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.

   
chmaiwald

@mulveling  Thanks for the explanation! That´s very helpful! I basically take from it that the amp is able to use them all, which is great. And easy to keep in mind when looking for possible replacements.

I did find some Mullard ECC33s and I´m tempted to give them a try. I recently also came across some GTs at a reasonable price, I think I will buy a nice pair next time.

 

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.