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Thread: Diagnosis madness

  1. #1
    PenultimateTone Member Demanic's Avatar
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    Default Diagnosis madness

    Or maybe it should say "Diagnosis, madness".
    I've been trying to diagnose a problem for the last several months, to no avail. Two separate amps, one a solid state Randall and the other a tube Jet City, seem to be suffering from the same problem: a volume drop off/swell. It almost sounds like a slow tremolo effect. When I start playing, the signal sounds fine, loud and clear. Then, as I continue to play, it gradually becomes more muted. If I stop playing and start again, it goes back to full strength only to gradually mute again. I've tried different guitars, different effect setups, played directly into the amps with no effects, used different cords. I started to think that it might be the power coming out of the outlet, so I ran both the amps and the power supply for the pedals through my Furman power conditioner. Still the same problem.
    Any thoughts as to what else I can check?

  2. #2
    Super Toneologist TMD's Avatar
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    Default Re: Diagnosis madness

    That’s weird. I got nothin’.

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    A Ficus ehdwuld's Avatar
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    Default Re: Diagnosis madness

    my buddys amp did that when the speaker was under sized
    amp wanted 16 ohm
    he put in 8 ohm
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    Administrator Mincer's Avatar
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    Default Re: Diagnosis madness

    I don't know the solution, but I have experienced 2 different amps with the same issue. One was a friend's, and the other was provided backline. I don't know what the outcome turned out to be. But you're not crazy.
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    PenultimateTone Member Demanic's Avatar
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    Default Re: Diagnosis madness

    I'm fairly certain that the impedence is properly matched with both of the amps.
    And I know that I'm not crazy (at least in respect to this issue) but trying to diagnose something like this is maddening, given all the variables that need to be eliminated.

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    A Ficus ehdwuld's Avatar
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    Default Re: Diagnosis madness

    heat related with the one of the transformers overheating

    starts fine
    as you play it heats up
    resistance increases
    signal fades
    stop
    cools

    check speaker connections and maybe the cable

    are these heads and cabs or combos?

    if head and cab, same cab?
    EHD
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    Mojo's Minions
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    Default Re: Diagnosis madness

    Since, you have isolated each variable to both amps producing this issue independently, I'm going to skip the gear conjecture and go for the wild stuff -power

    You running a washer/dryer in the house around these times? are you near an industrial area? do you generally do these tests around the same time each day?

    have you measured the voltage at the socket? if it wanders heavily between 110V and 120V, it can cause the amp to draw more current when the voltage drops and less current when voltage rises... Or if it is dipping below 110V is can really start to pull hard and have dramatic tone changes.

    How does the step down transformer to your house look/sound? maybe it's at it's last breath and when you plug in an amp it

    also, long shot, but it could be your ears -human brain starts to dull the senses once incoming information is recognized, maybe with as long and as much as you play it's happening much faster.
    For me, when everything goes wrong thats when adventure starts. Yvonne Chouinard

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    Mojo's Minions Gtrjunior's Avatar
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    Default Diagnosis madness

    Very strange. If it was just the tube amp Id say the power tubes are on the way out. But since youre getting the same issue with the Randall, Im not so sure.

    I also think you may have a power issue somewhere. Either in the house or as part of the amp circuit. More likely the house, Id think.

    Try the amps on a different household circuit and see what happens.
    Also, Im sure you already did but unplug all fx and plug straight into the amps. If you have fx plugged in and the power to the fix is suspect it may cause the issue youre describing.

    Good luck.

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    Mojo's Minions dr.barlo's Avatar
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    Default Re: Diagnosis madness

    Are you getting this issue with the same cab? If so, maybe it's the speaker?

    Or... Could you measure the voltage in the power line when that happens? You'd need a multimeter and some knowledge. It's easy, but still you are gonna tap in into the main power line. If you were to see a consistent drop in Voltage, then the issue has to do with the main power in your place.

    B

  10. #10
    PenultimateTone Member Demanic's Avatar
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    Default Re: Diagnosis madness

    Two different amplifier heads into two different cabs. As I said, I believe that the impedence is properly matched for each, 1x12 cab with a 16 ohm speaker into the 16 ohm output of the Picovalve, 2x12 cab with 2 16ohm speakers wired in parallel into the 8ohm output of the Randall.
    The problem appears whether I am running through pedals or going directly into the amp. However, it only seems to occur when I'm running distortion, either with a pedal into the clean channel or in the case of the Randall the distortion channel straight in. I should mention that I use bridge pickups that are considered high output in conjunction with distortion. And it sounds normal for the first second or two of a fast palm muted run, then seems to lose volume and clarity. Then as soon as I stop and restart, the volume comes back up and then fades out. I'm starting to think that maybe the front end of the amps are compressing the signal, but it seems like this was not always the case.
    I've also considered that the power coming out of the outlet is dirty, which is why I've tried running everything through my power conditioner. A power conditioner suppose to clean up the current regardless of what comes from the outlet?
    I also considered ear fatigue, but I've been testing in short bursts of only a few minutes and my wife in a different room is able to hear the fluctuation.
    I have a third amp in the room that I'm going to try running through to see if there's any difference in response.

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    A Ficus ehdwuld's Avatar
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    Default Re: Diagnosis madness

    is there an effects loop on these amps?

    jump the effects loop with a patch cable

    I have this problem with all my amps
    EHD
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  12. #12
    Ultimate Tone Slacker
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    Default Re: Diagnosis madness

    Quote Originally Posted by Demanic View Post
    I've also considered that the power coming out of the outlet is dirty, which is why I've tried running everything through my power conditioner. A power conditioner suppose to clean up the current regardless of what comes from the outlet?
    The inexpensive power conditioners are essentially glorified power strips. Even the moderately priced ones with a voltage meter on the front aren't fantastic, but they would at least show any irregularities in power.

  13. #13
    Mojo's Minions
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    Default Re: Diagnosis madness

    Quote Originally Posted by chadd View Post
    The inexpensive power conditioners are essentially glorified power strips. Even the moderately priced ones with a voltage meter on the front aren't fantastic, but they would at least show any irregularities in power.
    That was my next question for Demanic... What are you using for conditioning? if it's just filtering without an isolation transformer conversion or AC/DC/AC isolation, it may not be cutting it.
    For me, when everything goes wrong thats when adventure starts. Yvonne Chouinard

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    LoveMachineologist jeremy's Avatar
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    Default Re: Diagnosis madness

    could be a power issue, but sound like both amps have a borderline failing component. you have other amps that done exhibit this behavior from the same outlets?

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    A Ficus ehdwuld's Avatar
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    Default Re: Diagnosis madness

    my Laney solid state would play for a bit then just stop
    there is a switch on the send jack that opens and allow the signal to re route
    through the loop
    this switch gets held open by the jack being in it all time
    or gets gunk in it
    fades away as the metal heats up
    and opens the switch

    my Belair Tube amp does it too

    all my amps with Effects loops do this

    I have all the loops bypassed with a patch cable when not in use

    Jeremy or or one of ya'll told me about this 10 years ago

    Try it

    what could it hurt
    EHD
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    PenultimateTone Member Demanic's Avatar
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    Default Re: Diagnosis madness

    The power conditioner is a Furman ML-8. Don't know if it's just a glorified power strip, though it certainly may be.
    It's also possible that it's a component in both of the amps getting ready to fail, and if so, I wish that it would just hurry up and get it over with.

    Sent from my Alcatel_5044C using Tapatalk

  17. #17
    mild old man perv Aceman's Avatar
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    Default Re: Diagnosis madness

    I was on board with a power problem until you said Furman. I'm out.
    Quote Originally Posted by Bad City
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  18. #18
    PenultimateTone Member Demanic's Avatar
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    Default Re: Diagnosis madness

    Did some more investigating today. Per advise offered, I checked the loop on the Randall. I'm running a 31 band eq in it and I noticed that the send and return volumes were both maxed, so I backed them off to 1 o clock. Bumped the master on the eq slightly to compensate.
    I also checked the power supply feeding my pedals. The junction where the wire meets the transformer was frayed and I could see copper. Replaced it with a new power supply. Ran the Randall through it's paces (with an X2N and a Metalzone) and it seemed to hold up just fine.
    Warmed up the Picovalve and gave it a check and it seemed good too.
    Hopefully it holds up. I think that the power supply was the primary issue and the fluctuation that I thought that I heard playing direct was due to the loop levels being maxed in the Randall. I'll put it down to ear fatigue playing direct into the Picovalve (no separate gain channel on that one).
    So, as it's been said, so far, so good (and yes, so what).
    Thanks to all for the assistance.

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  19. #19
    A Ficus ehdwuld's Avatar
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    Default Re: Diagnosis madness

    so it was all of the above

    sweet
    hope it works out
    EHD
    Just here surfing Guitar Pron
    RG2EX1 w/ SD hot-rodded pickups / RG4EXFM1 w/ Carvin S22j/b + FVN middle
    SR500 / Martin 000CE-1/Epiphone Hummingbird
    Epiphone Florentine with OEM Probuckers
    Ehdwuld branded Blue semi hollow custom with JB/Jazz
    Reptile Green Gibson Custom Studio / Aqua Dean Shire semi hollow with piezo
    Carvin Belair / Laney GC80A Acoustic Amp (a gift from Guitar Player Mag)
    GNX3000 (yea I'm a modeler)

  20. #20
    PenultimateTone Member Demanic's Avatar
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    Default Re: Diagnosis madness

    Quote Originally Posted by ehdwuld View Post
    so it was all of the above

    sweet
    hope it works out
    That's what makes diagnosing electrical stuff such a b#$ch. I just hope that it holds.

    Sent from my Alcatel_5044C using Tapatalk

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