(Webmaster note: Special thanks to ToneTimes2 of the FDP for writing his excellent NOS tube review and allowing me to include them here.)

Note that these are not my (Justin's) reviews. If you would like to add your own reviews to this page simply email it to me.

Power Tube Review
Hi everyone. This past weekend I did some tube tasting in my HRDx. I finally got a multi-meter and have been switching out power tubes, including Tung Sol 5881s, and Sylvania, GE, and RCA 6L6GCs as well as the Sovtek 5881WXTs the amp came with.

Soundstaging refers to how "isolated" the notes sound. It seems to make the unmitigated notes fly out of the amp. Good soundstaging means that nothing gets in the way of the notes, and the sound one hears is a truer representation of what is being played. This is my own definition, which was hard to come up with. I guess its not an easy thing to define. The definition of others might vary.

My setup otherwise goes like this: no mods done, original speaker changed to a 61 P12N, I have a Tungsram 12ax7 (my personal favorite) in V1, a telefunken 12at7 in V2, and the stock GT 12ax7 in V3.

Here are my results:

Tung Sol 5881
I was disappointed with the sound of the Tung Sols. I have read that the HRDx circuit is based on the bassman circuit, and with TS 5881s being the original power tubes of the bassman, I thought this might be a match made in heaven. I dont know that these tubes sounded bad, just not what I was looking for. One good thing I can say is that the soundstage blew away anything I have ever heard before, even the highly acclaimed GEs. The notes seemed to come alive, but they also seemed kinda "lonely". This much soundstaging seemed to take away from the tone IMHO.

Sylvania 6L6GC
The Sylvanias sounded ok in this amp. I actually like these tubes but was not extremely impressed with them in this amp. Bass was good but the missing mids from the Sylvanias really showed against the rest of the competition.

Sovtek (Groove Tubes) 5881WXT
The WXTs, surprisingly, were excellent sounding. They were well balanced and really didnt seem to have any weaknesses. While they were not the best sounding tubes in the group, they are a fine choice.

GE 6L6GC
The GEs were brighter than the others with the exception of the RCAs, something I find that helps rectify the "dark" sound that the amp has IMHO. They also had a complexity of sound that were all their own. Awesome tubes!

RCA 6L6GC
The RCAs were the winner though. Unbeatable balance, booming bass, well represented mids and great high end. These tubes were more characteristic than the rest, with great authority and soundstage. They are currently in my HRDx which is where they will stay.

I didn't test any current production tubes as I do not have any, but I do have a pair of SEDs on the way. Can't wait to see how they compare to the RCAs and the rest of the bunch. I'll probably creep up on a pair of JJs soon as well. I'll post my results when I get them.

Basically no surprises, other than the WXTs, which btw I liked better than the Sylvanias.

(Webmaster note: Special thanks to Fulton of the FDP for allowing me to add his great review to my website.)

I recently had the opportunity to A/B several current production 6L6's. My intent being to find a tube that could "fill in" when my favorite NOS Philips 7581A's are gone.

As mentioned, the following observations were compared against the Philips 7581a's and NO other NOS tube. I was searching for a tube with the same (close) characteristics such as headroom, punch, clarity and detail, deep bass...etc to the 7581a.

All tubes were biased by ear and then measured in a "blackfaced" '69 Super Reverb and Vibroclone. Surprisingly enough all measured between 18.8 - 19.3 static watts dissipation. I typically find the 7581a to sound it's best for me at 19swd. This gave a bias range between 38mA - 41 mA with plate voltages of 469-499v.

(Webmaster note: The power amps of the Hot Rod Deluxe and Deville are closer to the blackface Super Reverb than any other Fender amp. They are so close, in fact, that they are almost exactly the same.)

Here's what "I" observed.............

SED/Winged "C" 6L6GC (Formerly Svetlana)
A very popular tube. Power output was comparable to 7581A. Bass was not as deep as 7581A nor was the punch. The high-end was somewhat veiled and not as forward as Philips. Actually it sounded flat to me with MUCH less detail and clarity.

Headroom was average and controlled overdrive. This tube sounded OK, but nothing really impressed me.

New Reflector "S" Svetlana 6L6GC
This is a totally different tube than the previous SED brand. These are made in the Sovtek/Reflector Russian facility. This tube had the same power as the SED version.

Bass was deeper and this tube has some serious mids. High-end was brighter and more detailed than the SED and had more headroom. A very stout sounding tube.

A better sounding tube than the SED version to me. Still far from the 7581A however.

Ruby 6L6GCSTR
A great sounding tube! I was actually pretty impressed with this version..... very good power. Good bass and depth....a little less than the Philips but better than the previous two.

Had great chime and clarity. A forward presentation that made the notes really jump out.

Surprisingly had a good amount of headroom and much more then the SED and Reflector. Nice tight overdrive....never got mushy. I really liked this one!

Ruby 6L6GCMSTR
A new improved version of the 6L6GCSTR. Thicker glass and better supports.

Had a cleaner bass response than the GCSTR , but this gave the impression of less depth. Nice enough high-end , but not as detailed nor clarity as the GCSTR. Mids were however fuller here than the older version. Nice headroom, but the GCSTR still had a little more.

TAD 6L6GC-STR (Black plates)
AWESOME!!!! This tube really blew everything out of the water!

Huge deep bass and spectacular punch. Really big soundstage! Better clarity and detail than ALL the others tested. Perhaps even better clarity than the Philips. Notes and harmonics really jump out and everything just sounds right. A tight and focused sounding tube for sure!

While nothing can or ever will touch the 7581A's headroom, these are VERY close! They are close enough that I don't miss the extra headroom of the Philips. These tubes are excellent quality and workmanship all around.

I'm so glad that the TAD's are available. They really set a new sonic standard for current production tubes.

Very satisfied that I found my new favorite tube.

Mojo Tone is the only US distributor of the TAD tubes. They are from the Tube Amp Doctor in Germany.

(Webmaster note: All names are copyright of their respective owners. This site has no affiliation with any of the aforementioned companies or their products. All the information here is based on the writer's personal opinions, and should be taken as such. It should be noted that only one sample, out of many many tubes, has been used to form an opinion; therefore, this one tube may or may not be an accurate indication of every power tube produced by the company. It should also be noted that the guitar itself, speaker, etc. plays a role in balancing the sound. For example, a speaker that is "middy" may sound better with one tube, while a bass heavy speaker sounds better with a different tube. The reviewers may not be into the same type of music or "sound" that you're into also. These are all things that should be taken into consideration when choosing a tube based on someone else's opinion.)

Last updated on August 3rd, 2004

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