Jump to content
GDan

Does anyone get any utility out of the deep dive "bias" etc parameters for the amps?

Recommended Posts

Yes but it is subtle. The main one I use is Sag. turn it down for a looser feel. Turn it up for a more compressed tighter feel.

 

Here's some Bias info.

 

The Bias control affects the balance of distortion between saturation and cutoff in the power tubes. Proportion changes depending on the idling state of a power tube; if it's idling hot, then there will be more saturation and less cutoff, and if it's cold there will be more cutoff and less saturation. The bias control affects where the idling state of the tube is "located"; if it's hot or cold.
Another way of putting it might be that we can virtually change the value of the cathode bias resistor in a cathode bias amp.

Share this post


Link to post
Share on other sites

I find that the bias can make a difference in some amps but not so much on others.  I can't remember which amp model it was but I remember not liking the sound when I change the bias setting in either direction from the default. Others seem to allow you to change the raspiness of the amp. At least, that's what I hear.

Share this post


Link to post
Share on other sites

Yes but it is subtle. The main one I use is Sag. turn it up for a looser feel. Turn it down for a more compressed tighter feel.

 

Actually it's the other way around. When you turn up the Sag, you're increasing compression.  It feels looser because the bass notes tend to mush together more - great for that bluesy feel but not so good for metal chugging.  The less compressed setting is actually with the Sag turned down.  This is like an amp with lots of headroom in the power stage and hardly gets saturated enough to sag and compress.

  • Upvote 2

Share this post


Link to post
Share on other sites

Most of the amps I use, I need to mess with the bias a bit to get them just right. Turn Hum all the way down while I'm at it, and I sometimes mess with Sag.

Share this post


Link to post
Share on other sites

Actually it's the other way around. When you turn up the Sag, you're increasing compression.  It feels looser because the bass notes tend to mush together more - great for that bluesy feel but not so good for metal chugging.  The less compressed setting is actually with the Sag turned down.  This is like an amp with lots of headroom in the power stage and hardly gets saturated enough to sag and compress.

 

I'm sorry you are right. I'm tired and not at home. I will correct that in my post and add some bias info.

Share this post


Link to post
Share on other sites

I use sag and bias all the time, bias-x less. It's unclear of I'm making GOOD use if them...

 

[EDIT] Wasn't thinking about hum and ripple. I do sometimes change those, though I can't exactly describe how they change the tone except at max, when you can hear actual hum. In theory I'd think less of both would be good, but things feel a feel less warm to me with none. I tend to lower both for higher gain stuff, going for punchier, less mess.

 

However, as I said, I'm not sure I'm actually making good choices here. Higher gain tones are my short suit in general, probably because I don't listen to or play them a lot. Is the upper end of Andy Timmons considered high gain?

 

Most of my patches have snapshots for four drive levels, and the driviest one always gives me trouble. I can never figure out of its maxed-out sounding enough, too harsh, or going to completely disappear in a band mix like overly distorted tones tend to do.

 

Anyway, I try to play with all the controls we've been talking about to work on that, with no-idea-how-much success. I should get my act together and record something, see what you folks think.

Share this post


Link to post
Share on other sites

I use sag and bias all the time, bias-x less. It's unclear of I'm making GOOD use of them...

 

Hey! I resemble that remark.

Share this post


Link to post
Share on other sites

Bias-x and ripple the only ones that are too subtle to me but I have not played with them on every amp model in the Helix, just the ones I use or gravitate towards.

Share this post


Link to post
Share on other sites

If you find a "Clean" amp just not sounding very clean, bias!!!   USUALLY turning up bias makes an amp cleaner (more headroom, more voltage for the tube), if the "dirt" is coming from the power section. IME.

Share this post


Link to post
Share on other sites

I adjust some of the tube parameters using the same method I use to design many of my presets; I run the looper to free up my hands.  I tend to set the ripple and hum down close to zero adding a bit more in when I want additional "flavor".  I set the Bias according to what sounds best to me for a given amp and I also use a tip from sminchk67 (runs the Helix channel) and strum a big chord to help me find the sweet spot for the bias. Once I set the Bias I usually set the Bias-X in the same general area as the Bias unless I can easily hear a difference when I move its bar. Not for any good reason but because I find it difficult to hear a significant difference when I adjust the Bias-X bar on many of the amp models.  I would be interested if anyone has a good practical method for setting Bias-X. Sag is a little tricky because not only can it change the tone and compression but it also determines the "feel" to a certain extent. I usually set it to what sounds good when the looper is playing and then I may end up adjusting it again depending on how it feels when I am playing.  I believe there used to be a section under the amps on helixhelp.com that described the various tube parameters but I don't see it any more. 

Share this post


Link to post
Share on other sites

If you find a "Clean" amp just not sounding very clean, bias!!!   USUALLY turning up bias makes an amp cleaner (more headroom, more voltage for the tube), if the "dirt" is coming from the power section. IME.

It's the other way round, turning down for colder bias gives more headroom, turning up for hotter bias makes it distort more easily.

  • Upvote 1

Share this post


Link to post
Share on other sites

Turn Hum all the way down while I'm at it....

Amen. The fact that the parameter is there at all is amusing to me. Who's turning the "hum" UP? Has anyone had occasion to say to themselves, "This tone would be perfect if it just had some useless, extra noise"?

  • Upvote 1

Share this post


Link to post
Share on other sites

Amen. The fact that it's there at all is amusing to me. Who's turning the "hum" UP?

 

"I've finally got this thing sounding just the way I want. Let's f@#! it up with some useless, extra noise".

I initially thought turn it down, why would I want hum?! But do find that thins things out a lot, so generally set at 4-5.

Share this post


Link to post
Share on other sites

It's the other way round, turning down for colder bias gives more headroom, turning up for hotter bias makes it distort more easily.

 

After again reading about Bias, there seems to be an inverse relationship between bias voltage and current etc.....  but i do find the Litigator amp is cleaner with Helix Bias control turned up.  Not sure if that is raising voltage and "under-biasing" the amp or vise versa.  I guess it depends on how Line 6 is implementing that setting in the Helix.

Share this post


Link to post
Share on other sites

... I just typed and then erased a post, because I am finding the whole thing still a bit confusing; I've scanned quite a few articles, and there seems to be some disagreement, or at least, differing opinion or interpretation, on how it all plays out.

 

 

Here's one I read among many; seems to be pretty straightforward, yet seems also to favour Class AB amp configurations for their overdrive characteristics...

 

http://www.guitarplayer.com/miscellaneous/1139/class-a-vs-class-ab/14204

 

 

... I'm one to continually tell people to not worry about the names and the numbers on the knobs; just dial with your ears. If it sounds good and behaves as you like, then it's good.

I did however want to get a better grasp of this aspect, and now feel a bit lost on the topic again =]

Share this post


Link to post
Share on other sites

From my time playing with tube circuitry and reading points like "[bias setting will] virtually change the value of the cathode bias resistor in a cathode bias amp" it brings up a picture in my head of what's supposedly happening to the guitar signal. I can't completely hear if my theory is correct but maybe someone can chime in. 

 

The gain stages in the amp (in real life) aren't limitless and those limits are what creates the distortion of the signal (this distortion is a large part of what Helix wants to model obviously).   If you imagine a sine wave (representing a simplified guitar signal) the peaks of that sign wave will get clipped by the limit of the gain stage [e.g. overdrive].   In tube amps, the shape of that clipping depends on the a number of factors like the type of tube AND it's bias.   

 

Shifting the sign wave "up" (by adjusting the bias respective to the min and max possible in a gain stage) means that the top peaks get clipped more.   Shifting the sign wave "down" means the bottom troughs get clipped more.   A bias set "in the middle" should have equal clipping on the top and bottom of the wave.  In tubes, the the clipping of the sign wave tops has a different characteristic (changes the sign wave in a different way) than when it clips the bottom of the wave.  Normally biasing "hot" in a preamp tube is supposed to give a warmer/smoother distortion and biasing cold gives a crispier (more like fuzz) distortion to the signal. Biasing in the middle gets you both.   

 

 

 

 

 

 

Share this post


Link to post
Share on other sites

Experiment; put on a super clean setting with a 'tube' amp.

Dial the bias all the way up.

Dial it all the way down.

 

Down; you hear 'less efficiency' (ie; quieter) and distortion come into play.

Up; gets louder toward middle of adjustment, then gets a bit quieter toward the top of the range, but clarity improves along with that.

 

I did this simple experiment using WhoWatt 100 with low drive (3.8) and master at 10 - biasx at zero for all of this also.

  • Upvote 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...