tube choice for Audible Illusions L1


I have a Audible Illusions L1, and it has humming noise on the left channel. I suspect it is the tube. Also, I would like to smooth the sound a bit more. The recommended and current tube I have is 6h23neb. However, I have someone previously recommends Svetlana 6n1p. I would like to try it out, but it says on the AI FAQ that "6NIP tubes should not be substituted as they require additional filament current and their use will compromise performance."
What does compromise performance means? Does it mean the tube life will decrease? But it won't do any damage on the unit, am I correct?

Also, from the tube store, I can't specify the brand. Is it important to order a specific brand?

Besides the 6h23neb and 6n1p, is there other suggestion that will help smooth out the sound, or make it less harsh?

Thanks.
gte357s
I can't imagine the harshness you describe is coming from your Audible Illusions preamp. The best person to talk with regarding tubes for your preamp is Art Ferris, the guy that designed it.
Well ... harsh may not be the right word, but maybe due to some of the recording, some song has very strong glare ... I don't know if it is the right word also. Usually when hearing female vocals. The bottom line is, got fatigue after hearing for a while. Some recordings are ok. Anyway ... just want to try out some other tube to see if it will improve the sound to my taste.
You could try older 6h23eb (the ones with the rocket logo) if they are still around. They are a bit softer sounding than the ones made @ Refektor (sp).

I used Siemens 7dj8 in the phono section of a Mod 3a, but never tried them in the line section. Maybe someone here has?

The 7dj8 was durable in the application and had a nice smooth/liquid sound (akin to old production Mullard and Amperex 6dj8's).