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XFRMR At Monitor Amp Input?



 
 
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  #1  
Old August 23rd 05, 02:55 AM
Joe Kramer
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Default XFRMR At Monitor Amp Input?

Hi Friends,

I'm currently investigating possible ways to connect my unbalanced
recording system to the balanced input of my Hafler P3000. Besides
fiddling with several cabling solutions, I also have a dual Jensen
transformer unit, which I normally use on some inputs of my recorder.

After doing an A/B comparison (as best I could) between hard-coupled
versus transformer at the input of the amp, I thought initially that the
transformer tilted the frequency response toward the low end and lacked
crispness. But after some more listening and mixing through it, I now
realize what I originally heard as a lack of high end was really the
removal of some harsh upper blurriness, and it allowed me to better
distinguish between, say, maracas, tamborine, and acoustic guitar
strumming. The upper-mid to high frequencies seem to sit apart better
with the transformer, not to mention the system is dead quiet now. The
mix actually translates well on other speakers, too.

My question has to do with consensus or corroboration. Before I go and
cough up the dough, any opinions, advice, words of warning about mixing
through transformers? Is there a downside? Anyone else have the
experience of hearing the improvements I think I'm hearing? Thanks.

Regards,
Joe
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  #2  
Old August 23rd 05, 10:53 AM
Arny Krueger
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"Joe Kramer" > wrote in message
.net
> Hi Friends,
>
> I'm currently investigating possible ways to connect my
> unbalanced recording system to the balanced input of my
> Hafler P3000. Besides fiddling with several cabling
> solutions, I also have a dual Jensen transformer unit,
> which I normally use on some inputs of my recorder.
> After doing an A/B comparison (as best I could) between
> hard-coupled versus transformer at the input of the amp,
> I thought initially that the transformer tilted the
> frequency response toward the low end and lacked
> crispness. But after some more listening and mixing
> through it, I now realize what I originally heard as a
> lack of high end was really the removal of some harsh
> upper blurriness, and it allowed me to better distinguish
> between, say, maracas, tamborine, and acoustic guitar
> strumming. The upper-mid to high frequencies seem to sit
> apart better with the transformer, not to mention the
> system is dead quiet now. The mix actually translates
> well on other speakers, too.
> My question has to do with consensus or corroboration.
> Before I go and cough up the dough, any opinions, advice,
> words of warning about mixing through transformers? Is
> there a downside? Anyone else have the experience of
> hearing the improvements I think I'm hearing? Thanks.


When sonic accuracy is the goal, transformers are in the
necessary evil department.

IOW, if your system isn't broke without them, you probably
want to leave them out.

If you are getting hum in the link between your console and
your monitor amp, its probably a matter of grounding or
cabling.

The power amp should be plugged into the same outlet or plug
strip as the equipment that drives it.

If the cable from the source to a power amp with a balanced
input is now just shielded coax, you may get an audible
improvement in noise by replacing it with a cable that has
two wires, so that the balanced input is bridged across the
output terminals of the source. IOW, use a shielded
two-conductor cable and hook one signal wire to the shield
at the source end.


  #3  
Old August 23rd 05, 07:09 PM
Joe Kramer
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Arny Krueger wrote:

> IOW, use a shielded two-conductor cable and hook one signal wire to
> the shield at the source end.


Thanks for the reply Arny. Yes, shielded twisted pair with the "low"
signal grounded at the source end is the "minimal" or third best
solution to the problem according to Jensen themselves. (Jensen AN-003
paper). Not surprisingly, their first best solution is to use one of
their input transformers. I'd be skeptical of this myself, but in
practice it really does sound better than the hard-coupled arrangement.

> When sonic accuracy is the goal, transformers are in the
> necessary evil department.
>
> IOW, if your system isn't broke without them, you probably
> want to leave them out.


I'm not out to contradict conventional wisdom here (ie, transformers =
emergency situations only), but rather to collate some data on whether
anybody else has used a transformer-coupled monitor amp with good
results. Thanks again.

Joe


  #5  
Old August 24th 05, 12:56 AM
Joe Kramer
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Mike Rivers wrote:

> There's no reason why, in this application, a transformer should have
> more accurate signal transfer than direct wiring.


But there is a reason it might sound better: all kinds of spurious high
frequency garbage from radio signals, computer switching, and power line
noise can be carried into the sensitive amp inputs and cause
intermodular distortion. This would seem a good explanation for the
blurriness I heard -- difficulty distinguishing between similar sounds
in high registers. The transformer is allowing me to pick stuff out
easier now, although that may only be saying that my system (or my
hearing) is pretty lousy in the first place. . . .

> Have you tried the "impedance balanced" source approach, with a
> resistor to ground connected to Pin 3 that's equal to the source
> impedance of the hot side of the output? (you'll have to determine
> that value experimentally).


That was going to be my next approach. I might as well still try it,
but I'm liking the transformer more and more. Another side effect is
that my ears are far less tired after mixing all day. . . .

Joe
 




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