Mark IV with 6V6 - Triode? Pentode?

Mark I's, II's, III's and the almight IV

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SquierJVs
Bottle Rocket
Posts: 14
Joined: Sun Jan 27, 2013 11:06 pm

Mark IV with 6V6 - Triode? Pentode?

Post by SquierJVs » Sat May 18, 2019 4:24 pm

Hello all,

I've read the user's manual for both the Mark IVa & IVb. Both have the same info regarding the use of 6V6:
- "four 6V6's can also be used in the MARK IV ... but, ONLY when TWEED and SIMUL-CLASS are selected"

But nothing is said about the use of Pentode vs Triode modes.

Does anyone know if there is a requirement to use one or other? Or can this mode be switched to either depending on your mood?

Signed
Happy owner of a Mark IVa

woodbutcher65
Mark III
Posts: 211
Joined: Fri May 04, 2018 10:36 pm

Re: Mark IV with 6V6 - Triode? Pentode?

Post by woodbutcher65 » Sun May 19, 2019 11:16 am

Use 6V6 tubes ONLY when TWEED and SIMUL-CLASS are selected. Just like it says.

If you use any other mode, you're going to blow up the tubes. 6V6 tubes are limited in the voltages they can withstand.
In any other mode, the amp will over-voltage a 6V6.

stephen sawall
Single Recto
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Location: seattle wa usa

Re: Mark IV with 6V6 - Triode? Pentode?

Post by stephen sawall » Sun May 19, 2019 12:29 pm

I think it's fine either way ? Now I'm questioning it. Been many years since I put anything but 6L6 in the Mark IV.
The fact that Stephen appears from nowhere, is sentenced to death in an emotional public trial without anyone interfering at all and is then altogether forgotten as if nothing happened, is already suspicious.

SquierJVs
Bottle Rocket
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Joined: Sun Jan 27, 2013 11:06 pm

Re: Mark IV with 6V6 - Triode? Pentode?

Post by SquierJVs » Mon May 20, 2019 11:57 am

Well the manuals are very clear ... TWEED and SIMUL-CLASS _only_ with 6V6's (and all 4 need to be 6V6's).

But the selection of Pentode vs Triode is independent of Simul-Class and Tweed settings.

My question is whether there is a restriction? Or is just the guitarist's choice?

woodbutcher65
Mark III
Posts: 211
Joined: Fri May 04, 2018 10:36 pm

Re: Mark IV with 6V6 - Triode? Pentode?

Post by woodbutcher65 » Mon May 20, 2019 4:15 pm

The pentode/triode switch doesn't change plate voltage. It just determines how the screen is connected in the circuit.

You can mess with that switch with 6V6 tubes installed. Just don't do what it says NOT to do.

SquierJVs
Bottle Rocket
Posts: 14
Joined: Sun Jan 27, 2013 11:06 pm

Re: Mark IV with 6V6 - Triode? Pentode?

Post by SquierJVs » Wed May 22, 2019 8:22 pm

Excellent.

Thank you for that clear explanation.

Off to my local music shop to pick up the Mesa 6v6's I ordered. :-)

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