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I recently changed the rectifier (5AR4) of my ARC Ref2 mk II preamp. The old one was a Ruby 5AR4, replaced by a Phillips MiniWatt GZ34, Blackburn factory, 1965 (code f32/B5A1).
I was expecting a better control and tighter bass. However, i started having some boomy bass problems, on certain notes, not on all of the bass notes. That did'nt exist before.
I suspect that the new rectifier goes deeper on the bass and is exciting a room mode which was before not perceived.
I wonder if you agree with me or if there is a problem on the NOS tube. Can you give me some help?
pfmaudio
Follow Ups:
When you change out a rectifier, should check the plate voltages. They may change ---> need to adjust the idle bias of the output tubes.
Strong testing NOS GZ34 often have higher B+ voltages, than modern models.
Thanks for the advice! I have put back the ruby 5AR4 and the bass became as it was. Notes not bloated in certain keys and good bass articulation. I think I will not try the diode trick, as it far exceeds my technical skills and theARC REF 2 mk II is a reference piece of gear and ARC is a solid company developing excellent and reliable solutions.
I noticed that the PHILLIPS GZ34 logo on my tube has vanished in powder marks after 20 hours of listening. I wonder if this is normal. Can it be a fake tube? The etched codes are still there..f32/B5A1. The tube has 7 notches on the plates. Is it a 1965 or 1975? I heard the 1965 only had 4 notches.
N
My question regards for how long shall I have my ruby rectifier on good working conditions. I believe they have at least 2500 hours and don't know how long it lasts. Any idea?
Decidedly, the Mullard NOS appear to be the wrong way to go, in my gear and in my room. Too much bass energy, bloating some bass notes. The ruby 5AR4 is a better solution, at least in my listening conditions. Any alternatives suggested?
pfmaudio
I've had numerous instances when amps with vintage tubes sounded much worse than with stock tubes. Perhaps, this is not the problem of NOS tubes - most manufacturers voice their gear for modern tubes, in you case, for the Ruby 5AR4.
I have the same experience with the Cary SLI-80 - with vintage tubes, it sounds too slow and uninvolving, though quite good with some music genres. It just had more sparkle with the stock Ruby 6550C (aka Svetlana Winded C) tubes.
I had a similar but more subtle experience with brand new RCA / Mullard 5AR4s in my 60 watt monoblocks. Following about 10 hours of playing time it cleared up.
Is find a third rectifier to try. See if you get the same result.
Also you could put the ruby back in and try Eli's diode trick.
The series diode tweak did not originate with me. All I've done is spread the word.
Something from ARC rates to be PCB, not P2P. Traces might have to be cut, for the tweak to be implemented. On general principles, use UF4007s instead of noisy 1N4007s.
The only rational way for a rectifier to change the sound is by altering the B+ rail voltage. If the "Ruby" is on its last legs, install a properly culled Chinese 5AR4 from AA sponsor Jim McShane.
Eli D.
I would never entertain the diode trick as noted above with potentially cutting traces etc. The ARC piece is a high end component that just does not justify that kind of treatment.
Try another tube, call ARC and get one or you can temporarily use one of these for testing they come in handy.
Surplus Sales of Nebraska used to have mil-spec ones for cheap but they may be gone.
Good luck.
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