by Rob-NYC »
Tue Dec 27, 2011 11:56 am
If your goal is to use the existing amp and speakers -have you determined that the amp works correctly and given it's age has it been serviced? If the machine is not operative you can still test the amp by connecting a turntable with magnetic cart and hooking up the machine speakers. You will need to remove the muting plug in order to have sound.
The basics of doing what you want are:
1) Either building a simple adapter to reduce bass from the PC to match the phono input on the amp...Or modifying the amp for an input after the preamp stage.
2) Build/buy a sound activated switch. These come with a general purpose relay that is needed here to switch the juke amp's mute/squelch relay. Juke amps have an automatic gain control to keep the records all at the same relative level. Part of this circuit includes a squelch function so that after a period of silence the agc doesn't come all the way to full gain and thus blast for a few seconds when music starts. this function is in the mute relay's circuit and all that is externally needed is a set of contacts that close after the last track has played and open at first notes of a track.
There is no practical way of muting/squelching between songs as there would be normally with a mech playing records so you'll need to see if your PC program provides a fade-in or crossfade so that there is never silence for more than a few seconds or too quick a change in level between tracks.
IF the PC player has a smooth fade-up function it -may- be possible to eliminate the sound switch and just have the music fade up while the agc gets a chance to level it.
There is obviously more involved here, but these are what is basically needed for what you want to do.
Rob/NYC
"If we believe absurdities, we shall commit atrocities" -- Voltaire