Anyone bias by their amp by ear? Did my 5153 and JSX...

[loudgtr]

I've got a JSX and a new 5153 that I recently biased by ear. First I did the JSX, it has a bias adjustment on top of the chassis. I popped in some 6L6's and flicked the bias adjustment to "6L6", the adjustable knob was set at noon and I experimented turning clockwise and counter clock wise. It seemed to get stiff and harsh...going counter clockwise and got warmer and softer/buttery feeling going clockwise. It's set at 3 o'clock right now when looking from the back and sounds better.

The EVH is a 100 watter and I popped the chassis out and set it upside down on the cab. Looking at the chassis so that the bias adjustment is towards the top left, it was set at pretty much noon again and sort of glued in place with some "red stuff". I noticed again that it sounded warmer, more buttery with the slot a little left of noon...say around 10 o'clock. I prefer it this way. I'm guessing this is the bias being set "hotter" but I'm not sure. Interestingly enough I didn't mind how it sounded set a little right of noon, depending on the channel I was on and what I was playing. The stock 6L6 have printed on the bottom base of the tube with a sticker 'Red 9' and something else on it that I forget.

Anyways, just thought I'd ask how many of you set bias by ear? I don't have any tools to bias the amps. Just used my ear. No smoke ever came out so all is good thankfully.

 

[crwnedblasphemy]

I bias by ear....Makes a big difference.

 

[D-Rock]

I biased my JSX by ear too.
Countclockwise is hotter, clockwise is colder.
I have mine set at about 11 o' clock with EL34's.

 

[skoora]

I did that with a JMP2203 I used to have. Would basically use a power brake so I could at reasonable volume in the room hear what happened to amp when the Master got up there. I would still check with a meter and invariably ended up in the low/mid 30's which for that amp was pretty standard. I usually just incresed bias until it started falling apart a bit and then nudged it back so the headroom woud return. There was probably a good 10mA window of where it really didn't change tonally so these days I bias just at the bottom of that range and get good life out of the Power Tubes.

 

[loudgtr]

I biased my JSX by ear too.
Countclockwise is hotter, clockwise is colder.
I have mine set at about 11 o' clock with EL34's.

I originally had the JSX set with new (had them for a long time unused) Mesa 6L6 STR 430's at around 11 o'clock same as you and thought it sounded amazing!!!!! Tight, defined, focused...I really liked it. When a friend came over I tried a different set of 6L6's (NOS Phillips )and my buddy who's opinion I respect (bang bang bang) thought it sounded better when turned to the right. It was warmer sounding, but kind of mushy so we just eq'd differently.

Hmmmm, Soo thinking that was better...I biased my EVH to the same type of set up (over all response) I should've just stuck with what I thought was better.

 

[se7en]

Just remember if you bias by ear, remember to test it at volume. Generally a somewhat colder bias will hold together better at volume despite the fact that it may be a bit harsh at lower volume. The bias tends to drift as you turn up and can change over time...things to keep in mind anyways...

 

[D-Rock]

Just remember if you bias by ear, remember to test it at volume. Generally a somewhat colder bias will hold together better at volume despite the fact that it may be a bit harsh at lower volume. The bias tends to drift as you turn up and can change over time...things to keep in mind anyways...

+1. I adjusted the trim pot with the master at 8/10 and the ultra channel volume at 4/10. That is a fairly loud band practice volume level.
As Skoora stated...I turn the pot until it gets mushy/cloudy sounding, then I roll it back to retain some headroom.

 

[loudgtr]

Just ordered a bias tool online. Looking forward to seeing what I'm hearing.
Speaking with someone who has alot of knowledge on the subject, he said it's still wise to use some tools as biasing an amp by ear is like trying to set the timing on your car by ear.

 

[glip22]

If you don't care about your amp have fun. Personally I would choose a safe bias range and use my ear as well as knowing the current draw. We are talking about tubes that have limitations. Would you put a blindfold on and walk out in busy traffic to see how many cars you can avoid because its fun.

 

[VC4Ever]

 

[glip22]

 

[loudgtr]

If you don't care about your amp have fun. Personally I would choose a safe bias range and use my ear as well as knowing the current draw. We are talking about tubes that have limitations. Would you put a blindfold on and walk out in busy traffic to see how many cars you can avoid because its fun.

How you get biasing an amp by ear by varying slightly in either direction on the trim pot from stock set up...and walking out blindfolded on a busy street as the same thing well...

 

[glip22]

If you don't care about your amp have fun. Personally I would choose a safe bias range and use my ear as well as knowing the current draw. We are talking about tubes that have limitations. Would you put a blindfold on and walk out in busy traffic to see how many cars you can avoid because its fun.

How you get biasing an amp by ear by varying slightly in either direction on the trim pot from stock set up...and walking out blindfolded on a busy street as the same thing well...

In some amps one very small turn of the trim pot can increase your current draw by a large amount. For example if your tubes stock are drawing 30ma per tube, one small turn of the pot can bring the current up to 60ma. You can easily be operating your tubes outside of their specs which can cause failure. Failure can mean one of the tubes arc and send a voltage spike directly to your transformer if your fuse does not do its job. Believe me fuses do not always save you. Other damage can happen as well like burnt up screen resistors, pcb damage, etc..You are biasing blind. If you know the current draw of the tubes you have in in there and how sensitive your pot is thats a little different because you know you are in a safe range.

 

[D-Rock]

Peavey tech support has said many times that the entire range of the bias trim pot on the JSX is small and safe.
I can't say the same about other amps though, they will of course differ.

 

[api4u]

I bias by ear, but monitor adjustments with measuring equipment, as well. It helps you get a baseline you like, and to keep your stuff in safe ranges.

 

[loudgtr]

I ordered a Compu Bias. It's taking a while to get here...

One thing I read online about the Compu is that you cant bias with a guitar plugged in...so setting it while playing is not doable I guess. I'll read the manual once I get to make sure.

 

[glip22]

Peavey tech support has said many times that the entire range of the bias trim pot on the JSX is small and safe.
I can't say the same about other amps though, they will of course differ.

If the pot has a safe range through its motion then one probably cannot get out of the cold range to begin with.

 

[steve_k]

I ordered a Compu Bias. It's taking a while to get here...

One thing I read online about the Compu is that you cant bias with a guitar plugged in...so setting it while playing is not doable I guess. I'll read the manual once I get to make sure.

This is true of any bias meter. Compu-Bias puts their indemnity in the manual. I have been using one of these for the last few years, without problems. The reason is that bias plug breaks the ground. If you have the amp cranked and happen to pop a tube because you biased it too hot, voltage can travel back through the amp input, instead of to the fuse - to the guitar and to the strings and give you a hell of a jolt. You will look like Don King.

That said, you don't have to bias out of safe range. You don't even have to play the guitar while biasing to get peak performance. If you will give the amp a bit of volume with the bias meter hooked up, nothing plugged in, keep adjusting it up until you start hearing some hiss, then back it off a little bit. Check the bias and see where you are at. You will probably be in the 80-90% range.

70% is too cold for most amps, but, it is safe for vendors. Depends too how close to screen voltage you are and tube selection.

 

[bananaladonpcp]

You can bias almost every amp with a simple multimeter, alittle "know how", and simple math. And if you want it alittle hotter or colder you can adjust it.

 

[steve_k]

You can bias almost every amp with a simple multimeter, alittle "know how", and simple math. And if you want it alittle hotter or colder you can adjust it.

Absolutely. But, most people I see on this forum would end up dead or needing CPR.