Voice of Music VM 804 Console / 1223 Turntable / 20037 Amp Rehab

[sruncorn]

Hey All,

I picked up the VM 804 console a few years back from Audio Archaeology in Chicago (https://www.audioarchaeology.com/vintage-audio) as a gift for my wife.

I fully expected that it wouldn't work and I'd have to do some work on it, but I was pleasantly surprised to find out that it played records and sounded pretty good when it arrived! The only issue was that the speed of the platter would intermittently vary, annoying but my wife thought it gave it some character... I did not.

So I found Gary Stork at V-M Audio Enthusiasts in Michigan (https://www.thevoiceofmusic.com/) and he hooked me up with a replacement idler wheel and all of the instructions, manuals, and schematics to fully refurbish the turntable which I did and now it sounds terrific!

I haven't done anything with the built-in 20037 amp, it seems fine, though I have ordered some replacement tubes from The Tube Store in Canada (https://www.thetubestore.com/) to try to see if it improves the sound at all.

Oh, and I have it plugged in to power through a Tripp-Lite isolating transformer which has helped the unit produce a cleaner sound.

My question is this, I'd like to split the audio that is coming out of the turntable so that it still goes to the internal 20037 amp but so I can also route it to my modern Sony stereo amplifier to get the audio into the main room of the house.

There are 2 RCA type connectors for L and R on the underside of the turntable and I have connected 2 RCA Y-adapters (1 male to 2 female) to the turntable. I reconnected the RCA wires to the amp and that all works fine.

The problem comes when I connect anything to the other pair of split L and R wires, the VM 804 speakers start buzzing really loudly and no sound gets to the Sony amp.

I have assumed that I'll need a phono pre-amp for the audio coming out of the turntable but those usually require a ground wire from the turntable to the pre-amp and the 1223 turntable does not have a ground wire or even a ground wire connector that I've been able to find on the unit.

Anyway, obviously I am not an expert on any of this (I only know enough about reading an electrical diagram to get myself into trouble, ha!), so I'm reaching out to the smarter folks here to see if what I am trying to do is even possible, and if so, how I might be able to do it.

Thanks in advance to anyone that wants to chime in on this!

 

[cademan]

Welcome!

You don't need a phono preamp as that VOM turntable has a ceramic cartridge which is like line level.

The Y adapter thing should work but it sounds like you could be having ground loop issues. Be sure to connect the turntable from the VOM to the Sony's AUX or tape inputs but not the phono input as the Sony most likely has a built in phono stage for magnetic cartridge turntables.

If it were mine, I would construct some kind of jack panel with switches so you could switch between the VOM and the external connections to any other receiver/amp of your choice.

These things can be done and are being done all the time especially when multiple receivers, amps, turntables and speakers are being used.

 

[sruncorn]

Thanks for the quick response cademan, much appreciated!

I had suspected a grounding/ground loop issue, can you elaborate on a possible fix for this or point me to some further info that is relevant to the VOM (or similar) gear? I'm having trouble finding useful info on such vintage gear.

As for the jack panel idea, I like that idea a lot! I am assuming that would involve modifying the 20037 amp circuitry, any guidance on how to proceed with that?

Sorry for my novice status on all of this, I was so proud of myself in getting the turntable working so well, I may have gotten "out over my skis" a bit on this bonus round of modification, ha!

 

[cademan]

As for the jack panel idea, I like that idea a lot! I am assuming that would involve modifying the 20037 amp circuitry, any guidance on how to proceed with that?

No need to modify anything. Just plug in some Y's to the turntables RCA's and then run one pair to the amp and the other pair to a panel in the back which would contain female RCA jacks and maybe a switch to either turn the turntables RCA's on or off, or internal or external only.

Assuming that you only get that hum when the volume on the VOM is turned up but no hum when turned down, this would indicate a ground loop so maybe try turning the plug around at the wall socket to the VOM??

Also try only one RCA cord at a time to rule out a possible broken ground wire in cheap RCA cords.

 

[sruncorn]

Thanks for this additional info, I'll be working on this again over the weekend and report back!