Colliseum Mk IIC+ question

I'm still a newbie to Mesas and have been trying to learn all I can about my "new" amp.

Assuming my amp came with 415s, what would be a good readily available substitute 6L6 that wouldn't loose the Mesa gainy tone? I keep hearing JJ's are what locals love, but most don't play Mesas or like lots of gain. Perhaps EH be closer than 440 Mesa 6L6s?

Also, which sockets do you pair-off the matched sets into? Work from center out, or do the matched sets pair side by side, two at a time? I'm new to swapping tubes myself and would like to do it myself since bias is not required.

Gain isn't going to be affected by your power tubes. Preamp tubes will do that.
12ax7 having the most 'gain' (call it 100%) then onward down the line to the 12au7 (call it 20%)
With the 12at7 and 12ay7 being in the middle (60% and 45% respectively)

For current day production 6L6 power tubes find some "Winged C's". The label looks like this: =C=

I don't remember the power tube pairings on the Colis right now.
But do a search it's been discussed beforehand.

The SED =C= SV6L6GC is an excellent tube, full tone from lows to highs and very rugged.

You are wrong to assume that there is no bias to be concerned with. ALL tube amp powertubes require a bias voltage to operate, Mesa uses a fixed bias that is not adjustable. You can not just stick in any grade of powertube. Be sure that your tube supplier selects tubes that will run properly in a Mesa amp.

I'm not sure how your powertubes are paired but if you by a matched set it doesn't matter.

Dom

Hey,

Your tubes are paired from the center two out. So 3&4, 2&5 and 1&6 are pairs. If you order new tubes, tell the seller which amp and model you are getting them for. If the seller is good, they will get a set to match your bias. Also when you run it on half power, it just changes the resistance to drop the voltage across the tubes in order to drop the wattage, but all tubes are still in use.

On a side note, your amp is probably in need of service, and when you get a chance, maybe sending it to Mesa is a good idea, especially since it was run with 4 tubes before you got it. Your amp is far too rare and valuable and it would be ashame to burn something up. That being said, I'm not trying to tell you what to do, just a suggestion...

Scott

I more vote for =C= 6L6s.

I appreciate all input. The largest I can find of matched sets is sets of four. Mine takes six 6L6s, so I hve to go with three matched pairs, that's why I needed to know how to pair them, and appreciate that info. I've just gathered the STR440 isn't as good as past available models.

Thanks again for all your help.

Contact Doug Preston at Doug's Tubes. He will set you up with a matched sextet. I've been dealing with him for years and have had nothing but good results. Any powertubes I have ever got from him were always matched within a few mA's.

Dom

domct203 said:

Contact Doug Preston at Doug's Tubes. He will set you up with a matched sextet. I've been dealing with him for years and have had nothing but good results. Any powertubes I have ever got from him were always matched within a few mA's.

Dom

Click to expand...

I've used eurotubes mostly but have talked to Doug as well and ordered I think a tungsol from him too. I'm reconsidering using JJ 12AX7 exclusively in my new stiletto II but we'll see. I thought Mesa tubes are re-branded JJ's???