DBX on the 688

[funfair sascha]

Hi,
I recently got a 688 and I'm a bit confused about the DBX implementation.
As far as I got it there's no option to activate/deactivate DBX on the surface but just the 2 switches on the backside (one of them broke, which is quite unfortunate).
So.. to my understanding no matter if you want to use DBX or not, you always have to switch :
- 'out' while recording and 'in' while mixing if you don't want to use DBX
- 'in' while recording and 'out' during the mixing process if you want to use DBX
unfortunately the manual isn't clear about that.
Did I get this right?
Thanks for your help.

 

[Phil Tipping]

I don't have one of these machines but as far as I know, dBX is a compression/expansion system which operates when recording & playing back individual tracks. This means if you record with dBX on, you must also play those tracks back (which is what you do during mixdown) with dBX on, otherwise the compression/expansion process will be unbalanced and you will not hear the original signals.
Some multi-track recorders allow for one track (usually one which is next to the edge of the tape) for sync pulses, and in this case, dBX is disabled for that track only to avoid confusing the sync detection.

 

[funfair sascha]

@Phil Tipping, Thank you, I know about all this.
My question was: Is the only way to enable/disable DBX the way I described?
I think I must have missed something, because.. let's say you record track1: DBX switch is on 'in'.
Then you want to record track 2 while listening to track one. DBX switch still has to remain on 'in', but then the only way to listen to track 1 is without DBX, because you cannot put the switch on 'out' while recording. I don't think it works that way. So.. what am I missing?

 

[Max Relic]

The manual says DBX switches should be normally set to IN, this ensures the best bandwidth and dynamics from the tape. As the 688 is MIDI Sync capable, track 8 can be used to stripe a clock sync FSK signal (a stream of two-tone signals) and play it back without the need to touch the DBX 5-8 switch, because the noise reduction engine is automatically disconnected for the sync track when it's in use.
I would keep both switches always in the IN position.
As @Phil Tipping said, if you record to tape using DBX then you have playback using DBX in order to get a signal that is faithful to the original.

 

[funfair sascha]

@Max Relic, I know. I read the manual. But 'in' and 'out' refer to DBX on incoming signal/DBX on outgoing signal, right? So when I do the mixdown (no incoming signal, just outgoing signals) the switches have to be on 'out'. But that also means that when you listen to track 1 while recording track 2 in 'in' mode, you don't hear the DBX on track 1.
Or am I getting it wrong and 'in' and 'out' just means 'on' and 'off'? In this case that's a weird labelling.

 

[Max Relic]

AFAIK the IN and OUT labels must be read as ON and OFF. The DBX circuit is placed right before the record/play head.
Reading the whole manual takes some time, especially if one hasn't the machine to verify described procedures, as is my case. Nevertheless, from what I've read so far there are various operating situations described step-by-step, as was the custom of Tascam, and I guess the answer to your question lies there.

 

[Max Relic]

The 244 Owner's Manual explains how the DBX works (page 56), you can download it here Tascam 244 Owner's manual

 

[Phil Tipping]

As Max said. DBX should be in the same state (on/off) for both recording and playback. DBX compresses the signal as it's recorded, and decompresses (expands) it during playback.
Sounds like the confusion is in the terminology. I guess in/out means on/off in the context: when it's on, the compression/expansion circuitry is 'in' the signal path?

 

[funfair sascha]

I see. It sort of makes sense, thank you all.
Although labelling the whole thing on/off would make everything clearer right from the start.

 

[Max Relic]

The terms In/Out for On/Off are not that uncommon in the music gear industry. IIRC a switch for bypassing the DBX compander appeared for the first time on the Porta One multitrack cassette recorder (1984) as a mean for reproducing tapes recorded on other devices; it seems Tascam has kept the same nomenclature to these days, i.e. see the Master Equalizer button on the Model mixers series.