kobayashi 300B push-pull - 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 16th November 2008, 04:28 PM   #1
n_dori is offline n_dori  Albania
diyAudio Member
 
Join Date: Oct 2008
Location: Athens, Greece
Default kobayashi 300B push-pull

Hello to everybody!
I decided to build a 300B push-pull amplifier. I found a design by Satoru Kobayashi

http://www.audiocraftworks.gr/gr/pag...koba300bpp.pdf

The output transformer will be Lundahl LL1679-PP 4K5 - 8.
Maybe I'll change 6N1P tube with E88CC
300B tubes are from Electro Harmonix

Any suggestions on this?
I need your opinion

Thank you
  Reply With Quote
Old 16th November 2008, 07:15 PM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
I'm not a big fan of the in put stage/phase splitter.

IMO, making it a true LTP with a CCS on the bottom would be better.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 16th November 2008, 08:48 PM   #3
n_dori is offline n_dori  Albania
diyAudio Member
 
Join Date: Oct 2008
Location: Athens, Greece
@ planet10

thanks for your response

you mean something like the one in this design
  Reply With Quote
Old 16th November 2008, 09:02 PM   #4
diyAudio Member
 
Join Date: Sep 2003
Location: London
Totally agree with CCS under differential pairs. How about something really good like ECC40 into a pair of 71A, transformer coupled with e.g. Lundahl LL1660 into the 300bs. That's a terrific combination.

Andy
  Reply With Quote
Old 16th November 2008, 10:52 PM   #5
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Default Re: kobayashi 300B push-pull

Quote:
Originally posted by n_dori
Any suggestions on this?
I need your opinion
Not a big fan of floating paraphase splitters (an LTP is barely more complex) since the biggest weakness of this implementation is uneven harmonic distortion across phases.

Other than that, he does everything else right. 300Bs require adequate grid drive, and here's one design that includes that.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 17th November 2008, 11:13 AM   #6
Alex M is offline Alex M  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: Hampshire, UK
How about Kevin Kennedy's push-pull 300B amp project ?

I am just starting to build this, and it seems comprehensively designed,. It has a proper regulated HT supply, as well as a regulated -200V bias supply which ensures the differential circuits work properly. The regulation may seem overkill, but since the main expense in this kind of project is iron and output valves, this may not be the case...

Alex
  Reply With Quote
Old 17th November 2008, 02:40 PM   #7
n_dori is offline n_dori  Albania
diyAudio Member
 
Join Date: Oct 2008
Location: Athens, Greece
@andyjevans
it sounds a good idea but it's out of ny budget. Maybe later

@Alex M
I'll try this design too. Actually I am going to build the output stage and try diferent driver stages.
Another idea is EF86 input, 12AX7 LTP and 5687WB CF directly driving 300B grid.
  Reply With Quote
Old 17th November 2008, 07:27 PM   #8
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
Quote:
Another idea is EF86 input, 12AX7 LTP and 5687WB CF directly driving 300B grid.
That's far too much gain, unless you're thinking of having a heap of global NFB (which I wouldn't recommend).
  Reply With Quote
Old 18th November 2008, 12:59 AM   #9
tomsyl is offline tomsyl  United States
diyAudio Member
 
Join Date: Mar 2005
Location: Hawaii
Default The Kennedy PP 300B amp looks like an excellent design

and two people who I trust on these issues have praised it highly, so I'm also slowly collecting parts for one. The OPTs were made by Jack Elliano of ElectraPrint for a very reasonable price, though shipping was costly because they are very heavy - at least 15 pounds, maybe more.

I have a 7591A amp built by Kevin Kennedy using Peerless transformers and with his typical regulated PSs, and it sounds very good. He's reputed to be a careful, clever designer.

The Lynn Olson design is supposed to be very good as well. I know of one example having been built, but it's pretty costly due to all of the iron used. Link.
  Reply With Quote
Old 18th November 2008, 01:41 AM   #10
diyAudio Member
 
Join Date: Nov 2005
I agree - the first stage should be differential instead, for better balance. The ECC88 would be a good choice for the first stage to reduce gain and distortion. 6CG7/6SN7, too, would be good.

I would be inclined to seek higher damping factor and reduced distortion, and might try to separate the second stage into a push-pull pair with separate (unshared) cathode resistors - then apply 3-6dB feedback to their cathodes from the output tube plates. Otherwise, since you are using a high quality output transformer, it may be helpful to add ~6dB global feedback.

Of course, I suspect just changing the first stage tube to ECC88 and running it differential will improve the distortion, and you may feel satisfied without feedback
  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
300B push pull amp billr Tubes / Valves 5 14th July 2008 01:47 AM
Push Pull 300B preliminary zigzagflux Tubes / Valves 18 28th August 2007 10:14 AM
What should B+ on 300B push-pull be? andy2 Tubes / Valves 8 12th July 2006 04:33 PM
300b Push Pull Interstage Tsf brsanko Tubes / Valves 7 2nd March 2005 01:46 PM
300B Push-Pull and PSE mozfet Tubes / Valves 1 5th August 2002 07:32 PM


New To Site? Need Help?

All times are GMT. The time now is 08:44 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