#1
so i want to run my amp at half the power


i researched and found out that i need to
-plug out either the two outer or the two inner tubes
-run the amp at half the ohms(i run it at 16ohms now so i guess i'l have to run it at 8 after pulling out the tubes)


so the question is
will i have to replace the current 5amp fuse with a 2.5 amp fuse??,not all guides which i have read include the changing fuses part i also read somewhere that 6505 has more than one fuse so do i need to replace the other fuses too
and lastly does 6505 has resistors that bleed the caps when the amp is switched off or.....
thanks
Gear:
Peavey 6505 120W Head
Ibanez Rga32 (FOR SALE)
Laney Lv412a Cab(FOR SALE)
Soon To Get::
Boss DD20
Morley Bad Horsie II
#2
You shouldn't need to change the fuse.
I think the 6505 has resistors on the filter caps, but I don't recall for sure. You shouldn't be anywhere near them just pulling tubes and changing the impedance switch, anyway.
#3
I don't think you'll need to change fuses, as fuses are associated with the current coming in and not the output, generally. I've never heard of that being a part of doing this.

As for the caps, I'd guess no... But either way you assume that they don't. Either learn to bleed them or just avoid them like the plague.
Quote by Cathbard
Quote by Raijouta
Unless its electronic drums.

BURN THE WITCH!!!!!
#4
Quote by deepsal
and lastly does 6505 has resistors that bleed the caps when the amp is switched off or.....

Even if it does, you should always assume an amp doesn't.


That said, I don't think there's any reason to be worrying about that - you don't need to open the amp up.

Just pull the outer tubes, halve the impedance selector and you're good to go.


More importantly - why would you even need to halve the power of a 6505? That amp is built for 100% preamp gain, and 50W is going to be just as loud as 100W in real world use. All you're going to do is lose a bit of headroom.


I don't know if Cathbard or someone will back me up, but I'd say modding the 6505 to have bias adjustment would make a much more drastic change. The amp is biased very cold to prolong tube life - so much so that I think I remember seeing that it's actually only around 75W RMS. It's a really simple mod and probably wouldn't cost much.
Last edited by kyle62 at Dec 8, 2011,
#5
I don't think they do have bleed resistors but I'm not 100% sure. You shouldn't need to go near the caps anyway.

The fuse should be fine. You definitely wouldn't drop it in half because the power amp section doesn't account for all the current draw. You could drop a 4 amp one in there if you are worried but I wouldn't be too concerned, if a fault occurs it will blow a 5 amp fuse anyway.

The rest is right, pull two tubes and drop the impedance selector down a notch. Not sure why you'd want to do it on a 6505 though. People pull tubes to get power tube distortion at lower volumes for rock and blues. Are you trying to play blues on a 6505????
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
#6
Quote by deepsal
so i want to run my amp at half the power


i researched and found out that i need to
-plug out either the two outer or the two inner tubes
-run the amp at half the ohms(i run it at 16ohms now so i guess i'l have to run it at 8 after pulling out the tubes)

If the cab you have in your sig is the one that you are using with the amp then that cab is a 8 ohm cabinet http://www.laney.co.uk/show_spec.php?prod=lv412a
Otherwise everything else seems to be proper, however like everyone else has said, pulling two power tubes will turn it into 60W & that is not going to give power tube distortion easily either without an attenuator neither will it sound better than at full power, infact you will be losing slight amount of low end if anything.
#7
Hey what now? 60W (or 50W) is too loud to get easy power tube distortion? Hmm. so I've been doing it wrong for all these years? Who woulda thunk?
Gary Moore must be spinning in his grave.
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
wrote the wrong impendence in a hurry but nevertheless
and no neither am i looking forward to play blues on it nor am i looking for some power tube distortion i want to see how it would alter the tone
and i cant get the bias mod done because there arent any amp techs in my city
Gear:
Peavey 6505 120W Head
Ibanez Rga32 (FOR SALE)
Laney Lv412a Cab(FOR SALE)
Soon To Get::
Boss DD20
Morley Bad Horsie II
#9
Quote by deepsal
wrote the wrong impendence in a hurry but nevertheless
and no neither am i looking forward to play blues on it nor am i looking for some power tube distortion i want to see how it would alter the tone
and i cant get the bias mod done because there arent any amp techs in my city

Ah, fair enough. I quite like 50/60W'ers. Not just because of the power tube breakup, I just like the tone. I suspect that it's because the sound is produced by one valve at a time and not two so you are listening to the actual sound of a tube and not some complex interaction of multiple tubes.
I like simple preamps like in Champs and 18W'ers too. When you change a valve you can really hear the effect of the new tube without it being corrupted by the others. Change one preamp valve in a 6505 and you can hardly tell any difference between a Sovtek and a JJ (unless one was faulty), you have to swap them all at once to really pick it. Even then it isn't as dramatic as changing V1 in a Champ.
Try it and see. You are on the right track. Just pull the two tubes, dial down the impedance switch and try it. With a 6505 I doubt it'll do much to the tone if you aren't clipping, but hey, you won't know until you try.
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
Last edited by Cathbard at Dec 8, 2011,
#10
Quote by Cathbard
Ah, fair enough. I quite like 50/60W'ers. Not just because of the power tube breakup, I just like the tone. I suspect that it's because the sound is produced by one valve at a time and not two so you are listening to the actual sound of a tube and not some complex interaction of multiple tubes.
I like simple preamps like in Champs and 18W'ers too. When you change a valve you can really hear the effect of the new tube without it being corrupted by the others. Change one preamp valve in a 6505 and you can hardly tell any difference between a Sovtek and a JJ (unless one was faulty), you have to swap them all at once to really pick it. Even then it isn't as dramatic as changing V1 in a Champ.
Try it and see. You are on the right track. Just pull the two tubes, dial down the impedance switch and try it. With a 6505 I doubt it'll do much to the tone if you aren't clipping, but hey, you won't know until you try.

The amps you mentioned sound best when pushed into powertube breakup. But the 6505 has a really flat sounding poweramp right? So would pulling tubes make that much of a difference?
#11
Quote by GS LEAD 5
The amps you mentioned sound best when pushed into powertube breakup. But the 6505 has a really flat sounding poweramp right? So would pulling tubes make that much of a difference?

Probably not a lot but it's a pretty quick thing to try.
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
#13
Quote by deepsal
wrote the wrong impendence in a hurry but nevertheless
and no neither am i looking forward to play blues on it nor am i looking for some power tube distortion i want to see how it would alter the tone
and i cant get the bias mod done because there arent any amp techs in my city

Then you'll need to plug the 4ohm out from the amp into the 8ohm cab input. I'm assuming the store near you gave you proper speaker cables during the purchase? Cause the ones around my place or Mumbai uses regular instrument cables for connecting amps & cabs.

If you want to improve your Peavey's tone then replace that cabinet. I remember there were 5150 combos in that store at your place, you could always go there and ask them to try those out directly & then with that cab. You will understand why I typed this out when you hear it in person Although I'm guessing the original 5150's shipped with good quality speakers.
And if you are having a hard time selling the cab off then you could always try to sell the speakers off separately for around Rs.3.5k each.
The wood can be used for building a hardshell case for the amp since no one builds those here & importing one could cost around 15k because of the shipping weight and also some for making a pedalboard I suppose
The amp tech shortage is not just in your city but in the entire country
#15
Yeah Sheffield were being used in those & also the cabs as well I think. People didn't seem to like those much & were replacing them as well.
But haven't heard those in person to compare with Celestion R50's. If those sheffield were/are tonally better than atleast Celestion 70/80s(which sound atmost decent n closed back cabs but not in open backs) then those will blow those R50's off to oblivion.
EDIT: ^Your MG is gone, yay good riddance!

EDIT:Apparently most peavey owners found the Sheffields 1200 to suck big time, so results will vary in comparison to low end Celestion offerings. Sigh
Last edited by dahelunover at Dec 9, 2011,
#16
Just came across this. I run my amp at half power frequently and dont havent ever bothered removing the outer tubes. Is there a specific reason people this?
Last edited by andyhatescrass at Jan 29, 2012,
#17
^ you really shouldn't bump other people's threads to get your own answers. start your own thread or PM me. the answer is that you'll save life on the other two tubes. for short periods or to experiment it is no big deal, but if you plan to run that way long term then there is no reason to pass current through tubes you are not using. PS: you can't do this with every single amp either so start a thread if you want answers specific to yourself.
#18
Indeed. From what you have said we can offer no advice at all. There are several ways different amps provide different power outputs. Removing tubes is something you can do on most 100W A/B amps when they have no built in facility to cut the power.
Start your own thread, explain what amp you have and what your questions are regarding that amp specifically.
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