
I would like to hear your tube experts opinion on this: a few weeks ago, I had a few separate "incidents" where one of my left channels 6CA7 tubes would red plate for a couple of seconds with a buzzing noise from the speaker, then start working fine again.
I immediately thought either hot bias or tube is going bad. My amp doesn't have user friendly bias adjustment.
The dealer recommended to swap the tube with one on the right channel, to see if the problem followed the tube (bad tube) or do the same thing on the same position (bad bias), before I decide to take it in.
I did the swap, the problem is gone completely, and it's been working perfectly for over a month now.
Should I still be worried or follow the old "if it ain't broke, don't fix it"?
 
renpar61 said:
I would like to hear your tube experts opinion on this: a few weeks ago, I had a few separate "incidents" where one of my left channels 6CA7 tubes would red plate for a couple of seconds with a buzzing noise from the speaker, then start working fine again.
I immediately thought either hot bias or tube is going bad. My amp doesn't have user friendly bias adjustment.
The dealer recommended to swap the tube with one on the right channel, to see if the problem followed the tube (bad tube) or do the same thing on the same position (bad bias), before I decide to take it in.
I did the swap, the problem is gone completely, and it's been working perfectly for over a month now.
Should I still be worried or follow the old "if it ain't broke, don't fix it"?
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I’m not claiming to be a tube expert, but if everything seems to be working fine I’d keep using it but keep an eye on it for any suspicious behavior.

I had bias problem on my Willsenton R8 that disappeared after some tube rolling. I do keep a close watch on that #3 socket as it seems to need more bias adjustments than the other but otherwise everything else is working fine and sounding good.
 
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Reverted back to the EL34 tubes as I really want to hear what the stock power tubes offer and then be able to compare the KT120's later on. Kinda cheated myself out of that by throwing the KT120's in right away. I'm also using the 4ohm tap for the C7's and like the results so far but need to do some real comparisons.
 
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