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The manual just isn't cutting it.

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Hi all!

 

I've been backwards and forwards through the manual and previously owned an hd500x and had the same minor annoyance. Could somebody PLEASE point me toward comprehensive info about the power amp section/page?

 

I see that Line6 is offering free classes that cover the topic but the closest one to me is over 2 hours away.

 

I totally get the master control and oddly enough I'm understanding the "hum" knob. Instinct dictates that hum is bad and I couldn't understand why they even added it till I cranked the master and fiddled with the setting. Now I find myself actually dialing in a decent amount of it. As far as bias, I've burned out more than a few tubes over the years by biasing them hot for that delicious "inch from death" tube tone goodness. But the control in the helix doesn't seem to work the same way. I really prefer what the manual describes as a "colder a/b setting". As far as ripple or bias-x I have absolutely no clue.

 

Any help or link to a more DETAILED explanation is appreciated!

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Hi all!

 

I've been backwards and forwards through the manual and previously owned an hd500x and had the same minor annoyance. Could somebody PLEASE point me toward comprehensive info about the power amp section/page?

 

I see that Line6 is offering free classes that cover the topic but the closest one to me is over 2 hours away.

 

I totally get the master control and oddly enough I'm understanding the "hum" knob. Instinct dictates that hum is bad and I couldn't understand why they even added it till I cranked the master and fiddled with the setting. Now I find myself actually dialing in a decent amount of it. As far as bias, I've burned out more than a few tubes over the years by biasing them hot for that delicious "inch from death" tube tone goodness. But the control in the helix doesn't seem to work the same way. I really prefer what the manual describes as a "colder a/b setting". As far as ripple or bias-x I have absolutely no clue.

 

Any help or link to a more DETAILED explanation is appreciated!

 

I will try to help a little.

 

Hum. You got it. Although I like it off almost all the time. No, all the time, on both HD and Helix

 

Bias... for me, the sweet spot is never all the way up or down, it's in the middle somewhere, and is different for each amp.

 

Bias X? I think that's mostly really high gain settings, which I never use.

 

Maybe some other geniuses will pipe in.

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Regarding the hum control. What I'm saying is that I actually like it and tend to set it above %50. It's sort of a soft ring modulator kind of sound that's very musical with low to moderate gain amps (my fav).

 

I totally agree with your assessment of the bias control. I've been going to 35 or 40 % with the fender and marshall type amps but it really sounds great cranked to 9 or 10 on the vox's. What I don't understand is why it sounds like arse at about %65 on a plexi model when IRL a hot biased plexi sounds like molten sex.

 

The bias-x thing is really buggin me though. The manual says set low for tight bottom with high gain and set high for more compression. I'm no wordsmith but to me this is the same creature.

 

Any ideas on the bizarre and mysterious "ripple" control?

 

 

Thanks for the help Peter!

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Any ideas on the bizarre and mysterious "ripple" control?

 

haven't seriously messed with it, no... anybody else?

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About the Ripple Control? The manual says things get freaky at higher settings so I guess they get frequey, lol.

 

 From WIKI

The most common meaning of ripple in electrical science is the small unwanted residual periodic variation of the direct current (DC) output of a power supply which has been derived from an alternating current (AC) source. This ripple is due to incomplete suppression of the alternating waveform within the power supply.

As well as this time-varying phenomenon, there is a frequency domain ripple that arises in some classes of filter and other signal processing networks. In this case the periodic variation is a variation in the insertion loss of the network against increasing frequency. The variation may not be strictly linearly periodic. In this meaning also, ripple is usually to be considered an unwanted effect, its existence being a compromise between the amount of ripple and other design parameters

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Am I the only one who doesn't think they make any noticeable difference then?

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Am I the only one who doesn't think they make any noticeable difference then?

 

Depends on the amp and the settings. Hum and Bias certainly make a difference.

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Im not getting it. Bet most people couldn't tell if I posted clips up and asked if the settings were A or B :)

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If you cant figure out the "Ripple setting".....Drink some, lol.

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Am I the only one who doesn't think they make any noticeable difference then?

I thought so too until I CRANKED the master control. The hum control has an obvious and tangible effect. The ripple, not so much.

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About the Ripple Control? The manual says things get freaky at higher settings so I guess they get frequey, lol.

 

 From WIKI

The most common meaning of ripple in electrical science is the small unwanted residual periodic variation of the direct current (DC) output of a power supply which has been derived from an alternating current (AC) source. This ripple is due to incomplete suppression of the alternating waveform within the power supply.

As well as this time-varying phenomenon, there is a frequency domain ripple that arises in some classes of filter and other signal processing networks. In this case the periodic variation is a variation in the insertion loss of the network against increasing frequency. The variation may not be strictly linearly periodic. In this meaning also, ripple is usually to be considered an unwanted effect, its existence being a compromise between the amount of ripple and other design parameters

Excellent description! But it's been decades since my electronics training in the USAF and you may have taken my "DETAILED" remark a smidge too literally! *grinz* I'm just trying my best to figure out why these interesting settings were even included in the hardware/software clusterfark that is the flagship of the L6 line.

 

I certainly don't have these controls on my physical amp and it costed a boatload more than the Helix.

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Excellent description! But it's been decades since my electronics training in the USAF and you may have taken my "DETAILED" remark a smidge too literally! *grinz* I'm just trying my best to figure out why these interesting settings were even included in the hardware/software clusterfark that is the flagship of the L6 line.

 

I certainly don't have these controls on my physical amp and it costed a boatload more than the Helix.

 

I got Ya! I do that sort of thing for fun and it teaches me something I never really thought about. I agree with you wholeheartedly. I'm still using the HD500 when I first got it I didn't even know how to ask a question, lol. I just read some stuff here and there on and off and the twisted knobs trying to figure it all out like puzzle. These days the HD500 is not as big of a puzzle to me.

 

Just keep twistin' 'till ya can't twist no more. :) and don't forget play guitar :)

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The Best thing is record the guitar with the looper  and tweak the settings while looper is playing....

Forget the conventional wisdom and just observe how these settings affect the amp.

 

The bad part is, looper always sound different than playing live..

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Here is probably the best explanation I've come across for bias, bias excursion, and sag. The info is specific for the HD but is useful nonetheless: http://blog.line6.com/2013/pod-hd-amplifier-extras—using-the-sag-bias-and-bias-excursion-settings/

As for ripple, not completely sure, but it's linked, or related, to the hum parameter. I usually just leave these alone, because I really don't hear a difference either way for the amps I tend to use.

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Here is probably the best explanation I've come across for bias, bias excursion, and sag. The info is specific for the HD but is useful nonetheless: http://blog.line6.com/2013/pod-hd-amplifier-extras—using-the-sag-bias-and-bias-excursion-settings/

As for ripple, not completely sure, but it's linked, or related, to the hum parameter. I usually just leave these alone, because I really don't hear a difference either way for the amps I tend to use.

That was VERY useful. I was only able to listen on my tablet speakers but I think I get the gist. Time for some experimentation.

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The Best thing is record the guitar with the looper  and tweak the settings while looper is playing....

Forget the conventional wisdom and just observe how these settings affect the amp.

 

The bad part is, looper always sound different than playing live..

This was something I really enjoyed when I was using Amplitube and trying out "re-amping". Tweaking the tone while not playing was kinda cool. I'm not really set up for it at the moment but that should change soon.

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If L6 is using the terms as they are used in electronics, then a search for a term as it relates to power supply ripple will definitely cause weird bias related sound. Poor supply filtering causes hum, which older tube amps have a null control to minimize hum. Alternately the tube amplifier terms can also be searched; bias, biasing, classes of amps, etc. Although I have no idea what bias X is. Not really a term I've come across in my electronics work.

 

I hope this helps. Lots of the reading may be too in depth and the terms that L6 is using may or may not apply.

 

 

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If L6 is using the terms as they are used in electronics, then a search for a term as it relates to power supply ripple will definitely cause weird bias related sound. Poor supply filtering causes hum, which older tube amps have a null control to minimize hum. Alternately the tube amplifier terms can also be searched; bias, biasing, classes of amps, etc. Although I have no idea what bias X is. Not really a term I've come across in my electronics work.

 

I hope this helps. Lots of the reading may be too in depth and the terms that L6 is using may or may not apply.

You're spot-on with the technical aspects of it all. What I'm really searching for is an explanation that even a lowly plank-spanker like me can understand. I'm looking for terms like "more bass" or "accentuated high-mids" or "gritty vs smooth". Things like that.

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You're spot-on with the technical aspects of it all. What I'm really searching for is an explanation that even a lowly plank-spanker like me can understand. I'm looking for terms like "more bass" or "accentuated high-mids" or "gritty vs smooth". Things like that.

 

This fellow goes into these settings a bit in his video. I think he is stumbling in the dark to some extent like the rest of us but he sheds some light on the subject nonetheless. 

 

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The manual for such a product must explain every parameter of any effect or setting. Currently the manual maybe covers 50%. The rest is trial and error. There is no excuse for it.

 

Smaller companies often are better with these things as there are too many meetings and discussions and too little action. Some intern could write a proper manual in a week. Wouldn't need all the different languages even. But it ain't gonna happen.

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In a video I just watched about EQing amps on the Helix, it was said that "Ripple" basically does for the high end and fiz what "hum" does for the low end and boominess.  This "sounds" logical but how true this is I don't know as I haven't had much experience with this adjustment yet.

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While I can't comment on "Hum" as that varies from ear to ear, I can tell you what I know about bias (in the electronic sense). Also, I don't know if this will really help with how you're trying to set everything.

 

I used to work in the film industry in post-production audio. We would have to set the bias for every roll of film/tape. It is essentially a point of saturation that yields the best frequency response at 0 db when running tone through the machine. We would be able to tell where the optimal bias setting was by looking at a VU meter.

 

What would happen was that (with the deck set to record) we'd run a tone from an oscillator, crank the bias, watch the VU meter needle go from minus to 0 and keep cranking until the needle went way into the positive side and then, while still cranking, the needle would start coming back to 0 and that's where we would stop. Going past 0, still cranking away and watching the needle fall back to 0 would ensure the tape could yield a full frequency response.

 

For tubes, you're setting a certain amount of voltage hitting the plate by using a resistor or combination of resistors until you can measure a full response without everything getting fried.

 

I guess the approach to Helix would be to try going past what sounds good initially to see if you can get to a point that sounds better if you keep cranking away. I don't know if this will help, but this is how it's done in "Analog Audio Land."

 

 

 

 

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While I can't comment on "Hum" as that varies from ear to ear, I can tell you what I know about bias (in the electronic sense). Also, I don't know if this will really help with how you're trying to set everything.

 

I used to work in the film industry in post-production audio. We would have to set the bias for every roll of film/tape. It is essentially a point of saturation that yields the best frequency response at 0 db when running tone through the machine. We would be able to tell where the optimal bias setting was by looking at a VU meter.

 

What would happen was that (with the deck set to record) we'd run a tone from an oscillator, crank the bias, watch the VU meter needle go from minus to 0 and keep cranking until the needle went way into the positive side and then, while still cranking, the needle would start coming back to 0 and that's where we would stop. Going past 0, still cranking away and watching the needle fall back to 0 would ensure the tape could yield a full frequency response.

 

For tubes, you're setting a certain amount of voltage hitting the plate by using a resistor or combination of resistors until you can measure a full response without everything getting fried.

 

I guess the approach to Helix would be to try going past what sounds good initially to see if you can get to a point that sounds better if you keep cranking away. I don't know if this will help, but this is how it's done in "Analog Audio Land."

That actually makes some sense to me. I'll experiment with that technique.

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That actually makes some sense to me. I'll experiment with that technique.

Let me know if cranking away on the bias helps. I haven't gotten into tweaking that setting yet. The other thing to keep in mind is that the shift, or improvement in tone may be subtle and may not be apparent until you're really hitting the unit with some serious output from your guitar.

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Let me know if cranking away on the bias helps. I haven't gotten into tweaking that setting yet. The other thing to keep in mind is that the shift, or improvement in tone may be subtle and may not be apparent until you're really hitting the unit with some serious output from your guitar.

Ok. So I messed with it with what you described in mind. I can't find the secondary "zero point" you talked about on the Helix, but there was a definable "center". And it was slightly different (higher or lower), for each amp model i tested. I discovered that the tone was "punchier" below the peak and more "diffuse" or "vintage" sounding above it. I also found that the noise floor was really high dialed right in to the center point but the tone was still good. Can't quite come up with a descriptive for it. Further research is definitely in order.

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This article might be helpful: The Last Word on Class A. It describes different amplifier classes (A, B and AB) and output stage technologies (single-ended and push-pull). The amplifier class and output technology, and whether the amp has a negative feedback loop have a big impact on sag, ripple, bias effect, and bias excursion. Here's a few key takeaways from the article in terms of tone not technology:

 

Fender/Marshall style amplifiers:

  • Use class AB fixed bias, push-pull output stages with a phase inverter and negative feedback loop
  • This makes the amp sound tighter, especially at lower frequencies
  • It generally better for cleaner tones
  • Power supply ripple and noise are canceled because of the push-pull output stage and won't have as much effect.
  • The transition from clean to distorted will be fairly abrupt, and will have more odd-order harmonics which can sound harsher
  • These amps will generally exhibit more sag because of large changes in plate voltage when the amp is overdriven. Some quick notes on preamp vs power amp distortion
    • Preamp distortion is controlled by the amp Drive control. This tends to be be asymmetric (involving cutoff and saturation) and contains a lot of even-order harmonics that sound good.
    • Power amp distortion is controlled by the Master volume. In a class AB, push-pull amplifier, the even-order harmonics will be cancelled causing a somewhat harsher tone.
    • Sag will have a greater compression impact as the Master volume is higher. 
    • So you have three volume controls, that behave very differently: 1) Drive that controls the preamp drive and distortion, 2) Master volume with control the volume, distortion, and sag in the power amp, and 3) Level, which just controls the output level and has no impact on tone.

Vox style amplifiers:

  • Use cathode biased output tubes and no negative feedback which will generally accentuate  sag and bias excursion effects
  • The transition from clean to distorted is smooth and more gradual, providing more control of distortion with the guitar volume control and how you pick

So these power amp controls, Master Volume, Sag, Hum, Ripple, Bias and Bias X may be quite different with different amplifiers, and will have little effect if the Master Volume is turned down. This might be why sometimes they don't seem to do anything. Pick an amp with no negative feedback, and run the Master Volume high and these controls will generally have more impact on tone.

 

Regarding the effect of the bias control - whether you bias hot or cold, this will have an impact on how the amp distorts. Bias is used to set the tube's operational point. 

 

Under or Hot Biased (lower negative grid voltage): The tube has higher idle current, runs hot, gets more full sounding, then harsh as bias voltage is reduced further, might get muddy at high volumes, shorter tube life, will be noisier, has less crossover notch, saturation distortion occurs earlier (since the tube is already conducting a lot, and pushing the grid more positive pushes closer to saturation). There’s no impact on cutoff distortion (since there's a lot of room to push the grid negative).

 

Over or Cold Biased (higher negative grid voltage):  The amp can become sluggish, more crossover distortion but more saturation clean headroom, weaker sounding, can lack sparkle, tubes last longer but amp doesn't respond as well.

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This article might be helpful: The Last Word on Class A. It describes different amplifier classes (A, B and AB) and output stage technologies (single-ended and push-pull). The amplifier class and output technology, and whether the amp has a negative feedback loop have a big impact on sag, ripple, bias effect, and bias excursion. Here's a few key takeaways from the article in terms of tone not technology:

 

Fender/Marshall style amplifiers:

 

  • Use class AB fixed bias, push-pull output stages with a phase inverter and negative feedback loop
  • This makes the amp sound tighter, especially at lower frequencies
  • It generally better for cleaner tones
  • Power supply ripple and noise are canceled because of the push-pull output stage and won't have as much effect.
  • The transition from clean to distorted will be fairly abrupt, and will have more odd-order harmonics which can sound harsher
  • These amps will generally exhibit more sag because of large changes in plate voltage when the amp is overdriven. Some quick notes on preamp vs power amp distortion

  • Preamp distortion is controlled by the amp Drive control. This tends to be be asymmetric (involving cutoff and saturation) and contains a lot of even-order harmonics that sound good.
  • Power amp distortion is controlled by the Master volume. In a class AB, push-pull amplifier, the even-order harmonics will be cancelled causing a somewhat harsher tone.
  • Sag will have a greater compression impact as the Master volume is higher. 
  • So you have three volume controls, that behave very differently: 1) Drive that controls the preamp drive and distortion, 2) Master volume with control the volume, distortion, and sag in the power amp, and 3) Level, which just controls the output level and has no impact on tone.

Vox style amplifiers:

  • Use cathode biased output tubes and no negative feedback which will generally accentuate  sag and bias excursion effects
  • The transition from clean to distorted is smooth and more gradual, providing more control of distortion with the guitar volume control and how you pick
So these power amp controls, Master Volume, Sag, Hum, Ripple, Bias and Bias X may be quite different with different amplifiers, and will have little effect if the Master Volume is turned down. This might be why sometimes they don't seem to do anything. Pick an amp with no negative feedback, and run the Master Volume high and these controls will generally have more impact on tone.

 

Regarding the effect of the bias control - whether you bias hot or cold, this will have an impact on how the amp distorts. Bias is used to set the tube's operational point. 

 

Under or Hot Biased (lower negative grid voltage): The tube has higher idle current, runs hot, gets more full sounding, then harsh as bias voltage is reduced further, might get muddy at high volumes, shorter tube life, will be noisier, has less crossover notch, saturation distortion occurs earlier (since the tube is already conducting a lot, and pushing the grid more positive pushes closer to saturation). There’s no impact on cutoff distortion (since there's a lot of room to push the grid negative).

 

Over or Cold Biased (higher negative grid voltage):  The amp can become sluggish, more crossover distortion but more saturation clean headroom, weaker sounding, can lack sparkle, tubes last longer but amp doesn't respond as well.

That's the ticket right there! Gives me plenty to chew on. Thanks everyone!

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