Input Impedance Question - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 28th January 2013, 01:34 PM   #11
Loren42 is offline Loren42  United States
diyAudio Member
 
Join Date: Sep 2008
Location: "Space Coast" Florida, USA
Quote:
Originally Posted by Mooly View Post
If your feeding this from a tube amp then you must be certain that not only is the tube amps output cap OK but also that it has a high value resistor to ground (even if its 10meg) on the output. If not and its floating then the cap could charge to some high voltage and this would zap the IC as soon as you connected.
Good point. I'll simply replace the cap with a new one just to be sure.
  Reply With Quote
Old 28th January 2013, 01:48 PM   #12
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Quote:
Originally Posted by Loren42 View Post
Good point. I'll simply replace the cap with a new one just to be sure.
If it needs it then yes

But it must be terminated on the output side to ground via a high value resistor (which it may already have). If it hasn't and you leave it floating, then the output will assume whatever voltage is on the other side of the cap (tube amp... could be 50v to ??? who knows) and that would instantly zap any solid state unit you attempted to connect it to.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 28th January 2013, 03:47 PM   #13
Loren42 is offline Loren42  United States
diyAudio Member
 
Join Date: Sep 2008
Location: "Space Coast" Florida, USA
Quote:
Originally Posted by Mooly View Post
If it needs it then yes

But it must be terminated on the output side to ground via a high value resistor (which it may already have). If it hasn't and you leave it floating, then the output will assume whatever voltage is on the other side of the cap (tube amp... could be 50v to ??? who knows) and that would instantly zap any solid state unit you attempted to connect it to.
Here is the PAS 3 circuit. Not likely that there will be DC on the output since at least two caps would need to fail (double fault).

Click the image to open in full size.
  Reply With Quote
Old 28th January 2013, 04:10 PM   #14
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
It is not for a capacitor failure.
That 510k , connected form 7 to 1, is the grounding resistor to prevent you blowing up the next stage.
Measure it to make sure it is still operational.
__________________
regards Andrew T.
  Reply With Quote
Old 28th January 2013, 04:30 PM   #15
Loren42 is offline Loren42  United States
diyAudio Member
 
Join Date: Sep 2008
Location: "Space Coast" Florida, USA
Quote:
Originally Posted by AndrewT View Post
It is not for a capacitor failure.
That 510k , connected form 7 to 1, is the grounding resistor to prevent you blowing up the next stage.
Measure it to make sure it is still operational.
Ah! Thanks! I will do that.
  Reply With Quote
Old 28th January 2013, 06:07 PM   #16
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I saw this, and thought of you ,
Alittle disaster story
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 28th January 2013, 06:13 PM   #17
Loren42 is offline Loren42  United States
diyAudio Member
 
Join Date: Sep 2008
Location: "Space Coast" Florida, USA
Quote:
Originally Posted by Mooly View Post
I saw this, and thought of you ,
Alittle disaster story
Thanks. I needed that.
  Reply With Quote
Old 28th January 2013, 06:16 PM   #18
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Your welcome. Now check that 510K
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  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
Question about preamp input impedance cumesoftware Solid State 3 15th July 2012 10:29 AM
input transformer and impedance question milen007 Tubes / Valves 6 26th February 2012 02:04 AM
input impedance of mosfet question? AudioGeek Solid State 2 9th November 2009 03:11 AM
Chipamp input impedance question EBM_dude Chip Amps 6 26th October 2009 04:52 PM
Amp input impedance question ? sam9 Solid State 9 21st April 2005 02:28 PM


New To Site? Need Help?

All times are GMT. The time now is 09:56 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