Connecting mono RTR to stereo receiver (REC/PB cable)

[I968]

Hello everyone,

I would like to connect my late 1960s Grundig TK 145 deluxe mono reel to reel to my Pioneer SX-434 receiver. I want to make a cable that will connect the tape in and tape out of the receiver to the combined in/out DIN connector of the TK 145. I have read "Why not wye?" article on Rane audio site and devised a simple summing box for my cable. The receiver side will have 4 RCA jacks, the reel side must have a 3-pin DIN connector.



Will this work or is there a terrible blunder in my design? (please don't bash my head in, I am internet self-educated)

Thanks a lot for any help with this.

 

[jsg1974]

I have seen different types of Din to RCA converters, most are 5 pin din to 2 or 4 RCA, but all I have seen are stereo.
Not familiar with old mono machines , what throughs me off is using the same Din point for signal and out; I'm sure someone will come along soon.
If you had the manual to see which pins to use you could very easily make your own.

 

[I968]

Alright, I have constructed the cable (the DIN end has three pins, one for input, one for output and a common ground/shield) and it seems to be working fine except for one thing. When I plug it into the receiver, it's fine, but when I plug it into the Grundig, the volume level (and I feel sound quality too) of whatever I'm listening to on the receiver (radio, turntable, aux in) drops to about the half, maybe less. That's when the Grundig is in playback or standby. When I press "record" on the Grundig, the volume level on the receiver goes back to normal.

Any ideas on this?
Thanks

 

[revox-b77]

I expect it is the 470. ohm resistors. I am not seeing a need for them. Can you not simply Y the r+l Hots PB and r+l Hots REC and send them along the appropriate wire?

 

[I968]

Well, the thing is I really shouldn't, because Mr. Bohn from http://www.rane.com/note109.html says we should never tie two outputs together.
I think that the "fault" is in the Grundig and the way it is wired internally. It was designed as a relatively simple and affordable consumer machine, mono; they probably didn't think anybody would want to use it with stereo equipment in the plug-and-play manner I would like to use it, without having to switch my receiver into mono mode all the time. All the Grundig's manual says about connecting it to a receiver is to use a mono cable and switch the receiver into mono every time:



Lead type 360 is a mono cable, with 3-pin DIN at both ends and a 22K resistor wired between the in and out wires:



The full manual for the Grundig TK 145 deluxe can be found here: https://www.flickr.com/photos/132762513@N04/albums/72157655421254646 or here (registration required): http://www.hifiengine.com/manual_library/grundig/tk-145.shtml .

Thanks

 

[dhnash]

I don't think your explanation of the way lead type 360 connects is correct. If it has a 22 K-ohm resistor wired between pins 1 and 2, pin 2 will be connected to circuit common when the lead is plugged into the MICRO-RADIO jack and pin 1 will be connected to circuit common through switch contacts 30 and 31 in PLAYBACK mode and to the amplifier input through switch contacts 31 and 32 in RECORDING mode. The 22 K-ohm resistor is not wired between the in (pin 1) and out (pin 3) wires.

 

[I968]

Yes, that is correct, you're right, dhnash, it's my mistake. I misread the diagram, of course pin 2 is always the common ground...
But it still doesn't solve my problem with my original design. Oh well. I guess I'll just have to try with lead type 360 and see what it does.

 

[eddisc]

All THIS to avoid selecting Mono on your receiver? Really?? You COULD just leave the power OFF on the tape deck....

 

[I968]

I have 5 tape recorders and all of them will be connected to a mixer and everything will be connected to everything and the more buttons and switches I have to interact with the more room there is for error.
So I just wanted to have it go through this stereo-mono adapter cable.

But yeah, I used a normal cable and will have to remember to switch.