[triod750]

What does need have to do with anything?

Do I need to explain that to you?

 

[bcowen]

Do I need to explain that to you?

No need.

 

[Xcalibur255]

KR KT150 in the flesh.

I had been planning to do this later in the future, but decided to bite the bullet and go for it.

Some very initial impressions: they sound nice, definitely voiced differently than the Tung-Sol KT150 and in my opinion better based in an initial listen. I will withhold any critical evaluation until they have some hours on them but it's promising based on the initial listen. I did encounter a bit of harshness and shoutiness in a couple of test tracks which surprised me because this has never reared its head in this amp with any of the other tubes I've used so far. I'm fairly confident it will go away with some hours, but the mere existence of it is a tad bit worrying.

I'm honestly kind of underwhelmed by their build quality. For what they cost I don't think they are particularly well made. EML tubes feel far better made for example, and my new production Gold Lion KT66 also feel like they are much higher quality. One of the tabs that holds the mica to the glass is bent in the wrong position and just rattles around loose inside one tube, not doing its job at all. I also had to put them through my NOS tube pin cleaning process because the pins were rough and gritty enough that they were resisting going into the sockets more than I was comfortable with. I'm not getting any noise/microphonics though which is what actually matters though, and I hope it stays that way.

Supposedly the vacuum hardness on these KR tubes is very good and they are supposed to last a long time. Given they are operated very conservatively in this amp I am hoping I'll get a good return on investment by getting quite a few years of use out of them, but I hear stories of early failures on KR tubes too so who knows how long they will go. I'm looking forward to see how much they improve with use and am fairly optimistic that they won't be a bad decision. Time will tell.

 

[L0rdGwyn]

What would a Western Electric KT88 cost I wonder

 

[UntilThen]

What would a Western Electric KT88 cost I wonder

Less than a GEC KT88

 

[bcowen]

KR KT150 in the flesh.

I had been planning to do this later in the future, but decided to bite the bullet and go for it.

Some very initial impressions: they sound nice, definitely voiced differently than the Tung-Sol KT150 and in my opinion better based in an initial listen. I will withhold any critical evaluation until they have some hours on them but it's promising based on the initial listen. I did encounter a bit of harshness and shoutiness in a couple of test tracks which surprised me because this has never reared its head in this amp with any of the other tubes I've used so far. I'm fairly confident it will go away with some hours, but the mere existence of it is a tad bit worrying.

I'm honestly kind of underwhelmed by their build quality. For what they cost I don't think they are particularly well made. EML tubes feel far better made for example, and my new production Gold Lion KT66 also feel like they are much higher quality. One of the tabs that holds the mica to the glass is bent in the wrong position and just rattles around loose inside one tube, not doing its job at all. I also had to put them through my NOS tube pin cleaning process because the pins were rough and gritty enough that they were resisting going into the sockets more than I was comfortable with. I'm not getting any noise/microphonics though which is what actually matters though, and I hope it stays that way.

Supposedly the vacuum hardness on these KR tubes is very good and they are supposed to last a long time. Given they are operated very conservatively in this amp I am hoping I'll get a good return on investment by getting quite a few years of use out of them, but I hear stories of early failures on KR tubes too so who knows how long they will go. I'm looking forward to see how much they improve with use and am fairly optimistic that they won't be a bad decision. Time will tell.

Thanks for the nice write-up! I'm a bit surprised (or maybe dismayed) with the build quality issues you noted. I have 2 pairs of 300BXLS tubes that are quite honestly works of art from the construction and fabrication quality standpoint. The first pair has close to 10k hours and still sound great. But they are ~25 years old and were made when Dr. Kron was still alive and running the show. I picked the second pair up 6 or 7 years ago as backups for the original pair, and while I've only played them around 100 hours just to be sure they were good to go, they look every bit as good inside as the older pair. Your report makes me think the overall quality has gone downhill since then which is very disappointing

 

[L0rdGwyn]

Thanks for the nice write-up! I'm a bit surprised (or maybe dismayed) with the build quality issues you noted.

Same, I don't typically go for new production tubes, but the few times I've considered trying some out, they were KR. I like that they tend to use similar construction to the tubes' NOS counterparts, so disappointing to hear the quality isn't quite up to the price point.

 

[L0rdGwyn]

 

[Isaacc7]

Got a bunch of tubes today, hooray! I'm a big fan of 6v6 tubes. Love the 7c5 (the same as a Sylvania 6v6) and also really like the Ken Rad and GE 6v6 as well. Turns out that the 6v6 has a little brother, the 6aq5. It has the exact same electrical characteristics but in a smaller 7 pin tube. I love finding similar tubes in other bases and voltages to save money. True to form the 6aq6 is quite a bit less expensive than the equivalent 6v6 and that allows me to buy some more exotic marques. It may seem petty but I love that I can cross some of these companies off my tube collection list.

First up, Mullard!

I already have more than a few Mullard el38 tubes but it's always good to have more Mullards! Interested to hear a smaller powered output tube from them.

Here's another British company, one that's new to me. Brimar

These really look the business as they say. There's just something about black glass tubes that I love. More tubes in the next posts!

 

[Isaacc7]

I've never listened to any French tubes so this brand is new to me.

Great looking black plates!

And now for the tube collecting highlight for me. I've always wanted to hear stuff from this brand but was put off by the price.

I'm so excited to cross Telefunken off my list!

 

[Isaacc7]

The last tube I got is another differently based version of a popular tube. The oddly named 5B/254m is a two-for for odd bases, it is a loctal and has a top cap!

I've been led to believe that it is essentially a loctal 807 tube. I have some great Sylvania 5933 and a variety of 6gb6a tubes already but I couldn't pass up these British made beauties. They also supposedly have a wicked blue glow to them too! I broke my no more damn adapters rule for these but I can't resist another 6l6 variant.

 

[leftside]

The last tube I got is another differently based version of a popular tube. The oddly named 5B/254m is a two-for for odd bases, it is a loctal and has a top cap!

I've been led to believe that it is essentially a loctal 807 tube. I have some great Sylvania 5933 and a variety of 6gb6a tubes already but I couldn't pass up these British made beauties. They also supposedly have a wicked blue glow to them too! I broke my no more damn adapters rule for these but I can't resist another 6l6 variant.

Billington strikes again! I have similar tubes from Martin: 5B/255M - double halo version and double D getter version. They are nice tubes.

 

[leftside]

I've never listened to any French tubes so this brand is new to me.




Great looking black plates!

And now for the tube collecting highlight for me. I've always wanted to hear stuff from this brand but was put off by the price.


I'm so excited to cross Telefunken off my list!

Looks like new. Great haul.

 

[Xcalibur255]

Thanks for the nice write-up! I'm a bit surprised (or maybe dismayed) with the build quality issues you noted. I have 2 pairs of 300BXLS tubes that are quite honestly works of art from the construction and fabrication quality standpoint. The first pair has close to 10k hours and still sound great. But they are ~25 years old and were made when Dr. Kron was still alive and running the show. I picked the second pair up 6 or 7 years ago as backups for the original pair, and while I've only played them around 100 hours just to be sure they were good to go, they look every bit as good inside as the older pair. Your report makes me think the overall quality has gone downhill since then which is very disappointing

This is my first experience with KR so I can only judge by what I have on hand. I don't consider the quality to be *bad* per se, it just isn't quite to the level I was expecting for the price. When I bought my EML 274B more than 10 years ago my impression is much the same as you describe your old 300Bs: meticulous works of art. Honestly, though, at the end of the day all that matters is how they sound. The loose support piece bothered me only until I powered the tubes on and could confirm that they weren't having noise issues. That's what really matters to me.

I'll add some additional thoughts when I feel they have made some break-in progress.

 

[mordy]

The last tube I got is another differently based version of a popular tube. The oddly named 5B/254m is a two-for for odd bases, it is a loctal and has a top cap!

I've been led to believe that it is essentially a loctal 807 tube. I have some great Sylvania 5933 and a variety of 6gb6a tubes already but I couldn't pass up these British made beauties. They also supposedly have a wicked blue glow to them too! I broke my no more damn adapters rule for these but I can't resist another 6l6 variant.

Possibly this information is helpful from Radiomuseum:

Country: Great Britain (UK) Brand: Standard Telephones and Cables Ltd. (STC); London, Foots Cray Tube type: Beam Power Tube beam power Identical to 5B/254M = CV428 Similar Tubes Different connections: 5B/254G ; 5B/255M Multiple differences or of other kind: 5B/257M ; 5B/258M ; CV2347 Base Loctal-8, B8G (Sylvania, 1938) Filament Vf 6.3 Volts / If 0.9 Ampere / Indirect / Specified voltage AC/DC Description This is one of a range of reliable beam power tubes from STC. The 5B/254G, 5B/254M (CV428), 5B/255M (CV391), 5B/256M (CV499), 5B/257M (CV2220), 5B/258M (CV2347), were developed from the 5B/250A (807)with similar characteristics to the 807. The range comprises single and double-ended and wire terminated versions and were widely used in military and civilian equipments for both audio and radio frequency applications up to 125 MHz. Total anode and screen dissipation <25W. Power outputs from a pair at 60 MHz class C can achieve 40W with anode voltages of 600. At audio frequencies a pair in class AB2 can achieve 80W rms.