Tascam dx-4d noise reduction with Revox

[sixtiesman]

I have just won a pair of these units on ebay.

I have a Revox C278 eight track recorder half inch with no noise reduction on board. So I thought I could simply acquire some NR units to hook up to the Revox. Now that I come to read old threads on here it seems there is a "control cable" and worse, some people ask "is my dx4d compatible with....."

Have I gone wrong here or do these NR units work with any eight track recorder?

[A Reel Person]

there is an internal mod to jumper the control cable & bypass it.

From what I gather, the control cable tells the DX unit when to encode & decode, but the mod/jumper makes the DX encode/decode full time.

[sixtiesman]

Thanks Dave

So all I have to do is hope that the manuals are with the units when they arrive!

Does any reader know where the jumpers are?

Does anybody know how good these units are?
Pro or consumer?

thanks to all who read this

sixtiesman

[A Reel Person]

One thing's for sure, dbx-I really quashes tape hiss while remaining relatively transparent, as long as it's used within it's parameters.

I don't know specifically where the jumper point/mod would be, but there are probably a few real techy types that might be able to give you more specifics. I agree, that with the DX-4D schematic in hand, it should be easy to figure out.

I have one DX-2D that was internally jumpered, prior to my acquiring it off eBay, 'bout 2 years ago. If worse comes to worse, I could open 'er up & take a look-see.

[sixtiesman]

Dear Dave

Thank you for all the helpful information. They have arrived, not very well packed, not pristine, a few scratches but they were the right price.
The seller said he had bought them with a Tascam tape deck, so chances are they are wired for use with the cable?

I will take one apart and have a look.

There are schematics available on ebay for $13.....

I'll let you know how it goes.

sixtiesman

[sixtiesman]

Well I took the plate off the bottom only to reveal the underside of the printed circuits! No clues at all. No big red switch saying "for use with other tape recorders such as Revox" So I put it back as I ran out of time.

Does any reader have the information?

Thanks for reading this....

sistiesman

[A Reel Person]

If/when I get the time, I might pop open the DX-2D that was jumpered, & compare it to the one that's not.

Better yet,... it might be easier to look into the DX-4D "manual", (if you could call it that), as well as the Tascam 38 manual for clues. There might be a diagram of the control cable & how it's contacts are made inside the 38.

At this point, I have no clue, 'cept to assume it must be simple & easy!

[sixtiesman]

Dear Dave

So you are using the Tascam dx unit(s) with a Tascam tape deck and not some other make of recorder?

Are you using the rig without using the control cable?

I found some old threads about this problem and although shorting out pins seemed to do the trick for someone, it wasn't apparent to me which machine or which pins!

thanks for your help

sixtiesman

[A Reel Person]

...............

[jpmorris]

I have the basic schematics in the manual. I have the units too.. but since I never even unpacked them, it would be a shame to open them now.

I got these before the recorder, and ended up with a TSR-8 instead, so I have 8 channels of DBX and no use for them. Maybe I should just put them back on ebay..

Anyway. The connector looks like this:

Pins 1-3 go into the 4DX unit. Pins 4-6 are connected directly to pins 1-3 on the cascade output. Pins 2 and 5 seem to be ground.
So basically pins 1-3 control the first unit and 4-6 control the second one if two are linked. How the control works I'm not sure, but they both go into an op-amp which feeds some kind of opto-isolated connector to the guts of the system.
Note that there are only two terminals, so unless it's using different light levels to signify different states, it's a simple on/off switch.

Since there are two inputs, I'd hazard a guess that you join pins 1 and 3 together to activate it. You could try that while playing back an existing recording - if the treble suddenly gets out of hand, it's DBX decoding a plain tape.

The only other possibilities are linking 1 and 2, and linking 2 and 3.

**EDIT**
..or linking all three, though I doubt it..

[A Reel Person]

Yeah,... and I believe if the control pins are shorted correctly, the LEDs will turn on, indicating an active channel. Without the control cable signals being met,... the LEDs will not light.

That's IIRC.

[sixtiesman]

Thanks to all contributors......

I will try the units this weekend


regards

sixtiesman