[bcowen]

How many times do I need to tell myself to stay the off off of ebay? I just won 8 of the Cossor 807 tubes. I put in what I considered a low-ish bid on two lots. Figured it would be nice to have a set of backups. To my great surprise and chagrin, I won both lots. Groan... I did get a deal but sheesh...

Apparently at least one more.

Doesn't work for me either....

 

[bcowen]

Think about this jewelry encrusted pair of headphones from Focal instead:
https://www.focal.com/en/partners/utopia-tournaire

$100,000.00 without stand

No stand? Deal killer. I'm out.

 

[bcowen]

Nobody like my DIY solution? - Must be doing something wrong...

I like everything but the appearance. Personally, I'd peel that off and go with @A2029 's suggestion on the heat shrink, especially the type with adhesive. Would be a permanent fix and look, um, well....better? You can use a hairdryer if it's a pretty high wattage one. Even a Bic lighter will work, as long as you're careful and don't hold it in one place too long (and end up melting the heat shrink).

Black, red, multiple sizes, enough left for the next cable(s), and inexpensive:

https://www.amazon.com/Wirefy-200-Heat-Shrink-Tubing/dp/B089D82FLG/ref=sr_1_4?crid=10SBUPBHDE7HT&keywords=heat+shrink&qid=1665251935&qu=eyJxc2MiOiI1Ljc1IiwicXNhIjoiNC43MSIsInFzcCI6IjQuNTYifQ==&sprefix=heat+shrink,aps,127&sr=8-4

And here's a $10 heat gun if you want to go all in.

https://www.amazon.com/TruePower-01-0712-Mini-Heat-Blue/dp/B00GVMFV6O/ref=sr_1_23?crid=3ITW984ATDFAL&keywords=heat+shrink+mini+heat+gun&qid=1665252187&qu=eyJxc2MiOiIxLjUyIiwicXNhIjoiMC45MiIsInFzcCI6IjEuMDAifQ==&sprefix=heat+shrink+mini+heat+gun,aps,97&sr=8-23

 

[Isaacc7]

I finally got some tubes I had been looking for. The KT81 are advertised as a 7c5 equivalent. A GEC 6v6? Oh yes, please let me have it! Got some in today:

So yippee right? Well, there are a few issues. First of all, while they share the same base and pin out as a 7c5 (loctal 6v6), turns out they are not electrically equivalent. The kt81 is the same as a kt61. The KT61 is the MOV equivalent as an El33 basically. That's good right? Well... I've got a few problems.

A) The max voltage these can take as a pentode is 250v so I can't use them in my current amp.
B) While they can go up to 350v in triode I won't be able to use them in my upcoming amp because the KT61 must be used with auto bias. They are just too twitchy. If they drift just a bit they can go into runaway. Fixed bias is risky.
C) I already own a fair number if N34 tubes which are the 12v equivalent of the KT61. They also look quite a bit better than the kt81

So I'm glad to have my collector itch scratched, and I already have the necessary adapters for these, but I won't be able to use them any time soon.

 

[leftside]

KT61 (and EL33 and related siblings) and KT63 are very fine tubes. And can be had for bargain prices compared to KT66 and KT88.

 

[Isaacc7]

KT61 (and EL33 and related siblings) and KT63 are very fine tubes. And can be had for bargain prices compared to KT66 and KT88.

Much like 807/6l6gb/6l6g are quite a bit less expensive than the 6l6gc. If you’re willing to live with less power you can get great sound at a lower price. Here on head-if seemingly everyone is only using headphones so should be quite happy with lower powered tubes. My problem with the kt61/kt81/n34 is that my amp with auto bias runs the screens at 260v and the anode ate just under 300v. My upcoming push pull amp can go as low as 250v in triode but is manual bias! Arghhh! having these, by all accounts, great tubes and not be able to use them is maddening.

 

[ThanatosVI]

Does anyone have experience with the new KT88-S4A Carbon?
Those are a 2022 release from the german company BTB-ELEKTRONIK. (Probably like for tubeampdoctor they Made a Design and some Chinese or czech company is producing the tubes for them)
There are also EL34 and 6550 tubes of that series respectively.

Furthermore I found Linlai KT88. Linlai doesn't have a Bad Reputation for a Chinese manufacturer. However Linlaiglobal doesn't list them, therefore I am not sure if the available tubes are fake to begin with.

 

[whirlwind]

KT61 (and EL33 and related siblings) and KT63 are very fine tubes. And can be had for bargain prices compared to KT66 and KT88.

Amen brother, love the KT63 tubes....one of the best bang for the buck tubes that I have found!

 

[mordy]

Does anyone have experience with the new KT88-S4A Carbon?
Those are a 2022 release from the german company BTB-ELEKTRONIK. (Probably like for tubeampdoctor they Made a Design and some Chinese or czech company is producing the tubes for them)
There are also EL34 and 6550 tubes of that series respectively.

Furthermore I found Linlai KT88. Linlai doesn't have a Bad Reputation for a Chinese manufacturer. However Linlaiglobal doesn't list them, therefore I am not sure if the available tubes are fake to begin with.

BTB Elektronik is a tube dealer and not a manufacturer. Why don't you ask them directly where the tubes are manufactured?
Re Linlai they have a retail division and a wholesale division with different items and different prices. I always wondered if the same tubes sold on eBay for less (gray market?) are the same quality as the more expensive similar tubes. Personally, I suspect that some Chinese manufacturers manufacture the same tube under different names and versions with different prints, color schemes and more or less fancy packaging at different price points (much like certain alcoholic beverages that are all the same but sold under different brands and different packaging and prices points).
In the past vacuum tubes were made in different versions with special propensities indicating longer life, more vibration resistance, and less microphonics, but never in different quality levels.

 

[LoryWiv]

My goodnes, upgraded my phone after 6 years and as an unexpected benefit, camera quality is markedly improved. Here is my current pentode tube roll in Feliks Euforia AE: Ken-Rad VT-107A (6V6GT) driving Genalex KT88. For an amp. not designed for pentodes, running these triode-strapped beauties with adapters in Euforia produces glorious results. Also, the Genalex KT88 are the only newer production tubes I've ever tried that I kept. They hold their own well with some lauded NOS power tubes. Anyway, I know, photo or it didn't happen:

 

[darktooth8]

My goodnes, upgraded my phone after 6 years and as an unexpected benefit, camera quality is markedly improved. Here is my current pentode tube roll in Feliks Euforia AE: Ken-Rad VT-107A (6V6GT) driving Genalex KT88. For an amp. not designed for pentodes, running these triode-strapped beauties with adapters in Euforia produces glorious results. Also, the Genalex KT88 are the only newer production tubes I've ever tried that I kept. They hold their own well with some lauded NOS power tubes. Anyway, I know, photo or it didn't happen:

I just went down a pretty extensive KT88/6550 journey. I've spent more on tubes than I thought possible...
These current production gold lions are up there on sound. I'd place it at number 1 or number 2. Unfortunately on my amp they have a very low level hum. Could be it's placement to other electrical equipment as well, but I solved them with another new production KT88 tube, by KR audio. If you aren't familiar with them, I found this cool video of how they're made - the founder was pretty passionate about tubes and designed some the size of your forearm


This Euforia looks decked out. I wonder what these tubes sound like on an OTL! You have me curious.

 

[darktooth8]

My quick takes on the tubes I tried
All using NOS 7025A RCA (Quieter/less microphoic 12ax7) and NOS mullard 5AR4 rectifier tubes on ampsandsound nautilus w/ chord qutest/zmf atrium/hd800s

NOS GE 6550 - Sounded claustrophobic so I didn't spend much time with them. Took them out pretty quickly.

NOS Tung sol 6550 - Very punchy bass. Almost too punchy with the 5AR4 mullard as rectifier tubes. Recessed mids. Swapping out for 5U4G rectifier tubes gave everything a bit more wetness. This filled out the mids again, but still felt more closed off than KT88s.

JJ/Telefunken black diamond (JJ rebrand) KT88s - Great sound, good mids, but less full sounding. Somewhat lacking in that tube magic, and closer to the very good SS amp. Overall quite nice, but, microphonic and picks up some sort of electrical/network sound in my old house in the attic

Genelex Gold Lion new production KT88s - Great overall sound and the bass is great while maintaining the sparkle of the mids. For some reason my pair has a slight intermittent hum that comes and goes on these though. Wish they didn't because they sound great when music is playing, and they look great too

The KR audio tubes I mentioned are my favorite. It fulfills my criteria of quiet background, plus the midrange fullness is really great. I thought I wanted a lot of bass when I started all this, but the 6550s actually are too bass forward for me. The KR audio has that fullness and punch but it's not so in your face. These sound great with both types of rectifier tubes, the 5AR4 I actually like more with these (and are less harsh on the KT88s due to slower heat up time) bc it has a nice dry punch to it allowing the midrange of the KT88s to be present, the 5U4G slightly wets the surface of the sound, which is really nice too, but not necessary on the these power tubes.

Anyway, I'm new to tubes in general, just my impression.

What adapters are you using on your euforia? if I swap one type of tube will I have to swap the other?

 

[ThanatosVI]

My quick takes on the tubes I tried
All using NOS 7025A RCA (Quieter/less microphoic 12ax7) and NOS mullard 5AR4 rectifier tubes on ampsandsound nautilus w/ chord qutest/zmf atrium/hd800s

NOS GE 6550 - Sounded claustrophobic so I didn't spend much time with them. Took them out pretty quickly.

NOS Tung sol 6550 - Very punchy bass. Almost too punchy with the 5AR4 mullard as rectifier tubes. Recessed mids. Swapping out for 5U4G rectifier tubes gave everything a bit more wetness. This filled out the mids again, but still felt more closed off than KT88s.

JJ/Telefunken black diamond (JJ rebrand) KT88s - Great sound, good mids, but less full sounding. Somewhat lacking in that tube magic, and closer to the very good SS amp. Overall quite nice, but, microphonic and picks up some sort of electrical/network sound in my old house in the attic

Genelex Gold Lion new production KT88s - Great overall sound and the bass is great while maintaining the sparkle of the mids. For some reason my pair has a slight intermittent hum that comes and goes on these though. Wish they didn't because they sound great when music is playing, and they look great too

The KR audio tubes I mentioned are my favorite. It fulfills my criteria of quiet background, plus the midrange fullness is really great. I thought I wanted a lot of bass when I started all this, but the 6550s actually are too bass forward for me. The KR audio has that fullness and punch but it's not so in your face. These sound great with both types of rectifier tubes, the 5AR4 I actually like more with these (and are less harsh on the KT88s due to slower heat up time) bc it has a nice dry punch to it allowing the midrange of the KT88s to be present, the 5U4G slightly wets the surface of the sound, which is really nice too, but not necessary on the these power tubes.

Anyway, I'm new to tubes in general, just my impression.

What adapters are you using on your euforia? if I swap one type of tube will I have to swap the other?

If you want to continue your new production tube rolling there are still some of good quality.

Sophia Electric KT88
E.A.T. KT88
KT88-S4A Carbon (just released this year)
6550C-S4A Carbon (same story)
Soon to come TAD KT88 Redbase

Personally I only have experience with the Sophia Electric which are great Especially in soundstage and detail.
Thanks for the impressions of the KR KT88, they've been on my list for a while but their huge price increase was a turn off

 

[darktooth8]

Thanks! appreciate the recommendations

 

[Isaacc7]

Got in a bunch of adapters in preparation for my new amp. Most of them were the second pair to complete the push pull configuration. One tube I have yet to try until now is the 5b/254m by STC.

They are shrunken down 807 tubes made in the Footscray factory. Yes, I said shrunken down, check out the size difference between them and my usual Corror/Mazda 807.

They are positively tiny compared to the old ones. That can be a big advantage if you're dealing With a small enclosure. The downside to these tubes is that they require a unique adapter that actually cost more than the tube! It's a funky combo, a loctal base with a top cap. There are versions without the top cap for a little more. I wonder if they have the same pin out as the 7c5 (loctal 6v6)? I've always been a sucker for 807 tubes and unloved oddball versions of mainstream tubes so I was always going to get this. Not sure how much sense it makes for sane people though. Still, at 10GBP per tube plus $25 for the adapters they aren't much money and they have a great reputation for sound quality. I'll let you know what I think.