Tubes Asylum

EL38 in a Cronus II magnum

173.23.140.228

oreillyreally

A

I have been using EL38 (instead of EL34) in my Rogue Cronus II Magnum for a bit, but am wondering if I have adjusted the bias properly. For the EL34 I had it set to 30, but with the introduction of the EL38, I had to increase the amount on the dial to get it to even show any amount. I have it set to 20 for the EL38 but should have left it set to the previous or reduced the bias by half and then inserted the EL38, even though I the meter doesn't register anything (I hear that one should maybe even reduce the bias by 2 times of the EL34 @30, but am again not sure how to proceed). There is no red plating, distortion or the like, just a clear reproduction, actually better than the previous NOS EL34 they replaced...

Edits: 09/09/23 09/09/23

Follow Ups:

RE: EL38 in a Cronus II magnum - dericmc@live.com 11:08:10 11/08/23 (0)
I have never heard of EL 38 I looked in my books I saw it as EL 38 6CN6 uses basing 8EW where El 34 basing is 8ET
RE: EL38 in a Cronus II magnum - Mendel 19:31:44 09/23/23 (0)
I know that the Rogues can take EL34 and even EL37, but this is the first I've heard of EL38. A quick look on eBay shows that those tubes are not exactly cheap, but less than NOS EL34 and EL37. Not a big fan of top caps, but I may have to give them a try.
Not sure about bias but I would think similar to EL34 would work.
RE: EL38 in a Cronus II magnum - Tre' 20:23:57 09/09/23 (0)
I read that they will red plate at 25 watts (can only see it in a darkened room). Even though they are rated at 25 plus 8 for the screen grid. They were saying to run them at 18 watts total dissipation at idle. This was in triode mode.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
- https://rec.audio.tubes.narkive.com/12sQdJgo/el38-6cn6-triod (Open in New Window)
RE: EL38 in a Cronus II magnum - geoff 17:59:47 09/09/23 (3)
I have never heard of that tube. Did you already have a set, or seek them out?
- EL38 is great in triode - andy evans 02:38:14 09/11/23 (1)
  I used EL38 in triode for a while - probably the best pentode in triode output I've used, with EL12n a close second. I don't like using tubes with top caps, but the sound was marvellous. Especially the "fat bottle" ones.
  - RE: EL38 is great in triode - Paul Barker 05:08:24 04/20/24 (0)
    I just popped in here to see if I could validate my experience with the Mullard EL38 triode set. What you said is my experience. Its not a clone of the EL37 with a top cap. But a different tube in its own right. Dont look for operating points from EL37 and certainly not from the EL34.
    
    Ive had to order a new uTracer. When built I'll trace the triode curves. But I found for now 300 ohm cathode resistor 380v anode volts holds it at max dissipation. 400v and its dissipating 29watts.
    
    I dont get any plate hot spots at 380v.
    
    Its much more lively than an EL84, I like the tone of the EL34 triode but this valve is more live sounding. Foot tapping body engaging live music.
    
    Quad 57's love it. As soon as I tried it I went back on ebay to buy another nos pair.
    
    Im not excited by low power dht's these days. Too polite and boring.
- RE: EL38 in a Cronus II magnum - oreillyreally 19:19:55 09/09/23 (0)
  As my op I have been running them for a month or so, with adapters, but my question is: am I doing the bias wrong re EL38 vs EL34 on this particular amp...
  
  Edits: 09/09/23

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