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Post by jbgtr on Jun 26, 2009 10:27:14 GMT -7
I currently have JJE34L power tubes in my KT. I recently got a matched pair of GT E34LS tubes to try.
Myles, I know you mentioned before, though I couldn't find the thread, that the GT E34LS is a 30 watt tube and the JJE34L is a 25 watt.
The GT's I got are a power rating #6.
Because the #6 is one of the middle ratings, is a rebias absolutely necessary? If I were to put them in without rebiasing, what exactly would happen? Would they be running "too cold" or "too hot"?
Also, I was reading in an earlier thread that you can swap the 5ar4 for an SS without rebias as the B+ only increases a small amount.
If I were to switch to an SS, thus increasing the current 1-2 mA, would the GT E34LS #6, be ok to swap without a rebias?
Sorry for the long-winded post! ;D
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Post by Darkside on Jun 26, 2009 14:44:45 GMT -7
Just to jump in here, my KT45 came with the SS rectifier, if I swap it for a tube rectifier, a 5AR4, do I need to re bias?
Thanks!
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Post by Darkside on Jun 28, 2009 17:24:20 GMT -7
I think I've found the answer myself on the Dr Z website: "KT-45s can have a Solid State Rectifier or a Tube Rectifier; it is a matter of taste. The Tube will soften the amps response and lower its overall wattage. With the Solid State Rectifier installed, adjust the bias pot for 480 Volts DC at the Center Tap. With a 5AR4/GZ-34 Tube Rectifier, set the center tap for 440 Volts DC."
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Post by Darkside on Jul 2, 2009 23:52:47 GMT -7
Hi Jamieb82, I put this question to Myles in the "ask the experts" section, here's what he said about the rebias: "Yes ... the bias is set close enough that dropping in a SS rectifier is really nothing more than plug and play. The amp will be a bit tighter and have a bit more wattage as the plate voltage will be a few volts higher but not enough to change things much. I always carry a SS rectifier as a spare on the road as the are very reliable compared to new production tube rectifiers." Hope that helps you!
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Post by jbgtr on Jul 5, 2009 9:10:42 GMT -7
Thank you Darkside, and Myles
that is awesome, good to know!
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Post by Darkside on Jul 5, 2009 11:46:50 GMT -7
Indeed! I have a nice Mullard GZ34 here that I was dying to try out in the KT, good to know I can just drop it in!
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Post by jbgtr on Jul 5, 2009 18:16:11 GMT -7
i just tried out a Sovtek SS rectifier. definitely a noticeable difference. Though, I can't say whether I prefer one to another. I was just playing "tatoo" from live at leeds, and the clean tones are absolutely remarkable, sounds just like the recording, minus my playing
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Post by Darkside on Jul 6, 2009 5:28:48 GMT -7
The doc did say the KT was voiced towards the live at leeds sound, sounds like you found it! How cool is that!
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mtbuckaroo
New Member
Guitars, Cadillacs...
Posts: 5
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Post by mtbuckaroo on Apr 21, 2010 22:57:24 GMT -7
Just to add to the database, I checked bias on the KT45 I received today. With a Weber WZ34 and a pair of GT EL34Ms (rating 3), it was running at 455 plate voltage and biased cool at 31mA. I popped in a JJGZ34 to see the difference, and it was actually running a tad bit hotter on the plate voltage - opposite of what I expected. Bumped the bias setting on the tubes up to 33.5mA and have it running at 451 plate voltage. Bottom line is that this Weber Copper Cap and this particular GZ34 tube are darn near interchangeable. I'm not getting the variation of 480 and 440 plate voltage as between solid state and tube as suggested by the Z website.
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Post by timford on Apr 22, 2010 1:52:53 GMT -7
The weber is probably made to be very similar to a normal gz34 so it can be interchanged on the road without rebias if need be to get through a gig. The ss which comes with the KT45 measured around 476 on my compubias (from memory), and the NOS gz34 I've got in there now is around the 453-6 mark, although it was 442-4 when I first set up some seimens el34s on the kt45. Can't use the seimens with the ss rec as they are not recommended above 450, and I've already killed one tube by biasing too hot. From what I gather, they are not as tough as the jjs etc. How are you liking it so far? And what speakers? I haven't looked at the other posts yet so I might be about to find out
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