Triode/Pentode on 10W Channel 3

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mace

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Hi,

Does the triode/pentode switch do anything in 10W setting on channel 3? On my amp it does not and it's fresh back from service (some resistor issue causing static, unrelated to pent/triode switch). I'd swear the switch used to beef up Channel 3 in 10W,...but maybe I'm remembering wrong.

Then manual states that the tri/pent switch only affects the "middle 2" power tubes, and in 10W mode, the "right 2" tubes are being used (when viewed from the back). This has me thinking that the switch does nothing at the 10W setting.

So, can anyone comment if this switch does anything at the 10W setting? I wrote Mesa but haven't heard back.

Thanks,

Mace
 
The way the manual was written, pentode and triode are available in the 10W mode. It does not state it directly but leads you to believe pentode is selectable for 10W function. I think I tried to hear the difference many moons ago but generally do not use 10W mode.
 
Hi,

I heard back from the Mesa. The 10W, channel 3 setting is hard wired pentode, so no chance to switch it. The triode/pentode switch only works at 45 and 90W settings (when both middle power tubes are active).

I'd swear I've used that switch at the 10W setting (which I use mostly at home) and never thought about that it wasn't doing anything. :shock:

Later,

Mace
 
It has been a while.... I do recall not hearing a difference between pentode and triode in 10W but that would contradict the manual. At 10W using cathode bias I am certain some characteristics will be lost based on the bias topography change. 45W and 90W switches back to grid bias and disconnects the diodes and diverts the cathode to ground vs the high watt resistors mounted inside the chassis. Very interesting design.

Manuals sometimes may not be accurate when a product is released and even long after until the issue is pointed out.
 
Hi,

Thanks for the info. I'm not sure the manual is *wrong*, per se. I think it is not clear. There is no statement that "Channel 3 pentode/triode switch is only active at 45W and 90W settings". Then manual does mention that the pent/tri switch changes the inner tubes.

OK... so just now I did another search in the manual and found this: "The 45 and 10 watt settings in combination with TRIODE will give you a more laid back attack characteristic and a more harmonically complex voice filled with nuance." (version 140612 of the manual, which is from 2014)

So, now I'm more confused. On the phone the Mesa tech stated clearly that the switch had no effect at the 10W setting. hmmmm

Could someone with a Mark V set it to channel 3, 10W, strike a low E chord and flip the pent/triode switch back and forth and see if has any effect on the tone?

Thnaks,

Mace
 
My amp is at our rehearsal space but I will check it next week if nobody else does it by then. However, especially in single-ended A operation, I would think there'd be a significant difference between pentode and triode - so it seems probable that what they told you on the phone is correct. The manual is funny to read but is left wanting in many areas.
 
Had to warm it up a bit as I have not been playing guitar lately. CH3 at 10W setting, the pentode/triode switch has not effect. Did not matter how loud I had the masters set to or where the bass control was placed. No notable difference between the two modes which is what I remember when I first tried it. It is only effective in 45W and 90W power settings. Actually I thought the amp sounded better in the 10W setting.

Hope this helps.
 
Thanks! Confirms 10W Ch3 is hardwired pentode. Manual needs updating and the Mesa tech was correct. 8)

Later,

Mace
 
mace said:
OK... so just now I did another search in the manual and found this: "The 45 and 10 watt settings in combination with TRIODE will give you a more laid back attack characteristic and a more harmonically complex voice filled with nuance." (version 140612 of the manual, which is from 2014)

That reads to me like they made a typo and put "10" instead of "90" there.
 
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