Recommend output tubes for tube PA conversion (50H-B26 to ???)

[g1]

I expect excessive plate dissipation with 6V6s and a Zaa of 3.2k. Doubling speaker impedance would help.

That was something I had considered but did not mention. I always figure you can tweak the load to reflect back your required impedance (when you want that, which seems not always the case). I realize there are some sacrifices made when you alter the load from what the transformer manufacturer designs it for, but I think they are usually negligible and affect only the lowest frequencies?

[J M Fahey]

Well, I never suggested 6V6, but 6L6 or EL34, both of which beat original tubes in all aspects, thatīs what gives me confidence enough to not worry about them.
Just stated that both will happily work with original supply voltage and load impedance,of course getting no more than original rated power.

6V6?.... not used or liked here (I know itīs the opposite in USA), that niche is covered by EL84, very popular.

[Helmholtz]

I realize there are some sacrifices made when you alter the load from what the transformer manufacturer designs it for, but I think they are usually negligible and affect only the lowest frequencies?

As OT bass cutoff frequency is proportional to R/L (R being the reflected load, L is primary inductance), doubling the speaker impedance will in theory "cost" one octave in bass response.
If that's noticeable depends on a number of things and NFB should at least partly compensate.

I think in most cases it will go unnoticed.

[35L6]

50HN5 should work in there

[35L6]

After socket rewire

[glebert]

50HN5 should work in there

Any idea how they sound for guitar?

[35L6]

I've never tried one but its one of many output tubes designed for radio and " low cost audio " . Any of them should sound fine if biased properly . Its the circuit and all that . It's close in specs to 50H-B26 , heater voltage and current , plate voltage . You may want to draw a load line ( see Merlin's page ) . As for plate load you can use 4 or 8 ohm speakers if you don't like the load you have now . You should be able to just tweak the circuit instead of complete rewire .

[35L6]

The great thing about using odd tubes is there is no paint by numbers . You have to figure things out and you learn about how the damn things work . With more knowledge you are better prepared to do good design .