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Great set of tubes for a B-15R?

J

justinmj

Jul 29, 2001
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#1
Hi All,
I posted this over at the Dudepit as well, but I thought I'd try here as well since this seems to be a fantastic information source. Anyway, I have this B-15R that I use for every record I've ever done for the past 6 or 7 years, and it's a dream. It originally had stock 6L6's for about a year, then the designer Obeid Khan at Ampeg told me to go with EL34's. As you can probably tell, I'm not very tube savvy. But I really noticed a cooler tone after that, much more "alive" sounding and a bit more output...I believe those were just stock Groove Tubes, though. Anyway, they failed recently, and a tech here in LA put in Sovtek 6L6's, and now my amp seems to have a lot less life. I think I should go back to EL34's, which Obeid agrees with, so he's sending me some Groove Tube EL34's because that's what they carry in house, but he also recommends Svetlanas. Now, I really want the best possible sound out of that thing, so does anyone have a recommendation of which tubes I should get? Should I go NOS? I also want great preamp tubes as well...I would love to know which and where to buy all of this stuff, if anyone has any thoughts. Thanks so much!
Best,
Justin Meldal-Johnsen
 
#2
Cool someone else who put EL34's in their B-15R. I use mine for recording also and I push it a little hard to get it to break up and blend it with a direct line sounds great. As far as tubes go I've got groove tubes in it right now there some hot rodded kind (GTEL34LS ?) but I'll agree that amp sounds so much better with EL34 than with 6L6's I've heard good things about sovteks and i also wanted to check out the new Mullards (made by EH) as far as pre amp tubes alot of people like JJ's or EH
 
#3
Try fat bottle (real) 6CA7's. They bias like an EL34 (they are equivalent substitutes), but have bigger bottom without being flabby. EH (Sovtek) makes nice ones, as does Ei. Groove Tubes sells a VERY overpriced Chinese copy of the old GE 6CA7 that they claim is US made, but it IS a great tube. If you like EL34's, you'll LOVE 6CA7's.

Svetlana EL34's are WAY overrated and they don't last. I had three sets in my Traynor in a year and they just never sounded good. (I replaced them with a set of Ei 6CA7's that have been in there for the past six and still sound awesome.) The new "Mullard" is just a repackaged old Sovtek EL34G.

There's also no reason to go NOS. I have REAL Mullard EL34's and they're nothing special.
 
#4
About equivalence of 6CA7 and EL34... Yah they are supposed to be, but......

You can nearly always go from EL34 TO 6CA7, but sometimes you can't go FROM 6CA7 TO EL34......

The bias is similar, but most EL34 I have tried have had a problem of "bias crawling" if the amp has a high plate voltage and was set up for 6CA7.

That is a situation where the bias seems unsteady, and keeps letting the plate current "crawl" upward as it warms up.... A kind of "thermal runaway". Makes bias hard to set in teh first place, and does not lead to confidence that it will stay set......
 
#6
Jerrold Tiers said:
About equivalence of 6CA7 and EL34... Yah they are supposed to be, but......

You can nearly always go from EL34 TO 6CA7, but sometimes you can't go FROM 6CA7 TO EL34......

The bias is similar, but most EL34 I have tried have had a problem of "bias crawling" if the amp has a high plate voltage and was set up for 6CA7.

That is a situation where the bias seems unsteady, and keeps letting the plate current "crawl" upward as it warms up.... A kind of "thermal runaway". Makes bias hard to set in teh first place, and does not lead to confidence that it will stay set......
Click to expand...

That's because a 6CA7 is a beam tetrode and an EL34 is a true pentode.

I also wouldn't put EL34's in a Bassman unless you wanted to turn it into a loud guitar amp. That's what Jim Marshall did!
 
#7
Hmmmm, interesting thread.

My B15R is from around 1998 and it still has the facatory installed 6L6 Groove Tubes. I love the amp, but yeah, it could sound better with different tubes. I like hearing the "alive" comment about switching to EL34's.
Does it really seem to have more outout with EL34's?
 
#8
Caca de Kick said:
Hmmmm, interesting thread.

My B15R is from around 1998 and it still has the facatory installed 6L6 Groove Tubes. I love the amp, but yeah, it could sound better with different tubes. I like hearing the "alive" comment about switching to EL34's.
Does it really seem to have more outout with EL34's?
Click to expand...


It seems louder because the EL34's have alot of mid to them and less low end so it cuts alittle bit better and overdrives alittle bit easier a very nice sounding overdrive. ^l^'s have more bottom or low end in them and EL34's are more in the midrange area ( still have good lows) this is why alot of guitar amps use EL34's (Marshall, Orange, Matamp,etc..) they overdrive nicely and sound good with guitar . Now I'm not saying that your B-15 is going to turn into a guitar amp with El34s they just have a more harmonic structure to the sound more open and "alive" I think they sound great you wouldn't be dissapointed with the switch. If you change to EL34's let me know what you think
 
#9
I think I'll do a tube swap in the next week or two, since I'll be recording in Jan, I'd like to try this out.
Since I'm a customer of Eurotubes I looked at their EL34 choices. His site says he's been experimenting with quad setups of matching 2 EL34 with 2 6L6's and getting a nice blend between the two for sound...says gets the bottom end from the 6L6's and the cutting mids from the EL34's.
I wonder if this mix would work in our B15R's? It's interesting for sure, but I probably won't do it.

Hmmm, he also has an E34L that's listed as a deeper, punchier more aggressive tube than his standard EL34. That sounds like the way to go.

Looks like I need to give him a call and see what's up.
 
#13
This has been a real interesting thread for me. I have a B-15R/B-15E and a 1967 B-15-N. The B-15-N just blows the B-15R away tonewise. I've been looking for ways to improve the tone of the B-15R and bring it closer to the B-15-N. I know there is not much I can do. I'm going to try switching out tubes and I'm looking at upgrading the transformers...someday. If anyone out there has found the magic bullet to greatly improve the tone of the B-15R, Please speak up!
 
#15
I found out the HARD WAY -$$$- that it's sometimes not good to swap 6CA7's for EL34's
they only lasted about 3 hrs- but were pretty to watch-fireworks!!!$$$
I replaced mine w/ JJ KT77's ( from eurotubes.com ) they sounded superb & AFAIK ARE an OK replacement for 6CA7's as they also do take a higher plate voltage. Sound great, were reliable & perhaps a bit deeper & tighter bass end than the 6CA7's were- but could've been coz the 6CA7's were OLD!!!!
 
#16
As PBG states the 6CA7 is not an EL34. The 6CA7 has pin 1 unwired while the EL34 has its' suppressor grid (G3) wired to pin 1. If your amp has pin 1 tied to pin 8 then the tubes are basically interchangable. If pin 1 is used as a tie point for other components (ala some Fender amps) you can use a 6CA7 but not an EL34.

Paul
 
#17
Sorry to resurrect this thread but it's the most relevant and I hate to make a new one.

I changed over to EL34's about 6 months ago. I much prefer them to the 6L6's but when I did it I just grabbed some cheap JJ's online to test the waters. Low and behold, they are failing on me. Even though it's probably not 100% necessary I have decided to change out all the tubes for some NOS/Mil Spec ones. The goal being to increase the longevity, minor tone improvements would be a bonus but not my first priority - especially since it seems that NOS should in theory sound better if not the same, so little tonal risk with the "upgrade".

That said, a friend has supplied me with 3 NOS Telefunken 12AX7's. They are smooth plates, have the diamond logo and the diamond on the bottom. So I know they are authentic and seem to be early 60's (smooth plate being the tell). Word is these are great for hi-fi amps. Some guitarist like them, some don't, depends on gain preference. I think for my application, they should be great. Got a decent deal so worth a shot. Any thoughts on these?

As for power tubes, I'm looking to grab a matched quad of NOS RFT/Siemens EL34's. They are Mil Spec. Hear they are good mid-priced NOS tubes, compared to the Tele's and Mullards. Any thoughts on these?

I'm open to suggestions on other brands but I'm sticking with the EL34's and 12AX7's for now. Thanks!
 
#18
Honestly, I'm pretty much done with NOS tubes, especially power tubes. They are insanely priced and just not as worth it to me as they were when they weren't insanely priced. Since you have the Mullards, give them a shot, but I'd try a different new brand of power tubes before I went with NOS. Maybe Tung Sol?
 

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