Can you hear bias adjustments?

Discussion in 'Amps and Cabs' started by Tone_Terrific, Jun 25, 2019.

  1. Tone_Terrific

    Tone_Terrific Supporting Member

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    I do not mean clear crossover distortion, I mean those who like 'hot' vs 'cooler' settings.
    Can you hear a few ma of bias variation in your tone?
    If so, do you hear it at all levels or only when driving the output into OD?
    Can you recognize hot (but safe) vs medium?
    Do you run your amps for best audible results or to spec targets?
     
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  2. Guinness Lad

    Guinness Lad Silver Supporting Member

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    Yes. Like setting a car idle, if it’s off you’ll know. I generally always prefer cooler, I don’t like the sound when it thickens up. You lose the lattice.
     
  3. woof*

    woof* Member

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    Not over the Internet
     
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  4. redacted

    redacted Member

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    I’d like to think so. The difference becomes more apparent if you plug your guitar directly into the FX return.
    I set my bias slightly cooler. I use EH 6CA7s in stead of EL34s, which are supposed to be biased slightly cooler (it’s minuscule) than EL34s.
     
  5. shibby

    shibby Member

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    I have a Mesa. Stock tubes are definitely cold

    When I order from a reputable tube dealer asking for hotter tubes for my Mesa it definitely sound and feels much better. It’s night and day for me imo

    Mesa sending out their amps running that cold bias is a total mystery to me.
     
  6. Baxtercat

    Baxtercat Member

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    I don't really [within the proper ranges of course].
    You can hear the volume levels change though.
     
  7. LaXu

    LaXu Member

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    Yes you can. Too cold and it tends to get fizzy, too hot and it can sound a bit indistinct, like it's thick in a bad way. Running in the correct range for the tube is where it works best. I think you can hear the extremes but would not be able to tell much of a difference in the suggested bias range.
     
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  8. amstrtatnut

    amstrtatnut Member

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    That reminds me. I have a scxd and everyone on internet says they are biased cold and sound better if biased hotter. I dont know what "better" means in this context. I have never biased that amp. I change tubes as needed and have never had an issue.
     
  9. Vanyu

    Vanyu Member

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    Nope ;)

    (Assuming there’s no xover distortion)

    I’ve always thought biasing was largely overblown (strictly tonally speaking), as long as I’m out of xover distortion I’ve found the differences to be minimal at best. I tend to bias my NMV 6L6/EL34 amps at 25mA, 30-35mA if it’s got a MV. I almost never hit 70% dissipation unless I’m trying to squeeze every last watt out of a bass amp or something like that. I almost always run my bias at a range where I know my tubes will live a long life, and it always sounds fine!!

    I see Mesa’s being brought up here too. They’re almost always biased in xover distortion territory IMO, especially running non-Mesa tubes! I definitely wouldn’t call Mesa’s stock fixed bias settings “operation range” for any tube! Mesa’s are, IMO, a great example of bias that’s “too cold”.
     
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  10. Tag

    Tag Gold Supporting Member

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    Absolutely, but in some amp designs a lot more than others. You can feel it as much as hear it. For most amps, the hotter the bias, the stiffer the feel to me. Shad biased my Dumble while I played and hit the sweet spot. It was on the cold side. Lou from Louis elecrics did the same for my twin reverb, and I also liked that on the cold side.
     
    Last edited: Jun 25, 2019
  11. Jason_77

    Jason_77 Member

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    You can hear a difference between cold and hot, but don’t expect to go back and forth between, say, 34mA and 36mA and expect to hear a difference.
     
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  12. FourT6and2

    FourT6and2 Member

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    Absolutely. And I can prove it. Or at least you can. Plug your guitar in and play while adjusting the bias. Just don't go over 70%. I find I most always prefer a colder bias (around 55% - 60%). It will sound pretty much like a subtle gain/saturation control. I prefer to let the amp work harder to get more saturated. If I need more gain, I'll turn the gain knob up. Colder bias will make the amp tighter and clearer. I play modern high-gain stuff, so that works in my favor.
     
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  13. Tone_Terrific

    Tone_Terrific Supporting Member

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    I find the volume goes up with the current to a point. Easily seen/measured, too.
    I don't hear much diff after crossover distortion cold and a certain mushiness comes in at too hot.
    Volume change is easily compensate for.
    That seems to go against general consensus.

    Crossover distortion can reappear as power enters the clipping point, but that may be normal.
    I bias on the cool side above crossover and don't worry about a bit creeping back in at full power.
    Most players do not use full power.
    Special cases with smaller amps might need special attention.:cool:

    Checking/adjusting bias on SS amps remains in the mystery zone where the magic smoke can escape.:oops:
     
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  14. HotBluePlates

    HotBluePlates Member

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    That's why I tend to hear.

    And the "increased volume" for hotter bias is the fact that you've reduced the bias voltage, which is reducing the drive signal require to reach peak plate current, meaning the same preamp/phase inverter signal is driving the power section harder.

    I haven't scoped it, but I suspect the "mushiness" with hotter bias is increased distortion (slight flattening of the wave). However, I also seem to remember I hear that effect when it's way too hot for typical Class AB operation. I don't recall hearing a definite difference without a pretty large change in idle current.
     
  15. Guitar Dave T

    Guitar Dave T Member

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    Absolutely. Big, noticeable differences in feel and tone over small adjustment range, more with classic Marshall and tweed Fender circuits than blackface/silverface type Fender circuits, in my experience.

    I like to set the bias by voltage, then fine tune by ear, then do a final biass check to make sure the amp is still within acceptable, safe range.
     
  16. MrKite89

    MrKite89 Member

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    Yes and no. Define "few mA". I definetely hear a 5-10% swing in total plate dissipation.

    I always play my amps at least where they "kick in": around 4-5 on a DRRi Vibrato channel for example, so I don't know (and I don't care) if there's the same difference at 2-3, but I guess a little less, since around 7-8 is even more than around 5.

    It can be difficult: if it's my amp\my guitar, and the amp is cranked, probably yes.

    I bias my amps by ear, while checking the numbers: if they're not crazy high\low I don't care for exact specs. Same with my guitar setups: string action, neck relief, pickups height...I just use the numbers to check the adjustments made to satisfy my hands\ears. :)
     
  17. Tag

    Tag Gold Supporting Member

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    Absolutely! Its yet another good reason to not go by what you read, but what your ear tells you. I always had my amps biased "hot" because I always read it sounded better. It wasnt until Shad had me do it by ear that I found out I preferred a colder bias most times. I had a DRRI that was so stiff, and always read it was because Fender sent them out cold.
    Exactly the opposite was true.
    :dunno
     
  18. ledzep618

    ledzep618 Supporting Member

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    I once bought a ’67 BF Bassman of unknown history, clearly modded at a local music shop for cheap. It sounded like cold, tinny garbage with the treble rolled off but just sounded so wicked when you turned the treble up, I mean this thing was a fire breather as you went up the dial. I assumed someone had messed with something inside, maybe built in a gain stage and cocked up the wiring a bit. Took it to a tech to confirm and it turned out someone wired in a fixed treble value and then homebrew wired the treble pot to be a bias adjustment knob. Now this is not a particularly safe way of operating an amp so I had it reverted it original specs...I hated it after that, couldn’t get that hot bias mojo back within safe operating specs. So to answer the question, yes.
     
  19. MrKite89

    MrKite89 Member

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    It's been my experience, in fact. Mine was biased around 60% with JJs and was too fizzy\sterile for me. By ear I settled to ~75% which sounds\feels much better to me.

    But as I said before I tend to run my DRRi (stock C12K speaker) at ~5-6 (with FX pedals) or even 7-8 for a straight blues\RnR tone. It would be interesting to know how you, and others who prefer a colder bias, generally set\play their amp. :)

    IME: too cold or hot just sounds BAD. In the middle on the cold side = better for cleans (tighter), on the hot side = better overdriven tones\response (creamier).
     
  20. Tag

    Tag Gold Supporting Member

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    I agree. If your cranking the power section, a hotter bias xan sound better. Something I rarely do. A good reason the Dumble sounds better colder as well because once the power amp srarts clipping on a Dumble, it can start to lose a bit of its signature sound, but most amps do. Once the power tubes start distorting, amps become more and more similar sounding.
     
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