#1
I just replaced all the tubes in my 6505+, and now I just need to adjust the bias and I'm done. I talked with a guy from Eurotubes and he said "-the 6505+ and 5150 II models have a very small adjustable bias range in comparison to a lot of amps, I suggest turning the pot all the way counter-clockwise"

Well, I know what he's talking about, (the little "screw" you turn) but in all the tutorial videos, the people are always using some sort of probe and adjust the bias while the amp is on, and with the standby on. (meaning the amp is operational)

Do I have to turn the amp on and then turn the bias all the way counter-clockwise? Or can I just adjust it, and then power on the amp?
Mesa Single Rectifier
Marshall 1960A vintage
Rg3exfm1 w/ EMG 85/81
Big Baby Taylor Acoustic
Ibanez TS808
#2
To be honest if you dont know how to bias and amp you shouldn't give it a go, if you really think it needs biasing take it to a tech. Most 6505's don't need biasing after retubing unless your after the bias mod. If your using similar tubes to the ones that were in last the chances are such minimal bias is needed that there is no point unless your a bit of a perfectionist

Worst that could happen is there run to warm which is some peoples opinion would be good, or they could run cold which could mean your new tubes last longer.
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#3
so no damage would occur from adjusting the bias while the amp is off and then turning it on?
Mesa Single Rectifier
Marshall 1960A vintage
Rg3exfm1 w/ EMG 85/81
Big Baby Taylor Acoustic
Ibanez TS808
#4
you need to turn the amp on to bias it.

and no, you can't do it while the amp is on standby, it must be on to make the measurements you need.


edit:

If I were you, I'd just let a tech do it.
Last edited by al112987 at Dec 3, 2008,
#5
Power needs to be running through the tubes to get there reading. Obviously dont touch anything you shouldn't be touching while an amp is on or your hair will stand on end at the least haha XD. Like you said the guy from Eurotubes said about there being minimal range, i have never changed the bias as its usually worked out in favor for me.
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#6
Quote by Silence&Solace
Power needs to be running through the tubes to get there reading. Obviously dont touch anything you shouldn't be touching while an amp is on or your hair will stand on end at the least haha XD. Like you said the guy from Eurotubes said about there being minimal range, i have never changed the bias as its usually worked out in favor for me.


I don't have any probes to read anything lol. I'm planning on just turning the amp on, letting it warm up as normal, flipping the standby and slowing rotating the biaspot counter-clockwise as instructed with a plastic handle screwdriver. Unless you think I shouldn't.. that's all I'm trying to clear up lol
Mesa Single Rectifier
Marshall 1960A vintage
Rg3exfm1 w/ EMG 85/81
Big Baby Taylor Acoustic
Ibanez TS808
#7
Just get a cheap multimeter from radioshack and read up, biasing is as simple as reading what that multimeter says and turning the bias adjustment till it reads what you want it to read.
I don't give a shit if you listen to me or not
#8
You need a multimeter to get the bias right, or you'll blow **** up.

$10-20 at Radio Shack, little yellow thing. Get the $5 12v battery to go with it.
Then there's this band called Slice The Cake...

Bunch of faggots putting random riffs together and calling it "progressive" deathcore.
Stupid name.
Probably picked "for teh lulz"

Mod in UG's Official Gain Whores
#9
How do you know you need to go counter clockwise if you don't have a meter XD. I'd suggest not, the bias range is so minimal you wont even notice the difference anyway.
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#10
Quote by Silence&Solace
How do you know you need to go counter clockwise if you don't have a meter XD. I'd suggest not, the bias range is so minimal you wont even notice the difference anyway.



Because peaveys are set very cold from the factory, turning it counter clockwise will lower the negative bias voltage which in turn runs the tubes hotter, I think. I know the trimpots for the bias adjustment in my BJr work this way.
I don't give a shit if you listen to me or not
#11
Quote by Kevin Saale
Because peaveys are set very cold from the factory, turning it counter clockwise will lower the negative bias voltage which in turn runs the tubes hotter, I think. I know the trimpots for the bias adjustment in my BJr work this way.


He still wouldn't know how far to turn, but thats usful information to me i didn't know peavy did that, you'd think theyd make them run warmer so they had a better sound and satisfied the customer more.
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#12
Quote by Silence&Solace
How do you know you need to go counter clockwise if you don't have a meter XD. I'd suggest not, the bias range is so minimal you wont even notice the difference anyway.


I asked Eurotubes, and they said that the 6505+/5150II has such a small range that I should just turn it all the way counter-clockwise after the tubes are installed.
Mesa Single Rectifier
Marshall 1960A vintage
Rg3exfm1 w/ EMG 85/81
Big Baby Taylor Acoustic
Ibanez TS808
#13
Quote by touji-za-nai
I don't have any probes to read anything lol. I'm planning on just turning the amp on, letting it warm up as normal, flipping the standby and slowing rotating the biaspot counter-clockwise as instructed with a plastic handle screwdriver. Unless you think I shouldn't.. that's all I'm trying to clear up lol



Ok. Now I KNOW you need to take it to a tech to get this done.

The entire POINT of biasing is to setting an idle current in a range that depends on your plate voltage (and power dissipation) that allows the power tubes to sound their best while operating safely. If you're not taking any readings while you're biasing, then you really have no clue what you're doing when you're turning that trimmer.
#14
Do it right and get a multimeter, and set it within the proper range instead of taking the easy way out.
Then there's this band called Slice The Cake...

Bunch of faggots putting random riffs together and calling it "progressive" deathcore.
Stupid name.
Probably picked "for teh lulz"

Mod in UG's Official Gain Whores
#15
Quote by Silence&Solace
He still wouldn't know how far to turn, but thats usful information to me i didn't know peavy did that, you'd think theyd make them run warmer so they had a better sound and satisfied the customer more.



Then someone who just wants to swap could potentially put a "hot" set of tubes in the amp and they would melt down and potentially damage the amp. Not to mention the tubes last longer. If they were smart they'd just give the adjustment more range, or better yet, have pairwise bias adjustment so you wouldn't have to have a matched quad.
I don't give a shit if you listen to me or not
#16
Quote by Kevin Saale
Then someone who just wants to swap could potentially put a "hot" set of tubes in the amp and they would melt down and potentially damage the amp. Not to mention the tubes last longer. If they were smart they'd just give the adjustment more range, or better yet, have pairwise bias adjustment so you wouldn't have to have a matched quad.


Supose but peavy could just change the god awful stock tubes they have in then people would want to change themn as soon as they get the amp.
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#17
Quote by Silence&Solace
Supose but peavy could just change the god awful stock tubes they have in then people would want to change themn as soon as they get the amp.



It all comes down to price. They could also replace those crappy sheffields with something good.
I don't give a shit if you listen to me or not
#18
Quote by Kevin Saale
It all comes down to price. They could also replace those crappy sheffields with something good.



I supose if you have the know how, you might aswell build your own amp from scratch, id have no idea how to do that XD be fun experiment to try though
Equips:

Ibanez RG2550E
Jackson DKMG
ESP LTD EC 200 QM
Peavey ValveKing Head & Slant Cabinet
Peavey 5150
Ashdown Fallen Angel 4x12 Cab
Ibanez Tubescreamer TS9
#19
Quote by Silence&Solace
I supose if you have the know how, you might aswell build your own amp from scratch, id have no idea how to do that XD be fun experiment to try though



Yup, but a lot goes into designing too, not to mention if you don't do a good job it could sound like crap.
I don't give a shit if you listen to me or not
#20
The accessible bias trim pots Peavey supplies for the player to adjust has a small and safe range of sweep. It's totally safe to turn this dial and leave it at any position. Counter clockwise being the hottest. Keep in mind your tone will sound thicker and crisper with the bias dial set high, but you will also most likely experience some added noise from your poweramp.
MARSHALL JVM 210H
PEAVEY JSX
KRANK 412
MESA 412
FENDER STRATS
DIMARZIO
CELESTION
#21
I wouldn't say that, power tubes can vary a huge amount and plate voltage can vary as much as 20% from amp to amp with different tubes. The trimmer is a fine tuner because the bias is already set a reasonable range by the bias circuit inside the amp, but I would not say that the entire range of sweep for the trimpot is safe. Otherwise it completely eliminates the need to bias the amp.
Last edited by al112987 at Dec 3, 2008,
#22
Quote by al112987
I wouldn't say that, power tubes can vary a huge amount and plate voltage can vary as much as 20% from amp to amp with different tubes. The trimmer is a fine tuner because the bias is already set a reasonable range by the bias circuit inside the amp, but I would not say that the entire range of sweep for the trimpot is safe. Otherwise it completely eliminates the need to bias the amp.
The trim pot provided is small in sweep for a reason. As long as you use the factory recommended tube types your safe to adjust to your ear. These trim pot dials on the Peavey 6505+, XXX and JSX don't even fully turn in a complete circle. They are more of a horseshoe shape in sweep. If you want to access these amps full bias sweep they need to be opened up and have the bias screw turned. This is where a tech would come into the picture.
MARSHALL JVM 210H
PEAVEY JSX
KRANK 412
MESA 412
FENDER STRATS
DIMARZIO
CELESTION
#23
he told you to adjust it full on, because even with the pot wide open, it's still going to run on the cold side. The 6505+ has a very small sweep on the bias pot, but there are simple mods out there to increase it's range.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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