• Registered: 2008-01-25
  • Posts: 20

Topic: Vox AC30 CC head

Anybody got one of these?
I bought one and have spent about two weeks doing tube drops to try to get it to rock.Let me tell you that changing tubes is a #@$@#! You have to pull the chassis.  I ended up with JJ el-84's for power, an old Mullard for the rectifier,(which made more difference than anything else) and a combo of JJ 803, EH, and Tung Sol 12ax7 for the preamp section. Like I said before the rectifier tube was the biggest change. I put a JJ GZ-34 in there and the amp started to smoke!!!!twice!!!!! but the mullard really did the trick. It came with a sovtek that was totally pud. So that just goes to show that power tube regulation via the rectifier CAN make a difference in tone. Who'd a thunk?

  • From: Detroit
  • Registered: 2006-06-02
  • Posts: 5,807

Re: Vox AC30 CC head

how experienced are you with electronics?

I've heard when you replace tubes, they need to be checked or calibrated with the amp somehow, since the last set of tubes likely had a different tolerance or level of reaction to the energy/sound of the amp. So every time new tubes go in, the amp needs to be tweaked.

- Nic from Detroit... posting on JB's Forum since 6-2-2006
Ask me about my handwound Great Lakes Guitar Pickups
Since 2010, Bonamassa fans have taken advantage of my JB friend discount = my cost + shipping. cool

3 Reply by topshelf (edited by topshelf 2008-01-30 14:55:43)

  • Registered: 2008-01-25
  • Posts: 20

Re: Vox AC30 CC head

NPB_EST.1979 wrote:

how experienced are you with electronics?

I've heard when you replace tubes, they need to be checked or calibrated with the amp somehow, since the last set of tubes likely had a different tolerance or level of reaction to the energy/sound of the amp. So every time new tubes go in, the amp needs to be tweaked.

You're right, you always need a bias adjustment with new, matched, power tubes! However, this particular amp is cathode biased so you can't do that. I won't go into the types of tube amps that require bias adjustment and which is which here but you can find a wealth of information on the net about that subject. Thanks for your input!