Ampeg V-4B Bass head trouble

[copperandstars]

Hello,

I recently aquired a vintage Ampeg V-4B bass head. The thing is amazing, besides one little problem...it distorts quite badly if you turn it up above three. Do you have any idea of what could cause this? Tubes? I have no idea when they were least changed, it could have been many years. Let me know if you have any ideas.

Thanks!

Ryan

[charger]

Sounds like a power tube problem. What kind of tubes are in there? These things originally had 7027s, which are monster tubes. Sovtek recently started making them again, but for a long time they were out of production, so most Ampeg owners had to go with 6L6s or something else (6K11s?). Anyway, if it distorts horribly on 3, something's wrong, it should be pretty clean (but punchy) up to about 5 (with the master volume cranked). Also, it should be pretty darn loud on 3, so if it's not, something is wrong. First thing to do is check the tubes. The bias might also be off, if the tubes were replaced. When you change tubes, it's a good idea to get them re-biased (any competent amp tech can do this). I can recommend the new Sovtek 7027, they sound pretty darn good.