Tube placement

[thebigz]

I just bought a Laney AOR 50 off ebay, and the guy said he is going to pack the tubes separate for shipping. I have read that sometimes the placement of the tubes in certain slots will affect the sound. I'll get the amp in a couple days, any advice as to how I should put the tubes in?

[Chief_CrazyTalk]

The power tubes should be keyed so they should only fit one way, the right way. I assume you meant the preamp tubes?

Those should fit only one way as well. As far as which tube to put in which slot...you probably have three, maybe four. You'll just have to see which type they are. I remember some amps came with 12ax7s in the preamp gain stages and sometimes a 12au7 or 12ay7(?) for the phase inverter. For some reason. I believe they have slightly less gain than the 12ax7 but I could be wrong. There may be other reasons for that as well.

I've always used ordinary 12ax7s throughout the pre section and that's worked fine. You can always play around with tube placement too...no harm done.

[Twitch]

I remember some amps came with 12ax7s in the preamp gain stages and sometimes a 12au7 or 12ay7(?) for the phase inverter. For some reason. I believe they have slightly less gain than the 12ax7 but I could be wrong.

12AT7 usually, and yes, less gain. For the OP, having hotter tubes in the first positions will get you more preamp distortion, quieter tubes in the first positions will get you a quieter amp and so on and so on. However, if you dont have a tube tester, than your options are A. call eurotubes and tell them you want hotter or quieter or whatever characteristic you want from your preamp, or B just keep swapping them around in the positions till you find which order suits your fancy. As far as your power tubes, these can make a difference too, but theyre NOT plug and play. When replacing power tubes, you SHOULD rebias the amp. Some amps arent very picky about this as youre bias current may only change a few milliamps per tube depending on how close the two sets of tubes are. For instance, if using Groove Tubes, going to the next highest or next lowest of their rating scale replacing the tubes you were already using, you bias change wont be much. You should always at least check it just to see how far of it may be though. If its too low, your amp may sound like hell, if too high your tubes life will be shortened or you may fry something else when the excess causes a tube or two to fry prematurely. Hope this helps, and welcome to the world of tube amp maintenance.

[Spivonious]

Usually the tube closest to the power tubes is the phase inverter. When retubing, I'd spring for a "balanced" 12A_7 for that position. You want even gain on both sides of the tube in the phase inverter. For the others, it really doesn't matter, as they're probably all just gain stages.

Biasing is important too. Too cold/low and your amp will sound lifeless, too hot/high and you'll get a more out-of-control sound but the tubes will burn up a lot faster.

If you're not familiar with biasing, you may wish to take it to a tech when you get it. Biasing requires the amp to be powered on and there is a lot of current in there waiting to electrocute you.

[DonP]

Put the tubes in the way it sounds the best.

[Cygnus X1]

The AOR 50 uses all ECC83 (12AX7A) preamp tubes, including the PI.
Manual here:

http://www.laney.co.uk/manuals/AOR50H-100H%20Manual%20-%201989%20-%20Issue%201.pdf