HiBrent
Hi Ike, Matt and Monte,
Thanks so much for the input. Lots of ideas there. Believe me, right
about now I can use them so it's very much appreciated. No days off
here until the week after next so I'll be doing a bit each night post
session. I'm preparing myself for a slow and frustrating hunt on this
one. Sounds like I was vaguely on the right track at least.
To respond to Ike's questions:
-Do you only hear the noise when a solo is engaged?
Yes.
-Does the noise print to the 2-mix?
No, but the noise floor of the master left bus does read a little
higher on our DAW meters, but this noise is not audible in the way
the solo circuit noise is (eg with the the master fader up the noise
floor for the left master bus reads 5-10db higher than the right down
at -90 odd.. The DAW meters also show extraneous noise on the left
master bus when the impedance of the master fader changes (up or
down), and the settling time is a lot slower than the right side.
-Are the monitors clean with another source selected?
Yes. This is only a problem when solo is engaged except for the
convoluted routing problem mentioned below.
You might also try removing U-4 on the Monitor module altogether.
If the noise is still present, but at a reduced level, than as Matt
suggested, it may be coming from a channel module. If the noise is
the same level, that would point to Q-103, the Left Solo switching FET.
With U-4 removed there is silence on the circuit.
Q103 has already been changed out, as have Q101, Q102, 104, Q115, Q118
& Q119.
Matt's last email has triggered my memory with regard to mentioning
hum. We recently attempted some mixing to stems out the first 16
busses, summing in the box and bringing the DAW 2-mix back into the
control room extra input. This created ground loop issues but for the
first hour or so there was also a god awful hum when monitoring the
return to the control room extra input. (sounded like a ground was
missing and a lot like transformer hum). It slowly dissappeared.
Tightening all the screws on the power supplies, the ground bus,
individual module screws and cleaning the bucket frame and the
underside of the modules had no effect.
I'm starting to see a pattern. Could this hum be a product of the same
short and also be an indicator that the short isn't necessarily close
to the solo amps?
Is the noise hiss AND hum now?
If so then if it has a short it may be 'further away' but bear in mind
if the fault is say 20 Ohms the mix amp will be aiming for over 50dB
gain so any loops can produce a significant noise.
I don't have a schematic for the monitor section but if you could email
the relevant 'chunk' of the monitor strip and possibly the 'solo' bit of
a channel I may be able to suggest more. I don't know what U4 does for
example.
Matt S
Thanks again all, I learnt a lot from those few emails. I'll come back
after I've done a bit of prodding.
Brent Punshon
Head Gap
Melbourne, Australia
Ph:+613 9480 6280
www.headgap.com.au
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please send
an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to
all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at: http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to mailto:[email protected] with
"unsubscribe neotek" in the message body. If you have any difficulties, or
questions --please send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any message
or reply sent to the list will be automatically forwarded to all subscribers.
Vive Le Neotek!
Thanks.
