Preamp tube shoot-out

[SoSomething]

OK - I mentioned in another thread that I had ordered a bunch of different preamp tubes to try in my SED SVKT88 - loaded Splawn Pro Mod. In order to set up a the scenario I need to give you some context, so here goes:

The Pro Mod is an early model, with a shared EQ over all channels and no "3rd Gear Mod." It's a very stripped-down head rated at 100 watts - the set-up is not unlike a 5150 II with clean, OD1/OD2, and Solo available on the footswitch. The amp runs on a quad of KT88s and has three preamp tubes. Before I started experimenting, the amp was loaded with the stock JJ's 12ax7 tubes in all three preamp positions.

In stock form the amp sound very thick and tight, with smooth mids, and plenty of gain on tap for all forms of metal. That's as descriptive as I'm going to get to start - if you want to know more about how the amp sounds in stock form, check out the clips on the Splawn website. Most of the clips are of the Quick Rod, which is more 80's-sounding in vibe but shares the same basic tonality as the Pro Mod - the Pro Mod is just a bit thicker with more bottom end.

The tubes used in my experiments are listed below:

Electro-Harmonix 12ax7 Gold Pin (full set)
Electro-Harmonix 12ay7 (one tube)
NOS JAN GE 12at7WC (one tube)
JJ's ECC82 (12au7) (one tube)

My first test was to leave the stock JJ's 12ax7 tubes in the V2 and V3 positions and try each new tube one at a time in the V1 position (being that the V1 position has the most effect on the gain structure and tonal balance of most tube amps) to give me an idea of what each tube's general characteristics were going to be. I'm pretty surprised with the results, and very happy with the outcome of this experimentation. The impact that each tube had on the tone and feel of the amp was much larger than I expected it to be.

The results of my totally non-scientific experiments will follow in my next post.

 

[SoSomething]

As mentioned above, the following descriptions are based on the tested tube in the V1 position of the preamp with the stock JJ's 12ax7s in V2 and V3.

EH 12at7 - My first impressed was "bleh." While it tipped me off right away that I was going to be a lot of variance between tubes, I didn't like what I got. Considerably less gain, but no warmth. It sounded brittle and sterile. There are probably good rock tones living in this tube with the amp pushed really hard to warm the poweramp up, but I was running the experiment at a moderate "band rehearsal" volume and at that level it didn't perform like I wanted.

JJ Tesla ECC82 - Even less gain, but a lot more fun. This was the lowest-gain tube of the bunch, but it had a lot of the warmth and vibe that the EH 12at7 was lacking. The clean tone was bright and clear, but the real joy was in OD2, which is typically set up as my metal rhythm sound. With this tube it was knocked way back to a rock (not even hard rock) tone that would have been right at home with some James Gang or early Rush -style music. The high mids were maybe a tad too present, but if I'd have allowed myself to mess with the EQ during this phase I probably could have fixed that. This tube would be pretty useful in the studio.

NOS (packaged June of 1966) JAN GE 12at7WC - I totally expected this tube to be the best in the V1 position. It's made to a much higher spec than today's tubes, and besides - older is better, right? Um.... not in this case. There were things I really, really liked about this tube and other things that just would not work. I lost a good bit of gain from stock form with this one, and a lot of the tightness was replaced by a looser, more open sound. The good is that the mids were huge and the top-end was silky smooth but still not really "dark" sounding, and the amp sounded really organic and warm. In fact if my band never played metal stuff I would probably have stuck with this one, especially since the clean tone was also just as warm and organic, but when you're slamming 32nd-notes to a blast beat, you need more definition than this tube can provide in the V1 spot.

EH 12ax7 Gold Pin - First impression: noticeably higher gain that the stock JJ's, and perhaps a little more "scooped" sounding under the same EQ settings (which I didn't change during this whole thing). This was the only tube where the gain went UP instead of DOWN. I also noticed that the sound was a bit more compressed and solid - thicker without being muddy at all. Strangely enough the clean tone didn't really change other than get a little more present (which was a good thing).

I liked the way the amp sounded with this tube so much that I went ahead and put the EH Gold Pins in the V2 and V3 spots and well, which really tightened up the sound. With all three of those in, the amp sounded more brutal than before, and allowed me to back off the gain a bit to get a better tone on the clean channel as well. It was a bit more compressed and much more focused in terms of balance between hi/mids/lows. More gain, and yet it now stopped on a dime. I did have one gripe, though - I didn't like what using all three of the EH Gold Pins did to my lead tone. It became almost TOO gainy compared to the rhythm sound I was happy with, and it kind of lacked dynamics. The notes did not bloom at all - they were just there, and sounded a little scratchy to me. Not a terrible sound, but uninspiring. I like a little bloom - I want my leads to sing.

So I had an idea. . . (continued next post)

 

[006]

So far this is a very informative and helpful thread, especially since I'm looking to try some new preamp tubes in my 5150. Can't wait for the next part.

Maybe I should order a bunch of different tubes for my preamp section and try them all out on my 5150, to do a review like you have done.

~006

 

[Fragle]

when i got my 5150 i bought several preamp tubes, e.g. JJ, EH, sovtek, and svetlana, in order to replace the OLD stock preamp peavey tubes (talking about a block letter head...LOL)
to make a long story short, the EH12ax7 sounds best to my ears. at first i prefered the JJ 12ax7, but after the first band rehearsal i swapped it for the EH and never looked back.....the JJ's much too dark, the EH has good bottom and a nice top end sparkle

 

[SoSomething]

. . . (continued from reply #2)

As mentioned above, I had completed what I considered to be "phase 1" of my testing; the results of which made me decide to leave the EH Gold Pin 12ax7 in the V1 position due to it's very satisfying tonal balance but tight, articulate gain structure. At this point when playing heavy rhythms on OD2, the amp was very metal-friendly, but each note of every chord could still be heard clearly.

I'm now going to use some strange descriptions to kind of help people understand what I was hearing. When you plug into a distored guitar amp set-up and play a chord (be it a barre chord or inverted chord or whatever), there is a sense of seperation between the notes. By that I do not mean articulation, which I consider to be the perceived "clarity" of each note within a chord, but rather a sense of the "space" between those notes. Tones that have a lot of space between notes (or space between the dominant frequencies of each note in the chord) are what I would describe as "loose" or "open." Conversely, tones where the notes of a chord feel very "close together" are what I would describe as "tight," "thick," or "solid." Typically a good metal tone is the latter of the two. Note that in both kinds of tones, the clarity and presence of the individual notes can be equal - it's just a matter of how spread-out they sound. For reference, the rhythm tones on Megadeth's "Hangar 18" are pretty open, where those on the new The Haunted record are very, very solid.

As I said before, using all EH Gold Pins in the preamp provided a heavy and solid tone with very tight hit-you-in-the-ribcage bottom end and smooth mids. It was somewhat soulless for leads, though, and since I play most of the lead work in my 2-guitar band, this had to be remedied (hopefully) without sacrificing all the progress I had made on my clean and rhythm tones.

A - I didn't even bother trying the EH 12ay7 in any of the other positions. Based on what I learned of it already, it wasn't going to help. I don't like this tube much. I also did not put the stock JJ's 12ax7 back in any of the positions - I had already tried that more or less when I first tested a Gold Pin in V1 and the amp definitely sounded better running all three Gold Pins.

B - First I tried the JJ's ECC82 in V2 and then V3 to see if it would bring out some dynamics, but to be honest all I noticed was a harsher upper-midrange, a very slight decrease in gain in the V2 spot (compared to the Gold Pin) and basically no difference in V3. Moving on...

C - When I pulled the NOS JAN GE 12at7 back out and put it in V2, immediately the warmth and bloom I wanted from my lead tone was there, but that's about all I really liked from this configuration. I lost more gain than I wanted to, and there was almost too much bloom to the notes - so much that it adversely affected the precision of my rhythm playing. The low-end loosened up more than I wanted as well, but man did those single notes sing. I was getting closer.

As a last-ditch attempt to make all this worth doing (and because it was really the last combination I felt I should try) I put the JAN GE in the V3 position, and all of a sudden I realized why I did this in the first place. This config of a Gold Pin in V1 and V2 and the JAN GE in V3 is now my holy grail. It retained almost all of the gain (more than stock form) from running all three Gold Pins, it left the brutal but controllable low end intact, but it brought that sweet sweet bloom to my lead tone that had been lacking with every other config. The affect of the JAN GE is apparent on the rhythm sounds as well, but not in a bad way. It smoothes out some top-end but the tightness is still there. There is also maybe a bit more chug and grind to the sound, which for my purposes is a very good thing, and the single notes sound almost as big as chords do. When you grab a nice high note and really smack it, the note sort of goes "BwwWWAAAAAAAAAAAAHH!!!" through the amp.

I'll chalk this one up as a success. I hope you guys can find this useful in your own experiments.