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EL34/6L6GC Differences & Ampeg B-15R

gstaats

gstaats

Supporting Member
Mar 22, 2019
2,114
5,758
#1
First, I get that tube differences can be minor, are highly circuit dependent and can be seriously subjective. I have an ampeg B-15R and it has a bias switch on the rear for EL34s or 6L6GCs. Didn't do a mic'd recording yet - haven't had the amp in an appropriate space to do so. Rolling out the 6L6GCs for EL34s yielded an interesting surprise this weekend. The 6l6GCs appeared to be overall louder - but their breakup isn't a smooth tube over drive. The EL34s were overall quieter (I think) but pushing them harder yielded a much smoother tone and more controlled response when being pushed.

Anyone else have experience rolling between 6L6GCs and EL34s? Just an apex matched JJ set for both - will probably try a TAD set of both down the road. Looking forward to hearing what others have experienced!
20210809_140940.jpg
 
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#2
I was really surprised by this, but I liked JJ EL-34II (I bought EL-34II because JJ E34L was out of stock at that moment) better than JJ 6L6GC in a Traynor YBA-300. Surprised because I thought it would distort too much or too early. Didn't get too much distortion, and it was smoother, as you said. Just liked it more. I like beautiful, and I thought it was.
 
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#3
The amps has a lot of tonal options, especially when you start playing is the half power and impedance matches/mismatches. Also small tube options such as the 12AU7 and 12AT7 for the phase inverter make a difference.

The EL34/6L6GC switch sets the bias. It’s generic and conservative, it may not be optimal for your set of power tubes. To optimize it, a tech would determine which valued resistors to use for the bias circuit. They have to be soldered in. It might be worth exploring.

As you mentioned, the sound - both distortion and headroom, will change. This becomes more noticable when the amp is pushed.
 
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#4
My tech checked out the amp recently and picked up matched quads of EL34 and 6l6GC's. The bias was super close to correct as is - he showed me the numbers - it would be splitting hairs to re-bias. He did find a grounding issue and resoldered all panel connections. Overall I am happy with it. I think I am going to try different preamp tubes. Rolling different tubes through a different amp let me get super smooth breakup. I'll see if I can get that with the b-15R.
 
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#5
gstaats said:
My tech checked out the amp recently and picked up matched quads of EL34 and 6l6GC's. The bias was super close to correct as is - he showed me the numbers - it would be splitting hairs to re-bias. He did find a grounding issue and resoldered all panel connections. Overall I am happy with it. I think I am going to try different preamp tubes. Rolling different tubes through a different amp let me get super smooth breakup. I'll see if I can get that with the b-15R.
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Hello...
How has the tube rolling going? Very interested in the EL34 and 6L6 experience. My tech is very much a KT66 fan and has suggested that as an option. I have 2 B15R and am only changing up one of them. They start out pretty nice as is. I have rolled many Pre-Tubes and changed the driver to am eminence Kappa. I have heard the Delta and Beta are also good options. Back to the power tubes. Any suggestions for brand for EL34 and 6L6 or even the KT66? I also know its not an ideal tube time.
 
#6
northbynorth said:
Hello...
How has the tube rolling going? Very interested in the EL34 and 6L6 experience. My tech is very much a KT66 fan and has suggested that as an option. I have 2 B15R and am only changing up one of them. They start out pretty nice as is. I have rolled many Pre-Tubes and changed the driver to am eminence Kappa. I have heard the Delta and Beta are also good options. Back to the power tubes. Any suggestions for brand for EL34 and 6L6 or even the KT66? I also know its not an ideal tube time.
Click to expand...

Which driver did you put in it? I tried a kappalite 3015 too - the delta pro 15a is where I landed. It is heavier, but, sounds better. This isn't my daily driver either, so that isn't a big deal.
 
#7
gstaats said:
Which driver did you put in it? I tried a kappalite 3015 too - the delta pro 15a is where I landed. It is heavier, but, sounds better. This isn't my daily driver either, so that isn't a big deal.
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The Kappa-15LFA American Standard Series. More low end and warm smooth all rounded. The original is tighter with more mid push. I like them both.
 
#9
northbynorth said:
Hello...
How has the tube rolling going? Very interested in the EL34 and 6L6 experience. My tech is very much a KT66 fan and has suggested that as an option. I have 2 B15R and am only changing up one of them. They start out pretty nice as is. I have rolled many Pre-Tubes and changed the driver to am eminence Kappa. I have heard the Delta and Beta are also good options. Back to the power tubes. Any suggestions for brand for EL34 and 6L6 or even the KT66? I also know its not an ideal tube time.
Click to expand...

As far as tubes, here is where I've landed right now for tubes in my b-15r. My goal was to get a "wider" range of what I consider the sweetspot of a tube amp where the amp is in subtle OD, providing extra harmonics and some natural tube compression. I wanted to get this for both the poweramp and the preamp. Some combination yielded pretty fast breakup - not a lot of control to keep it in the sweetspot before it just sounded awful. In general, at least with the B-15R, my experience was that 6l6 tubes seemed to have a more harsh breakup. The EL34's seemed to be a slightly more mid forward and achieve a decent sweetspot for controlled breakup. For the power tubes, I ended up with TAD EL34 STR Red Base tubes.

I haven't done as much much rolling in the preamp. I did want to do the same thing of having a more subtle transition into OD territory. I ended up running 3 "TAD 7025 S" tubes. Unfortunately, they aren't made any more, but I did buy all the tubes I could on clearance from Stew Mac when they had them in stock and on clearance last winter. :bassist: I should have enough to last a lifetime. They were stupid cheap when they were blowing them out (before the tube price hike from the conflict in Ukraine) and I bought several to roll and really liked them. I then bought out their stock - didn't have too many at that point.

The end result is an amp that has a more subtle transition from clean to OD, and, much more useable OD tones.
 
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#10
gstaats said:
As far as tubes, here is where I've landed right now for tubes in my b-15r. My goal was to get a "wider" range of what I consider the sweetspot of a tube amp where the amp is in subtle OD, providing extra harmonics and some natural tube compression. I wanted to get this for both the poweramp and the preamp. Some combination yielded pretty fast breakup - not a lot of control to keep it in the sweetspot before it just sounded awful. In general, at least with the B-15R, my experience was that 6l6 tubes seemed to have a more harsh breakup. The EL34's seemed to be a slightly more mid forward and achieve a decent sweetspot for controlled breakup. For the power tubes, I ended up with TAD EL34 STR Red Base tubes.

I haven't done as much much rolling in the preamp. I did want to do the same thing of having a more subtle transition into OD territory. I ended up running 3 "TAD 7025 S" tubes. Unfortunately, they aren't made any more, but I did buy all the tubes I could on clearance from Stew Mac when they had them in stock and on clearance last winter. :bassist: I should have enough to last a lifetime. They were stupid cheap when they were blowing them out (before the tube price hike from the conflict in Ukraine) and I bought several to roll and really liked them. I then bought out their stock - didn't have too many at that point.

The end result is an amp that has a more subtle transition from clean to OD, and, much more useable OD tones.
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Thank you for the update/information! This is helpful!
 
#11
In my experience: at low to moderate volumes, preamp tubes have more tonal effect than power amp tubes and at high volumes most of the subtle difference of either type gets buried in the mix. Preamp tubes are pretty safe to experiment with, but power tubes require more care because the voltage level varies significantly in various circuits and what is safe in one can melt down in another and cause some major damage.
 
#12
gstaats said:
First, I get that tube differences can be minor, are highly circuit dependent and can be seriously subjective. I have an ampeg B-15R and it has a bias switch on the rear for EL34s or 6L6GCs. Didn't do a mic'd recording yet - haven't had the amp in an appropriate space to do so. Rolling out the 6L6GCs for EL34s yielded an interesting surprise this weekend. The 6l6GCs appeared to be overall louder - but their breakup isn't a smooth tube over drive. The EL34s were overall quieter (I think) but pushing them harder yielded a much smoother tone and more controlled response when being pushed.

Anyone else have experience rolling between 6L6GCs and EL34s? Just an apex matched JJ set for both - will probably try a TAD set of both down the road. Looking forward to hearing what others have experienced!
View attachment 4418327
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That's probably why Marshall amp players like EL-34s. I prefer hard tubes like 6L6's and 6550's for bass.
 
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#13
bobyoung53 said:
That's probably why Marshall amp players like EL-34s. I prefer hard tubes like 6L6's and 6550's for bass.
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In the 70s Marshalls shipped to the USA had 6L6s while the UK amps were still EL34s. This caused a lot of US guitar players to seek out UK amps which were perceived as having a smoother sound. All they really needed to do was have a tech rebias thie amps for EL34s, but since this was before the Internet Inflooenzers made us all aware of the wonders of tube swapping.

Sunn offered a number of similar amps in the late 60s, some with EL34s, some with 6L6s and the names were different. I have no idea why they did both or whether they sold both at the same time.
 
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#14
brianrost said:
In the 70s Marshalls shipped to the USA had 6L6s while the UK amps were still EL34s. This caused a lot of US guitar players to seek out UK amps which were perceived as having a smoother sound. All they really needed to do was have a tech rebias thie amps for EL34s, but since this was before the Internet Inflooenzers made us all aware of the wonders of tube swapping.

Sunn offered a number of similar amps in the late 60s, some with EL34s, some with 6L6s and the names were different. I have no idea why they did both or whether they sold both at the same time.
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I never really bought into the whole tube swapping deal for changing an amp's tone until I bought an SVT head out here in Lima about twenty years ago in which someone had thrown in 6L6's instead of 6550's. The amp actually sounded like a big Fender amp. This I noted before I checked the tubes, once I did I figured it had been modded because the voltages are too high in SVT's for 6L6's but nope. I took them right out when I realized but I was really surprised at the difference in tone. They were all old GE 6L6GC from Fenders you could see the claw marks on the bases and old Fenders were real common out here then. If they were modern tubes I doubt they would have lasted, none of them even glowed ruby red. The bias was set all screwed up too, one side was all the way hot, the other all the way cold.
 
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#15
I use to have the same B15R/B15E rig. Yes I did install EL series, but I used the JJ E34L tubes as Eurotubes said they're more intended for bass amps. But yes, it had noticeably more bloom to the sound and less 'hard'.

I don't remember if I had my old 12AX7 RCA's kicking around or if I simply used JJ's. But it was a great sounding rig, but in my old band it required both cabs to be heard. Wish I kept it.
 
#17
brianrost said:
In the 70s Marshalls shipped to the USA had 6L6s while the UK amps were still EL34s. This caused a lot of US guitar players to seek out UK amps which were perceived as having a smoother sound. All they really needed to do was have a tech rebias thie amps for EL34s, but since this was before the Internet Inflooenzers made us all aware of the wonders of tube swapping.
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??

AFAIK Marshalls shipped to the US had 6550s rather than 6L6.

To mod one of these amps back to factory EL34 spec requires swapping out at least three resistors and moving the connection for the feedback loop.
 
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