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KT120 tubes in Oddblocks
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6050
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Author:  gofar99 [ 05 Oct 2017, 15:52 ]
Post subject:  KT120 tubes in Oddblocks

Hi Everyone, I'm looking for info....has anyone used Asian tubes in the KT120 Oddblocks or even in class A single ended amps. I'm hunting for something to replace the Tungsol ones as the new ones can not handle the dissipation (at about 85%) in the amplifiers.

Good listening
Bruce

Author:  Geek [ 06 Oct 2017, 00:01 ]
Post subject:  Re: KT120 tubes in Oddblocks

KT-120 seem to be tied up by T-S this side of the pond... I see images for Shuguang Treasure KT-120, but no places to buy them :confused:

Author:  gofar99 [ 06 Oct 2017, 16:27 ]
Post subject:  Re: KT120 tubes in Oddblocks

Hi Everyone, I had a request for photos of the differences. The new tubes are only able to handle 75% (absolute max) of the rated dissipation in Class A U/L. Still about 25% better than KT88s and they cost the same. We knew it was too good to last. The early ones can do as much as 90%. I have a pair in my personal amps (for longevity testing) running 94%. Been there nearly 5 years and are just fine.

Notice the changed fins and different support structure in the new tubes. It kind of looks like they had to change the supports and then discovered the fins didn't clear them. So they squashed the fins. In off line correspondance I suspect that there ar enow two versions of the tube type. One for everyone except the big companies. Those are more like the old ones and bear the company's names and logos. Seems like we are all second class citizens.

Good listening
Bruce
Attachment:
KT120s Ae.jpg
Attachment:
KT120s Be.jpg

Author:  Geek [ 07 Oct 2017, 03:01 ]
Post subject:  Re: KT120 tubes in Oddblocks

If it were me, I'd just terminate all KT120 designs if I didn't have the funds to lawyer-up :bawling:

Author:  gofar99 [ 07 Oct 2017, 17:13 ]
Post subject:  Re: KT120 tubes in Oddblocks

Maybe I'll use 6C33s next :evil: 4CX1000s might do the job...except where whould I put the massive radiator needed to cool them? :hot:

Good listening
Bruce

Author:  Juancho [ 08 Oct 2017, 12:23 ]
Post subject:  Re: KT120 tubes in Oddblocks

I don't recommend 6C33s. Notoriously unstable and no production for many a year. 845s last forever and are really reliable. Could they run at eg 600v?

Author:  Geek [ 08 Oct 2017, 18:31 ]
Post subject:  Re: KT120 tubes in Oddblocks

I was pondering your issue, Bruce and came up with the same as Juancho, LOL!

845's IMHO are "mosfetty" in sound, so you'd need to squeeze some sonics from the driver. I'll happy share some circuits via email with you if you're interested :)

@Juancho - 845's are very forgiving of anode voltage, but they don't come into their glory under 800V. A good, ol' fashioned doubler supply a-la Citation-II (only more voltage) would be called for as Edcor won't make them (we designed the XPWR169-120) HV due to CYA liabilities. However, we did design with Edcor an 845 OPT, the EM0774 (unlisted, but available. See thread - http://edcorusa.com/boards/topic/241/mi ... m-the-list ).

Cheers!

*edit*
I just remembered the Oddblocks are PP.

850-900V B+ and this wee beastie should do:
http://edcorusa.com/cxpp100-42k

1KV-1100V this:
http://edcorusa.com/cxpp100-5k

Author:  Alpha Wolf [ 09 Oct 2017, 08:55 ]
Post subject:  Re: KT120 tubes in Oddblocks

I have used over 20 pair of edcorCXPP100-10K transformers at 1000v to 1100v with no problems for years with no prolbems. The only problem I ever had with Edcor was power transformers. Every one that I used went to a dead short with out any warning. I am talking about the 1100 volt 400ma 6v 4a 6v 2a that are no longer made. Ever since then I use only Antek power transformers. All of the edco r power transformers lasted a little short of 5 years. Never had problem with outputs though.

Author:  Geek [ 09 Oct 2017, 16:34 ]
Post subject:  Re: KT120 tubes in Oddblocks

Alpha Wolf wrote:
The only problem I ever had with Edcor was power transformers. Every one that I used went to a dead short with out any warning. I am talking about the 1100 volt 400ma 6v 4a 6v 2a that are no longer made.


Probably why Edcor discontinued my 1500V XPWR169 :confused:

Never had a PT problem from them, but I also overdesign.... I use a transformer that's only at 50-65% of its ratings when the amp is full tilt. Preamps I'll do 75%.

Cheers!

Author:  Juancho [ 09 Nov 2017, 13:31 ]
Post subject:  Re: KT120 tubes in Oddblocks

Good news guys, the latest set of KT120s I bought are completely happy at 124ma dissipation. I've set the amps there specifically for a customer. Once he's done his home demo I'll try at 137ma but these 120s are doing much better than 20 out of 24 KT150s tried over recent months

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