SORADO problem

[Oli]

Hi,

I did some setups with my bass heads last night for a recording session next month. Everything worked fine accept my SORADO (68' or 69' Model, SS rec., 6550 tubes, all other tubes with no marks) did an awful snary sound when I played the C on my bass. Didn`t matter what string, it was always the C. So I thought the vibration of the cab could do that to the tubes, but it was the same effect even when the amp was on the floor. All the other notes are fine.

Does that sound familiar to anyone?

Thanks & Greetings

Oliver  

[noel]

Perhaps you have a microphonic tube?

[MusicFox]

Almost certain a microphonic tube (usually preamp) can cause that effect. Might be your case. A brand new Fender pro Jr. did that to me right out of the box. One specific note or close to that. Sort of a glassy rattle with certain note. Some people say tapping LIGHTLY tubes with a pencil while turned on is a no no but if microphonic you will likely hear same bad sound. Google or search for techniques to properly diagnose this its simple but to be sure check around. Obviously substituting same type preamp tubes is easy no biasing needed. I found switching my 2 preamp tubes around did help too ultimately a new tube was inevitable. Preamp tubes are cheap unless your dealing with the inverter tube NOS 7199's (40 watt amp)or 6an8a's (60 watt amp or others)

[Oli]

Hi,

thanks for the answers. I'll check the 12 Ax 7 first, though the 6550seem to be very cheap ones from China.

Greetings

Oliver