Help with schematic understanding - 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 30th April 2009, 03:52 PM   #1
sumo is offline sumo  Japan
diyAudio Member
 
Join Date: Jun 2008
Default Help with schematic understanding

Hi, recently I've been looking for a 2A3 based SE amp to build and I have come across this page:

http://www2u.biglobe.ne.jp/~tossie/YZ-2A3-J.html
(This guy has a LOT of amp designs with schematics and pictures. Delete the "YZ-2A3-J.html" from the link. Worth a look! )

Its in Japanese but the schematic is pretty clear and there's a close up of the innards which helps a lot but, I am unsure about one thing

In the schematic there is a connection from one of the 6.3v filament wires from the transformer to between a 39k and 100k resistor. Its marked 65v. This is the first time I have seen this and I was wondering if anyone knows what it might be for? Some kind of bias?? Now I'm a bit a noob still so this might be a bit of a stupid question but I'd really appreciate some of your knowledge

Thanks!
  Reply With Quote
Old 30th April 2009, 04:10 PM   #2
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
Looks like they are elevating the 6.3V supply for the IDHT to a positive 65V DC. Having a positive heater with respect to the cathode keeps noise down.
  Reply With Quote
Old 30th April 2009, 05:11 PM   #3
diyAudio Member
 
Join Date: Oct 2004
Location: Maui, Hawai'i, USA
It also keeps the Vh-k rating of the driver tube from being violated. You might want to go to the TDSL and see what that rating is for the 6C8G. I'm not familiar with the tube.

I disagree strongly with the way this is implemented here. I don't like to attach it to only one side of the heaters, as we can get a hummy circuit this way. If there's a center tap on the 6.3v winding, attach it there. If there's not, use a pair of splitter resistors to attach it to both sides of the heater line, as see:

Click the image to open in full size.

Aloha,

Poinz
AudioTropic
  Reply With Quote
Old 1st May 2009, 05:21 PM   #4
sumo is offline sumo  Japan
diyAudio Member
 
Join Date: Jun 2008
Thanks for the help guys
That helped a bit. But what is Vh-k ? Its not in all the spec sheets. Is it Plate voltage? Or voltage between the heater and plate or something?
  Reply With Quote
Old 1st May 2009, 05:30 PM   #5
pointy is offline pointy  United Kingdom
diyAudio Member
 
pointy's Avatar
 
Join Date: Mar 2009
it may mean the directly heated cathode (see image)
Attached Images
File Type: jpg capture.jpg (10.4 KB, 114 views)
  Reply With Quote
Old 1st May 2009, 05:35 PM   #6
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
Quote:
Originally posted by sumo
Thanks for the help guys
That helped a bit. But what is Vh-k ? Its not in all the spec sheets. Is it Plate voltage? Or voltage between the heater and plate or something?
It's the maximum allowable voltage between heater and cathode. It is in every full datasheet, just not necessarily identified as Vhk. V could be a U, k could be c, and so on.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 2nd May 2009, 11:07 PM   #7
sumo is offline sumo  Japan
diyAudio Member
 
Join Date: Jun 2008
Aha! Thanks for that! Now it makes a bit more sense
  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 understanding a schematic graemechambers Parts 8 15th January 2007 08:01 AM
Need Help Understanding/Optimising a Schematic ak_47_boy Tubes / Valves 43 22nd October 2006 12:28 PM
need help understanding voltage regulator schematic (using CCS) from Raleigh Audio jarthel Tubes / Valves 21 29th September 2006 11:08 AM
Amp understanding / help bear-hifi Pass Labs 1 7th February 2006 05:56 PM
Amp understanding / help bear-hifi Solid State 2 7th February 2006 03:26 PM


New To Site? Need Help?

All times are GMT. The time now is 03:00 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