Need some advice about JJ EL84s in a Rocket 44

Hi,
I need a little advice. I recently picked up a quad of EL84s to put into my Rocket 44 from an online eBay vendor. They're matched, I did ask them for something in the Mesa bias range but I think they just ignored that and sent me whatever. Anyway they are replacing a set of Valve Art EL84s which have been running in my amp for several years with no problems and were definitely in the right range. The Valve Arts had stickers on their boxes that said 21/5.4. The JJs came with a sticker that said 27.5/6.90. I'm not 100% sure what these numbers mean. Are the lower numbers on the bottom related to the Groove Tubes scale, or is it the transconductance and power draw ratings? Does anyone think it will be cool to load these into my Rocket? Thanks in advance.

I tried them out. They seem to be generating a lot more heat than what I had observed before. I changed back to the old set.

I've never had a good experience with JJs in my Maverick. The Mesa-branded JJs are the only ones that ever sound right to me. I'm not sure why they're so different, but I've resigned myself to order tubes directly from Boogie or from a local dealer.

I've heard many times that the Mesa tubes are actually JJs. If so, what's the secret? Does JJ make those tubes exclusively for Boogie?

It's more about Mesa choosing tubes that are middle-of-the-road in terms of break up and then testing them for future potential faults -- although I have heard they don't burn them in but that is hearsay. There is a common comparison with the Groove Tubes scale where 1 = the earliest breakup and 10 = the least breakup/highest headroom. Apparently all the Mesa selections fall in about the middle of the GT scale; around about 4-6 and they have their own colour code within that general range.

I have had JJs in the amp before and they sounded good. It's mainly about getting a supplier to choose tubes in the right range if you're not going to go with the Mesa-branded tubes which cost a small fortune in Australia; $79 before delivery for two EL84s from the official Mesa importer which Pro Audio in Canberra.

wildschwein said:

Hi,
I need a little advice. I recently picked up a quad of EL84s to put into my Rocket 44 from an online eBay vendor. They're matched, I did ask them for something in the Mesa bias range but I think they just ignored that and sent me whatever. Anyway they are replacing a set of Valve Art EL84s which have been running in my amp for several years with no problems and were definitely in the right range. The Valve Arts had stickers on their boxes that said 21/5.4. The JJs came with a sticker that said 27.5/6.90. I'm not 100% sure what these numbers mean. Are the lower numbers on the bottom related to the Groove Tubes scale, or is it the transconductance and power draw ratings? Does anyone think it will be cool to load these into my Rocket? Thanks in advance.

Click to expand...

The first number (21, 27.5) is probably the idle current draw, though it's not clear what plate voltages they were using. Point is, the new 27.5 WILL run hotter than the 21.

I use Eurotubes for my DC-3, which is notorious for running hot. They sell JJs, and they know how to measure and match tubes, especially for Mesa amps.

My DC3 has JJ EL84s in it and it runs really comfy. Sounds good too. Good enough that I just put a set in my Marshall DSL401. That amp's bias is adjustable,though.

dodger916 said:

wildschwein said:

Hi,
I need a little advice. I recently picked up a quad of EL84s to put into my Rocket 44 from an online eBay vendor. They're matched, I did ask them for something in the Mesa bias range but I think they just ignored that and sent me whatever. Anyway they are replacing a set of Valve Art EL84s which have been running in my amp for several years with no problems and were definitely in the right range. The Valve Arts had stickers on their boxes that said 21/5.4. The JJs came with a sticker that said 27.5/6.90. I'm not 100% sure what these numbers mean. Are the lower numbers on the bottom related to the Groove Tubes scale, or is it the transconductance and power draw ratings? Does anyone think it will be cool to load these into my Rocket? Thanks in advance.

Click to expand...

The first number (21, 27.5) is probably the idle current draw, though it's not clear what plate voltages they were using. Point is, the new 27.5 WILL run hotter than the 21.

I use Eurotubes for my DC-3, which is notorious for running hot. They sell JJs, and they know how to measure and match tubes, especially for Mesa amps.

Click to expand...

Cheers for that. Yeah, I didn't measure anything but noticed the extra heat right away. The sound was cleaner and more brittle than usual. I'm just keeping them for back ups and have some other JJs in the correct range on the way.