300B SET amp input sensitivity, Help. - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 December 2010, 08:16 PM   #11
el156 is offline el156  Portugal
diyAudio Member
 
el156's Avatar
 
Join Date: Apr 2010
Location: ALBUFEIRA ;PORTUGAL
Quote:
Originally Posted by manp111 View Post
You are talking about the grid of the input tubes?
Yes ,the grid of the input tubes !
  Reply With Quote
Old 15th December 2010, 08:26 PM   #12
diyAudio Member
 
Join Date: Jun 2010
Thanks Tom for the clarification.

I found a better solution: instead of lowering the input sensitivity of the 300B amp I think I can increase the input sensitivity of my 845 amp.

I found a resistor from the input tube grid to the positive input and a resistor from grid to ground in the 845 amp. It seems like I could remove these two resistors to increase the input sensitivity. What do you guys think of this? This would be a much easier solution.
  Reply With Quote
Old 15th December 2010, 08:29 PM   #13
diyAudio Member
 
Join Date: Jun 2010
The 845 amp also has two volume pot.
  Reply With Quote
Old 15th December 2010, 08:41 PM   #14
diyAudio Member
 
Join Date: Jun 2010
Quote:
Yes ,the grid of the input tubes !
Thank you very much for the information. This forum and its members are wonderful.
  Reply With Quote
Old 15th December 2010, 08:44 PM   #15
diyAudio Member
 
Join Date: Jun 2010
Can I just remove the resistor from grid to ground? Or do I need a lower value resistor?
  Reply With Quote
Old 15th December 2010, 09:08 PM   #16
tomchr is online now tomchr  United States
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Greater Seattle Area
Quote:
Originally Posted by manp111 View Post
I found a resistor from the input tube grid to the positive input and a resistor from grid to ground in the 845 amp. It seems like I could remove these two resistors to increase the input sensitivity. What do you guys think of this? This would be a much easier solution.
Schematic?

On most tube amps you'll find a resistor in the range of 470 kOhm to a few MOhm connected from the grid of each tube to ground. That resistor is needed for bias stability and does not appreciably affect the overall gain of the amp. Leave it!

Sometimes you'll also see a resistor of a few kOhm in series with the grid. Those are called grid stoppers and are used to avoid oscillations in the tube. They are needed.

~Tom
  Reply With Quote
Old 15th December 2010, 09:10 PM   #17
diyAudio Member
 
Join Date: Jun 2010
Got it. Thank you.
  Reply With Quote
Old 15th December 2010, 09:20 PM   #18
diyAudio Member
 
Join Date: Jun 2010
I don't have a schematic for this amp.
  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
Yaqin MS-300B SET amp Rodango Tubes / Valves 18 26th November 2010 08:09 AM
300B Set amp some variations MartinV56 Tubes / Valves 0 12th February 2008 09:22 PM
Input sensitivity on amp? suspencefull Solid State 25 3rd September 2006 07:44 PM
pentode driven 300b set amp - any info? trioderob Tubes / Valves 5 17th February 2006 01:52 AM
Leach amp input sensitivity Has Solid State 6 4th November 2003 08:14 AM


New To Site? Need Help?

All times are GMT. The time now is 04:49 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