Behringer PMH300 noisy phantom - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

Instruments and Amps Everything that makes music, Especially including instrument amps.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th February 2009, 04:09 PM   #1
diyAudio Member
 
Join Date: Feb 2009
Default Behringer PMH300 noisy phantom

I noticed last year that the first two channels on my PMH3000 had intermittent crackles on them when using phantom powered mics. If dynamic mics are connected and the 48v switched off all is ok. All other channels are fine even with phantom powered mics.
This year channel 2 has got much worse and is completely unusable with the 48v switched on.
Has anybody else had similar problems ? I have disassembled the unit and tried to swop the larger capacitors around in the front end (between ch2 and ch3) but had no joy at tracing the source of the noise,
thanks
gary
  Reply With Quote
Old 19th February 2009, 01:40 PM   #2
diyAudio Member
 
Join Date: Feb 2009
Does anyone have a schematic diagram for the input stage of a channel on this mixer to show the phantom powering ?
  Reply With Quote
Old 19th February 2009, 04:27 PM   #3
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
I've got an MX802 circuit, but really theres very little in phantom powering - just two 6K81 resistors feeding 48V to the input pins.

Perhaps the coupling capacitors from the input to the ampliifer are leaky?, they have to block the 48V DC.
__________________
Nigel Goodwin
  Reply With Quote
Old 18th March 2009, 01:39 AM   #4
diyAudio Member
 
Join Date: Feb 2009
Thanks for your reply.
Yes Ive had a closer look and see what you mean. The curcuit is very simple around the XLR. Ive pulled the two 47uF/50v caps that couple the XLR to the mic input and some more caps are on order.I'll let you know how I get on
regards
Gary
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Phantom Power might be Bad? mistermisfit Solid State 12 10th February 2010 08:22 PM
+/-15V from +48V Phantom Pilbromatic Parts 4 9th August 2009 05:46 AM
whu 6800ohms for mic phantom pwr? SemperFi Instruments and Amps 3 19th February 2009 04:20 PM
noisy noisy noisy noisy noisy tube dsavitsk Tubes / Valves 50 20th February 2006 04:07 PM
phantom powering non-phantom mics karambos Instruments and Amps 8 3rd January 2004 09:21 AM


New To Site? Need Help?

All times are GMT. The time now is 09:43 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2