Retubing my Mark V combo?

[dodger916]

This applies when the tubes are installed into a FIXED bias amp such as a Boogie. This means that the Groove Tubes will draw close to the same current at idle as the corresponding color codes of MESA tubes. The red color code idles cooler and is further from clip (breakup) , and the white color code idles hotter and is closer to clip (breakup). Reds = headroom , White = quicker distortion. 8) This is what Marcus was saying.


The early and late breakup that Groove Tubes is talking about is the tubes installed into an ADJUSTABLE bias amp with the tubes biased to the same current draw. That is, if you took a #5 tube and a #10 tube and biased them do both draw 70% mpd, that the #5 would distort sooner and the #10 would have more headroom.

Thanks for the explanation, Joey.

So then is it correct to say that:
1) The higher the percentage of max plate dissipation an amp is biased, the earlier breakup will occur?
2) Assume an amp whose FIXED BIAS is "50". A tube drawing "80" will be biased at 62.5% (50/80) of max plate dis., whereas a tube that draws "75" will be at 67% of mpd.
3) Therefore, the tube drawing 75 will have earlier breakup.
4) If that's the case, Mesa Red tubes draw more than Mesa White.

I'd love to know if I'm seeing this correctly.

 

[JOEY B.]

So then is it correct to say that:
1) The higher the percentage of max plate dissipation an amp is biased, the earlier breakup will occur?
2) Assume an amp whose FIXED BIAS is "50". A tube drawing "80" will be biased at 62.5% (50/80) of max plate dis., whereas a tube that draws "75" will be at 67% of mpd.
3) Therefore, the tube drawing 75 will have earlier breakup.
4) If that's the case, Mesa Red tubes draw more than Mesa White.

I'd love to know if I'm seeing this correctly.

Answers:

#1 - The higher the percentage of max plate dissipation a TUBE is pulling in idle current draw, the earlier breakup will occur. This will be determined by the negative voltage at pin #5 of the power tubes. -30V at pin #5 will make the tube run hotter than -50V at pin #5, for example. This value is not adjustable on MESA amps without adding a bias pot or changing resistors in the bias circuit.

#2 and #3 - you lost me, I am not understandind your meaning.

#4 - Mesa Red tubes draw the least idle current, and MESA White tubes draw the most idle current, in a fixed bias MESA/Boogie amp. 8) I have confirmed this with my Bias-Rite on several MESA amps.

 

[dodger916]

So then is it correct to say that:
1) The higher the percentage of max plate dissipation an amp is biased, the earlier breakup will occur?
2) Assume an amp whose FIXED BIAS is "50". A tube drawing "80" will be biased at 62.5% (50/80) of max plate dis., whereas a tube that draws "75" will be at 67% of mpd.
3) Therefore, the tube drawing 75 will have earlier breakup.
4) If that's the case, Mesa Red tubes draw more than Mesa White.

I'd love to know if I'm seeing this correctly.

Answers:

#1 - The higher the percentage of max plate dissipation a TUBE is pulling in idle current draw, the earlier breakup will occur. This will be determined by the negative voltage at pin #5 of the power tubes. -30V at pin #5 will make the tube run hotter than -50V at pin #5, for example. This value is not adjustable on MESA amps without adding a bias pot or changing resistors in the bias circuit.

#2 and #3 - you lost me, I am not understandind your meaning.

#4 - Mesa Red tubes draw the least idle current, and MESA White tubes draw the most idle current, in a fixed bias MESA/Boogie amp. 8) I have confirmed this with my Bias-Rite on several MESA amps.

Thanks alot, Joey. I have other questions about this, and I may start a new thread in Tubes if I can't find what I want elsewhere. Thanks again.
Frank

 

[igfraso]

From the Groove Tubes website: http://www.guitaramplifierblueprinting.com/Rating.html,

Mesa scale Groove Tubes scale
Red 4
Yellow 4
Green 5
Gray 5
Blue 6
White 6

Lower numbers will start to distort at lower volume settings on your amp, ...
High numbers will have to be driven at higher volume levels to begin to reach output stage distortion.

except that's the opposite progression from what a Mesa tech told me:

RED
"Headroom" available: Very High
Clipping: Low

YELLOW
"Headroom" available: High
Clipping: Low

GREEN
"Headroom" available: Medium High
Clipping: Medium

GREY
"Headroom" available: Medium High
Clipping: Medium

BLUE
"Headroom" available: Medium Low
Clipping: Medium High

Best Regards,

Marcus Daniel | Customer Service
Mesa/Boogie | MESA ENGINEERING

so i don't know which one is right.

Thta's exactly the same thing that Mike Bendinelli told me.