AMI K200 jukebox add Raspberry Pi - UK Vintage Radio Repair and Restoration Discussion Forum

Don_Zalmrol · 27th May 2017, 2:57 pm

Hi all,

I'm look into adding my raspberry pi that is running pi musicbox to my AMI K200 Jukebox.

I have two inputs, one on the main amplifier and one on the add-on amplifier.
The one on the add-on amplifier is connected with the record player.

The main amp has one free input. But when I connect the raspi to it, no sound is audible. When you play a record, decouple the record player, you can hear sound, but it's the wrong signal*.
So this leaves me to believe that both inputs go through the mute-relay.

I have not yet looked at the amplifier circuit itself, so it could be that the mute relay has a normal open and normal closed connection.

So I was thinking of going that direction. This way I can play music from the raspi and when someone selects a record, the raspi stops.

Before I go mucking about, I wanted to see if nobody here did something similar or has some pointers that could be helpful.

Thanks!

* I still need to bring it down to a phono signal (so I need to build an inverted RIAA)

julie_m · 28th May 2017, 11:07 am

I'd inject the Rπ signal downstream of the muting relay and RIAA preamp.

Note that on some AMI models, one channel had its signal and earth leads swapped at the cartridge, and a third speaker wired between the two channel outputs; the unilateral inversion led to this receiving the sum, rather than the difference of the two signals. If yours is like this, you will need to add an op-amp to invert the signal in one channel.

You can use an opto-isolator connected to a GPIO pin to detect a voltage somewhere in the juke box electronics, so the Rπ can silence itself when a real record is played. If your juke box already has a selection receiver installed, you might even be able to control the juke box from the Raspberry Pi!

Don_Zalmrol · 29th May 2017, 7:33 pm

Thanks Julie.

I will look at the downstream option.
Who knows there could be an NC contact I can use, would be even better

The AMI K200 is from the 60's. So the cartridge L and R are simply placed together. Nothing special so far I can see.

Reminds that I need to place a 1K resistor between both connections!
Unless that is not necessary in a phono connection?

Great idea about the selector.

It has a two-dial selector system with the first one that does the letters A->K and numbers 1-20.

Not quite sure how I could make this work, perhaps with a multiplexer?
But that would be a different project.

First I need to be able to hookup my rapsi to my juke.

Thx!

27th May 2017, 2:57 pm	#1
Don_Zalmrol Hexode Join Date: May 2009 Location: Ghent, Belgium Posts: 273	AMI K200 jukebox add Raspberry Pi Hi all, I'm look into adding my raspberry pi that is running pi musicbox to my AMI K200 Jukebox. I have two inputs, one on the main amplifier and one on the add-on amplifier. The one on the add-on amplifier is connected with the record player. The main amp has one free input. But when I connect the raspi to it, no sound is audible. When you play a record, decouple the record player, you can hear sound, but it's the wrong signal. So this leaves me to believe that both inputs go through the mute-relay. I have not yet looked at the amplifier circuit itself, so it could be that the mute relay has a normal open and normal closed connection. So I was thinking of going that direction. This way I can play music from the raspi and when someone selects a record, the raspi stops. Before I go mucking about, I wanted to see if nobody here did something similar or has some pointers that could be helpful. Thanks! I still need to bring it down to a phono signal (so I need to build an inverted RIAA)

28th May 2017, 11:07 am	#2
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: AMI K200 jukebox add Raspberry Pi I'd inject the Rπ signal downstream of the muting relay and RIAA preamp. Note that on some AMI models, one channel had its signal and earth leads swapped at the cartridge, and a third speaker wired between the two channel outputs; the unilateral inversion led to this receiving the sum, rather than the difference of the two signals. If yours is like this, you will need to add an op-amp to invert the signal in one channel. You can use an opto-isolator connected to a GPIO pin to detect a voltage somewhere in the juke box electronics, so the Rπ can silence itself when a real record is played. If your juke box already has a selection receiver installed, you might even be able to control the juke box from the Raspberry Pi! __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

29th May 2017, 7:33 pm	#3
Don_Zalmrol Hexode Join Date: May 2009 Location: Ghent, Belgium Posts: 273	Re: AMI K200 jukebox add Raspberry Pi Thanks Julie. I will look at the downstream option. Who knows there could be an NC contact I can use, would be even better The AMI K200 is from the 60's. So the cartridge L and R are simply placed together. Nothing special so far I can see. Reminds that I need to place a 1K resistor between both connections! Unless that is not necessary in a phono connection? Great idea about the selector. It has a two-dial selector system with the first one that does the letters A->K and numbers 1-20. Not quite sure how I could make this work, perhaps with a multiplexer? But that would be a different project. First I need to be able to hookup my rapsi to my juke. Thx!