HA-2 Wheatfield headphone amp query - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

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 11th August 2009, 05:15 PM   #1
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Default HA-2 Wheatfield headphone amp query

Have a quick question regarding this design.

Does the cathode resistor of the 6AS7 CF output stage need to be bypassed?

I assume yes as it shows 2 links to ground off the cathode resistor of 2K 20W.


http://www.pmillett.com/Wheatfield/manual.pdf
  Reply With Quote
Old 11th August 2009, 06:25 PM   #2
DougL is offline DougL  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Wheaton IL.
Blog Entries: 30
No,

Bypassing that resistor would effectively ground the output for AC.
The grounds shown are probably unused pins on something.

HTH

Doug
__________________
Scienta sine ars nihil est - Science without Art is nothing. (Implies the converse as well)
Mater tua criceta fuit, et pater tuo redoluit bacarum sambucus
  Reply With Quote
Old 11th August 2009, 06:30 PM   #3
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
That resistor is labelled as a TO-220 device, so I guess there are probably 4 pads on the PCB for it, and the middle 2 should be grounded.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 11th August 2009, 06:30 PM   #4
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Thks Doug. That makes sense.
  Reply With Quote
Old 11th August 2009, 07:03 PM   #5
diyAudio Member
 
whitelabrat's Avatar
 
Join Date: Dec 2006
Location: Maryland
no bypassing on that 20w 2k resistor. i used a 25w, thermal grease, and an el grande heat sink. that sink gets hot too, but not painful.

i'm having a real bear of a time hunting out some bad hum on mine. i'd suggest avoiding the 200 series hammond transformers like the plague. mine has some serious mechanical noise.
  Reply With Quote
Old 11th August 2009, 07:33 PM   #6
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Quote:
i used a 25w, thermal grease, and an el grande heat sink. that sink gets hot too, but not painful.



Thks for the heads up. I've got a couple of 2.2K 20Watts I was going to try. Maybe attach them to a heatsink I've got hanging around.
  Reply With Quote
Old 11th August 2009, 07:46 PM   #7
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Quote:
i'm having a real bear of a time hunting out some bad hum on mine. i'd suggest avoiding the 200 series hammond transformers like the plague. mine has some serious mechanical noise.
What current are you running your tubes on? I was hoping I could use a little less B+.
I plan to use 6080's.

I see he's using about 95 mA.
  Reply With Quote
Old 11th August 2009, 08:20 PM   #8
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
I could probably get about 240/250 B+ out of my transformer with max 200mA.


psu (275V secondary, 52ohms): (CRCRC)

100uf
225 ohms
470uf
225ohms
470uf
  Reply With Quote
Old 11th August 2009, 08:25 PM   #9
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
100 uF is too big for a tube rectifier.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 11th August 2009, 08:28 PM   #10
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Sorry leadbelly forgot to mention I'm going to use a SS power supply.

And yes you are very right. I use 0.47uF in my tube rectifiers.
  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
UK Law query john blackburn The Lounge 35 15th May 2009 09:59 AM
query Professor smith Multi-Way 2 5th May 2009 01:47 AM
query on the PSU of a preamp ray_ben Tubes / Valves 2 1st January 2006 10:40 PM
BOZ query to chocky JC Fardo Pass Labs 1 21st December 2005 06:21 PM
Clock query Horn_aficionado Digital Source 5 2nd January 2004 06:35 PM


New To Site? Need Help?

All times are GMT. The time now is 05:32 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