Guitar Amp Power Tubes Comparison
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- Опубликовано: 27 ноя 2016
- 4 Power tubes played in a Pure Tone Amps - Little Star with a Gibson Les Paul 1959 Standard Reissue. The tubes are:
1960s RCA 6L6 GC Black Plate
2010s JJ 6L6
1950s GEC KT66
2010s Marshall Branded EL34 
Видеоклипы
Wow...that old RCA 6L6 has a very unique sound!
+MrThunder Thanks man
I thought so myself! RCA was the best
Yeah, it’s louder.
Wow you put a lot of work for this, i love your channel and the way you develop the videos. Thanks for all the information, greetings from Argentina!
+Giuliano DeMiguel Thanks! Greetings from Sweden!
To my ears, the 60's 6l6 had it and I'm no vintage tube snob, seemed to have the power and clarity.grat work as ever.
+jadefire1985 Thanks :-)
Great test Johan! 👍
They all sound good and close. If I have to pick one, I'd say the RCA had a presence that the others lacked in comparison. Cheers Jonas
+JonasSweden1 Thanks! :-)
Another EXCELLENT comparison, thank you. I really love the RCA...it's a bit more focused.
Mother of God! Man, I'm addicted to your channel!
Cheers from Brazil.
+aschneider70 Thanks man, Cheers from Sweden!
Merry Christmas Johan!!!! from Sunny Sanpedro California! Your the best Tone Master! and you always make it easy for us Guitar Nerds to get the best sound we need without your help it would be difficult Rock on brother! !!
+Brandon Hupp Merry Christmas my friend!
Johann!You don´t even need electricity any more to make anything sound good!You´re a Legend!Thx for the cool videos!Keep on rocking!Greetings from Austria!
All had their merits, none sounded bad. For snob value I'd go with the KT66 ;)
+gingataff Cheers! :-)
I go with RCA 6L6, really punchy and awesome. But speaker and MANY other things in the circut are a huge contributor to the tone!
Fun stuff! You test things that guitar players really want to hear, thank you! I like the the EL34 and KT66 best but they all their own tone/groove.
+John Miller Thanks man, good to hear that!
This was humbling. The differences are there, but very subtle. Makes me rethink what I thought I knew about tubes.
+DavidVeeGuitars Thanks, yeah many small factors contributes to guitar tone
Hi Johan, once again, another great video, and thanks for all the time and effort you put into making these videos for all of us rock n' roll enthusiasts. The RCA sounded the best, it has a bit more bite which i like to hear, all the others sounded very similar at least IMO.
Brilliant work my friend and keep on rocking!
+19bluesguitar72 Thanks my friend! :-)
Your videos are done very well because the sound bites are short and sequential, good job. I like the KT 66 sound the best.
+kerrytheman Thanks Kerry!
Interesting. The only difference that I heard was the low end response between the tubes with the el34 being a little "softer" and the 6L6s being a little stronger. Well done!
+Potato McFetus Thanks :-)
Those GECs are the bee's knees. Honestly the new tubes have nothing to be ashamed of, and the brightness of the beam tetrode 6L6GC helped it hang in there. I've never had GECs before, but still have RCAs, Sylvanias and GEs. Thanks again Johan.
best sounding was and most distinctive was the RCA 6L6. Second best was the EL34, but it was really close to the other tubes in sound quallity. I used to run a mixed quartet of 6L6"s (metal envelope Mil spec) and EL34"s. Best of both worlds.
Man i tell u I usally like the El 34 sound, KT66 is killing it this time that's a dam good set
Man, that RCA has some low mid/bottom end mojo....love it
Agree! 100%
Thanks for all the great videos! How about a video of the effects of different biasing settings of the power tubes to the sound?
this is why we LOVE our Brother Johan !!!!
+David Amason Thanks my friend! :-)
wow thank you for the comparison I'm an EL34 EL84 tube guy but on this clip, i must say I did like the 6L6 tube hummmmm.
+William Pereira thanks :-)
Very interesting comparison! Not a whole lot of difference! I thought there would be bigger differences! Good work! (I'm still an EL34/84 guy!)
+Blues Bengan Cheers!
People don't even realize that there is no true comparison unless you change the output transformer for each tube. The kt66, el34 and 6l6gc are all going to perform their best at different primary impedances on the output transformer primary winding. Although its true these sound different in your amp, its still not a fair fight unless the OT primary winding is addressed.
I like the KT66 best in this clip, but i know it could sound better or worse depending on the OT its matched with in a particular amplifier.
All that being said, thank you for taking the time to make the video. It is interesting. And nice chops too.
They all sounded very similar to me. I wonder if this is because the amp had just one power tube. If another amp with a different configuration of tubes was used for this test then perhaps there may have been more variation in sound between the tubes.
i liked the RCAs, the KT66s were a close second. the RCAs sounded nice and clear, with extended highs and lows, i liked the midrange character they had too. makes me want to track down a pair and build a JCM 800 2204 ish clone. nice video buddy.
+Bruce Carey Thanks man!
I won't bother saying what I thought would happen, because what happened wasn't anywhere near as extreme as I thought it would be.
A person could easily use any of those tubes and just vary speakers.
In the meantime, I received my new Fender Elite Tele today, but still can't open it for another couple of hours because it was pretty cold over night so I'm letting the box come get to room-temp to be safe.....one would think getting older would make being patient easier....but not when it comes to new toys!
Thanks for the video Johan!
+Rick McCargar hahaha, I feel for you my friend! :-)
Subtle but definite differences between all of them. I like to low end of the KT66, and the RCA has a slightly different color tone as well. I think my least fav was the Marshall tube, but it certainly gives the Marshall type overdrive tone. Another good video!
wizzells I Fully agree ! Great tests as usual Johan!
+wizzells Thanks! :-)
1950s GEC KT66 sounds Great!!!!!
+Glauco Santiago Thanks!
It may just be my speakers, but I had a hard time telling the first three apart at all. The last one sounded a bit brighter, but not a whole lot. Thanks Johan.
+Noeffnwaypal Yeah, the differences are not that big. The older tubes have a better dynamic and is easier to play though
I found the KT 66 to be thicker sounding. Rock on.
+CHAISE HOMBRE Cheers!
love all your videos keep it up! ... "LezGO!" :)
+awwnawmang hahaha! Cheers
Very cool.. I thought I would be swayed towards the EL34, but I like the tone and sustain on the KT66..
+Jeff Meyer Thanks Jeff!
black plate rca had a bit more bite and a bit less mids, and also more open than the JJ. Definitely my favorite, but that was my opinion coming before I watched the video. I think we love our hate what ever we want to notice, and that influences or playing style. Excellent video.
+jess d Thanks, that's is a very good point. We're all biased
The RCA was more open with more mids . Kt66 was close to RCA with a flatter response .The EL34 was the most compressed with early brake up. JJ 6L6 had flat response less output than KT66 & RCA6L6 . Great Video !!\m/!!
+LRoy Shreding Thanks! \m/
Johan Segeborn Your welcome !\m/!
KT66 - Put out a little more volume than the rest, had a little more bottom end. Lots of top end (as bright as the RCA), a little cleaner sounding than the others.
EL34 - Least amount of bottom, smoother top. More centered around the mids. Less definition and clarity than the other tubes. All of my favorite amps use EL34s, yet this was my least favorite tube of the bunch here.
JJ 6L6 - Balanced sound. Less low end than the KT66, had more top end clarity than the EL34, but was darker than the other 2. The response seemed to be shifted a little lower, overall, than the RCA.
RCA 6L6 - More top than the JJ. Maybe less bottom end, but it's brighter, so the top end seemed to take over more. More clarity without really being any harsher, but I think I preferred the JJ's darker and lower tone.
That's how I hear it. Great comparison as always, thanks for sharing!
wow, perfect timing for me.....I found a 1965 Silvertone 1484 at a garage sale, with 2 original RCA 6L6 GC's and 4 amperex 12ax7's.... testing the new JJ's and others.
The only one I could hear a difference in your test was the RCA, slightly softer/warmer......maybe the GEC too.....same in the Silvertone compared to JJ....though new JJ' made the Silvertone clear and louder......new versus old. thanks as always.
+rcolang1 Thanks, glad the videos are put to some good use :-)
I use the JJ KT66 in my Marshall plexi, wonderful punch for my strats
+Jonas Jørgensen Yeah KT66 is such a aggressive yet smooth sounding tube. I love it.
Cool video, I think I like the KT66 the best.
Johan do you take requests? Is there any way you can get your hand on a Bogner Ecstasy 101B? It is supposed to have a really cool "Plexi" mode, would love to hear it through same cab as some real plexi's.
+blablabla Thanks! I do indeed take requests, if I get my hands on a Ecstacy I'll do a clip. Cheers Johan
The JJ’s sound good here! Mine sound kinda thin. Can kt66 be plugged in direct where the amp requires 6l6?
I love this kind of demo, especially the long try at the end ! :) Now my 2 cents :
RCA : Very balanced and vintage/soft 6L6. I really would own a pair of it !
JJ : Modern, high fidelity, maybe too much for my taste, too brigth/harsh.
EL34 : Typical of marshall sound, i dislike their cutoff low ends but i like their limitation in the highs (it's avoid the sharpness of the 6L6) and their agressiv/percussiv mids.
KT66 : Better than the JJ 6L6, works in the same category. I don't find them really musical or well balanced.
Natures vids on the right are also great : beautifull trees, mountain of rocks, nice reflect of the nature life, all things i love IRL. Cheers man !
+dafxtone Glad to hear it! Cheers Johan
dafxtone I disagree about the KT66 not being musical. I thought it was the most musical. The mids are shaped just perfect
i understand autobias. but i wonder if it also automatically adjusts primary impedance on the output transformer. from 6L6 to KT66 is quite a stretch using the same impedance. might not show the capabilities of each tube really. but still good comparison and i dont like to admit that the differences are not very big at all. i love rolling tubes :D
+max bauer Thanks, Pure Tone Amps left a comment below, you can ask there. Cheers
The GEC KT66 and the RCA 6L6 'black-plate' have a nicer sonic appeal. Of those two I prefer the KT66 power tube as they sound thick and juicy. Which was one of the reasons I bought a Marshall #2466 'VintageModern' head to add to the 'herd'. I also upgraded the transformers to Mercury Magnetics 'Axiom' line of iron for that amp along with NOS pre-amp tubes as well. That particular head driven with a 'good' dirt pedal, J Rockett Audio '10 ton Hammer', in the low dynamic range pushing an EVH 4X12 cabinet is pure sonic nirvana. And only gets better with a half dozen or so Belgium beers! Cheers.
+Viking Mike Cheers my friend! I love Belgium Beers, I'm often in Gent!
Those RCA Black Plates sound pretty great!
Awesome vid.
Any tips on buying old tubes?
Godspeed
+King Dilph Thanks! Let me think about it, and I'll make a video about what to think of when choosing and buying vintage tubes. Cheers Johan
Loved the RCA.
+CIRCLE OF TONE Your friend for guitar tone Thanks, yeah that's the one that ended up staying in the amp
Hey Johan, I just came accros a Marshall 2201 30w Bass combo from 1977, do you know this amp ? it looks like really rare (and uggly xD ) but might sound right, just like a Lead 12 louder and in a 2x12 format. On top, a lot of them were hand-signed by Jim ! Any thoughts ?
+Armanthio haha! Cool, I just googled it. Hadn't seen it before. Have you played it?
No, unluckily... It is at 700 kms... But it is sold for 50€, which is more than a deal with 2 70's greenbacks in and Jim's signature ^^ Damn, I was hoping that you would know this model but no problem, if I manage to get it, i'll give you a review, comparing it to a lead 12 and a 18w plexi clone. Thanks anyway, cheers !
Once upon a time, in the deep dark Swedish forest , lived 4 valves! Johan out them into a Marshall and they all lived happily ever after.....
+Peter Butler hahaha, a beautiful fairytale:-)
Good morning!, is there some diference between marshall tube and The marshall tube svetlana?, if yes, whats is The bettor?, thanks to all!!!.
Grymt Johan. Djävligt intressant. Tror du det finns en övertro på olika rör allmänt annars?
+Tommy Köllner (Sonofamustangford) Tackar Tommy! Ja jag tror att det allmänt finns en övertro på att bra ljud beror på enskilda viktiga faktorer, medan det egentligen är många små utbytbara bidrag.
Great video thanks. Whilst they all sound good, I prefer the GEC as it sounds more present/stands out more with a tighter sound to my ears! :)
+Norman Paul Martin Thanks man
Dumb question but how does a tube handle the high voltage put into it going to the speaker?
I'd like to see a comparison between a marshall plexi with a tube rectifier and the other with a solid state rectifier.
+Chad rocknroller I compared 15 plexi a while back, some had SS and some Tube rectifiers. I can demo it in the same amp soon too if you want! Cheers
Interesting Comparison, i prefer KT66's but in this clip RCA 6L6 sounds the best for me.
By the way, beautiful views on right ;)
+hartman165 Thanks! Glad to hear that :-)
Def the KT66 for me. It sounded smoother than the other three.
+Tim Brannen Thanks Tim!
ive been tone searching so much i can hear a huge difference with my cell phone speaker. suggestions for dsl40 please. and does the amp have to be biased?
+Tone Fingerz Hi, for a 40watter 1x12 I'd go with a G12-65. And setting a good bias for the Output tubes has a great influence on sound and wear.
RCA Blackplate 6L6 all the way, but I knew it would win. Got a pair in my '64 Pro 1X15. Beats every other tube I've tried by far. Good NOS matched pairs are fetching outrageous prices on ebay these days so the secret is definitely out.
I REALLY preferred the RCA... My least favourite by equally as much was the JJ...
that RCA wow, *drool*
+pleadguitar thanks :-)
Kind of surprised with the results since I've done a similar test at home with a Jet City Picovalve. I couldn't hear a discernible difference in your tubes. The exception was the 1960s RCA which seemed to be breaking up slightly less.
My test at home, I could hear a pretty big difference between the KT66, EL34, and 6L6. Perhaps it has more to do with how the power section of the amp is driving the tube.
it configuration. if class b configuration the tube are likely to not brake up. they only make current of signal bigger. also how it interacts with power transformer. tube have capacitance and transformers have inductance. this two properties interact with each other in class b configuration it the power transformer that distorts.
Hey Johan, can you do a el34, kt77, 6ca7 comparison?
+Rob D Yes absolutely! :-)
Johan, will you ever start an FAQ series?
The forest tubes looked the best to my ears.
;-)
It is hard to believe that there is no dramatic difference.
I once replaced JJ 6L6GC with nos russian 6p3s-e in JMP 2204 clone and difference was night and day. I couldnt put my guitar down. But I havent recorded that tube swap, I wish I did.
I recorded my strat with my handmade bridge pickup and replaced it with also my handmade singlecoil sized P90. Playing live difference was huge, but recorded sound was almost the same. Just a little more low end.
I guess recording somehow makes big differences hard to notice. Maybe my micing technique is bad.
Johan, playing that guitar live you heard same differences as in youtube video ?
+kumpiz Yeah, it sounded like that in the room too. Often when we change one thing with an amp we unknowingly end up changing several things making the difference bigger. My experience is that tubes are one of many small contributors to good sound. Cheers Johan
People make such a fuss about that "British" EL34 sound, and that "American" 6L6 sound. But there's hardly a difference here.
+Ameer Saban Yeah the difference between British and American sound comes from many small contributors and some big ones like speakers. Cheers
Ameer I'm giving you my thoughts and these can be used for many posts here. The American sound and the British sound is not only on the tubes. It is on the speakers as well and other factors. But the EL34s used in the same amp have more high mids and highs while the 6L6 types have more low mids and rounder highs. The Jensen speakers that contribute to the American sound have more highs than Celestions and not too many high mids. Celestions usually have more aggressive mids. I love using my Marshalls and Hiwatt through Jensen speakers too for more clear and bluesier sounds.
And there is a difference even small. The recorded sound loose some feeling compared to what you really hear and when the amp is not cranked these diffrences may be more clear.
I do understand - but there are numerous ads/videos I've seen that promote their amps by saying things like "and they've got a set of EL34's to give you that famous British tone".
The 2 more recent ones sound more trebly - not well balanced. You can tell right away from the first riff! The vintage ones sound similar, the GE has a little bit more lows. Excellent video as always
+jo sg Thanks Jo!
Can you run EL84's in that amp? I would love to hear the differences! Thanx Jason!
Damn spell check!
+Jimmie Marchisotto Hi, no EL84 has a different socket than these tubes
Johan, I'm curious. For last couple videos,, you put landscape video alongside your guitar playing. Is there any particular reason for this ??
For the tube itself, I can hear subtle different. But, it isn't enough to prefer one tube over another.
+Rendy Andrian Hi, I've used landscapes from time to time on this channel. Just showing where I'm at :-)
I like them all ;)
+Fulltone Thanks :-)
RCA all the way. Excellent video.
KT66 is the "winner" for me... Correct me if I'm wrong but, didn't marshall use those in their bluesbreaker initially??
lol had some RCA 6l6gc tubes in my peavey classic 100 2x12 from the 80s but think they were getting kinda dead so just ordered some bugera ones.
I got the Marshal jvm with el34 and love it. but I can't really tell the difference to be honest
+Travis Sanders The differences are indeed subtle. It's many small factors that make up an amp. Cheers
Personally I was totally digging that RCA tube. Although very subtle the difference was between them all (except the KT which I thought was the most different sounding). The RCA had some gnarly harmonics going on in the mid range and still had a little thump in the bottom. The JJ wasn't bad. Surprised how similar the EL and the 6L6 sounded here. Since the same circuit is running the different tubes instead of comparing two totally different amps the difference is subtle.
+X Crow Yeah, when we think of the sound of different tubes we usually think of entire circuits. EL84-Vox, EL34 Marshall, 6L6 Fender
Marshall and Les Paul, what could be better? Nothing! Unless it were my Marshall and...what ever humbucker you want to plug in. You got skills JS, play it loud and play it proud.
+shuggy1110 Thanks, glad you liked it!
I am very surprised that there is so little difference - my pick RCA for the extra detail to the sound.
+Marshall50w Cheers
For me, the absolute hand's down best sounding power tube for a Marshall is the NOS EL34 Mullard.
Flametopology nice profile pic!
Dagger 323 Right-on buddy!
I like the RCA 6L6 best and the GEC
+StealthParrot Thanks :-)
KT66... very full range... RCA very warm to my ears while EL34 and JJ 6L6 sound pretty similar, again, to my ear... i should try some on my Egnater Tweaker 15 that is cathode biased and works with every pair of eight pin tubes... (a very great sounding amp with JJ 6V6, while stock uses a pair of Electro Harmonix Egnater branded..)
Totally agree. KT66 has the "edgiest" charakter, non compressing and full rangy. The SVT EL34 and JJ 6L6 are close to each other, can't really tell the difference there. The RCA however blew my mind - full body with very high detail. Tubes are great, aren't they?
+HaenC _ Thanks :-) they are indeed!
wow...... Ok the KT66, 6L6 rule in my opinion. I knew it allready since I tried them. But that blackplate is smokin'. I love them due to the lower mids fullness. Any comments about the amp?????????????
+PureToneAmps I love it!! Such full and balanced tone! And I can't believe the amp only weighs 3kg and almost fits in the guitar case. :-)
hahaha. Thanks Johan. i'm glad you like it. It really fits and gives such a sound for bedroom levels. It also does the semi cranked bluesy thing great. Thanks.
+PureToneAmps it does indeed!
any info on where to get one of these Little Star amps?
hello Alexander. Please check my page facebook.com/PureToneAmps or email me at mserpetsidakis@yahoo.gr
Before any comparison using old valves, they all need to be tested on something like a Amplitrex AT-1000, to see if they are all still strong gain wise, and close to factory rated new spec., otherwise its a more dubious outcome.
Weak testing valves, means less bass response, more compression.
But... for the sake of the fact Johan went to a lot of trouble to satisfy his fellow tone chasers like myself.....
RCA 6L6 more open, least compressed, clearer, more even in the mids. More headroom. Great for a blues sound.
GEC KT66 also slightly open, slightly more extended frequencies in the low end, thicker low mids, slightly louder.
Marshall EL34 (AKA Svetlana Winged C at a guess) breaks up a bit earlier, slightly congested/brash in the upper mids. Great for Rock. Sounded slightly quieter/ compressed, less bass. Does it still test strong after 6 years of use?
JJ 6L6 breaks up later, slightly wider/ more frequency response to EL34, slightly more open to EL34.
Good quality NOS old valves are almost impossible to find and expensive these days, so sticking to using JJ power Valves.
JJ EL34 are good enough for AC/DC live, so good enough for me.
+ROCKO STIFFREDI The GEC measured basically according to spec RCA just slightly below. Thanks for your elaborate feedback
Surprisingly the GEC KT66 and the RCA 6L6 sounded the best. Somehow the JJ 6L6 sounded a lot like the EL34 at least to my ears. I'm sure in different amps these would all sound different due to different biasing and voltage. But there is something about some of the older tubes that is not reproduced with the new ones. Different anode material perhaps?
+Andrew Shepherd Yeah that would be interesting to investigate. Back then tubes was a central component, today it's a peripheral enthusiast component. Cheers Johan
I prefer the RCA, it's fuller and more dynamic than the others. KT66 sounds also good, while the Marshall EL34 sounds thin and fizzy (maybe that's why most modern Marshall amps sound thin and fizzy too?)
+Danilo Battocchio Yeah, EL34s are harder to be a balanced tone out of, but when it's done they have such a lovely edge
boy you can really hear those RCA 6l6gc open up I couldn't tell on the GEC KT66 they were 1st in the chain i had a hard time following them
Yeah the order the tubes are presented in makes a huge difference indeed
I prefer the KT66. Since I use this one my songwriting and overall guitar skills have increased dramatically ; )) ...even my singing.
Just joking, nice video!
But as I "said": There are faaar more important things that contribute to the sound.
+Kiryk Drewinski Thanks! Yeah, compare to speakers, tubes are very subtle
the GEC has something that goes missing with the EL34..The 6L6 kinda brings a little bit of it back along with something it only has....The RCA like goes all raggid and sags a lot. So I liked the GEC and the 6L6 best in this amp. Just more material there in the sound. Good job Johan!
Hey I wanted to add that when you started muting the guitar and running through all the tubes is where I could hear all the differences best. You give it low and highs at there loudest in a way like that which sends all those frequency through tubes pushing them so you can hear how the respond.
+Legend of the strings Thanks, I'm actually currently using the GEC in this amp
From the sound I heard that would be my choice 6L6 seconds.
This affirms my distaste for jjs . I retubed my 22 watt with jjs. They were out before the night was over and replaced with cheap Chinese tubs that sounded way better. I sense started useing tung soul and love them.
Hard to hear a big difference...What are your feelings and sensations while playing, Mr Segeborn? Thanks a lot...
+Matt Caruso The vintage tubes felt punchier and more open. Cheers
Was that on full “entasis” (volume)?
Very close to it at any rate. Cheers Johan
Thanks, I am looking for a portable low watt replacement for my JCM2000 DSL with an fx loop , “real” distortion and volume-roll clean, to adopt to my more modern rock sound, you’ve tried so many amps, could you give some advice? (OR15 sounds kinda good too imo)
I'm not sure. But that KT66 sounds pretty dang sweet..
Kt66 seens to be less compressed compare to the el34 but im not really sure. There were very small differences here
+Lars Sig Yeah, the EL34 was definitely less defined
That RCA looks so much like an NOS 6ca7.
Less differences than I'd thought. But I like the KT66 best. My son plays a JVM 210H with 6L6s 'cause the tech didn't have any EL34. The difference may increase if you got two biased pairs....
+juppheidi Yeah the difference was a little more pronounced in an earlier clip with 6 Power tubes and a Fargen Mini Plexi.
Most gain on the EL34. On the higher register KT66 and the EL34 sound almost identical. The 6L6 has the 2nd most warmth but falls between KT66 and 6L6 GC on gain. The 6L6 GC has the most warmth and the least gain.
I was surprised, the KT's sounded the most compressed. The JJ's were brittle.
I did a similar comparison a few years ago on the metroamp forum. Power tubes don't change the overall character of the amp, just certain qualities. The other big difference is in the feel of the amp when you dig in, which is hard to perceive on a recording. Here's a link to the one I did, you'll note it's tough to hear the differences until you know what to listen for: forum.metropoulos.net/viewtopic.php?f=13&t=44130
Wow, the difference is far less dramatic than I exspected it to be.
+error Yeah, the older tubes have better dynamics and spatial definition, but they have a similar character.
wow surprised how similar they sound
+rocknroor yeah, the difference lied in dynamics rather than tone
I'm. Watching this video through iPhone & they all sound the same, lol. Damn 😊
+Babillonia Yeah, you probably need to use Headphones. Cheers
based johan
GEC KT66!!!
In order: KT66, JJ 6L6 (!), RCA, Marshall EL34
+Thomas Webb Thanks Thomas
adjusts bias?
+fenderman fenderman No need for that in this amp