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fundamental amp question

Discussion in 'Amps and Cabs [BG]' started by Phaidrus, Apr 11, 2021.


  1. Phaidrus

    Phaidrus

    Oct 25, 2009
    Romance is balsam for the soul. Give me those bottles!
     
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  2. Phaidrus

    Phaidrus

    Oct 25, 2009
    Sounds like the function of the mirror in one's psychological development - without it you don't know who you are, or at least what you look like. But even then...
     
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  3. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

    Jun 12, 2008
    I still have my Carver receiver, though it got bumped from the living room years ago by a home theatre A/V receiver that's nowhere near as sweet for stereo - but does the surround and sub thing for movies.

    But back on the point of "getting that tube sound", when I first replied to this thread, I consciously decided not to go into the digital emulation realm. It's a spooky technical fact that, with decently designed and provisioned neural networks, we could do a superhumanly good job of "understanding" the behavior of tube amps, up to and including the effects of power supplies sagging under duress (not modeling the supply sag, mind you, but "knowing" how the sound responds under the input+controls+speaker settings where the sag occurs). I don't know if the Kempers are already doing that their in their profiles - I suspect not - but they, or someone else, will be able to do it. We're just talkin' audio signals here, and contemporary DSPs can slice/dice/juice and make julienned fries in less time than it takes sound to go a couple of meters.
     
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  4. Wasnex

    Wasnex

    Dec 25, 2011
    Let's put this in the proper context. If you were to compare each of the four amps in the comparison to another amp of same the model and year, there is a good chance it won't sound exactly the same either. This is true even if each amp is running the same tubes and has been biased to the same spec. If there is variation from one amp to another, it's impossible for the Kemper to sound exactly like all of them. Each Kemper sound profile will sound most like the specific amp it was modeled on.

    One point where the model can never perfectly match: AFAIK the varying impedance of the speaker(s) interacts somewhat with the global feedback loop and has some impact on response, feel, and/or touch sensitivity. This is assuming the amp uses global feedback. When you use a model, the speaker is not physically in the feedback loop, since the feedback loop only exists as part of the program.

    There may be other interactions between the impedance of the speakers, the impedance of the output transformer, and the output impedance of the tubes as well...sorry this is over my head, but they are all tied together. In this context, tube amps have much lower damping than solid state, to I would expect the interaction between amp and cab to be more significant...and this is one example were the term organic may be used.
     
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  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Also, when listening to the model, if it's not the same environment that the model was made in, it won't be exact either.

    Exactness is not the point of modeling IMO. The point is to get reasonably close to multiple models of amp and speaker combination so that the convenience and practicality of the model outweigh any concern over exactness.

    No two amps will be exact either, so focusing on what's most important about the meat and potatoes performance of an amp or speaker is where the utility (and value) of modeling is headed.
     
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  6. Wasnex

    Wasnex

    Dec 25, 2011
    My understanding is distortion shows up as harmonics, and part of the role of global negative feedback is to reduce harmonics (thus reducing distortion).

    Making the frequency response more linear could be perceived as extending the usable frequency response. My apologies for speaking unartfully. I am not an engineer.
     
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  7. Wasnex

    Wasnex

    Dec 25, 2011
    Good chance a model will be used with IEMs these days. At least that is how the people I know who have modelers are using them.
     
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  8. el murdoque

    el murdoque

    Mar 10, 2013
    Germany
    Well, yes of course. I did not mention that we used the exact same amps that were used to generate the model.
    The modeling process was done in a semi professional way. Good microphones, medium good room, people that knew what they're doing.
    Even though, the feeling in the room, both to the listeners as well as to the players was more similar to comparing two tube amps of the same model than to compare a real amp and a digital copy. Not even the owners of the amps were possible to identify their own amp. Everybody tried a few tricks and then honestly admitted that they were not able to identify the Kemper and all they could do was guessing.

    I would have been sure that the interaction between the head and the cab would give the Kemper away - especially the feedback, but apparently that was not the case. I'm not good enough with electric guitar to try for myself and no one thought of modeling a bass amp, so I can't comment on that - but I cannot imagine why this should not yield identical results.
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    IME, the results can be impressive, the drawback being that the user interface is more challenging than what many players (so far) are willing to navigate.
     
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  10. Wasnex

    Wasnex

    Dec 25, 2011
    I think something will always be lost in the duplication process. It's sort like the old Sci Fi theme that pops up in regards to clones. Clones can only replicate so many times before the process fails because of degradation in the replication process. (I.E. the DNA is not copied perfectly). IMHO, part of the variance you are hearing is likely due to the microphone, air, cables, electronics other than the guitars amp, etc.
     
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  11. Phaidrus

    Phaidrus

    Oct 25, 2009
    Something like what happened in

    Blade-Runner-8-1.jpg
     
  12. spatters

    spatters

    Mar 25, 2002
    This, of course, is why modeling amps are generally used with FRFR speakers or IEMs. By turning the speaker simulation on, you allow the modeler to simulate that feedback loop between output stage > transformer > guitar speaker.

    The implication here is that, with a high-end modeler like a Kemper that actually simulates those interactions, you'll produce a more accurate sound with the built-in cabinet emulation, plus FRFR or IEMs, than you would if you used a "real" guitar or bass cabinet!

    In contrast, a lower-end and less sophisticated modeler doesn't have any feedback between the output stage and the speaker model, and often the "speaker model" is just an EQ curve. In this case, a real guitar or bass cabinet would likely be an improvement.

    There's even more magic in digital emulation than there is in analog amp tech. And, since you can't see the code like you can see analog parts, it's very difficult to figure out what's happening under the hood.
     
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  13. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

    Jun 12, 2008
    That ain't no magic. That's math.
     
  14. spatters

    spatters

    Mar 25, 2002
    Absolutely! It's magic from the point of view of the player, though, even the sophisticated player...because of the black-box nature of digital signal processing.
     
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  15. ClusterFlux

    ClusterFlux Supporting Member

    Apr 11, 2018
    No. There is no magic. Where would it come from, anyway? Are vacuum tubes made by leprechauns?

    The super-realistic digital stuff is not cheap, but even a sub-$100 multi-FX unit or a bunch of plugins for your home recording setup can produce astoundingly good tones these days.

    If you're playing live, then unless you are playing on stage with high-end acts (how many Dumble amps does Santana have again? ;) ), most venues are going to have such crappy acoustics and/or drunken patrons and/or sound engineers who are too lax or busy or just unfamiliar with your tone, that the nuances of "real tube vs emulator" cannot possibly be discerned.

    Studio is a bit different. However, if you walk into a really good studio, they're likely to have whatever you need. Even there, though, I have a feeling that for bass, they're probably just going to have you go direct and tweak the sound in post.

    Y'know, get what you enjoy, but... Yeah, I don't think you are missing anything vital with solid state or digital emulation.
     
  16. Phaidrus

    Phaidrus

    Oct 25, 2009
    No, vacuum tubes (valves, for that matter) are not made by leprechauns, but some say they live in them.
     
  17. Wasnex

    Wasnex

    Dec 25, 2011
    I always thought the were powered by littler fairies fluttering around ;).

    ?q=tbn:ANd9GcRdm1O8KWZdSJEWrMPhhZytQ-JFZeNXbfcsTqECa_U9Lu9FBqRSBv5sDl_4WDL_baj0P9-oqdGl&usqp=CAc.jpg

    Fairy dust bottle
    images?q=tbn:ANd9GcRJUrvwQ21ZjwLUHtCMSV-LrK8Rc2JA_s_NOvS2f7uVqHitUgWcutA5fp2XMTc&usqp=CAc.jpg
    Tube glow
    upload_2021-4-12_16-44-5.jpeg
     
  18. Phaidrus

    Phaidrus

    Oct 25, 2009
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  19. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

    Jun 12, 2008
    I always thought the magic smoke was in the big electrolytic caps...
     
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  20. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    And this can happen in the oddest places - we’d call my 70s Yamaha B100 head ‘the solid state amp that thinks it’s a tube amp’ and was by no means a high-end piece built to do that. Similarly some earlier Peavey TNT-type 1-15 combos were tubey monsters.
     
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  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 8, 2021

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