do I need a cathode follower? - Page 2 - 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 18th July 2013, 08:22 AM   #11
diyAudio Member
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
You need the 0.1u screen bypass capacitor, otherwise your gain will be low, so leave that alone, now some suggestions:

1) Get rid of the pentode/triode switch and run in pentode mode only if you want the Vox chime.
2) Change the 680k to 200k, and connect it to the 20k pot, or better yet, replace both with a proper 250k log pot. Too much series resistance is killing the highs, you can add a bright cap across the 680k as suggested by djgibson51, if you do not have any other lower value resistors to replace it.

Jaz
  Reply With Quote
Old 18th July 2013, 08:31 AM   #12
diyAudio Member
 
Join Date: May 2010
Location: Hawkes Bay
Check out "The Valve Wizard - Small Signal Pentodes".
C3 does the same job as C2 ie prevents -ve feed back.
You could reduce either to boost treble (actually reduce bass) in this circuit.

Sorry jazbo - cross post

Last edited by djgibson51; 18th July 2013 at 08:33 AM. Reason: Cross post
  Reply With Quote
Old 18th July 2013, 08:43 AM   #13
emosms is offline emosms  Bulgaria
diyAudio Member
 
Join Date: Sep 2010
Thx all!
I have set 680k to prevent high voltage on the output.
Not sure if 250k will give usable output voltage range out, have some such pots at disposal.
The sound card would clip badly, mby even get its input burned.
---
Another pros for cathode follower solution?
(eliminating high resistance before output, handling the full voltage amplitude, plus low output impedance)
Still I will try it the simple way first, with a bypass cap on the output resitor.

p.s. the sound card has 250/400k (lo/hi) input impedance, no idea about the capacitance.
Tried both with 0.5m and 3m cables for the guitar, I dont hear such a big difference.

Last edited by emosms; 18th July 2013 at 08:59 AM.
  Reply With Quote
Old 18th July 2013, 09:01 AM   #14
diyAudio Member
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Quote:
Originally Posted by emosms View Post
Thx all!
I have set 680k to prevent high voltage on the output.
Not sure if 250k will give usable output voltage range out, have some such pots at disposal.
The sound card would clip badly, mby even get its input burned.
There is no high voltage after the output coupling capacitor, it blocks all the DC from reaching the soundcard. If you are only playing guitar through this preamp, I doubt you can generate enough swing to damage the soundcard's input. But to be safe, you should always have Zener clippers to protect over-voltage to the card.

Quote:
Another pros for cathode follower solution?
(eliminating high resistance before output, handling the full voltage amplitude, plus low output impedance)
Still I will try it the simple way first, with a bypass cap on the output resitor.
In this case, I don't think a CF will make a drastic difference, so probably not worth the trouble of adding another tube, but it is up to you.
  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
Help? 6n23p cathode follower ericj Tubes / Valves 20 25th November 2013 02:01 PM
cathode follower vlljpior Tubes / Valves 6 22nd March 2005 07:50 PM
Question about direct coupling a anode follower into a cathode follower. G Tubes / Valves 45 29th July 2004 06:47 PM
cathode follower ackcheng Tubes / Valves 2 6th July 2004 03:12 PM
cathode follower olvrkrg Tubes / Valves 3 21st February 2004 09:49 PM


New To Site? Need Help?

All times are GMT. The time now is 03:24 PM.


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