When buying vintage tubes, always request noise testing, especially with the older GT version. 6SN7's tend to be more microphonic or noisy than other small signal tubes.
@mulveling +1. Great info.
6SN7 GT instead of GTA/B?
I´ve been using the Willsenton R-800i for a while now and I´m very happy with it. I´ve been tube rolling a bit and in the 6SN7 position I kept putting GTA or GTB tubes. They sound nice.
Now I had a look at the manual again which doesn´t list these at all and instead focuses on GT or ECC32 or (afaik even more different) ECC33.
Being a total amateur when it comes to electronics I´m wondering if tubes with varying specifications (6SN7 GT vs GTA/B vs ECC32 vs ECC33) affect the tubes further down the chain. Without having any insight into the working of tube amps I´m inclined to say yes of course. But do they really do so in a significant way? Effects of different brands aside, what can the effect be on sound and on the 300B and 805?
If for example I had a pair of 6SN7 GTs (filament voltage Vf 6.3 Volts / If 0.6 Ampere) – the Willsenton is using one tube for each chanel in that position – and replaced them with ECC33s (Vf 6.3 Volts / If 0.95 Ampere) that sound exactly the same, wouldn´t the other tubes and by this the sound be affected?
Maybe I´m complicating things, but ever since I saw this it´s been bugging me.