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A little thing I'm wondering about EQ sections

Discussion in 'The Workbench' started by jensbrix, May 15, 2012.

  1. jensbrix

    jensbrix Active Member

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    Why is it that some people often says that "X amp is responding much more to the EQ than Y" and such, when like 90% of all the Marshall have the same values in the EQ section. Like, why is many people EQing a DSL or a JVM much different from 2203s and 1959s when it's the same EQ values? In my head they should respond the same to the EQ, but for some reasons they don't, is it because of the gainstages or the impedances or ?

    Very confused as you can hear :)
     
  2. Söulcaster

    Söulcaster Well-Known Member VIP Member

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    I'm not sure why, it just is. My AFD has the most responsive EQ of any Marshall I've owned. And change the EQ on one and it affects the EQ on another, it's gr8....

    Sure there is a technical reason but, I'm not a technical person.

    Peace
     
  3. Micky

    Micky Well-Known Member VIP Member

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    It has a lot to do with the total of all that is connected.
    Your guitar is the biggest variable, what works for you and your guitar might not be the same for someone else. Speakers, room ambiance and a lot of other stuff also contributes...
     
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  4. jensbrix

    jensbrix Active Member

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    Yes I'm completely aware of that, but I've heard people say that fx the tone of a DSL changes alot more when twisting the EQ knobs, then the tone of a 2203, but basically the schematic of the 2 EQs are almost the same
     
  5. Ken

    Ken Well-Known Member

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    When you say "values" you mean the pot resistance I assume. But it's the circuit design that matters. It's a fact that the JVM and DSL EQ (for example) have a much greater effect on tone than a 900 or 800 series EQ. That's just the way they were designed. So you use them differently, as has been discussed.

    Ken
     
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  6. jensbrix

    jensbrix Active Member

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    The circuit design is the same also (as far as I can tell)
     
  7. Ken

    Ken Well-Known Member

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    Well, a real tech should chime in but the 4100 and DSL's EQ section looks completely different to me after comparing the two on the Dr. Tube site...the DR uses op-amps and the DSL regular transistors (and tubes).

    Ken
     
  8. Macro

    Macro Well-Known Member

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    To expound on what Micky is saying, you could take the exact same amplifier, cabinet, and guitar....play it in one space, think one thing about the eq, then take it all to a different location with different acoustics and have a totally different experience.

    Unless you are sampling the output with a spectrum analyzer, I am assuming that we are talking about peoples opinions that they form when listening to their sound. Gear sounds different in different places. Now factor in that not only are the people you see commenting on this in different places...they are using different types of gear, have very different signal paths, and introduce all kinds of unknown and independent variables to the experiment.

    EQ's are a function of their environment, and the way in which we percieve sound is purely subjective...and quite dynamic. I would venture to guess that if you took the same circuits and sampled them in the same room, using the same connections, same guitar, etc...a spectrum analyzer would show very similar results in the output. Still, two people sitting in front of the sound could have very different opinions regarding how much impact the EQ knobs were making to the tone.

    Consider your baseline :)
     
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  9. jensbrix

    jensbrix Active Member

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    Ken: cant speak for the 4100, but its a very odd marshall too, so aint taking that into consideration.

    Okay guys i get your point. But one should think, that if he was the owner of 2 heads, and compared the same place, same cab, etc, and would still say one made bigger impact than another. Thats what i dont get, because the eq is just a mathematic equation, and should act the same in 2 amps with same values. Its puzzling me why people still claim one to make bigger difference
     
  10. SmokeyDopey

    SmokeyDopey Well-Known Member VIP Member

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    Tech question for who ever can answer it:

    An EQ knob... If we want to "bypass it", to pretend it's not even on the panel, should it have to be put it on 10, or put it halfway?

    Meaning the "5" position would be like ZERO (0), and when rolling left (7 o clock) it goes -5, and when rolling it to the right (5 o clock), it goes to +5.
    Does this make sense?


    Edit- Some grammatical issues there.
     
  11. Ken

    Ken Well-Known Member

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    Yes, this is exactly it.

    Old Marshalls have the EQ just cut tone, so everything on 10 is "no EQ". To do that on a DSL, put everything at 5.

    While the point about room acoustics is well taken, the DSL EQ is NOTHING like the 4100's to my ears as far as how much even 1-2 notches higher or lower effects the tone.

    Ken
     
  12. jensbrix

    jensbrix Active Member

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    If we want to bypass the EQ section of a Marshall as much as possible, you'd have to put everything on 10. This is still far from a bypass though, which is not possible.

    The middle position meaning bypass applies pretty much for EQ pedals that use active circuits to control the tone. However, the circuit in any Marshall i think is passive, and no matter what it will take some signal, depending on the settings it will rob more signal of certain frequencies.

    Dude, you have no idea what you're talking about. Please don't tell people this when it's absolute nonsense. The tone circuit in "an old Marshall" and a DSL is almost the same, and reacts almost the same way. Putting everything at 5 on a DSL doesn't at all mean that you're bypassing. Neither does it to put everything on 10. You should learn some electronics and learn how to read schematics before answering questions with these statements
     
  13. jensbrix

    jensbrix Active Member

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    Also, please tell me how it is a "fact" that a JVM or DSL EQ has greater effect on tone than a 900 or 800.
     
  14. Ken

    Ken Well-Known Member

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    You are of course correct; to remove the EQ you need to do some surgery.

    But to MY ears a 900 on 10 is as "natural" as it gets (NOT counting the presence of course; that needs to be on zero) while on a DSL it's on 5. My ears stand behind that simplification.

    I can read a schematic, and I compared both before posting. While the circuits might perform the same function, they seem to do it with different components and with very different sonic results.

    Ken
     
    Last edited: May 15, 2012
  15. jensbrix

    jensbrix Active Member

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    I don't believe that small differents in components does the difference.

    And what is as "natural" as it gets? Have you ever heard the amp with the EQ section bypassed (either your DSL or 900) ? The "bypassed" EQ should then sound exactly the same as the true bypassed circuit in the amp?

    When i look at my tone stack calculator, no matter how much i crank the mid knob (or anything else for that sake) the mids are always cut more than the rest of the spectrum. So i don't think you get "natural" sound from putting all on 5.

    I have one idea about why quite a few guys EQ their JVMs (probably also DSLs) with EQ pots from like 0-3. The EQ pots respond much more drastically in relation to each other in these low settings, BUT you also sacrifice quite alot gain. While you have plenty of gain on tap in a DSL or JVM, you don't have that much gain in say a 2203 - so you're kinda "forced" to put the EQ knobs higher, to lower the loss of gain. Therefore, the EQ knobs doesnt change the tone as drastic at high settings, as they do at low settings.

    I honestly don't believe that there's magic happening in the EQ section, which is why I think it's wrong when people says that one amp makes bigger EQ changes than another. Because they don't mathematically (and I've studied math lol :fingersx: ) I think the reasons are to find another place in the amp, and this is what puzzles me
     
  16. Ken

    Ken Well-Known Member

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    Good point about the older Marshalls needing EQ for gain. The DSL responds much better (IMHO) with lower EQ settings than higher, and with the mega gain the amp has available this makes sense. No one runs the bass at 10 on a DSL but on an 800 that's not uncommon. (On an 800 if I can play loud, I have bass on 10, mids on 5, treble on 10 and presence 5. At least to start out.)

    I agree Marshall EQ isn't rocket science, and if the 800 series and DSL series have the same EQ response I'm amazed, because there's no way a DSL sounds as good as an 800 when you dime everything.

    As for "natural" sound, the mid scoop you noticed is part of the Marshall sound as per the designers I suspect. Mid scoop is traditional metal; the scoop button on the DSL is far less popular than the designers imagined I suspect however, because it seems to just cut out frequencies. It records really well but is underwhelming live IMHO.

    Back to your original question, I'm confused now. I agreed with you that the DSL has a different sound in the EQ than an 800, and I attributed it to design. You said no, the design is not different enough to account for it. But the gain EQ adds makes it a better fit for for a lower gain amp like an 800 than a higher gain amp like a DSL. So you answered your own question!

    Ken
     
  17. Macro

    Macro Well-Known Member

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    If you have a DVM and a few potentiometers (of the same value) sitting around, try this...

    Take all the pots...check the resistance at fully closed and fully open to ensure that they even have the same terminal measurements. Assuming they do, now rotate all of the knobs to the halfway position. Dial them in as closely as you can....all of them should have been adjusted equally. Now measure them again. Are they all showing the exact same resistance?

    If you are lucky and have extremely precise and synchronized pots, maybe they are close. More likely, they are a few kOhms off....at least. That affects the filter.

    Also consider the filter circuits themselves.....(capacitors and inductors)
    As they heat and cool, their values change. Different amps have components in different places....some closer to tubes and transformers (hot), some further away with sufficient airflow to cool them. That all biases the EQ adjustments....even though its the same schematic on paper....in the chassis, with a few hundred degrees of ambient heat, and very different airflow patterns, you will get variations.

    Ok, I am splitting hairs here...but these are the things that contribute to differences...and its also the reason why boutique electronics break the bank. It takes an engineer to design the circuit, but it really takes an artist to lay it out in a way that promotes the design. This is what system architecture is all about....and it isnt cheap :)
     
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  18. jensbrix

    jensbrix Active Member

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    Well, if the difference in pot values is making the difference in the EQ response, there should be difference between two 2203s as there are difference between a 2203 and DSL
     
  19. Macro

    Macro Well-Known Member

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    True.

    My point is that there are all kinds of variables involved.

    The only way to properly validate it (in my mind anyway) would be to use a function generator to produce a constant tone and feed it to the input of two amps that have the same schematic design (but sound differently to the ear). Using an oscilloscope with two inputs, start tracing the circuits on both amps simultaneouly. Theorhetically, if the design of signal path is the same, the output waveforms will match. Continue to trace the signal to see where the variance is presented....then move the reference point to there and continue to trace to see if further deviation along the signal path occurs.

    Granted, this is a lot of work to validate an answer to your question, but it will absolutely produce an answer that is backed by direct observation. I dont have a scope or a second amp that is of similar design, but if anyone wants to lend me both I will gladly perform the experiment :)
     
  20. jensbrix

    jensbrix Active Member

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    Okay, so we kind of agree I guess :) The things is, I've heard those rumors so often, that I wanted to know if it was other parts of the amp that made an impact on the EQ, because I don't think that one amp responds more than another.
     

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