Line voltage fluctuation ......

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by rockon1, Sep 13, 2006.

  1. rockon1

    rockon1 Member

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    So I thought my rig sounded nice today,punchy strong . I flashed on checking the voltage in the house today.Probably has nothing to do with the tone but my train of thought "hot",power,voltage..... Last time I checked it was around 116 volts. Today it is 124 volts! Almost 10 volts higher than the last time I checked. I guess I can add this to my list of "why my rig sounds different day to day" things.lol!
     
  2. brad347

    brad347 Member

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    it makes a HUGE difference.
     
  3. rockon1

    rockon1 Member

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    OK I feel a little better. Thought it might have sounded(no pun intended) crazy.
     
  4. brad347

    brad347 Member

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    Consider that Van Halen used a variac all the time in the 80s.

    voltage at the wall will affect pretty much every voltage in your amp proportionally.

    i happen to be of the belief that it's one reason why vintage amps have 'something.' They were all designed to run on 110 volts or so, and when we run them at 120-125, which is common nowadays, we are running everything in the tubes a bit hotter. This is certainly not good for tubes, but can be good for tone.

    Like Dallas amp guru Craig Wallace once told me, "everything sounds good right before it blows up."
     
  5. hasserl

    hasserl Member

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    I always record the line voltage when checking/recording voltages in the amp. It gives me a reference if I need to recheck them at a later date.
     
  6. rockon1

    rockon1 Member

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    I plugged back into the amp a few minutes ago and while it sounded good it seemed it lost a tad of punch. Maybe it was in my mind but I rechecked afterward and the voltage was down to 119.
     
  7. brad347

    brad347 Member

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    i think this is the single most overlooked factor in teh quest for electric guitar 'tone.'
     
  8. devbro

    devbro Member

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    So what's the solution for gigging? Will one of those Furman AR-15's work?
     
  9. scottl

    scottl Member

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  10. rcboals

    rcboals Supporting Member

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  11. fullerplast

    fullerplast Senior Member

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    I'll be interested to hear your thoughts Scott, once you've checked it out. The 3V regulation on paper is better than the Furman but $700 street price for the ETA is getting a bit steep. When I measured the Furman over the entire range of 95 to 140V, the output stayed between 117V and 123V with eight tap jumps at about 5V intervals. Over the more normal range of 115 to 125V, the output was generally between 118V and 122V, vs the ETA 114V to 120V spec. It could be that the actual ETA range is tighter, but you'll need to measure it.

    The sequential power up/down could be useful for effects loop equipment (power up the loop stuff before the amp), but otherwise I don't see it being used much for guitar amp applications.
     
  12. fullerplast

    fullerplast Senior Member

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    That nominal output range of 105.6V to 132V won't do much to prevent tone changes due to normal line fluctuations. It will let you get through a gig with ultra-low or ultra-high voltages, which is what you were concerned about in your previous thread. Two different goals.
     
  13. scottl

    scottl Member

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    The 114v to 120v range is when the wall is 107v to 145v. It is 117v to 120v in normal use, w/ 3v tap intervals. I think the graph is an error. THis is from the manual. The 114v -117v range is probably when the unit encounters low range input. We'll see....

    When the power switch is placed in the "ON" position, the digital voltmeter display indicates the regulated
    AC voltage supplied to the 8 black outlets. The digital voltmeter display will read between 114 volts and 121 volts
    when the incoming AC voltage is approximately 90 volts to 138 volts. The displayed value under this closely regulated
    condition by the microcomputer, will remain on and be updated as the output voltage varies within the bounds
    of 114 volts and 121 volts regardless of the variation in the input voltage.

    It also has a digital readout for output voltage and much better filtering according to my sources. And it is closer to $600 if you ask for a discount. I needed another rack unit for my GCX and Eventide. I am retiring my 1215 to the amp tweaking room... lol

    I'll have the ETA next week to try. I'll report back.

     
  14. fullerplast

    fullerplast Senior Member

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    Sounds good Scott. One thing you may want to check out is the amount of hysteresis around the tap voltage points. If you have a variac (and I'm sure you do...), set the input voltage at a threshold and compare where it switches up to the next tap, vs where it switches back down. The worst case for these types of regulators is when you wall voltage is sitting right at a threshold. In those cases, your output could actually fluctuate more than your input voltage, especially if the hystersis is not done properly.
     
  15. donnyjaguar

    donnyjaguar Member

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    Does this AC power regulator produce a true sine wave output? There's no mention of this in the documentation. If it doesn't, I wouldn't use it on vacuum tube equipment.
     
  16. landru64

    landru64 Member

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    a. where do you ask for a discount?
    b. if i read this correctly, it can still function down to 80 volts. is that right?
    c. what's better about the filtering?
     
  17. GuitarNorton

    GuitarNorton Member

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  18. fullerplast

    fullerplast Senior Member

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    That's not a regulator, it's a balanced AC power system; with the goal being a very quiet ground reference. Each leg of the AC is 60V, 180 degrees out of phase with each other. Doesn't do a thing for voltage fluctuations. You'd still need a separate regulator in front of that to handle voltage fluctuations.
     

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