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What's my best option to run a homebuilt poweramp?

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  • What's my best option to run a homebuilt poweramp?

    Okay, so I modded an old organ amp into a tube poweramp. It needs a pretty hot input signal to go. It really sings when I feed it a signal from the output of my mixer, but amplifier line out levels aren't good enough, so I sometimes connect speaker-out of solid state amps to the input and again it sings. The SS amps all give it each their own sound, as does my mixer. But, I want to use the amps and the mixer for other stuff.
    Now, I'm cheap, but I want to keep it a 'tube' setup, so I thought of buying one of those high-gain tube mic preamps (like the behringer mic-200) or maybe a Valve Junior. I think the pramp would work, but I think I might be asking for trouble connecting the VJ speaker out to the poweramp, like I did with SS amps.
    Is there an easy way to connect a speaker out from a tube amp to my poweramp, or am I better off just going with the preamp? What do you think?

  • #2
    take a look at(Google) the Firezog line out mod..My kid uses this on a 5 watt SE amp to drive a 50 watt amp. Works pretty good. Simple mod and the line out level is adjustable.

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    • #3
      Originally posted by macdillard View Post
      take a look at(Google) the Firezog line out mod..My kid uses this on a 5 watt SE amp to drive a 50 watt amp. Works pretty good. Simple mod and the line out level is adjustable.
      Yeah, that's what I'm talking about! I think it might work. I wonder, though, if the output level would be high enough, because the factory line-out on all my SS amps is not high enough to drive the poweramp, but it is on my mixer. I'm going to read more about the circuit to see if I can tell how high a level the output would be.

      It's weird because my mixer output is supposed to be line level, but drives the poweramp into light distortion, yet I can also put the speaker out from my Sunn Coleseum 300 into the input of the poweramp and it drives it about the same amount. I get equal volume control with either of them, even though one is only line level and the other is speaker level rated 300 watts @ 2ohms. Weird?

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      • #4
        Do you have a schematic for the power amp? Adding a tube input stage shouldn't be too hard if the power transformer can handle the extra heater current draw.
        -Mike

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        • #5
          Originally posted by defaced View Post
          Do you have a schematic for the power amp? Adding a tube input stage shouldn't be too hard if the power transformer can handle the extra heater current draw.
          I do have a copy of the original Hammond F40, but not with any of the changes I made.
          I thought about trying to put in some kind of a preamp section, but to tell you the truth, I'm not well experienced with this stuff and did only what I felt was within my ability. This was my first project, and I'm still trying to figuire out what I did wrong on my second project (a Hoffman AC-30) so creating a preamp section from scratch is beyond my capability. I can usually follow a schematic like a recipe, but making up the recipe myself is another story. If you have a suggestion...
          Attached Files

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          • #6
            Issue resolved (I hope)
            I happened across the echo/reverb/preamp unit that was removed from an old Schaller KV-50 amplifier for cheap. It was designed to run a tube poweramp section. And even though it's the SS version, it's still vintage 1960's and has the features I'm looking for.
            I'm hoping I can figuire out how to connect it, though. I could only find one guy with a schematic, and it's in German and he'll only accept euros. But, I'll keep looking.
            Thanks everyone, for the suggestions, and wish me luck.

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            • #7
              ...and the moral of the story is 'Ebayer Beware".

              I got the unit that was supposed to be complete with preamp/echo/reverb, and it's not much more than a faceplate and the the controls/switches. I think I'm going to try that Firezog thing, I guess.

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