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Problem with noise using a 65amps Ventura

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  • #16
    Haven't listened to your video yet, but I already found a problem with the 4 cable method which in my eyes explain why you have problems with "65" and not with the others ... and it's not a "65 defect" or at least there's nothing "broken" but a level/impedance matching one.
    Here's the rub:
    The Line 6 POD HD500x which i originally was using has a line level/stomp signal switch for the fx loop. I have in line level and putting to stomp increases noise more.
    If you had a bunch of separate pedals and rack effects, you would use pedal distortions at plain guitar levels at preamp input, and space/ambience ones at amp loop at line levels ... everybody happy.

    But here you can select POD loop level either guitar/floor pedal level or line level .... the small detail is that you are selecting both POD loop level send and return at the same time.

    BUT the 65 preamp has guitar level input and line level loop send/receive .

    So if you select POD loop floor pedal levels, the 65 preamp will get the proper signal at its input but the output present at 65 loop send is way too high for the POD (remember, that loop was set for floor pedal levels) , very probably that strong preamp out level will be noisy ; while if you select POD loop line level, now the 65 preamp will receive a too strong signal at its input, catching any and all noises coming from POD (and exaggerating any Guitar noise).

    The only way to solve that is that in any future POD model, they let you work with the distortions at floor pedal level and the ambience ones at line level set independently.

    So far you can't do that.

    And why doesn't this happen with the other amps?

    Modern amps which use tubes but also carry a lot of silicon inside, generally for "auxiliary" jobs such as loop or reverb, for that very same reason use "mild" loops, relatively close to floor pedals so POD is not stressed to cope, but a "Purist/Classic/Vintage" design such as 65, which abhors silicon, often does not have a real loop send/return but they simply cut some signal wire (often preamp out to power amp PI in) and add a couple jacks.

    Problem is , such a method runs at high impedance, both send and receive and high voltage levels.

    They call that "line levels" but are often higher.

    A typical Line level would be "0 dB" 0.775V or "1 dB V" 1V , while you can have higher voltages at PI inputs, specially if the power amp has NFB .

    The typical Fender NFB network is 820:100 meaning it has just 8X gain meaning it needs a STRONG signal to drive it.

    Many amps cut that line and call it a Loop ... I don't much agree with that.

    -----------------------------------------------------------

    IN A NUTSHELL: the POD loop treats the 65 preamp as an external effect (the Boss explanation says exactly that and it applies to others), big problem is that most effects are either floor pedal level in and out or line level in and out, while the 65 Preamp (and 95%b plain preamps out there) is
    * floor pedal input (it expects a guitar straight in)
    * line level output (it expects to drive a power amp)
    so
    * no switch setting will make both levels happy.

    Now, guitar multi-effects units generally come with effects of both types. This poses a problem, since you want some of the effects before the preamp and some of them after it. To solve this problem, one can (ab)use the effects loop of the unit by connecting the cables as follows:
    Notice that they recognize it's a klunky way to do things, that's why they call it (ab)use

    This way, the amp's preamp effectively becomes an external effect for the unit so that you can place some effects before it and some effects after it using the effects ordering functions of the effects unit. This is called the four cable method.
    ------------------------------------------------


    Seeing it in another way: the point behind ancient design "purist" amps such as this 65 (c'mon, : EF86 preamp, 3 knobs, it screams 1950's ) is to straight plug a guitar in it and wail away .

    -----------------------------------------------------------

    Seeing it in yet another way:

    use the POD as your full front end, even for "plain - non effect sounds" , get trigger happy with all emulations, plug its output into 65 loop return and use it as a honest 20W tube power amp to smooth POD's "digitalness" ... whatever that means.

    Not a bad combination and I bet you won't have hum problems that way.
    Last edited by J M Fahey; 02-19-2015, 07:42 AM. Reason: Quoted external explanations
    Juan Manuel Fahey

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