6CA7 Mikael Abdellah's KT88 SE amp?

[porkchop61]

I just got a pair of Shuguang KT66's from the Tube Depot (Sino) to try in this amp. Very nice looking tubes, no silkscreen on the outside, brown bases. They sound very good, very similar to a 6L6GC (surprise).

I did have a question about the blue glow in these tubes. I've never used an amp with KT66's, so maybe this is normal.
I get a blue glow along the inside of the seam where the plates are welded together, is this normal? Usually I see this phenomenon on the inside of the glass where there are holes in the plate. Just curious, both tubes exhibit this same phenomenon, so it's probably not an issue.
Anyone have any experience with this on Chinese KT66's?
Glenn

 

[Cycline3]

I just got a pair of Shuguang KT66's from the Tube Depot (Sino) to try in this amp. Very nice looking tubes, no silkscreen on the outside, brown bases. They sound very good, very similar to a 6L6GC (surprise).

I did have a question about the blue glow in these tubes. I've never used an amp with KT66's, so maybe this is normal.
I get a blue glow along the inside of the seam where the plates are welded together, is this normal? Usually I see this phenomenon on the inside of the glass where there are holes in the plate. Just curious, both tubes exhibit this same phenomenon, so it's probably not an issue.
Anyone have any experience with this on Chinese KT66's?
Glenn

Mine do this... I use a pair in my headphone amp wired as triodes for the output stage. They sound great and look great. I have one in a little SE guitar amp - and it sounds way better than a SED SV6L6GC that I have to compare it with. All in all, I'm impressed with these tubes.

As for the blue glow - it's normal in output tubes and has been even when they were making them in the USA and Western Europe. As long as it's that light blue glow along the plate or outside glass, you're fine. What you need to watch for is if it gets cloudy and starts to look similar to a florescent light bulb. Then you have an air leak and the tube is dead... and will wreak havoc in your amp quickly.

Tubelab has a great picture at the bottom of his page here.

 

[porkchop61]

Thanks Cycline3.
I thought this was normal. thanks for confirming.
This was the first time I've seen this on the inside of the plate structure. Usually I see this on the inside of the envelope.

I'm very impressed with this tube for being so inexpensive. I may try a pair in my 6L6 PP guitar amp, the only thing I have to change is the heater transformer. These KT66's require quite a bit of current.

Glenn

 

[seel34]

hello , living in the netherlands ,i tryed out many different el 34 over the year in diferent amps ,and my favorites are nos old brown based tesla,s ,
frown the nowadays produced tubes i would recomend winged c from the sint petersburg factory , if you use them in triode i would recoment the hazen grid modification ,see my other post on this subject ,its the best 50 cents i ever spent grtz ko

 

[scott17]

Porkchop, do you have some pics of your rig? Love to see both externals and internals if you have them.

I'm interested to see your layout etc. One day I hope to build this amp myself.

Hi,

I was perusing this thread for info on 6CA7 and I came upon your post. If you are still interested in building the amp, check this out.
http://www.diyaudio.com/forums/vendors-bazaar/180897-kt88-se-basic-master-kit.html

This amp sounds fantastic. You will be very pleased.

Scott