Modification of 300B SE Amplifier - 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 21st August 2012, 06:24 PM   #1
diyAudio Member
 
Join Date: Feb 2011
Default Modification of 300B SE Amplifier

Any idea if changed the input stage 6SN7 from SRPP to parrallel connection. Is that help to reduce the over gain of the circuit? Do concert if the current of the input stage will be more than the driver stage (maintain the SRPP).. Should I maintain the 1.5K cathode resistor as is in order to keep the same current flow over the input stage... I have to calculate the new value of the plate resistor afterward.

Please share comment.
thanks!


300BSch (Patrick) | Flickr - Photo Sharing!
  Reply With Quote
Old 21st August 2012, 06:26 PM   #2
diyAudio Member
 
Join Date: Feb 2011
Click the image to open in full size.
original schematic enclosed
  Reply With Quote
Old 21st August 2012, 08:49 PM   #3
diyAudio Member
 
Join Date: Nov 2011
Location: Athens
You can reduce the gain by simply remove the bypass capacitor in the first SRPP stage.
  Reply With Quote
Old 21st August 2012, 10:32 PM   #4
diyAudio Member
 
Palustris's Avatar
 
Join Date: Aug 2006
Location: Cape Cod
You can remove the entire first stage by connecting the input to the second SRRP stage.
  Reply With Quote
Old 22nd August 2012, 02:37 PM   #5
diyAudio Member
 
Join Date: Feb 2011
I did tried to remove the bypass cap fron the input tube and yes, the gain reduction achieved but it lose the "mid" gthe high and the bass are both acceptable) ... May be too much reduction that I'm not sure and thus consider making something in between.
  Reply With Quote
Old 22nd August 2012, 04:54 PM   #6
palmas is offline palmas  Portugal
diyAudio Member
 
Join Date: Jun 2007
What is the supply voltage?
  Reply With Quote
Old 22nd August 2012, 06:13 PM   #7
diyAudio Member
 
Join Date: Feb 2011
the plate of the lower tube : 185Vdc
cathode of lower tube : 4Vdc
  Reply With Quote
Old 22nd August 2012, 06:14 PM   #8
palmas is offline palmas  Portugal
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Angelpat View Post
the plate of the lower tube : 185Vdc
cathode of lower tube : 4Vdc
the top triode plate voltage?
  Reply With Quote
Old 22nd August 2012, 06:28 PM   #9
diyAudio Member
 
Join Date: Feb 2011
370Vdc
  Reply With Quote
Old 23rd August 2012, 11:54 AM   #10
palmas is offline palmas  Portugal
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Angelpat View Post
370Vdc
With that voltage you can use the 6SN7 in a griunded cathode configuration, with both triods in parallel (Rplate=10k to 12k and Rcathode=1K and 8uF).
You'll get about 23dB of gain (14x), but you'll have only about 60kOhm of input inpedance.
I suggest you use one triode only, making the triode 1 for the left channel and the 2 for the right one, so you can trade tubes between channels and have a pair of "new" triods.
For that you can use the same values for resistors and cap and get about 20dB gain (12x), but have an input impedance of more than 160kOhm.

Let me know if you need some recalculations or new specification.
  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
Recommended 300B SE Amplifier Designs gaborbela Tubes / Valves 35 22nd March 2013 03:49 AM
Mono 300B SE Amplifier JPS64 Tubes / Valves 43 22nd May 2011 04:25 PM
FS: Golden Tube Audio SE-300B II Special Edition Valve Amplifier coh-b-pyky Swap Meet 1 24th April 2010 09:31 PM
An intriguing 300B SE-direct-coupled-amplifier Antonio Tucci Tubes / Valves 27 8th February 2006 10:34 AM
For Sale - 300B SE Amplifier ThorstenL Swap Meet 0 26th June 2003 08:37 PM


New To Site? Need Help?

All times are GMT. The time now is 10:14 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