Amplifier Power tubes - important to sound?

Siemens never made a 6550. 

@dogearedaudio : I don’t believe you. The 807 uses a top anode cap and a seven pin socket. It is not swappable with octal power tubes. I had some in my tube collection.

I don’t believe you. The 807 uses a top anode cap and a seven pin socket. It is not swappable with octal power tubes. I had some in my tube collection.

I thought that was odd too. Maybe a weird typo?

I’ve used a Williamson amplifier (pair of Heathkit W5) with Gold Lion (Russia) KT66 and it was very "powerful" sounding with strong bass, good "slam", and plump full mids. The same amp, fitted with vintage GE 7581A (near KT66), sounded more airy, spacious and articulate with a gorgeous midrange - but leaner in bass.

Sadly, power tube rolling becomes quite painful in amps using more than a quad. Vintage/NOS is pretty much out of the question. BUT once you get so many push-pull pairs in parallel - that’s where the real magic and beauty of tube power lies for me. On just one push-pull pair per side, I will certainly prefer the tonality of EL34, 6L6GC / KT66 over KT88 - at least until I run out of power,

@carlsbad2 : The 807 is a seven pin top cap connector anode tube. It is not swappable with octal power tubes. So how can you compare it to the common octal power tubes as you claim?

@jasonbourne71 They make adapters.  Very common.