Fender HRD - Preamp Out and Power Amp In Jacks

Discussion in 'Amps and Cabs' started by Slideman, Nov 25, 2007.

  1. Slideman

    Slideman Supporting Member

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    I'm not too astute on daisy chaining amps or working two amps in combination... so I need a little help or clarity on how this works.

    Is the Preamp Out jack used to daisy chain another amp and controlling the preamp section of the other amp? Are the controls interactive on both amps or just the one that's chained to the second?

    Is the Power Amp In jack used to connect the preamp of another amp to the HRD? For example if I used my Pro Junior and connected it to the Power Amp In Jack, will my Pro's preamp now/solely be running through the HRD?

    thanks for any input.
     
  2. blackba

    blackba Member

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    You can use these an effects loop, use the preamp out into the pedal or effects processor and the power amp in on the return of the pedals or effects processor.

    The preamp out can also go to a power amp in or power amp of another amp for more power/different options. The power amp in would be for connecting another preamp into the HRD.

    If you connector your pro juniors preamp out to the power amp in of the HRD you will have both the HRD and Pro junior working, only think you are bypassing is the HRD's preamp. Please keep in mind tube amps need a speaker load at all times....
     
  3. Slideman

    Slideman Supporting Member

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    blackba,

    OK -- so for my Pro Junior, I unhook the internal speaker, connect a speaker cable, and then run it to the power amp in of the HRD? Thanks for the help.
     
  4. Rosewood

    Rosewood Member

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    Whoa, wait a second, the preamp out would be used to drive an effect or power amp in on another amp, or say preamp out to the guitar input of the pro junior. The problem with pre out driving guitar input is noise and signal maybe too hot. It works best when you can go pre out to power in on a similar amp. Connect pre out to guitar input on the junior and see if the noise and gain are ok.
     
  5. Rosewood

    Rosewood Member

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    BTW, if you are trying to get the sound of the pro junior with more power you could wire an L-pad to the speaker connection to pad the signal then plug into the power amp in of the HRD. Is that what you're trying to accomplish?
     
  6. Slideman

    Slideman Supporting Member

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    Rosewood,

    I wanted to try both the HRD powering the Pro (as you mentioned) and vise versa... but I would really like to try the Pro Junior preamp in the larger HRD cab just to see how the cab changes the tone and response.

    Thanks for your help.

    STeve
     
  7. blackba

    blackba Member

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    No, you don't want to unhook the speaker.

    An amp has 3 basic building blocks. I am simplifying a bit overall.

    preamp - Power amp - Speaker

    The preamp out is right before the power amp. With those 2 connection points you would use instrument cables.

    If you run the preamp out of your pro junior into your HRD, you will have both amps going, you are using the full amp of the Pro Junior and power amp and speaker sections of the HRD.


    Another thing you can do is take the speaker cable from the HRD and plug it into your pro junior (unplug the pro junior's speaker). Then turn on the pro junior and see how it sounds. Keep the HRD off in that case....
     
  8. John Phillips

    John Phillips Member

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    No, absolutely not - you'll blow the Pro Junior's output transformer if you do that. A tube amp must have a proper load (speaker or dummy load) on the speaker output at all times.

    Unfortunately the PJ does not have any other means of getting a signal out of it, so unless you buy or make a box to do it, you can't do this.

    What you would need is some sort of signal splitter with a level pad, to go between the PJ and its speaker. You could also use an attenuator as a dummy load, many of which do have line outputs which you then connect to another amp, but they're expensive.
     
  9. Slideman

    Slideman Supporting Member

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    John -- thanks for that very important fact!

    I think I just might try utilizing the Pro Junior's preamp into the HRD cabinet (by unplugging the Pro's speaker and connecting the HRD speaker to the Pro) -- since they are both 8 ohm, I assume this should be OK.
     
  10. John Phillips

    John Phillips Member

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    Yes, but that's not using the PJ's preamp, its using the whole PJ amp, including the power section.

    (Just going through a different speaker.)

    It's important to understand exactly which bits do what! :)


    FWIW, I've repaired a few tube amps over the years where someone did exactly what you first thought of, without realising what would happen :(.
     
  11. blackba

    blackba Member

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    You can connect the HRD speaker to the pro junior that is fine, but you will be using the pro junior's whole amp (preamp and power amp). Make sure when any amp is on it has a speaker load as John said. This is very important. Also you must use speaker cables for speaker loads.
     

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