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Amplify line level to post preamp level

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  • enor
    replied
    Originally posted by geldo79 View Post
    Once again, I'd like ask the question why the 8Ohm resistance in my line out box has to stay when I use a Leslie Kit. I still don't understand that point. When I use my line out box and also the Leslie Kit, I would have two dummy loads, and that will attenuate my signal. What would happen if I cut out the dummy load from my line out box? The amp would see the dummy load in the Leslie kit when set to "Echo" and that would be fine....or not? I am also wondering if the two dummy loads are responsible for the distorted signal in my case. I know that the line out box worked 100% normal and without distortion when connected to a leslie clone (without leslie kit).
    The internal amp will not see the Leslie kit at all, since you've inserted an fx loop between the line out and the Leslie kit.

    The internal amp will only "see" your line out circuit; from then on the signal will be taken care of by your external effects, and passed on to your intermediate amp/mixer. This extra amp/mixer, then, is the unit which will "see" the Leslie kit and benefit from the dummy load there.

    Leave a comment:


  • geldo79
    replied
    Once again, I'd like ask the question why the 8Ohm resistance in my line out box has to stay when I use a Leslie Kit. I still don't understand that point. When I use my line out box and also the Leslie Kit, I would have two dummy loads, and that will attenuate my signal. What would happen if I cut out the dummy load from my line out box? The amp would see the dummy load in the Leslie kit when set to "Echo" and that would be fine....or not? I am also wondering if the two dummy loads are responsible for the distorted signal in my case. I know that the line out box worked 100% normal and without distortion when connected to a leslie clone (without leslie kit).

    Leave a comment:


  • geldo79
    replied
    I tried the setup yesterday. The results were not satisfying. The signal was distorted (no leslie overdrive!), even when I reduced the output of the AO29. When selecting the internal speaker only, the sound was also distorted. What could be the reason? Using the line out without a leslie(-kit), the signal was ok.

    Leave a comment:


  • Tim_at_Jonas
    replied
    Originally posted by enor View Post
    Right. I would prefer a powered mixer to a line mixer, for the above reason.

    However - I have successfully used the ART Tube MP (a mic preamp with plenty of drive) to drive a Leslie 760, with enough "oomph".
    By preamp, I was including line level stages (as preamps tend to have one).

    When we finish the AO28 we are repairing, I'll try to measure what it takes to drive a 122 to clipping and report back.

    Leave a comment:


  • geldo79
    replied
    I will do a test today. Using the normal setup (AO29->8010->Leslie) I get a nice crunch out of the Leslie. Thus, the AO29 should be loud enough. At the moment I don't really want to
    modify my amp. If I could solve the issue without modifying anything, it would be fine.

    Leave a comment:


  • Wes
    replied
    It'll be enough to drive it loudish. MAYBE full output. MAYBE.

    If you want to drive the Leslie into deep clipping, you gotta get a real amp stage in there.

    The preamp isn't what's key; what it's key is how much of a voltage swing the outputs are capable of. +4dBu is only 1.2VRMS.

    If your AO-29 is loud enough and you just want reverb, you might be better off modifying the amp to have an effects insert if you are good that stuff. You could even add some gain that way. Look at the installation instructions for the Organmate Reverb for ideas.

    Wes

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  • geldo79
    replied
    Ok.

    Would a Yamaha MG10 be able to drive my Leslie? It's only a line mixer, but with mic. preamp.

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  • enor
    replied
    Originally posted by geldo79 View Post
    BTW is it correct that the resistor in the 8010 Kit is a 16 ohm resistor.....not 8 ohm?
    Thats what i can see in the datasheet.
    I don't know, but it makes no practical difference in this application.

    Leave a comment:


  • geldo79
    replied
    BTW is it correct that the resistor in the 8010 Kit is a 16 ohm resistor.....not 8 ohm?
    Thats what i can see in the datasheet.

    Leave a comment:


  • enor
    replied
    Originally posted by Tim_at_Jonas View Post
    I doubt that any common solid state preamp circuit would be able to handle it. My bench generator will do 9V and it will not drive a 122 anywhere close to clipping.
    Right. I would prefer a powered mixer to a line mixer, for the above reason.

    However - I have successfully used the ART Tube MP (a mic preamp with plenty of drive) to drive a Leslie 760, with enough "oomph".

    Leave a comment:


  • Tim_at_Jonas
    replied
    I doubt that any common solid state preamp circuit would be able to handle it. My bench generator will do 9V and it will not drive a 122 anywhere close to clipping.

    Leave a comment:


  • enor
    replied
    Originally posted by geldo79 View Post
    One more question: There is also a dummy load in the line out. This has to be removed anyway, or not? The Leslie kit has its own dummy load.....so i think i have to get rid of the resistor in the line out box.....??
    No, absolutely not!

    When you disconnect the organ speakers, you need a dummy load in place of the speaker as you take the signal down to line level - the one in the line out circuit.

    Then you feed this line signal to a powered mixer / guitar amp, meaning you’re once again up to ”speaker level”. Depending on how the amp is designed it _might_ be fine without a dummy load, but definitely not so if you should happen to want to use a tube amp as the extra booster after your effects. So, I would make sure to have a dummy load after the intermediate amp as well; better safe than sorry, so the dummy load in the Leslie kit stays.

    But - if you should happen to use a _preamplifier_ instead of a power amplifier as your intermediate amp, it likely won’t be able to drive the Leslie at the right level if the dummy is in place. So, with a preamp inserted, snip the 2nd dummy out.

    Leave a comment:


  • geldo79
    replied
    One more question: There is also a dummy load in the line out. This has to be removed anyway, or not? The Leslie kit has its own dummy load.....so i think i have to get rid of the resistor in the line out box.....??

    Leave a comment:


  • geldo79
    replied
    Originally posted by enor View Post
    You will have the potential to overdrive the Leslie, yes, but isn't that what you want?
    Yep!

    Think I'll give it a try. This seems to be the easiest way to integrate effects into my setup. And it has the advantage that I can EQ the signal using a mixer.

    Leave a comment:


  • enor
    replied
    Originally posted by geldo79 View Post
    Sounds good. But won't I be able to make the signal too hot? Lets say I use the "line out
    from a spinet" from the Hammond Wiki, put this is a mixer and turn up the volume
    to maximum? I am just wondering if this works in any way, or do I have to be careful?
    You will have the potential to overdrive the Leslie, yes, but isn't that what you want?

    If you use a powered mixer, use the Leslie kit "as is", including the dummy load
    If you use something else that's more of a preamp (mic preamp, mixer without power stage) you might want to disconnect the dummy load from your Leslie kit.

    Leave a comment:

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