5150 Bias settings (Samples)

[Lasse Lammert]

yo.
I just changed the tubes in my 5150 again and while I was adjusting the bias I thought I'd quickly record a riff so you hear the difference.

stock my 5150 came with 12mA (my friend's even had 8mA!!).
it should be somewhere between 32 and 42mA.

here are some rough clips 12,18,28,32,40mA so you can hear the difference.

I have TAD (chinese) in the preamp now the JJ were way muddier. (I'm still using a JJ as a phase driver).


I didn't reamp or anything, just played a quick riff with the strat real sloppy. no TS
anyway, hope this helps

Biascomparisons

 

[GuitarHack]

Definitely fuller at the higher settings, as I have recently rediscovered. I have mine currently at around 36mA at 500V, I am going to bump them up to around 40mA to get them closer to 70%.

What powertubes did you put in?

 

[Lasse Lammert]

I'm using JJ powertubes in my Recto and 5150.
usually runnning them around 55%....went a bit lower this time (just above 50%) cause it's just getting to expensive having to replace the tubes so often for all the amps.

 

[GuitarHack]

What symptoms were you getting that made you change tubes? Pops, Red-plating, less low-end? I am a fan of JJ also. Ruby are extremely similar also. I would use either.

 

[Lasse Lammert]

What symptoms were you getting that made you change tubes? Pops, Red-plating, less low-end?

none of those. it's just been 2 years again since the last retube so it was time.
powertubes die slowly, you usually don't realize anything till you pop in the new ones and hear how the amp comes alive again

 

[GuitarHack]

OK. I just assumed that your past hot-biasing may have caused some actual tube failure rather than just old age.

 

[Lasse Lammert]

OK. I just assumed that your past hot-biasing may have caused some actual tube failure rather than just old age.

no, I didn't really have them extremely hot...just about 68-70% I'd say

 

[Nebulous]

Oh, are the pops a result of hot- biasing? Damn. Seems the 6L6s didn't like it as much in the JSX compared to the EL's.

 

[Lasse Lammert]

I think it's impossible to bias the tubes in the JSX hot (w/o modding it).
Even in the highest position mine had about 45% plate dissipation (both EL34 and 6l6. am running 6L6 in it now)

 

[poidaobi]

You need to 'Bias-Mod' to do this correct?

I've never been a fan of fucking with my amp if it sounds good though.

 

[Lasse Lammert]

You need to 'Bias-Mod' to do this correct?

I've never been a fan of fucking with my amp if it sounds good though.

yep.
"biasmodding" isn't really "fuckng with the amp" though. you just put something in that should be there in he first place.
and it's really worth the 10 minutes of work and 1$ in parts.

 

[kev]

Thanks lasse, i'll check these clips when i get back from work. If you have time, would you be able to post or link to a short guide of modding the amp? Im very tempted to and may be even more tempted after I hear your results!

This looks like a good one - http://www.blueguitar.org/new/schem/peavey/modnotes/fja_5150_bias_mod.pdf I guess all you are doing is esentially switching a fixed resistor for a variable one and voila!

As an aside, would you say this latest combo of tubes is your favourite in there so far?

 

[Lasse Lammert]

Thanks lasse, i'll check these clips when i get back from work. If you have time, would you be able to post or link to a short guide of modding the amp? Im very tempted to and may be even more tempted after I hear your results!

This looks like a good one - http://www.blueguitar.org/new/schem/peavey/modnotes/fja_5150_bias_mod.pdf I guess all you are doing is esentially switching a fixed resistor for a variable one and voila!

As an aside, would you say this latest combo of tubes is your favourite in there so far?

yep, that guide seems to be fine.
dunno...my taste for tubes changes from time to time
it used to be chinese in v1 and JJ in the rest...after the shootout today I prefer all Chinese now...highgrade 7025 in v1 and 12ax7a-c in the rest (TAD)

 

[Metaltastic]

Is your Dual Rec bias modded too Lasse?

 

[kev]

Wow, epic difference. With a cold bias it really sits back... seems like running those tubes a bit warmer could be a mix maker. My 5150 is heading for the garage! I dont play the amp very often at all, as im more than happy to use simulators to practice with...

How high to take it I wonder? So this has been responsible for my shit tone all the years...

 

[Metaltastic]

Here ya go Kev, ignore the vid and just scroll down!

http://www.eurotubes.com/euro-Generic-Bias.htm

 

[Metaltastic]

And btw Lasse, I had the bias at around 38 mA on my JSX and the knob wasn't even all the way up I don't think; how are you measuring the bias? Cuz I've heard those terminals on the back are really inaccurate, so I used a bias probe (goes between one of the power tubes and its tube socket)

 

[kev]

Here ya go Kev, ignore the vid and just scroll down!

http://www.eurotubes.com/euro-Generic-Bias.htm

Cheers bro! Wonder why they left it so low stock. Its like the signal has been eaten @ 12ma

 

[Lasse Lammert]

And btw Lasse, I had the bias at around 38 mA on my JSX and the knob wasn't even all the way up I don't think; how are you measuring the bias? Cuz I've heard those terminals on the back are really inaccurate, so I used a bias probe (goes between one of the power tubes and its tube socket)

the thingies in the back are useless. you have to half the value to get the real value....so if it shows 40mA that's actually 20mA per tube.
I built my own probe, similar to the weber

Cheers bro! Wonder why they left it so low stock. Its like the signal has been eaten @ 12ma

yeah, and my buddy's was even colder (8mA').

I guess they're doing that to avoid warranty issues....tubes that cold pretty much last forever.

 

[pifos_2]

hey Lasse where are you ordering your preamp tubes from ?