AnalOg Posted October 25, 2005 Share Posted October 25, 2005 I have a Quad of EH EL34's that I bought about 2 years ago with the intent of running them through the Marks. I was detered because I was told that I would have to do some mods in order to use them. Can anyone give me a little insight on what has to be done or checked for that matter? Tom Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted October 25, 2005 Share Posted October 25, 2005 Just replace the 5AR4 rectifier with a 5U4, rebias and you're good to go. Quote Link to comment Share on other sites More sharing options...
dbflash Posted October 25, 2005 Share Posted October 25, 2005 Guy, Sounds easy enough. What difference in sound can he expect compared to KT88's or 6550? Deeper bass, sweeter mids, etc. Thanks for any info. Danny Quote Link to comment Share on other sites More sharing options...
AnalOg Posted October 25, 2005 Author Share Posted October 25, 2005 I currently bias my kt88's at 70ma, what do I bias the el34's at. Tom Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 25, 2005 Share Posted October 25, 2005 50 ma for the EL34. Quote Link to comment Share on other sites More sharing options...
AnalOg Posted October 25, 2005 Author Share Posted October 25, 2005 Thanks Marvel Tom Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 26, 2005 Share Posted October 26, 2005 Don't do it Tom!!! The 5U4 will not drop enough voltage and EL34 will sound like crap compared to KT88's trust me on this its just simply a poor match. Also the voltages will be to high in the amp every where. The falacy is that 5U4 will drop 45 volts off the B+ and this is true if you kept the KT88's in there biased at 70mA but in reality you will have to lower the bias to about 45mA on the EL34's to keep them from cherry red syndrome which will cause way less voltage drop across the power supply so every thing you gained by switching rectifiers you lost! Then factor in your losing the slow start feature and even biased at 45mA with 500V on the plate the EL34 will not last long no way no how. (the 5U4 acts much like a SS rectifier throw the switch and the voltage is instant on) Craig Quote Link to comment Share on other sites More sharing options...
AnalOg Posted October 26, 2005 Author Share Posted October 26, 2005 I remember you saying something to that affect, when I told you I wanted to run IL34's in the Marks. I wonder wy Triodes rebuild manual says it's O.K. to running plug and play. Tom Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 26, 2005 Share Posted October 26, 2005 Hey believe old Ned and go for it. You can run them no problem just be ready to burn through some tubes and be depressed when it doesn't sound worth a sh!t. You know old Ned sells tubes Hmmmmm Craig Quote Link to comment Share on other sites More sharing options...
AnalOg Posted October 27, 2005 Author Share Posted October 27, 2005 Well ya got a point there. Tom Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 27, 2005 Share Posted October 27, 2005 Oh and let me clarify something. If you had a nice set of Mullard XF1 or XF2's you could do this with much better results. I have a set of XF2's and they can take the heat I've biased them up to 60mA with 515V on the plates without cherry red syndrome. The problem I'm speaking of is with all the modern EL34's that I have tried(orignal Svet's, EI's, EH and so on) just can't take the heat like those old battle wagon Mullards. But even with the Mullards I still prefer the sound of my sweet little Chinese KT88's much better tonal balance. Craig Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted October 27, 2005 Share Posted October 27, 2005 6CA7 ...??? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 27, 2005 Share Posted October 27, 2005 Basically the same tube for all intensive purposes. Quote Link to comment Share on other sites More sharing options...
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