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A "New" '67 Solarus combo and a lot of questions.

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  • #31
    I use a 100mv sine wave signal @ 1K.

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    • #32
      ..input signal voltage

      Originally posted by Jazz P Bass View Post
      I use a 100mv sine wave signal @ 1K.
      I've been using 150 mV which is the majority line level of the SS stuff I've been working on. But guitar signal signal voltage being all over the place has made me ask the question. I'm doing some reading right now but as I think about the question posed I'm kind of feeling like it doesn't matter that much. My Signal generator will only go down to 0.075 mV so I've tried that, 100 mV and 150 mV but have noticed any difference in the output as far as power calculations go. The question was also in reference to following a signal through an amps stages. So now I'm reading up on the topic of individual stages, design etc. Last night I hooked the amp back up to the cab and was pleasantly surprised and impressed with the response. I'm immensely grateful to all who've helped so far . What I noticed was very good signal and output but a little bit more noise than I'd expect. Which may be because I'm in a garage or may be due to a poor internal ground, a poor pot or otherwise poor component I believe. It may just be the way it is. Either way I intend to at least try to iron things out just a bit more. So,.. back to the books for a minute.
      Thanks again for your input,
      -Mark>
      Last edited by aavatech1; 06-24-2018, 04:31 AM.

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      • #33
        For test purposes this is what I use.
        Generally speaking:
        - Mic input: 5 mv's
        - Standard guitar input: 100Mv's
        - Active guitar input: 150-200 mv's
        - Power amplifier: 1-2 volts

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        • #34
          Originally posted by aavatech1 View Post
          The new dummy load arrived today and I decided to use the digital scope-meter instead of the Tektronix as it provides an RMS reading of AC signals. The results are displayed below. From the "Speaker" jack (16 ohm winding) I'm getting 16.30 VAC before clipping into an 8 ohm (200W) load. Then using the correct formula: (16.30^2=265.69) / 16 = 16.6 W (pic 1) Then at full volume max RMS voltage is (17.6^2=309.6) / 16 = 19.35 W (pic 2) Then from the "External" speaker jack (8 Ohm winding) 17.00 VAC (17.00^2 = 289) / 8 = 36.12 W Then at max volume: 19.2 VAC. (19.2^ = 368.64) / 8 = 46.08 W
          You must use the actual load resistor value for your calculations, not the impedance tap.
          A redo with 8 ohm used for the first numbers gives similar results to the second set of numbers. This surprises me a bit as I would expect more discrepancy between the 2 taps as far as power output goes.
          Otherwise, the power output still seems weak to me, maybe Loudthud or soundmasterg could comment as I'm not so familiar with Sunn.
          "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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          • #35
            ..math dyslexia !

            Originally posted by g1 View Post
            You must use the actual load resistor value for your calculations, not the impedance tap.
            A redo with 8 ohm used for the first numbers gives similar results to the second set of numbers. This surprises me a bit as I would expect more discrepancy between the 2 taps as far as power output goes. Otherwise, the power output still seems weak to me, maybe Loudthud or soundmasterg could comment as I'm not so familiar with Sunn.
            Jazz,
            Another good catch. Thank you very much. Believe it or not I actually did it right the first time and then looked at it and changed it to the incorrect calculation I posted. (..for heaven's sake!) And that given; I see what you're saying. I've got it back on the bench right now.. Last night I pulled out a classic amp book! I like this one.
            More to follow...

            Thanks again,
            -Mark> (Math dyslexic)
            Click image for larger version

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            Last edited by aavatech1; 06-24-2018, 08:53 PM.

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            • #36
              Test Test Test

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              • #37
                Greetings,
                The new 8 Ohm dummy load arrived and that's a "load" off my mind! (..sorry, couldn't resist! ack, there I go again)
                Anway, "soundmasterg" has been so kind as to instruct me on another method of measuring the output of the Solarus without interference from the pre-amp and tone stack stages. First, I've run a Sine wave (150 mV) directly from a signal generator firstly into: the front jack (for reference), then the signal was applied to the Triode grid of the 7199 (with the Pentode section separated) large enough to drive the output section to it's clean signal maximum and finally the signal directly applied to the Pentode grid with the Triode re-connected and the output section driven to it's clean signal maximum. It took/takes a bit larger voltage to drive the output section when applying a signal directly to the cathode so an HP model 200 Audio Oscillator was used.
                I've included images of the measurements taken with a scope-meter that displays 2 channels, both set for VAC (RMS) and DC. The output from the amplifier is displayed on Channel "A" (top left) of the meter in all images. The applied signal's voltages are displayed on the meter's Channel "B" (right) in all images. Signal input voltages were taken from Pin 9 (Triode) and Pin 7 (Pentode) respectively.
                Testing and tracing a signal through a tube amp in this way is rather new to me and soon I plan to follow a signal from stage to stage and test for other characteristics of properly or improperly functioning stages. I'll be posting those results as well. But for now the results of the 7199 input jack, cathode and pentode signal injection.

                Any and all observations and thoughts are appreciated. Meanwhile I'll be studying more.
                Regards,
                -Mark>

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                Last edited by aavatech1; 07-01-2018, 10:53 PM.

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