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Mystery Sano Stereophonic Amp

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  • Mystery Sano Stereophonic Amp

    Hey y’all! Does anyone recognize this model Sano? I just recapped most of the amp, sounding really great except the tremolo only works in one of the stereophonic inputs. Is that by design? Thanks!

  • #2
    I don't know that Sano even had model numbers for some of these amps, which were mostly made for accordion as far as I can tell. Seems like they are referred to mostly as Stereophonic and then by the wattage, I've seen 35 and 40 watts, often it says it on the control plate but I don't see that on yours. The amps that were labeled as Sano seem to have sometimes say "Hi Fi" in script on the speaker cloth.

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    • #3
      Originally posted by Steelwitch View Post
      Hey y’all! Does anyone recognize this model Sano? I just recapped most of the amp, sounding really great except the tremolo only works in one of the stereophonic inputs. Is that by design? Thanks!
      Sano, of Irvington NJ. As I'm sure you've figured out, not really stereo. It was intended for "stereo" accordion, with bass on one input channel - that gets no tremolo. And treble on another channel. Extra channels for the guitarist and maybe microphone. Some were equipped with output tubes that were sort of exotic. 8417 and KT77 I've found in those. But they work fine, and reliably, with a pair of 6L6GC. Output circuits I've seen are self biased, typically with a 200 ohm common cathode resistor. I usually measure around 20ish watts at clip.
      This isn't the future I signed up for.

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      • #4
        I always add a film cap to remove low frequencies from being sent to the small speaker. 5 to 10 uF works fine. If it's still working at all, the "tweeter" will last a lot longer that way.
        This isn't the future I signed up for.

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        • #5
          Originally posted by Leo_Gnardo View Post

          Sano, of Irvington NJ. As I'm sure you've figured out, not really stereo. It was intended for "stereo" accordion, with bass on one input channel - that gets no tremolo. And treble on another channel. Extra channels for the guitarist and maybe microphone. Some were equipped with output tubes that were sort of exotic. 8417 and KT77 I've found in those. But they work fine, and reliably, with a pair of 6L6GC. Output circuits I've seen are self biased, typically with a 200 ohm common cathode resistor. I usually measure around 20ish watts at clip.
          this all checks out! Thanks Leo, there are currently EL34’s installed. Sounds really nice! Is there a reasonable way of getting tremolo to work in all channels? I actually just noticed that the 8” speaker isn’t working at all.

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          • #6
            Originally posted by Steelwitch View Post

            this all checks out! Thanks Leo, there are currently EL34’s installed. Sounds really nice! Is there a reasonable way of getting tremolo to work in all channels? I actually just noticed that the 8” speaker isn’t working at all.
            Not much surprise on the 8". I'd swap in a Jensen MOD, inexpensive and perfectly adequate.

            I never attempted adding trem to the bass channel on any of the dozen or so I've worked on. Plenty of other channels for that.

            EL34 could work in there I'm sure - apparently they are in yours. Double check to make sure pin 1 - suppressor grid - is either at ground (best) or tied to cathode (2nd best but acceptable for this use I'm sure.) It's possible yours was originally equipped with KT77 and someone swapped in EL34 assuming they were totally equivalent. About as equivalent as a tetrode can be to a pentode...

            From observation it seems to me Sano was part of the New Jersey amplifier brain trust. Some resemblance to Ampeg (Linden) and Danelectro (Neptune). Some old Guild branded amps too. One day @ 1969 walking near the Woolworth's in Irvington, I ran across a re-purposed fire house on a side street, with a small sign out front: SANO. A further search shows they once occupied a building that straddles the Irvington/Union city line. Imagine walking in the front door from Irvington, and the loading dock out back is in Union. Or was it vice versa?
            This isn't the future I signed up for.

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            • #7
              You could rewire the inputs so it runs through both channels if you want.

              I've actually had a few of these in over the years, you could do a lot if wanted.
              Attached Files

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              • #8
                This amp seems to have some other problems, while trying to track down the source of some hiss I pulled V1 and the rectifier tube shorted out and fuse blown. Is this indicative of some kind of other power supply issue? I didn’t think one would cause the other.

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                • #9
                  Back to the tremolo too, I’m having an issue where the speaker is oscillating but not the dry signal.. this amp is kind of hard for me to follow without a schematic. I’m also seeing 120hz hum when I ground my scope to the chassis, but I initially assumed it was a ground loop. Not sure! Very confused by amps lol.

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                  • #10
                    Originally posted by Steelwitch View Post
                    having an issue where the speaker is oscillating but not the dry signal.
                    What does this mean?

                    How do you notice the oscillation?

                    - Own Opinions Only -

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                    • #11
                      Originally posted by Helmholtz View Post

                      What does this mean?

                      How do you notice the oscillation?
                      the speaker cone is thumping with the speed and gain control for the tremolo.. I can hear the tremolo, but it’s only affecting the hiss coming from the preamp, not the dry signal.

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                      • #12
                        Originally posted by Steelwitch View Post

                        the speaker cone is thumping with the speed and gain control for the tremolo.. I can hear the tremolo, but it’s only affecting the hiss coming from the preamp, not the dry signal.
                        Ok, so it's not parasitic HF oscillation but tremolo LFO signal getting to speaker output.
                        Reason might be unbalanced power tubes or one tube not operating properly.

                        Check tube idle currents with a bias probe or using the OT primary DCR method.
                        - Own Opinions Only -

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