6550 tube in MA50H HELP!

[jagermike66]

Hi there,

I guess this is aimed mainly at Steve.

Can I swap the El34s in my Marshall MA50H for a pair of 6550 valves without needing any component changes? I Know the bias will need adjusting but if i need to get components changed then im not going to bother!

cheers!

Mike

[SteveD]

Give it a try and see if the bias will play ball. If not I guess you'll need to change only one resistor.

You'll need to set the bias so the mVDC reading is the same or close to what it is for the EL34s, trim pots range allowing.

[jagermike66]

Cheers steve. So my current bias is reading at about 36ma for a pair of el34s if i remember correctly. If the trim pots will allow me to get this value using the other tubes then it is safe to run?

Also.....what about KT88s?

thanks!

[SteveD]

36mA per valve is pretty much spot on. Set the bias so it is the same with other valve types if the range of the trim pots allow.