#1
Hey,
I have a 100w splawn quick rod. I don't need 100w of volume. So I usually run it at half power. Will I be able to remove the outer 2 tubes and just play?

I have ran it at half power for a while with the tubes in. I think im clear enough on this subject to say that doing this is only wasting the life of the tubes I am not using, correct?
#2
Quote by andyhatescrass
Hey,
I have a 100w splawn quick rod. I don't need 100w of volume. So I usually run it at half power. Will I be able to remove the outer 2 tubes and just play?

I have ran it at half power for a while with the tubes in. I think im clear enough on this subject to say that doing this is only wasting the life of the tubes I am not using, correct?

Half power on a 100w amp is insane, your saying you run it on 5? You must be one hardcore fella. As for the question, I haven't a clue, but I doubt it tbh.
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#3
Quote by Any7423
Half power on a 100w amp is insane, your saying you run it on 5? You must be one hardcore fella. As for the question, I haven't a clue, but I doubt it tbh.


Not sure what you mean by running it on 5. Why is it so insane not to use all 100w?
#4
I think what he was trying to demonstrate is that half the volume of a 100 watt amp would be a 5 watt amp. The difference between 100 and 50 watts volume wise is very nominal. The reason people run amps like these at half power is to reduce headroom, introduce more sag, and save life on power tubes.


That said, I run my Quick Rod at half power mainly for these reasons. You can run your amp at half power with all 4 tubes in but Scott Splawn recommends that if you are going to do that as a long term solution, then you should pull the outer two power tubes and rebias your amp. I have a Blog in my profile on how to do this more specifically and I also have this info on the Splawn forums in the FAQ section.

I can also tell you how to take off those annoying retainers if you are interested:


#5
Did you find that you actually had to adjust the bias when you did it, 311? Or could you have gotten away with it as it was?

You also want to turn the impedance selector down one notch if you pull two tubes.
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#6
Cath - I think I could have left the bias alone under normal circumstances but the bias was so low as it were I had to do something. Scott just says to rebias - I think to protect himself/his amps.

And yes, thanks for bringing up the ohm drop. I knew TS knew about that already because he was the one asking about this earlier today in someone else's thread.
Last edited by 311ZOSOVHJH at Jan 29, 2012,
#7
Well it can never hurt to check the bias anyway. It can drift. That's just a Marshall power amp circuit isn't it? You shouldn't really have to change anything, esp if you have it biased somewhere in the middle. The dc current you drag in with the grid isn't going to change its voltage worth a jot by halving its load.. Guys used pull valves and stick 'em back in all the time on their Marshalls back in the day. Nobody ever bothered to rebias them. We were too stoned most of the time.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#8
I was wondering how long it would take for the voices of reason to show. Knew it wouldn't take long. Take care, all.
#9
my $.02 i run it at half power, all power tubes in both. the Nirto's poweramp tubes seem like they are dying slowly. once they die, i will pull the two KT88's out of the Promod and put into the Nitro and run both at 50w and bias. saves $150+ on power tubes. not much of a difference, it is notable, but you would likely have to be familiar with the amp to really evaluate it.

again, half power half Ohms
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#10
Remember that running at half power cuts a maximum of 3dB off your output volume. Not much, negligible at best.

In other words, like 311 said, you are not going to get a massive decrease in volume.
#11
Quote by 311ZOSOVHJH
I think what he was trying to demonstrate is that half the volume of a 100 watt amp would be a 5 watt amp. The difference between 100 and 50 watts volume wise is very nominal. The reason people run amps like these at half power is to reduce headroom, introduce more sag, and save life on power tubes.


That said, I run my Quick Rod at half power mainly for these reasons. You can run your amp at half power with all 4 tubes in but Scott Splawn recommends that if you are going to do that as a long term solution, then you should pull the outer two power tubes and rebias your amp. I have a Blog in my profile on how to do this more specifically and I also have this info on the Splawn forums in the FAQ section.

I can also tell you how to take off those annoying retainers if you are interested:




It would be great if i could get some info on how to take the retainers off. Thanks man.

I have been running my amp set at 8 ohms into a 16 ohm cab, so ill keep doing that after i pull the tubes. My amp was biased a little over a month ago by a tech, he should have biased each plate right? If so should i bother rebiasing?
#12
^ honestly - if it sounds good it is probably fine. I just know he highly recommends it. If it starts to sound 'warbly' it is probably too hot. Ideally - you will probably want to be in the 31 - 35 mA range. To take the retainers off you will need to get inside the chassis and and unscrew the retainers from underneath. This can be dangerous just like poking inside any other amp. The Splawns do incorporate bleeding resistors on the top of each capacitor but still. Personally, I wouldn't pay a tech to bias my amp - it is really easy once you know how to do it. You'll need a bias probe and a multimeter.

The thing to remember with the retainers is that the base stays on so you'll screw that back on after you clip off the springs. Do not try to remove using the top side phillips screw by itself - they are countersunk.