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Did you know that nearly 90% of ALL issues with tube amps are traced to tubes?

That means, when you have an issue, after ruling out your cables and guitar, suspect tubes first before thinking to sending to us or an amp TECH.

We highly recommend getting a backup set for your amp (if not a backup in full, try for a backup for each TUBE TYPE) 5w amps need one power tube of the 6V6 or 6L6 family (no KT66). Push-Pull need matched pair(s) of 6V6/6L6 family (no KT66). MOD84 is EL-84 pair. Really, you only technically need to have one good 12AX7 to use and test in all the driver stages (including reverb tube testing).

Yes, the 12AX7 is fine for testing the REVERB if a 12DW7 is not on hand, even though circuit is designed for 12DW7.

For the rectifier, it's the GZ34 or 5Y3. See our favorites below. The GZ34 is a slow start rectifier with highest voltage and most headroom. The 5Y3 rectifier is actually the least voltage though no slow startup..but less voltage on the tubes and a bit more compression/sag with some additional sweetness. Again, you can have different rectifiers for different flavors/response of amp.

Of NOTE, make sure you don't confuse the JJ 12AX7 and JJ 12DW7. They are VERY close in number on tube and it's easy to do. 12AX7 for JJ is ECC-83S while the reverb JJ 12DW7 is the ECC-832
. You drop a ECC-832 into the preamp driver or Phase Inverter/Tremolo spot, you'll get quite a different result. The 12DW7/ECC-832 is half a 12AX7 and half a 12AU7, much less gain on one side.

At the moment, all of our tube stock is going straight to new Swart builds coming out of the shop.  For now, we're going to pass the service to our friends The Tube Store and Tube Depot. Even Amazon can be used.

WE are currently recommending the JJ 6V6S or TAD 6V6
(or some ideas below) as the stock replacement for any amps with the EH or T-S 6V6 as we have found these tubes CAN red plate in some instances, especially if in the amps that have the tubes pointing down in PP. The JJ 6V6 does not have the most NOS style character and sounds closer to a 6L6 but is pretty robust. The TAD exhibits a bit more compression and old school take. But some might find them a touch soft in some instances.   Tube Store packages currently feature JJ and TAD as the only options so might be best to order with that sub. We like the fact they test their tubes.  The Tube Depot is also an option for new with good pricing. 
See the usual suspects below but don't be afraid to experiment with NOS options, especially with the Single-Ended beasts.

~ kelly holsten 

See individual amp tube requirements




These JJ ECC83-S come stock in every single Swart amplifier, from the ST-6V6se to the SST-30.  For the Single-Ended amps like the 6V6se, Atomic Jr, and STR variations, you might consider various NOS options. The first driver tube is really important in all the circuits. A 5751 brings slightly less gain. You're urged to experiment with more compelling options but this is a great, all-around new version of the 12AX7. ~ kh


Tung-Sol 12AX7

The Tung-Sol 12AX7 is used by us in certain situations where a little more gain is needed.  We sometimes employ this tube in the Phase Splitter/Tremolo section of AST circuits.  Ditto in the STR-Tremolo.  This can also be an interesting option in contrast to the JJ 12AX7, which might be a touch smoother with more bottom but not as hot.  It's a nice tube to have on hand as an option  ~ kh


JJ 12DW7/ECC832

The other stock tube in all Swart amplifiers with that magic all tube/spring tank reverb.  This is essentially two tubes in one, half a 12AU7 and half a 12AX7 complete with separate gain structures. This is another relative problem-free tube though we HAVE on occasion seen this tube get funky. And we've noticed those with smeared logos tend to act up more than others.  On the other hand, there are some NOS 12DW7 floating about online for reasonable prices but some act strange in the circuit.  We've not done a a-b comparison but you're encourage to experiment.  On the other hand, this JJ is a safe, consistent bet.  On the fly, a stock 12AX7 will do for testing and emergency services but the 12DW7 is the proper fit.  ~ kh


EH 6V6GT Matched Pair

Since 2004, we have used a variety of new tube production for our 6V6, from NOS Sylvania at the very beginning to EH, Ruby, Tung-Sol, and JJ.  The Tung-Sol turned into our favorites for quite a while but the production has not been standing the high bias for that sweet tone.  Bottom Line, we don't recommend them unless an Ip of 30 or less.  Of new stock, we were quite happy with the current runs of the EH 6V6GT....That is, until they started having red plating issues when pushed a bit in higher heat situations.  It's got some vintage sweetness though not quite the output of the JJ.  But it seems to get closer to the T-S paradigm then the JJ as of late. This WAS our STOCK 6V6 on all Swart 6V6 amps until late 2018. In 2019, we moved to JJ 6V6 and TAD because of the RED PLATING issues. ~ kh



JJ 6V6S Matched Pair

These are probably the most robust of the new 6V6, almost in the low 6L6 spec range, sometimes sounding a bit closer to their big brother then a vintage sounding 6V6 like the Tung-Sol.  Maybe the choice for the most clean headroom in a 6V6 but perhaps lacking some of the soul of the others.  Occasionally a rattle issue come up but most can be solved with tube rings.  They have gone out with a lot of stock AST, AST PRO, AST Master, and SST.  We still use them and a safe choice. It's now stock in many Swart offerings in 2019.  ~ kh



Are old favorite, the Tung-Sol, seemed to be a nice blend of vintage take in a modern bottle. But when they started to have issues red plating some years ago, we sadly stopped using them. The TAD 6V6GT-STR is an option that many feel has a bit more of that vintage take, that compression that's missing in the somewhat more 6L6 take of the JJ 6V6. I'm still not sure what I personally prefer on this front. The TAD can sometimes rattle and I've felt they were a bit soft sounding in the AST. But that was years ago. Many really do like this tube and worth a trial if interested. . ~ kh


Genalex Gold Lion 6V6GT

Another tube we've actually not had a ton of experience with but reason to believe it might actually be a compelling and excellent sounding option to try in either the push-pull or single-ended amps. OF course, this is another of the Russian New Sensor tubes and most come from the same place but we've seen some of the other Genalex Gold Lion tubes excell in various positions, including HIFI amps. So this might be a fruitful option. Give it a go and let us know what you think! ~ kh


NOS JAN-Philips 6V6GT

We get all sorts of questions about what NOS tubes will work in these amps.  To be honest, the answer is way more complex and highly subjective and conditional.  You can head down a worm hole, losing ducats and sanity and come out other side with empty pockets and depression.  The Law of Diminishing Returns can weigh heavy. That being said, there is some magic that can be had, especially with the Single-Ended amps.  I use all NOS in my 5w SE Swarts and a smattering in my PP Swart.  The JAN-Philips is not one of my favorites ala RCA, but it's built like a beast, lasts a while, has ok tone, and is easier to get.  That's something. Tube Depot features Sylvania version. ~ kh

JJ EL-84

The stock EL-84 we've been using for the MOD84 since day one. Really is a solid choice and very balanced from lows to highs. Indeed, a very rich sounding option in the new EL-84 world. Is it the best EL-84 made? Well, there is no doubt that the NOS original EL-84 still win out in most apsects but they are getting $$$ and harder to find. We think this is a great alternative in the new tube world. Seems ruggedly built, too. But...I would also suggest playing around with some other options if curious. Some good reports from the Genalex Gold Lion EL-84. - kh
Genalex Gold Lion EL-84

Yes, the stock EL-84 we've been using IS the JJ. But I have been hearing some good things about the Genalex Gold Lions and have liked others of their line, especially in audio amps. Right now have the Genalex Gold Pin ECC83 in a 300B Single-Ended Triode amp as the first driver and have to say, in my application it beat out a Telefunken 12AX7 Smooth Plate! So I actually finally heard back from a Swart customer that is VERY happy with the Genalex Gold Lion EL-84 in his MOD84. His direct quote to me was, "The Genalex Gold Lions are REALLY good! Warm, tight bottom and hot without being too toppy. I’m thrilled!" He also reported no microphonic issues, always a good thing. So I'll add this to the list as something to give a chance in the new tube bracket. Let us know what you find. Looking now for best source and will update. - kh

TAD 6L6WGC-STR Short Bottle Matched Pair

Hey, this just might be one of my favorite new 6L6 to get some of that 6V6 take.  Wait, it IS my favorite new 6L6, mainly because it keeps the soul of the 6V6 alive while adding a bit more headroom and output.  I like this tube in anything from the Atomic Jr to the AST circuits.  This beast avoids some of the slightly more sterile nature of the 6L6 retaining the 6V6's more organic angst and breakup.  More often then not, Michael runs a pair of these in his AST Head Mk II when playing with the freaks on band nights. I'm running one right now in my Atomic Jr for a different take.  Give it a whirl.  You might be smitten. Some still might prefer the regular 6L6 take which bring more headroom, clarity, and slightly less 6V6 vibe ~ kh


JJ GZ-34/5AR4

This is the stock GZ-34/5AR4 rectifier we have used in every Swart Amplifier besides the first year run of NOS 5Y3 that finally ran out, much to our chagrin.  This has been a pretty robust tube for the most part, despite suffering a few ups and downs in quality control.  Right now, it's probably the best new GZ-34 out there.  It's still stock in every Swart amp that leaves the shop.  If looking for the most headroom and output, the GZ-34 is the option.  We DO still love the 5Y3 for the extra sweetness and addictive compression. ~ kh


TAD GZ34 STR Selected

This has to be my new favorite GZ-34/5AR4 rectifier. In my opinion, compared to the JJ GZ-34, the TAD "Selected" version sounds more open, lively, and a touch sweeter.  It's probably a bit less voltage than the JJ with a touch more sag.  We don't have measurements yet, but in my back to back comparisons with the JJ, this tube shines and gives the Swart, especially the low wattage options, a bit more harmonic richness and complexity.  Just sounds like more going on with some extra layering, making the entire result less one dimensional.  The JJ might be a tad more headroom.... but in my view, this is the rectifier I go for.  It's almost like a cross between a NOS 5Y3 & a GZ34 sonically, though with more the GZ34 headroom.  A few have rattled a bit. And I don't have long term results, but it's in my Swart amps at home. ~ kh

TAD GZ34 STR Selected

Genalex Gold Lion GZ34

Like the Genalex 6V6GT, we've not had a ton of experience here. But again, this tube has REALLY worked well in many other applications that would leave me to believe it's a very good option for the Swart Brigade. I encourage you to take the plunge, even though a bit pricey. Now, I also DO love the sonics of the TAD Selected GZ34 but this tube is likely a VERY good sub for either. Let us know how you like it! ~ kh



It's no secret that I dig the NOS 5Y3 rectifier in some of our circuits, depending on mood and need.  I probably run a NOS 5Y3 in my AST 80% of the time at home.  I like the sweeter tone and more compressed breakup.  There is more sag evident.  If not needing the most headroom from the circuit, it's a great option and puts out 34v less on the tubes, a good thing for longevity.  But there has not been a proper NEW 5Y3 till now.  Introducing the JJ 5Y3S.  It's the first of the 5Y3 that actually measures as a true 5Y3.  Long term durability is still unknown but we can recommend this one based on their work with the GZ-34.  I'll do a follow-up when I get some time with it. There are sites still around that carry the NOS 5Y3, starting in the mid 20s and going up. EDIT Still prefer the NOS options is you can go that route but this is probably the BEST NEW 5Y3 option at moment that we have tried.  You can do with this for reduction in voltage and or opt for the TAD GZ34 above as a GZ34 with some extra sweetness due to a bit less voltage than the JJ ~ kh


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