In my last Today's Fresh Catch post (HERE) I mentioned the variety of NOS 12AT7 signal tubes and NOS rectifiers that I had purchased from Radio Electric Supply to try in my Leben RS-30EQ:

6X5GT, 4 pieces (NU, GE, RCA, JAN Raytheon), at $10 each for a total of $40.

6X5GT 2 pieces, Sylvania, at $10 each for a total of $20.

6X5GT 10 pieces, JAN Sylvania, $10 each for a total of $100.

12AT7, matched pair of GE 12AT7 triple mica, at $20 each for a total of $40.

12AT7, matched pair of RCA 12AT7 black plate, at $20 each total $40.

12AT7, two matched pairs of Sylvania 12AT7 triple mica, at $20 each for a total of $80.

NOS GE 6X5GT for the Leben RS-30 EQ phono preamplifier.

My Leben RS-30EQ originally came with a NOS GE 6X5GT rectifier like the one in the photo above.

Leben RS-30EQ phono equalizer.

The NOS GE 6X5GT rectifier failed after some years, and it was replaced. I thought the NOS GE 6X5GT rectifier had been replaced with another NOS GE 6X5GT rectifier, but as I was reminded when I pulled the top cover off, it had been replaced with a NOS Sylvania 6X5GT rectifier (below). 

NOS Sylvania 6X5GT rectifier.

I have no quibbles with the performance of my Leben RS-30EQ with the NOS Sylvania 6X5GT rectifier that's been hiding in its chassis for years now, with a sound that is natural, rich, smooth, detailed, spacious, and dynamic. 

NOS Sylvania and RCA 6X5GT rectifiers.

It's a little hard to tell in the accompanying photographs, but if you look closely you can see that both the NOS RCA & GE 6X5GT rectifiers have a single plate structure.

The NOS Sylvania 6X5GT rectifier's internal structure is much different than the NOS RCA & GE 6X5GT rectifiers, having a double-staggered plate structure with triple mica spacers, compared to the single plate structure with two mica spacers.

NOS JAN Sylvania 6X5GT rectifier.

For today's listening comparison I thought I'd compare the the NOS RCA 6X5GT and NOS JAN (Joint-Army-Navy) Sylvania 6X5GT rectifiers to the standard NOS Sylvania 6X5GT rectifier that has been providing years of listening satisfaction in my Leben RS-30EQ.

NOS JAN (Joint-Army-Navy) Sylvania 6X5GT rectifier (left), standard NOS Sylvania 6X5GT rectifier (right).

Other than the printing on the base of the military version of Sylvania 6X5GT rectifier, by visual inspection I couldn't see any difference between it and the standard NOS Sylvania 6X5GT rectifier. They appear to be identical from a structural standpoint. 

You should be taking these preliminary listening impressions with a grain of salt, rather than carved in stone truths, as the NOS Sylvania 6X5GT rectifier that's been in my Leben RS-30EQ has a lot of hours on it and is fully run-in.

Both the NOS JAN Sylvania 6X5GT rectifier and the NOS RCA 6X5GT rectifier have zero hours on them, and like any vacuum tube, they require some run-in time to reach their full musical & sonic glory.

Vintage Altec A5 Voice of the Theatre based audio-visual system.

All of my listening impressions were gathered from my vintage Altec A5 Voice of the Theatre based audio-visual system in the photo above (more HERE).

Soundsmith Carmen Mk II cartridge, Acoustic Revive PC-TripleC/EX headshell leads, and Schick graphite headshell.

I need to update my A5 page to reflect the Soundsmith Carmen Mk II phono cartridge, Acoustic Revive PC-TripleC/EX headshell leads, and Schick graphite headshell combination, which have taken up permanent residence on the Schick tonearm on my Thorens TD124 turntable, as well as the Acoustic Revive RCA Absolute FM interconnects that I use with the Leben RS-30EQ phono equalizer and the Oppo UDP-203 BluRay player now.

The new Leben CS600X in for review has taken the place of my trusty original Leben CS600 in the system, with my Leben CS600 moving into my vintage Altec 832A Corona loudspeakers based bedroom system.

Acoustic Revive RCA Absolute FM interconnects.

Lately I've been craving Tom Petty's music, so that's what I listened to for this little comparison. 

Tom Petty and the Heartbreakers.

Ok, let's swap a few rectifiers and give them a listen to see how they vary in performance.

NOS Sylvania 6X5GT rectifier.

First up for a listen was my NOS Sylvania 6X5GT rectifier (above), which has lots of hours on it. As I mentioned above, my Leben RS-30EQ with the NOS Sylvania 6X5GT rectifier sounds natural, rich, smooth, detailed, transparent, spacious, dynamic, and very musical.

NOS RCA 6X5GT rectifier.

Next I swapped the NOS Sylvania 6X5GT rectifier for the NOS RCA 6X5GT rectifier.

If you are wondering if different brands of rectifiers sound different, don't wonder any longer, the NOS Sylvania 6X5GT rectifier for the NOS RCA 6X5GT rectifier sound different, although part of that difference may be due to the NOS RCA 6X5GT rectifier not having any run-in time on it.

The NOS RCA 6X5GT rectifier wasn't quite as smooth, spacious, and transparent sounding as the NOS Sylvania 6X5GT rectifier, being a little more dramatic and forward sounding, with a little more chiseled imaging, and struck me as providing a stronger sense of beat and dynamics. 

Both the NOS Sylvania 6X5GT rectifier for the NOS RCA 6X5GT rectifier sound good in the Leben RS-30EQ phono equalizer, just a little different overall, and I enjoyed both of their presentations.

NOS JAN Sylvania 6X5GT rectifier.

Next I thought I'd give the NOS JAN Sylvania 6X5GT rectifier a listen. 

The NOS JAN Sylvania 6X5GT rectifier sounded quite a lot different from the NOS RCA 6X5GT rectifier in the same sorts of ways that the regular NOS Sylvania 6X5GT rectifier did, but provided just a bit more of everything. Even more natural, rich, smooth, detailed, transparent, spacious, dynamic, and again, very musical. 

Well, I'm quite impressed with the NOS JAN Sylvania 6X5GT rectifier, not only does it sound great sonically & musically, but I was also impressed by its Grateful Dead "Wall of Sound" style of presentation from my vintage Altec A5 Voice of the Theatre loudspeakers, which completely immersed me in the "sound-field".  

Given these are NOS tubes, I decided to clean the pins of the rectifiers with some Caig DeoxIT® D-Series, and gave each rectifier another listen. 

The Caig narrowed the difference in performance between the rectifiers, while maintaining the characteristics of their overall performance.

The NOS RCA 6X5GT rectifier benefited the most from the Caig, giving it a smoother and richer presentation, which keeping its other traits intact.

Again, the NOS Sylvania 6X5GT rectifier, NOS JAN Sylvania 6X5GT rectifier, and NOS RCA 6X5GT rectifier all sounded great, but if I had to pick a favorite at this point I suppose it would be NOS JAN Sylvania 6X5GT rectifier. 

For my tastes, NOS JAN Sylvania 6X5GT rectifier just did everything a little bit better, but I could easily - and will - live happily with any of them. 

I do recommend you get a little bit of Caig DeoxIT® D-Series general purpose metal cleaner to remove any oxidation and corrosion that might be present on the tube pins, it made a notable improvement.

Ok, that's all for now. I'll get to the other rectifiers and 12AT7 tubes in time, so stay tuned for much more to come!

As always, thanks for stopping by, and may the tone be with you!