Tubes

[Infliktor]

Tubes:   
Poweramp:                         V1, V2:                 6L6GC matched set.
Preamp:                             V3 (input tube):  ECC 83 / 12AX7, FQ selected;
                                         V4, V5:                ECC 83 / 12AX7 selected;
                                         V6:                      ECC 83 / 12AX7, standard;


Which of these preamp tubes affect the tone

What does FQ selected mean?

What does selected mean?

[AdamB]

That input tube affects your tone the most. It's nearest to your input jack and all your signal goes through it. Pick a high quality tube for this

[hamfist]

As Adam says, the input tube is traditionally considered to be the most important tone-wise, although in my experience, ALL the tubes can make a significant difference.

"Selected" just means that they have been chosen somehow using some criteria (probably being low noise) from a big batch from the factory (25% of which will be useless and thrown away).

Noise generated earlier on in the signal pathway is amplified by ALL gain stages, so becomes a problem manifesting as hiss through your speakers. That is why it is more critical to use lower noise resistors and tubes in the early gain stages.  However, a bit of tube noise generated in the last pre-amp gain stage , or in the Phase Inverter is hardly noticeable really so cheaper, more noisy, components are often used there to save money !

[jpfamps]

I would concur with the above. All the positions can make a difference.

I am very skeptical of "specially selected" valves, particularly if you aren't told what they are selected for. It seems a very good way of charging extra.

The only criterion it is worth testing for in a pre-amp valve is microphonics, although in my experience this doesn't always guarantee  that the selected valves will be microphony free.

[Gizmo]

i'm interested in tube advice too.

Picked up a cornford carrera last week. It currently has replacement El84 and El34 in it. Not sure they are special ones.

I wanted to get decent tubes to make the most of the amp. Was looking at putting in a decent El84 and a 6L6.

The pre amp valves can be changed for pretty much any type. Are they worth changing as well?

Any suggestions?

[hamfist]

Pre-amp tube changes usually make more of a tonal difference than power tube changes, unless you are running the amp well cranked most of the time.