Laney AOR pro tube 30 112 combo... Bias pot/switch?

[Pierre]

I just took the powertubes out to try and see where the biast trim pot was (it's what's usually used to bias right?) and I can't see any... So... do I need to bias this amp at all? From what I heard, yes, but there appears to be nothing with which to do so unless it's in the chassis and I have to take everything out... I'll try to take pics but my flatmate doesn't want to let me borrow his camera (which is understandable, it's a good one) so it may not happen.

[Zerberus]

Re: Laney AOR pro tube 30 112 combo... Bias pot/switch?

Many amps have the bias pots internally.

[Pierre]

Re: Laney AOR pro tube 30 112 combo... Bias pot/switch?

Mhmm yeaaah... I took the chassis off and indeed there's a single little pot with written PIHER spain on it. I guess that's the one then.

[Marcel]

Re: Laney AOR pro tube 30 112 combo... Bias pot/switch?

I would NOT touch anything if the amp is open. Lethal voltages even if the amp is unplugged!!

[Pierre]

Re: Laney AOR pro tube 30 112 combo... Bias pot/switch?

Oh I haven't don't worry! I'm not suicidal yet hehe... Look but not touch for now. When I do work on it I'll wear rubber gloves
Ahhhh I found this http://www.duncanamps.com/technical/lvbias.html
I understand most of it and it doesn't seem so hard, I should try it with my old power tubes sometime. Scott F advised me the Weber biasing tool and it seems very nifty but a bit expensive, so I'll probably just get the version with the head and use my own DMM. Now the question arises: without basic knowledge of amplifiers, but WITH basic security knowledge, a decent DMM and this tool, would I be able to perform this operation safely? It seems straightforward in terms of physical actions to take...

[Pierre]

Re: Laney AOR pro tube 30 112 combo... Bias pot/switch?

Bahahaha I'm evil, I just sent THAT to Laney...

Hey there
I have a pro tube AOR 30 112 combo and I have troubles understanding the preamp and stage gains on it. I read all the manuals but some things still confuse me.
Preamp 1 and 2 control different gain stages. Does this mean that each control one tube (other two being phase inverter and boost/AOR channel?)? Also, what is the difference between preamp 1 volume and preamp 1 level?
Thirdly, what happens when the AOR switch is pulled? A third preamp tube is overdriven?
So if I have preamp 1 on full and 2 at 0, I can adjust the over noise level using the preamp 1 level and master volume, and adding 'gain' using preamp 2 would give me less imediate OD than using the AOR switch?
And finally (loads of question, I'm really sorry...) the tubes in this amp are still original and I wish to change them. I'll do the biasing myself but if there are a particular set of power tubes you guys can advise for the amp, with the proper biased values, I'd be very grateful. I do believe I am set as far as preamp tubes are concerned, but there is one thing I am wondering. Should I place a higher gain tube in the boost slot, and use lower gain, quieter tubes for 1 and 2?
Thanks a lot for your time! I spent a lot of time researching this but it seems that most people possessing the amp have the same problems.