Comtek

``to avoid cross coupling the left and right outputs at low impedance.
(i. e. you could mess up the channel separation on other outputs being
driven off the same op-amps or transformer outputs``

that`s exactly right Courtney,that`s the problem with the psc4m
mixers..the 10 K resistor was an absolute must.the rf bleeding coming
back into the mixer from the comtek was also a problem with that
mixer.now,i have no problems with my sd 442 and 302,lots of options to
feeding comteks.
 >> Stay informed about: Comtek 

Comtek

Group: rec.arts.movies.production.sound Date: Mon, Feb 7, 2005, 3:21pm
(EST-3) From: aboisvert001 RemoveThis @sympatico.ca

I'm filing this next question in my "Damn-I-should-know-this" folder.
Can I feed both outputs of a cooper 104 to a comtek without blowing
something up?

Both hots to tip?<<<<<<<<<<<<

Should work with no problem for the Comtek but check your mixer to see
if it causes any audio problems.

Eric
 >> Stay informed about: Comtek 

It is always best to sum the two channels through a small resistive mixing
network to avoid cross coupling the left and right outputs at low impedance.
(i. e. you could mess up the channel separation on other outputs being
driven off the same op-amps or transformer outputs.)

Just put a 10K resistor from the hot on each line out to the tip on the
comtek jack.
This will also help keep the higher level line out from the cooper from
overdriving the input of the comtek. Or you could put a 20K pot with the
center tap to the comtek Tip and the other 2 contacts on the pot connected
to the hot pins from channels 1 & 2. Then the pot will work as a pan-pot
to balance the levels from each channel. (shield goes to ground and or the
low side of the balanced outputs)
20k pot
Chan 1 hot -----/\/\/\/\/\/\------ Chan 2 Hot
^
\ to tip of Comtek jack

You may have to experiment with the value of the pot. 10k to 100k should
work depending on the output level of your mixer.


---Courtney

<aboisvert001.RemoveThis@sympatico.ca> wrote in message
news:1107818467.431819.53860@o13g2000cwo.googlegroups.com...
> I'm filing this next question in my "Damn-I-should-know-this" folder.
> Can I feed both outputs of a cooper 104 to a comtek without blowing
> something up?
> Both hots to tip?
> The Cooper has balanced/unbalanced and mic/line outs.
> I'm using the tape out for an Iriver.
> Thanks,
>
> Andre
>
 >> Stay informed about: Comtek 

bypass the Comtek inputs with .01 ceramics, add further insulation with
transformers and you have an Engh box!! if you feed TC to Comtek the ceramic is
a must. wonder why no one uses ferrite beads to keep Tc from flowing back to
mixer/recorder?
try asking Andy Cooper
nicest guy in town
coopersound DeleteThis @charterinternet.com

wolf
 >> Stay informed about: Comtek 

Damn. You're 4 hours late. I just finished the cable according to
Courtney's suggestion and everything seems to be working fine. It
doesn't, however, compensate for the increase in volume. Then again,
I'm feeding a Comtek with 10$ headphones....
Thanks to everyone who took the time to reply.

Andre Boisvert
Montreal
 >> Stay informed about: Comtek 

Large amounts of thanks, Courtney.
I think I'll stick to the cable I made from your original suggestion
for now until I have a better idea of what I'm doing. (just started a
cd-rom course on electronics).
Andre
 >> Stay informed about: Comtek 

Careful if you use the circuit diagram in the Rane Note: It is designed to
drive a low impedance input from 2 low impedance outputs and will cause a
substantial amount of crosstalk with the resistors of the 450 ohm range.
You need to up the resistance to at least 4.7k (as stated in the text) to
raise the crosstalk figures to 74 db. into a low impedance load. Into a
high impedance load I would stick with the 10k bridging resistors.

If you need level control you could drop the summing resistors to 4.7K each
then put a 10K pot across the output with the pot center-tap to the tip of
the Comtek cable and the Left and Right contacts of the pot connected to
ground and Hot leads (after resistors) respectively.
or you could just use the input level control on the comtek to control your
level. (same function as the 10k pot)
---Courtney



<aboisvert001 DeleteThis @sympatico.ca> wrote in message
news:1108079765.848991.31450@c13g2000cwb.googlegroups.com...
> Damn. You're 4 hours late. I just finished the cable according to
> Courtney's suggestion and everything seems to be working fine. It
> doesn't, however, compensate for the increase in volume. Then again,
> I'm feeding a Comtek with 10$ headphones....
> Thanks to everyone who took the time to reply.
>
> Andre Boisvert
> Montreal
>
 >> Stay informed about: Comtek