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In my EL34 cathode biased build which is similar to the matchless chieftain, (tho different PT and OT and pre) do you think i should do as the matchless and have one 1k screen on each tube plus a common 1k for a total of three, or just the two 1k's....one on each tube?
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It's easier on the tubes with more resistance but remember that the first (shared) 1K actually looks like it's 2K to each screen...plus the 1K's for each one and you effectively have 3k resistance for each screen. But those amps run a lot of current and eat tubes so you might need that. IMLE, when you start getting much above 2K or so you can hear it...amp gets less punchy/alive and starts to sound weak/anemic (sort of like spent tubes sound). -
how can i tell whether i do? I'm not running the same trannies as the matchless. In fact, i picked them with zero consideration towards that amp's circuit. I only came to see it and decide on that design after i had the transformers. Mine are a hammond 272JX 300-0-300 PT and a 4k heyboer 50 watt OT. The PSU will otherwise be close with the same 32uf/32uf cap cap with a 20H choke between the 2 sides, and it will be cathode biased too.But those amps run a lot of current and eat tubes so you might need that.Comment
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For what this is worth, I typically will use a single SGR for each power tube. Also, for the EL-34, my spec'ed value is 5.6 K 3 watt.
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Isn't 5.6k kinda high? Being a noob, trying to fully understand this is hard. But from what i have read so far on the subject it seems like the trade-off between low and high values is tone vs safety. 5.6k seems like it's higher than anything else i've seen and i would worry it would cause the tone to become much too soft and mushy, no?Comment
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50,000 EL34 amps out in the real world over the last +40 years with only a 1K 5w screen resistor must mean something.Originally posted by daz View Post
Don't fret the smaller details until you are ready to tune for tone by yourself.
Use common sense and don't let all this personal opinion drivel from me or anyone else paralyze you.Comment
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I'm not worried....i'm not going to use 5.6k's. I was just curious. I'm just going to go by the chieftain schematic.Comment
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No. It would mean that the Matchless Chieftain would not have nearly the nice "touch responce" as compared to my model 18 and model 36 amplifiers.Originally posted by daz View Post
-gComment
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daz,
As long as it is sufficiently large then you have protected the amp/tubes. So you should be fine with 1K (or whatever your schematic says). But the bottom line is that you'll never really know any tonal difference until you try it yourself...we could try to explain it but there just isn't any substitute for hearing it yourself. So I would encourage you to build it to the schematic...then try other values and see if you hear a difference...and then decide which you like best.
When I have increased them over ~2K I didn't hear it get mushy...more like weak and anemic...but this was an amp that normally would have 1K.Comment
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