Steever Posted August 20, 2009 Posted August 20, 2009 (edited) I rolled in some Electro Harmonix 5U4GB rectifier valves tonight in place of the 5Z3P Chinese ones that were there. Most accounts indicate that it should be straight swap citing any possible electrical value differences as being trivial. The internals do look almost identical to the uneducated eyes (mine) even though the bottle shape is obviously quite different. Oh, the EHs do have a 5th pin wired to the bottom silica holder plate that the Chinese jobbies don't have. They're used with some KT88EHs and a couple pairs of smaller valves as well. The thing is though, they hiss. Both of them. Not through the speakers - no problems there at all but from the valves themselves. It's almost audible from my seat in the passages between songs. Swap back to the 5Z3Ps and the issue goes away - silence. When running the EH rectifiers I also notice a drop in perceived volume. Could this be because the new ones are brand new? The transformer runs cool and only warms a bit because it sits right behind the rectifiers and 4 KT88s. Any ideas what's happening? Edited August 20, 2009 by Winno
Steever Posted August 20, 2009 Author Posted August 20, 2009 I should point out that squeezing them whilst they're on eliminates most noise but remnants remain. Tapping the valve when it's off makes a noise light light bulb fillaments vibrating. Could this simply be a case of poor quality control?
NT3 Posted August 21, 2009 Posted August 21, 2009 Sorry Winno can't help you with this one. Presume they are not arcing. Perhaps a call to Evatco ?
Steever Posted August 27, 2009 Author Posted August 27, 2009 I took a drive out to see Mal and Carole to sort out the buzzing valve issue. They are both so helpful and an absoulte wealth of knowledge (Mal builds valve amps himself). In the end I left with some JJ/Tesla GZ34s. Got them home, plugged them in and no hissing and I got all my gain back plus some. Incidently whilst most people say that recitfiers make no difference in pp amps, I have to say that the 5Z3Ps sound a tad cleaner and more precise to me compared to the Tesla valves. Might give the Teslas a few hours first before I make final judgement though...
Recommended Posts