Dizengoff D864 head scratching behaviour....

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Dizengoff D864 head scratching behaviour....

Post by RhythmAce »

Hi all

Apologies for my first post being a plea for assistance - i hope i can offer some more valuable contributions in future!

I've recently bought a second hand Dizengoff D864 vari mu compressor and am struggling with some strange results from it. When used as an insert on a DAW return channel on my ASP 4816 all is fine and rosy - its a fine sounding beast - but when patched in after a mic pre amp during tracking the sound is thin and lacking in low end, almost like a steep high pass is engaged around 200hz. I have the unit accessed via a patch bay so whether its getting a line level DAW return or an amplified mic signal its all arriving from and to the same place. Im being careful to feed it pre amp levels that average around 0VU.

Any thoughts?

Many thanks

Sam
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Re: Dizengoff D864 head scratching behaviour....

Post by ef37a »

My first thought is that the compressor has an unusually low input impedance?
However, a five minute search has failed to find me a specification to check that.

A low input Z should not of course be a problem for modern gear and it seems from the excellent mixer it isn't but the mic pre design might have "economized" on the output capacitors ! Fine when driving >10k but cut LF for lower loads?

Dave.
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Re: Dizengoff D864 head scratching behaviour....

Post by James Perrett »

My first thought is that there is a wiring problem - is everything fully balanced and wired with the same polarity or could there be an unbalanced or impedance balanced output in the system? Have you tried connecting the output of the preamp directly to the input of the compressor?
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Re: Dizengoff D864 head scratching behaviour....

Post by RhythmAce »

Many thanks Dave and James - really appreciate your thoughts.

James your comments on wiring are probably where ill investigate first - certainly has that sound about it. Where im still slightly baffled is how a line level insert from the desk sounds fine when it's accessing the unit in exactly the same way as the different pre amps that ive tried that all exhibit that loss of low end. The unit only has in and out on XLR and they're going balanced to the patchbay. Is the unit seeing something different in terms of level when fed an insert compared to an amplified mic signal? In my old confused mind those are both at line level and shouldn't present anything drastically different?

Thanks again

Sam
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Re: Dizengoff D864 head scratching behaviour....

Post by ef37a »

Hi Sam, I think you need to do some more objective tests. Record a source of pink noise and see what the responses look like. Most DAWs have a crude RT Analyser or you can download one of several freebies. I like Right Mark.

Dave.
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Re: Dizengoff D864 head scratching behaviour....

Post by Mario Pietrangeli »

This may be really silly...

But is there a difference in level between the "output" of your pre-amp, and the output of the "send"from your ASP 4816?

I.e., if it's fine when you're using it as an insert (send/return), but it sounds like it's thin when you go from the output of your pre-amp to the input of the compressor... Assuming I'm understanding your point... are there line-level differences from the send of one device and the output of the other device?
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Re: Dizengoff D864 head scratching behaviour....

Post by Hugh Robjohns »

RhythmAce wrote:I've recently bought a second hand Dizengoff D864 vari mu compressor and am struggling with some strange results from it. When used as an insert on a DAW return channel on my ASP 4816 all is fine and rosy - its a fine sounding beast - but when patched in after a mic pre amp during tracking the sound is thin and lacking in low end, almost like a steep high pass is engaged around

Just for clarity, do you mean it's plugged into the console channel path inserts, or between an outboard Pre and the Daw or console?

And if in the channel path inserts, the channel preamp HPF is bypassed, right?

I suspect James is probably right, and there's a wiring issue in there -- a missing leg in the balanced wiring or a polarity inversion maybe.
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Re: Dizengoff D864 head scratching behaviour....

Post by RhythmAce »

Hugh Robjohns wrote:
RhythmAce wrote:I've recently bought a second hand Dizengoff D864 vari mu compressor and am struggling with some strange results from it. When used as an insert on a DAW return channel on my ASP 4816 all is fine and rosy - its a fine sounding beast - but when patched in after a mic pre amp during tracking the sound is thin and lacking in low end, almost like a steep high pass is engaged around

Just for clarity, do you mean it's plugged into the console channel path inserts, or between an outboard Pre and the Daw or console?

And if in the channel path inserts, the channel preamp HPF is bypassed, right?

I suspect James is probably right, and there's a wiring issue in there -- a missing leg in the balanced wiring or a polarity inversion maybe.


Thanks Hugh - your reply popped up and reminded me that i hadnt actually posted the culprit which is bad of me - just in case someone else is / was having the same problem. It turned out to be exactly as a few of you suspected - dodgy wiring on a patch bay point causing the signal to be polarity reversed - quite how i hadnt ruled that out is beyond me - the patch bay equivalent of leaving your glasses on your head whilst searching the house for them. Thanks so much everyone for your help.
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Re: Dizengoff D864 head scratching behaviour....

Post by Hugh Robjohns »

:thumbup:
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