Using a 25-2's DBX as external decoder?

[DEDKOwh]

I'm digitizing a bunch of 70's submasters.

Some of them were mastered with DBX on a 25-2.

The 25-2's pretty rough on these old tapes, so I'm using a BR-20T for transport.

I don't have a manual for the 25-2. Is there a way to route the signal from the BR-20 through the 25's DBX decoder?

 

[SkywaveTDR]

It is much easier to just get an unlocked DX-2D or DX-4D and go from there.

 

[DEDKOwh]

Bummer - so it isn't just plug-n-play.

I *do* have a DX-8. I reckon I could just use 2 channels from that guy, huh?

 

[SkywaveTDR]

People think all this stuff is so easy- it is not. Some older unit were play OR record not both and so in the RX9, DX4, DX44 and DX-8 they all require signals from the switching portion of the deck to control these functions. Then I am not sure what levels they specify as for input and output. The service manual for the unit would say but with the known history of the DX series other than the DX-4D or 2D these are notorious for relay related failures causing channels to cut out and sometimes change levels. It is those relays that were a real design problem. If someone would figure out a DIP relay retro fit then this would be the way to fix the cards but the dBx cards themselves had a good amount of failures from cracks and bad Tantalum caps which we replaced with new Electrolytics. Even in decks as new as the X2000R C363 a Tantalum cap still is found shorted on some units and so is common to be replaced with a cap that is an electrolytic.
Yes you might be able to use the DX-8 but it might also be a lot of trouble to do so. The levels have to match when you use such a unit as dBx is level sensitive which is exactly how they work.

 

[SkywaveTDR]

Most facilities that have good equipment will have a dBx unit in a rack so they can patch it in if needed. The DX-4D is a unit like that which could be patched into a rack. The DX-4D is a fixed level processor while the actual dBx units that have level adjustments on them are better for those jobs where the signal level is not referenced to -10dBV. The DX-4D as well as 2D need a FV signal system bypassed or modified. DBx required Tascam put a system in the decks to allow ONLY Tascam unist to be used with their dBx units. They did not want a DX-4D being used with a Studer , Fostex, Otari or other brand as it then affected their sales. It did not take long for those enterprising Technicians to figure out the FV signal was a 1Hz TTL square wave that could be generated by any NE555 IC but that why go to all this trouble when the detection circuit could be cut out or bypassed.

 

[DEDKOwh]

I've a stack of precious DBX-encoded 1/4" masters which I need to decode.

I appreciate the detection circuitry explanation. And the susceptibility to failure of the relays. Either may explain why a casual attempt to route 2 channels of audio through the DX-8 didn't appear to have any effect.

If this were easy, I wouldn't be asking for advice in a specialists forum!

Is anyone aware of legit software decoding of DBX1? I understand that there are licensing concerns, but surely some pro DAW has sorted this out. I haven't run across the right solution, though.

Here's a guy who did figure out DBX decoding, but - due to licensing - is unable to share the actual code: https://www.bobweitz.com/dbx_webpage/dbx.html

 

[BRDTS]

As a first gen Tascam dealer (25-2 was great) and user and synchronizer of all the products.....yeah, a standalone type1 dbx would come in handy. As mentioned, integrated Tascam dbx units had the relay circuitry....making them useless for mix/matching.

Software type 1 dbx......built in to u-he Satin.... as a side decode feature.....exactly for those with encoded tapes and no dbx unit. There are dolby a-b decoders in the program too.

I haven't tested the dbx in Satin as I have dbx units, but I did test Satin's various dolby decode functions on some 1971 dolby tapes....in tandem with testing alongside several old dolby standalone decoders......and Satin works great.

By the way....Satin as a tape recorder emulator is nice enough for one-pass stuff....where the effect is subtle.

But in real life in the old days, bouncing and comping multiple times between tape machine and console...would often create nice buildup mojo.

Satin and other tape sims fall apart when you experiment with routing signals back through multiple times. This is....in a daw....partially because there's no console in between....no physical wiring etc.

Basically, "subtle" is all these sims can do.

But yeah....for dbx and dolby decoding....Satin is the way.