Finally getting a 6505... again. Some questions about the bias

[Emdprodukt]

So this is the second time in my life I will get a 6505. but this time I want to get the best out of it.

First: Any recommendations which tubes I should get for it? it's in used condition and had no tube change for several years.

Second: I want to get the bias mod. What would be too "hot" and what would be too "cold"?


thanks in advance.

 

[Jaymz]

I got a set of JJ 6L6GC's for the power section in mine and I liiike!

 

[mick thompson]

i've just stuck with my stock tubes so far - no need to change them yet.

they are called ruby's i think - hard trying to find someone to do a bios mod to my 6505+ in ireland - we dont really have many amp tech's over here who know what they're doing

 

[Emdprodukt]

i've just stuck with my stock tubes so far - no need to change them yet.

they are called ruby's i think - hard trying to find someone to do a bios mod to my 6505+ in ireland - we dont really have many amp tech's over here who know what they're doing

as far as I know any tech who knows about high voltage and had an soldering iron in his hands should be able to do this mod but maybe I'm wrong.

 

[mick thompson]

as far as I know any tech who knows about high voltage and had an soldering iron in his hands should be able to do this mod but maybe I'm wrong.

yea but see this is ireland - our tech's and engineers have never heard of bios mods - i've been to every guitar shop in dublin city looking for an engineer & none of them know anyone to do the job. ill get it done when i get enough cash to ship it to the states

this country is amp dumb

 

[Emdprodukt]

yeah but you don't need to be an amp-tech to know how to solder a few resistors and wires without killing yourself. it's not micro-chip technology.
this is a pretty simple manual how to do it. show it to a tech. doing the mod itself should be no problem. now you need to find someone to do the bias or learn how to do it by yourself.

http://www.blueguitar.org/new/schem/peavey/modnotes/fja_5150_bias_mod.pdf

I mean... I don't know anyone from Ireland but something as this simple shouldn't be a problem. ship it to the states just for this mod...puh ... seems like a really expensive way to get this mod done!

 

[mick thompson]

i delt with electronics in the past for a year in school but only using a max of 9v DC - i wouldn't even touch this with a barge pole because id be too afraid of blowing my head off. after studying production performance in college we learned too much dangerous shit to do with electricity. i'd rather someone else takes the risk. as well as that i'd rather someone else sticks a bios warranty on it if in the case example there is no 3 phase power in a venue and i get a sudden surge through my amp, if i wired up something wrong i could seriously kill myself. electricity is not something i like to deal with unless i really have to.

 

[nwright]

MOst 5150/6505's seem to be biased in the 12-20mA range...A lot of dudes I know who do a bias mod go up to somewhere around 30-32mA.

 

[Emdprodukt]

i delt with electronics in the past for a year in school but only using a max of 9v DC - i wouldn't even touch this with a barge pole because id be too afraid of blowing my head off. after studying production performance in college we learned too much dangerous shit to do with electricity. i'd rather someone else takes the risk. as well as that i'd rather someone else sticks a bios warranty on it if in the case example there is no 3 phase power in a venue and i get a sudden surge through my amp, if i wired up something wrong i could seriously kill myself. electricity is not something i like to deal with unless i really have to.

of course you shouldn't do the mod by yourself.

 

[TheWinterSnow]

of course you shouldn't do the mod by yourself.

why not, 5150/6505 have a great discharge circuitry rendering them completely safe to work on when the thing is turned off, very simple mod, clip off one resistor, and solder a pot to two ends of a capacitor, glue the pot onto the board or chassis and you are good to go. Nothing in the circuit that you are modifying has even remotely lethal voltages, 30-40v max, the high volt caps are on a total other side of the amp away from reach but still read 0v on a meter.

If I were you I would read up and do it yourself, I did mine, before I started taking electronics classes, any idiot with soldering skills can do it without getting hurt.

 

[::XeS::]

My 6505+ comes with a 14mA bias. The ideal value (70%) with my plate voltage is 40/42mA.
The current depends from your 6505's plate voltage so you have to check it before.
Anyway the value is pretty much around 40mA. I've to say that I maxed my bias pot (the default one) sometimes ago and I like the "cold bias" sound better than the "hot" sound. Don't know why but it sounds less boomy and more aggressive/tight. I've also to change the shitty tubes I have now before doing a proper test.

 

[Josh Burgess]

My 6505+ comes with a 14mA bias. The ideal value (70%) with my plate voltage is 40/42mA.
The current depends from your 6505's plate voltage so you have to check it before.
Anyway the value is pretty much around 40mA. I've to say that I maxed my bias pot (the default one) sometimes ago and I like the "cold bias" sound better than the "hot" sound. Don't know why but it sounds more aggressive, less boomy and more aggressive/tight. I've also to change the shitty tubes I have now before doing a proper test.

Exactly, people read too much about the bias mod and think it's going to be some magical improvement, when all it really does is make the sound more warm and bassy, which probably isn't even what you want if you're playing high gain metal guitar.

All of the pros use stock 5150s... I think there's a reason for that.