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Author Topic: Understanding the 7-pin  (Read 2070 times)

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Offline Brian Skalinder

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Understanding the 7-pin
« on: April 28, 2003, 02:39:05 PM »
Leave it to Sony to co-develop the industry standard Sony/Philipps Digital Interface Format (S/PDIF) and then not follow the standard, nor use standard connectors on their portable decks.

I found useful this write-up on the Sony 7-pin from David Sanders.  The original may be found at David's website:

http://www.scitaper.com

I hope this page helps to clear up some confusion on the 7 pin cable used for Sony's portable DAT recorders. I personally have a Sony D8 recorder, I love it except for the 7 pin cable. Also some of this info may be skewed towards D8s since that is what I have experience with.

Personally I suggest you buy a high quality cable to begin with, made from Sony parts. I personally use Sony cables modified by the Oade Brothers. They are made to withstand the punishment tapers put on their equipment.

I initially thought I would build my own cable, but it appeared to be too fragile to try to take on the road. In addition to be being fragile the pins on the 7 pin are smaller than normal so there is a risk in damaging the jack on the deck.

There are two types of cables available, active and passive.
The passive cable is the simpler of the two, it pretty much just takes the signal and inputs it directly into the DAT deck. No extra circuits, this is the cheaper of the two cables.

The active cable has circuitry built into it, so it does more than just pass the signal into the deck. This cable is really the one to get if you can find one.

The easiest way to tell the two cables apart is the presence of a digital or analog switch, this shows the top of an Active cable.

This switch serves the purpose of selecting the input on the deck. For example, if you are running line in (say from a sound board) or if you are running microphones into the microphone input your would have the switch set to analog. However, if you are patching out of someone, or are using an external analog to digital convertor you would have the switch set to digital. Please note that the passive cable does not have this option, if you use a passive cable you have to go digital into the deck (there is actually a trick to get around this, more on that later).

Now more about the differences between the active and passive cables. It is helpful to understand that Sony's digital input is not based on standard voltages. I may have the exact numbers wrong, but I believe the D8 is based on 4 volts, and the M1 is based on 3 volts. The standard voltage for digital signals is 0.5 volts and some use 1 volt. However, Sony is pretty much on its own using these higher voltages.

How does this affect you? Well it makes things complicated at times. Basicly, machines that are based on lower voltages can usually understand higher voltage machines signals. But, higher voltage based machines sometimes can not understand lower voltage machines. Of course there are exceptions and there is really is no set rule.

When using a passive cable, a D8 is unable to understand the lower voltage based M1. However, swapping to an active cable (assuming you have one designed for a D8) should remedy this.

The difference between the two cables is the active cable has electronics to boost the voltage up. This enables higher voltage based machines to understand lower voltage based machines.

The safest bet is to use an active cable. For example, I have a Zerifo Inbox pre-amp / Analog to Digital convertor. I was unable use my passive cable with it, but my active works fine. But to add to the confusion, some people report that they have the same exact setup and a passive cable works fine (check out the active circuit link for more info about my problems). The popular Tascam DA-P1 can also be tricky to patch out of, Ihave come out of numerous ones successfully with my passive cable. However, I have read that problems occur when more than 2 DA-P1s are in line, I am not sure if an active cable would help this.

If you can find an active cable it is really the best and you will thank yourself later if you get one.

To further complicate things there are two types of active cables, a grey headed one and a black headed one. The grey headed one is intended for lower voltage machines like the M1, the black headed one is intended for higher voltage machine such as the D8. I personally have a grey headed active cable with my D8 and it works for my Inbox -> D8, but last time I tried I was unable to get a signal from an M1, go figure. Basicly, the difference is the black headed cable boost the voltage to a higher voltage than the grey headed.

If you can not find an active cable, you can build the active circuit. This circuit basicly boosts the voltage like an active cable. You could put this on the input of your passive cable to allow you to read lower voltage machines. Alternatively, you could put this on the output side of cable to boost the voltage so people with higher based machines with passive cables could patch out of you. I have also used a Midiman CO2 to enable me to input a signal that was too low.

The output on both the active and passive cables is based on the deck the cable is connected to. So an M1 will output roughly 3 volts (no matter what type of cable is being used), while a D8 will output roughly 4 volts (no matter what type of cable is being used).

So what about the analog digital switch? Well this is not a great solution (but its free), if you want to go analog in with a passive cable, put the deck in record / pause mode before inserting the passive cable (also remember to unplug before restarting after a set break).

The best solution I have found if you are wanting a patch is to get to the show early so you can be near the lead deck. There have been numerous occasions that I have seen people (including myself) get breaks in a tape because someone was to cheap to change batteries or tapes. Not to mention the headaches of trying to get a patch a few minutes before a show starts. And if you are going to be early in the chain do everyone else a favor and have fresh batteries and plenty of tape. If you are running your own mics test everything out at home before the show. Also most importantly enjoy the show, if you don't get a tape, a fellow taper will more than likely trade with you.

I hope this was helpful, if you see that I have anything wrong or have any suggestions shoot me an e-mail. Thanks to everyone who helped me understand this, namely Doug Oade and Todd Ramsden.
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