Mesa Rectifier and Tube Bias...

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My Triple was biased in the lows 20’s per side. Increased it to mid 50’s per side. Like it better back where it was. Need to get around to switching it.
 
Alot of the Recto PCB's have pads in the bias circuit to add a trimmer but its not really needed.
However if you wanna use pedals with your recto you'll have to mod the loop from parallel to series. Not hard.
For all R. Smiths accomplishments IDK why he didn't make loops switchable on alot of his amps.
 
BeZo said:
Let's say you had Mesa amps, but none had Mesa tubes in them for reference. How would you know to get the right Mesa tubes? Is there a spot for the color code on the circuit? Would you just have to measure and see? Guess and check?

Asking for a friend...
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In theory, all Mesa tubes are selected that they should run in an acceptable bias range in Mesa amps. It‘s not like a certain amp needs a certain color code tube as the bias range where the system runs in safe specs is quite large.
However, I have not seen any Mesa branded tubes hotter than gray so far.
 
shar-vell Dan said:
Alot of the Recto PCB's have pads in the bias circuit to add a trimmer but its not really needed.
However if you wanna use pedals with your recto you'll have to mod the loop from parallel to series. Not hard.
For all R. Smiths accomplishments IDK why he didn't make loops switchable on alot of his amps.
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Yeah I wished they were switchable too. Parallel is great if you are running something like a single chorus, but trying to get a wet/dry balance across multiple pedals can be impossible, and then obviously it's a problem with time-based stuff like delays.
 
BesaMoogie said:
In theory, all Mesa tubes are selected that they should run in an acceptable bias range in Mesa amps. It‘s not like a certain amp needs a certain color code tube as the bias range where the system runs in safe specs is quite large.
However, I have not seen any Mesa branded tubes hotter than gray so far.
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Having tested over a hundred Mesa 6L6 in 20-30 Marks & Rectos I respectfully disagree, there are combinations that will exceed 70% dissipation sometimes by quite a lot. This is the part where theory & practice don't align. Kind of like the battle between Ford engineers & mechanics. :LOL:

BLU does exist, it's just getting hot enough to not be common. I've seen them in the last few years. I've never actually seen a WHT.
 
A quick clip of the yellow Mesa tubes in El bias. They are the str445.



Amp is boosted in the clip.
 
STR445 are JJs which are notoriously cold 6L6s. You have to work pretty hard to find them hotter than YEL.

All this being said, on the mic, it's really not going to make much if any difference. Hell, going from 6L6 to EL34 doesn't really make a difference in a close mic recording setup. I used to think everything mattered until I started close mic reamping & level matching, and listening with good studio monitors. Turns out there's a lot that matters in the room that doesn't matter on the mic.
 
GJgo said:
Having tested over a hundred Mesa 6L6 in 20-30 Marks & Rectos I respectfully disagree, there are combinations that will exceed 70% dissipation sometimes by quite a lot. This is the part where theory & practice don't align. Kind of like the battle between Ford engineers & mechanics. :LOL:

BLU does exist, it's just getting hot enough to not be common. I've seen them in the last few years. I've never actually seen a WHT.
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Good to know. Did you take into account that 6l6 are running much hotter in Mark simil class on the outher pair?
 
Just for shits and giggles bias that baby on diodes and tell us what it says lol. Thus why they do that.. Case in point biasing 70 % on rectifier ...accidentally switching to diodes....Now you have a rectumfrier
 
just42dave said:
Just for shits and giggles bias that baby on diodes and tell us what it says lol. Thus why they do that.. Case in point biasing 70 % on rectifier ...accidentally switching to diodes....Now you have a rectumfrier
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For mine the 16 was on diodes and bold. Which is how I generally run them. I am finding it quite fun running them in El34 now.
 
I know you're talking about running super cold 6L6 in EL34 bias mode but it's still worth mentioning that generally speaking, (unless you have super cold ones) both diode & bold together is too much for EL34s. For anyone I'd always recommend getting a probe in there to test the limits of the tubes.
 
GJgo said:
I know you're talking about running super cold 6L6 in EL34 bias mode but it's still worth mentioning that generally speaking, (unless you have super cold ones) both diode & bold together is too much for EL34s. For anyone I'd always recommend getting a probe in there to test the limits of the tubes.
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For sure, with either selected the bias is too high. Have to have both spongy and tube rectifier selected even with cold tubes.
 
So what about the series2 single/rectoverb? It allows for EL34s to run while using diode/bold. (?)
Personally the only pair I've used in mine are the mesa str-447 yellows.
 
Just found some Blue 440s in my stash...

Going to drop them in the Mark VII soon.
 
In the VII Class A slots I suspect BLU might be mid-high 40s mA which is getting hot enough you might want to test your setup before just running them.

In the A/B slots I'd guess mid-high 30s which should be alright.
 
GJgo said:
In the VII Class A slots I suspect BLU might be mid-high 40s mA which is getting hot enough you might want to test your setup before just running them.

In the A/B slots I'd guess mid-high 30s which should be alright.
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I didn't feel like pulling the chassis to measure, but I believe you are correct. They sound great in the A/B slots.
 
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