12AX7 vs 6EU7 power draw

[ricach]

I'm adding a second channel which will require adding a third 12AX7. Will the 5Y3 rectifier carry a 3x12AX7, 2x6V6 load? I see Fender bumps up to a 5U4G with this kind of load. But I notice Gibsons will run 3x6EU7's along with 2x6V6's on the backs of a 5Y3. Does the 12AX7 draw more than a 6EU7? My PT is pretty hefty so I'm sure it'll handle the extra load.

[MWJB]

Another 12AX7 is only going to add a few mA, shouldn't be a problem. 6V6s are a bigger factor - 5Y3GT is rated at 125mA, your 12AX will only draw a few mA, allow 10mA at the very outside per 12AX, plus another 10 for the 6V6 screens, leaves you 42mA per 6V6 plate if cathode biased. In reality Dano/Wards/Silvertone made plenty of 2x6L6 &4x6L6 amps, running buckets of current, with 4x preamp tubes that run 5Y3s.

A good rule of thumb though is 2 preamp tubes max to one filter cap, so you may want to add another stage of filtration?

[MWJB]

Typo - that should be "& 4x6V6 amps".

[ricach]

Do you mean 2 preamp 'triodes' per cap, or 2 complete tubes (4 triodes)?

[MWJB]

2 complete tubes (4 triodes).