6L6 in Sixty-five head

maj

Hi all.  I am brand new to the forum.  I recently picked up a Sixty-five head (non reverb) with the phase inverter tube, which I gather makes this amp one of the earlier models.  When I checked the tubes, I was surprised to see that the amp has 6L6 power tubes instead of the 6CA7 called for on the tube chart.  The 6L6s and the 12ax7 are all Sylvania brand.  Am I correct in understanding that the Sixty-five, non-reverb head was the first model designed and manufactured by Music Man?  Is there any chance that I have an early head that would have been shipped with 6L6s, or is this definitely something that was changed by an owner somewhere along the line?  Thanks for any help and insight!

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Music Man Equipment
MM 2-10-65

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11 years 9 months

mm210 Tue, 01/13/2026 - 13:09

It sounds like an owner change. I'm surprised with the voltages that MM's produce that it hasn't smoked the 6L6's. I don't remember  ANY of the early versions set up for 6L6's. The later ones in the RP and Rd series yes. The fact that it has a 12a7 PI tells me it's early and SHOULD have 6CA7's or EL34's. 

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maj Wed, 01/14/2026 - 05:35

Thanks for your thoughts here.  I suppose the best thing to do would be to have someone who knows these amps go over it to see if any adjustments were made to allow the amp to run the different (wrong) power tubes. 

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Music Man Equipment
MM 2-10-65

Member for

11 years 9 months

mm210 Wed, 01/14/2026 - 09:22

Absolutely. I don't remember exactly what was needed but the two tube types ARE different. Also, in the RD's, I think they are cathode driven so that's a BIG difference. 

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