50M input impedance buffer? - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 5th December 2008, 06:05 PM   #11
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
if you use preamps with "stratospheric" input impedances like 10M and 50M, you will not want any substantial amounts of cable capacitance between the pickup and the preamp. just 10pf with a 10M input impedance converts your preamp into an active low pass filter with a corner frequency of about 1.6khz.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 5th December 2008, 06:22 PM   #12
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Default Re: 50M input impedance buffer?

Quote:
Originally posted by takodabut
Has anyone done design on very high impedance preamp buffers?
Yeah, 200M. Enough? For measurement of HV potential near HV line pilots.
  Reply With Quote
Old 5th December 2008, 09:42 PM   #13
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
Quote:
Originally posted by unclejed613
if you use preamps with "stratospheric" input impedances like 10M and 50M, you will not want any substantial amounts of cable capacitance between the pickup and the preamp. just 10pf with a 10M input impedance converts your preamp into an active low pass filter with a corner frequency of about 1.6khz.

The impedance of piezoelectric transducers decreases with increasing frequency. It may be 1M at few hundred hertz, but it'll drop at 6dB per octave so the filtering effect of a few tens of pF of stray capacitance isn't that catastrophic. Just keep the strays to something reasonable, and use a 10M gate bias resistor for the JFET buffer and all should be well.
  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
buffer and impedance matching Professor smith Pass Labs 5 16th June 2009 09:37 PM
TPA6120 without input buffer mr.duck Chip Amps 11 12th January 2007 10:46 AM
UCD 180 input buffer rotation Class D 63 12th October 2006 05:21 PM
connecting input directly to ucd, no input buffer mazurek Class D 20 19th July 2006 03:32 PM
Cathode Follower Buffer Input Impedance xcortes Tubes / Valves 5 1st December 2005 05:10 PM


New To Site? Need Help?

All times are GMT. The time now is 07:36 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