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  #1  
Old 05-19-2002, 02:31 PM
Mark_Knecht Mark_Knecht is offline
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Default +4dBu? -10dBV?

Hey all,
I'm trying to understand the specs for the 001 outputs. The Main Output is speced at +4dBu and are balanced (TRS). The other outputs (3-8) are speced at -10dBV and are unbalanced.

What voltages are these outputs putting out?

I did some Google searches, as well as a few searches here, but have not found the answers yet.

I'd like to take an output directly, or indirectly through a matching transformer, to the input of a stereo receiver. The receiver is speced at a sensitivity of 150mV with an inpedance of 50K Ohm. It is presumably unbalanced as it is using RCA jacks.

If you have a good web site I could bookmark for this sort of stuff I would certainly appreciate it.

Thanks,
Mark
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  #2  
Old 05-19-2002, 03:04 PM
nqmike nqmike is offline
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Default Re: +4dBu? -10dBV?

Mark,

You shouldn't need a transformer to take a -10 output from your 001 into your stereo receiver- as it is most likely rated as -10 as well.

In case I'm stating the obvious or that which you already know - good luck and don't bother reading the rest.

common analog audio operating levels lowest to highest-

mic level

instrument level (guitar, bass output)

line level consumer (-10)- standard configurations RCA, 1/4" bal and unbal,

line level pro (+4) XLR balanced, 1/4" bal,

speaker/powered level

The Sound Reinforcement Handbook distributed by Yamaha makes a great reference for audio geek info such as this.
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  #3  
Old 05-19-2002, 03:42 PM
Mark_Knecht Mark_Knecht is offline
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Default Re: +4dBu? -10dBV?

Mike,
Hi. Thanks for the info. The receive is rated "150mV Sensitivity and 50K input impedance". Since the spec was in terms of voltage, I thought knowing what -10dBV meant would make sense.

Next, my receiver is located (by the time I hide the cables here in the house) about 35 feet away from the 001. I didn't especially want to run an unbalanced pair that far and deal with noise and frequency response issues. We had a little thread the other day about this and I was starting to try out what was suggested.

http://duc.digidesign.com/cgi-bin/ub...;f=32;t=006889

I got myself a couple of 'Low Inpedance to High Impedance' matching transformers, along with some XLR adapters to/from TRS 1/4" and RCA as appropriate, and hooked up the Main outs (-4dBu-TRS) to the transformer, and the tansformer into the receiver. I got a really messed up signal. Worse, the messed up signal was there on EVERY input of the receiver!

I started checking the wiring diagram of the transformer and they've attached the balanced ground to the single-ended ground. I'm wondering if this is the problem? Since the balanced ground is probably carrying a bit of the signal on it by the time it gets to the receiver, maybe the signal is getting into the reciever that way.

The product on the Jensen Transformer web site talked a little bit about the 'Pin 1 Problem". Maybe I'm suffering from that.

Additionally the 001 and the reciever are plugged into different parts of the houses AC wiring. I'm concerned that running single-ended between the two might not be safe if the ground voltages are off. I'd rather do the isolated version with a transformer, even if I have to go get a different one than I bought today.

But again, I don't know the conversion between dBu or dBV and voltage, so I was wondering. Is -10dBV exactly equal to 150mV?

I hope this helps explain all of this craziness!

And thanks!!!

Cheers,
Mark

Quote:
Originally posted by nqmike:
You shouldn't need a transformer to take a -10 output from your 001 into your stereo receiver- as it is most likely rated as -10 as well.
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  #4  
Old 05-19-2002, 03:46 PM
Lalaman Lalaman is offline
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Default Re: +4dBu? -10dBV?

With this topic I would like to take a chance for an answer to a phenomenon with my stereo equipment...

Connecting LE outputs to the stereo amplifier I noticed the general volume level of the amplifier to sink significantly. The whole thing gets very quiet even when other devices like for example CD is selected for listening. When LE is disconnected or off the amplifier "recovers".
Since I am far away from digging the topic of balanced connections etc.pp.- Could you please give me an idea of what I am doing wrong or how the solution should look like?

Thanx in advanz!
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  #5  
Old 05-19-2002, 04:25 PM
Roly Roly is offline
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Default Re: +4dBu? -10dBV?

Hi Mark I didn't look too close at the dip switch layout on your Jensen but chances are that one of them will lift pin one. Roly
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  #6  
Old 05-19-2002, 04:48 PM
Mark_Knecht Mark_Knecht is offline
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Default Re: +4dBu? -10dBV?

Roly,
I don't have the Jensen yet. I have to order it. It does have a dip switch for doing exactly that. I found out about this issue while reading the manual for the Jensen unit on-line.

I had all the cables and adapters I needed to do this, so I just went to a local music store and got a couple cheap impedance matching transformers and tried hooking them up, but as I say, the grounds are hardwired inside of the transformer assembly.

Also, I don't know if it really matters, but these transformers are really for taking a low-impedance mic and matching it to just a high-impedance PA input, I think. Anyway, the impedances looked OK, so I thought I'd try them.

The is an 'XLR ground lift' adapter I could buy, but I think I'm just throwing money away on this. I'll just order the Jensen (expensive! but nice!) and do it the right way.

Thanks for your help. If you have any more info, I'd sure appreciate it.

Thanks,
Mark

Quote:
Originally posted by Roly:
Hi Mark I didn't look too close at the dip switch layout on your Jensen but chances are that one of them will lift pin one. Roly
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  #7  
Old 05-19-2002, 05:15 PM
Roly Roly is offline
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Default Re: +4dBu? -10dBV?

Hi Mark You can just cut pin one on the mic cable XLRs do it at the input end. Your description of the signal showing up at all inputs may just be crosstalk due to way too much input. Did you start with your stereo at normal playback level and then bring up the Digi? Roly
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  #8  
Old 05-19-2002, 05:40 PM
Mark_Knecht Mark_Knecht is offline
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Default Re: +4dBu? -10dBV?

Roly,
Hi. I got it working using the monitor outputs instead of the main outs. With the gain at about 8-9 o'clock and my stereo at about 9 o'clock also, I get a nice enough level for listening.

I'm not totally sure what was wrong before, but it is working now. It must have been that when using the main outs there was just too much signal as you suggest.

I'm not at all sure about the frequency response of these little conversion transformers though. I'll do some more listening, but I'll likely have to go get a real conversion set to be comfortable that things are not getting colored.

Thanks,
Mark
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  #9  
Old 05-19-2002, 06:12 PM
nqmike nqmike is offline
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Default Re: +4dBu? -10dBV?

Mark,

Exactly. You shouldn't be abzle to run the Main outs into your stero without a pad of some sort. Which, is why the -10 outs worked much better for you. If you still need db big V. little V, U conversion stuff- I can post it all up here tomorrow for ya. If ya can't wait. Electronic Musician posted an article a few months back with all of the math.

Just let me know.
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  #10  
Old 05-19-2002, 06:44 PM
Roly Roly is offline
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Default Re: +4dBu? -10dBV?

Hi Mark Glad things worked out, I am positive you will get better results with quality transformers. The makers of cheap ones arn't lying if they say the response is 20 to 20 but you won't see them offering a response curve.

and Mark cautiously entered the world of 5.1
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