Mark IV "A" Combo ECC82 or ECC83

[mordorstudio]

Hello,

If anybody can help me. I have an old Mark IV combo, It think it's "A" version because the serial and the footswitch inputs. I read here there are four ECC83 (12AX7) and one ECC82 in it. Can I use 5 ECC83 (I have fine NOS Tungsram tubes) in it ? Is it change the tone/gain or cause problem in reverb ?

Thank you!

 

[MrMarkIII]

I think you mean ECC81. The ECC82 is equivalent to 12AU7. The ECC81, equivalent to the 12AT7. The differences are not trivial.
ECC83 = 12AX7 = Gain Factor of 100
ECC82 = 12AU7 = Gain Factor of 19
ECC81 = 12AT7 = Gain Factor of 60
The Mark IVA uses a 12AT7/ECC81 for the reverb tube.
It probably won't break anything, but a 40% jump in gain between a 12AT7 and a 12AX7 may get you more noise.

 

[mordorstudio]

Thank you. I'm confused with the numbering. Maybe anybody tried it ? I'm hate noise, but more gain would be great on rhythm/lead channel.

 

[MrMarkIII]

It won't add gain to any channel, just the reverb part of the circuit.

 

[mordorstudio]

Ok, thanx again, so i leave it.