[Toonartist]

Probably closer to the 75-85mA range in Aegis based on those curves, which is pretty hot for Aegis. Someone could try it and take a measurement, but based on those curves I can't really give it a full endorsement.

Not worth it then.

The GEC KT88 do pop up at a reasonable price as single tubes every now and again. I just try to buy them from one seller so there is consistency in testing and if they’re reasonably close to the ones i have… grab it! They last for ages anyway so I can’t imagine needing more than one spare pair… especially as I don’t heavily use them!

 

[DenverW]

Not worth it then.

The GEC KT88 do pop up at a reasonable price as single tubes every now and again. I just try to buy them from one seller so there is consistency in testing and if they’re reasonably close to the ones i have… grab it! They last for ages anyway so I can’t imagine needing more than one spare pair… especially as I don’t heavily use them!

Your tube set is already pretty darn impressive .

 

[Toonartist]

Your tube set is already pretty darn impressive .

Cheers ... I may well add to it over time but I've stopped adding different tubes for a while as I wanted to backup the ones I had first. And, to be honest, I love the ones I have and didn't feel the need to try anything else. But I admit it is fun to try new ones out but safely!

 

[L0rdGwyn]

Oh sorry I should have said something else about the TT21 - The bias current I quoted assumes you are using a GZ34. With a higher voltage drop rectifier like a 5R4, The TT21 should bias at a more acceptable current

 

[Toonartist]

Oh sorry I should have said something else about the TT21 - The bias current I quoted assumes you are using a GZ34. With a higher voltage drop rectifier like a 5R4, The TT21 should bias at a more acceptable current

Thanks… in that case I’ll keep an eye open still. I still think i need to see a very competitive price to consider it. If they’re only a bit cheaper I wouldn’t bother!

@L0rdGwyn Also, i was just thinking the other day. Is there normally a tell tale sign if a rectifier tube is on the way out… and, what would happen if one failed. Is it likely to damage the amp or other tubes? Not sure how long to expect the Brimar 5R4GY to last!

 

[leftside]

Not worth it then.

The GEC KT88 do pop up at a reasonable price as single tubes every now and again. I just try to buy them from one seller so there is consistency in testing and if they’re reasonably close to the ones i have… grab it! They last for ages anyway so I can’t imagine needing more than one spare pair… especially as I don’t heavily use them!

Agreed. And the nice thing about the GEC KT88, is that once they started making the three getter version (two on each side and one on the top) in the mid to late 50's, the construction stayed the same until the very end in the 80's!

So, for those of us with a little OCD, who have ended up with multiple EL11, EL12, etc (with unlimited variations)... this is a real bonus.

The only thing you really have to watch out for with the GEC KT88 is the getter flashing on the sides. Once the nice silvering starts to disappear and you start to see a fair bit of browning/yellowing then the tube doesn't have much life left - no matter how strongly it may test. I used to see lot's of these on eBay.

 

[Toonartist]

Agreed. And the nice thing about the GEC KT88, is that once they started making the three getter version (two on each side and one on the top) in the mid to late 50's, the construction stayed the same until the very end in the 80's!

So, for those of us with a little OCD, who have ended up with multiple EL11, EL12, etc (with unlimited variations)... this is a real bonus.

The only thing you really have to watch out for with the GEC KT88 is the getter flashing on the sides. Once the nice silvering starts to disappear and you start to see a fair bit of browning/yellowing then the tube doesn't have much life left - no matter how strongly it may test. I used to see lot's of these on eBay.

Exactly. I tend to watch out for ones with good side flashing... similar in size to my NOS pair and that test well. The NOS pair I have were from 1980/81 but my spares are from 62. I believe they stopped manufacturing them in the UK in 1987 before selling the equipment to a company in China. The insides are identical, however, the actual size of the glass tube is different. The older tubes have a slightly longer top neck, more headroom for the top getter. It's about 5-8mm taller.

One thing buying them as singles, the seller can't slip in a part duff one as part of the pair I’ve seen a few that do a close ups on the better tube and the second tube a little further away has a smaller burned out looking side getter!

For those with the Aegis and the AC, the GEC KT88 really do pair well. I'd have been happy with one pair with the Meze Elites but when I heard them with the AC I knew I'd want some backups!

 

[Phantaminum]

 

[L0rdGwyn]

 

[mchuckp]

Wow! Great color!

 

[Toonartist]

Hell yeah.... very nice!!!

Red and black is a great combo

 

[AnyDave]

Wow! Great color!

Yeah, that thing will be warmed up before he even turns it on.

 

[cats4cans]

Any chance you’ve compiled some design theory books that might appeal to the noob with not as much soldering time as basic electronics (that don’t seem to directly apply much). I have very specific notions of what I’d like to build, but would very much like to optimize it to cut down on what will inevitably be shoddy initial implementation. I might even assign myself some homework projects aa warmups. At this point as much as I’d love to talk your ear off about it, I know how busy you must be. So I’d be ever so grateful for a reading list to help combat my insomnia.
Thanks

 

[whirlwind]

Not worth it then.

The GEC KT88 do pop up at a reasonable price as single tubes every now and again. I just try to buy them from one seller so there is consistency in testing and if they’re reasonably close to the ones i have… grab it! They last for ages anyway so I can’t imagine needing more than one spare pair… especially as I don’t heavily use them!

You are getting a nice collection of tubes for your amp

If you don't constantly use them in your amp, one spare set is all you would probably ever need.
That is a good thing, as those are not cheap .

Tubes last so much longer than most people think, a nice set of tubes will last years if they are not in your amp constantly.
I only use my favorite tubes when I am going to sit down with no distractions and get lost in the music. I never use my favorites with casual listening and surfing the internet.

 

[L0rdGwyn]

Any chance you’ve compiled some design theory books that might appeal to the noob with not as much soldering time as basic electronics (that don’t seem to directly apply much). I have very specific notions of what I’d like to build, but would very much like to optimize it to cut down on what will inevitably be shoddy initial implementation. I might even assign myself some homework projects aa warmups. At this point as much as I’d love to talk your ear off about it, I know how busy you must be. So I’d be ever so grateful for a reading list to help combat my insomnia.
Thanks

Hey @cats4cans , check this post:

https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/post-17748492