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It is my pleasure to report the full wave rectifier U77/5AR4 is an unqualified success. I have been using a pair for some months and in
comparison to old stock Mullard, Amperex, and others. The U77 are as
far as I can tell in no way inferior to OS tubes. It was kind of a
shot in the dark for me. I thought if New Sensor has the confidence to
label their own tube U77 they must have supreme confidence in it. My
trepidation came from previous 5AR4 issuances that worked but were
lacking in one way or the other from a sonic perspective.
At long last I can say there is a 5AR4 of current manufacture that sounds superb - at least to these ears.
Sections in my 4 samples are closely matched if not identical.
The musicality of OS Mullard/Amperex is sustained. At long last I am
able to say this.
Finally, a 5AR4 that comes up to the mark.
The U77 also stand up very well indeed even against the Western Electric
422A in direct comparison.
I continue to be somewhat amazed by this tube.
If you have a treasured stash of OS/NOS rectifiers and have been worried
that these are irreplaceable in terms of performance and listening pleasure I think you owe it to yourself to try the U77 for yourself and stop fretting.
In full disclosure my source for these tubes was a retail purchase from
McShane Engineering. Thanks, Jim. Thanks too for the extra care as in
noting transconductance of each section and the foam peanut inside the
boxe to stabilize each tube in shipping. I appreciate it.
I also acquired 4 KT-120 for another project not yet completed I have
been working on since 2003 the end of which is now in sight. Details
will be forthcoming at the proper time.
Follow Ups:
To various Mullards a swell as the Amperex Bugle Boys in a Scott 299c, two modded ST70s, and MKIII. Too bad, I wanted to be freed from the tyranny of the NOS 5AR4 game, but not even close. YMMV, and I am still going to try the Mullard reissue.
at $50 each, stay with the NOS? That's what I paid for the last Mullard I got...
nt
...some other parameter possibly like voltage drop at reference current? Or maybe arbitrary "quality factor" as read from his tester? Rectifiers don't have transconductance as such.
Pardon elektron's choice of words - the tube was tested for voltage drop and reverse voltage on my Amplitrex and for plate current on my modified TV-7B.
I also must tell everyone that Viridian's statement is the FIRST I've heard that hasn't been extremely pleased about the U77 Genalex (and the 5AR4 Tung-Sol for that matter). He's certainly entitled to his opinion, but his opinion does not appear to be widely shared it seems...
I often find my assessments of tubes to be at odds with general opinions. I am an outlier on tubes such as the JJ octals as well.Interestingly, unlike the OP, I always list the gear that I base my impressions on. Without that info, I am afraid there can be very little guidance that is useful. My early impressions of the Gold Lion GZ34 can be found at the link below. Unfortunately, I continue to find the sound somewhat unbalanced and incomplete, in my system. YMMV.
It is good to hear that many prefer this tube to NOS as the prices for vintage tubes are usurious at best.
Edits: 06/22/14
Did you give them the 50 hours yet? I have not tried that tube but many new production tubes seem to need a lot of time to settle in.
Here is an email from a customer I received a week or so ago. Just for "balance", here's what this well-seasoned listener had to say:
"Jim, as a quick follow up about your supplied U77 GL rectifier tubes:
After a couple of weeks of hearing, and really listening, I have to conclude that while not the latest in sweetness in the mids or absolute transparency in the top end (I’m nitpicking here the difference is minute) I also have to give credit where credit is due, the absolute best bass of the ones heard and rolled for comparison.
Balls to the ball the GL U77’s have the most amount of detail, oomph, punch, grunt, low end extension and apparent dynamics. Of the rolled group.
I would absolutely recommend these tubes without hesitation to anyone that really enjoys music and can hear the difference in a rectifier tube.
It is much easier to hear the effect of a driver or input tube or even a power tube, heck even a phase splitter tube you can hear more evidently than a rectifier tube. Mind you I am completely new to rectifier tubes first two pair of monos with rectifiers started early this year with a pair of Sofia Electric 300B based monos, now with a pair of super expensive (but amazing sounding) Synthesis Celebration also 300B based amps.
Lucky for me they both share same input tube, power tube and rectifier tube, only difference is the Synthesis use EL34’s for driver.
Thanks for a great pair of tubes at a great price.
This listener had a pair of NOS 5AR4 Sylvania/Philips in the amps most recently - just before the U77s.
I thought this review was thoughtful and upfront. Posted here for your reading pleasure...
I guess the question is, would you use a new issued GL U77/GZ34 in a precious 50 year old amp?
Yes!! Without a doubt.
This is very good news. As my stash of NOS Mullards, Philips, GE, And Sylvania 5AR4/GZ34 has been dwindling. Lately, I've been working on quite a few Fender and Vox vintage amps that use this great rectifier.
Guess I should try one out on one of my amps. Give a report from the world of guitar nuts.
8^)
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