LED biased EL84 headphone amp - Page 3 - 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 27th December 2004, 05:01 PM   #21
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
First rule of diy audio design: start with the parts you already have!
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2004, 05:17 PM   #22
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
Especially when you're a student trying to scrape together next months rent! hehe
Steve
  Reply With Quote
Old 27th December 2004, 06:19 PM   #23
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
IR LED's
Any thoughts on these? Apparently they take 100mA continuous and have a forward drop of around 1.35v, could be useful?
Steve
  Reply With Quote
Old 27th December 2004, 06:37 PM   #24
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Might be. I looked at Vishay's data sheet and from eyeballing the If vs Vf graph, it looks like the impedance is around 4 ohms or so at 50 ma. And the price is sure right.

Actually, in your application, the impedance is not really an issue, so these would certainly be worth giving a spin.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2004, 06:50 PM   #25
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
I saw that graph too, thought it was fairly reasonable up to 100mA. Shame you'd need so many to bias a big output stage though I was thinking maybe it can handle so much current partly because of the lower drop, and partly because it radiates infra-red?

I was thinking of using them on a plain common cathod 6n1p input stage for this amp, biasing with one red and one IR led, giving around 3V bias. With a 15k load resistor the operating point sits at about 6mA so unfortunately that 100mA capability wouldn't be put to much use.

Steve
  Reply With Quote
Old 27th December 2004, 07:56 PM   #26
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
OK, here's what I have now, all LED's being cheap red ones, though I'm not sure about the LED's on the 6n1p. I can't find any information about when grid current starts, so I think the bias of 3 - 3.4v is OK.
Cheers,
Steve
Attached Images
File Type: jpg audio circuit 1.jpg (65.8 KB, 412 views)
  Reply With Quote
Old 27th December 2004, 08:17 PM   #27
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Looks good, and with all those LEDs going, you'll be able to read a book with the room lights off.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2004, 09:23 PM   #28
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
Hello again! More questions unfortunately...
Been playing with this in PSU designer, as it's shown here it says the transformer is 380V RMS, I think this means I need a 190-0-190 transformer but I'm not certain. Once it settles down ripple comes out at 0.16mV which I guess is fine, I hope.
Cheers,
Steve
Attached Images
File Type: jpg untitled-1.jpg (65.2 KB, 322 views)
  Reply With Quote
Old 27th December 2004, 09:41 PM   #29
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
With a choke input supply, you'll need more like 380-0-380. Since the dynamic regulation requirements are minimal, I'd be more inclined toward a C-input supply, a lower voltage transformer, and (if I were feeling ambitious) a Maida-style regulator.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 28th December 2004, 05:53 PM   #30
diyAudio Member
 
baggystevo82's Avatar
 
Join Date: Dec 2003
Location: Herefordshire
Send a message via MSN to baggystevo82
Hello, This is the layout I've come up with now. I wish I had a better camera, but hopefully the general idea should be clearish. It all just about fits onto a piece of A4 which I'm happy with. Is the case of a normal electrolytic tied to the -ve or +ve terminal? I think the JJ's are completely insulated, but I don't think the ones I intend to use as output are, and this could be a danger if it's the +ve that's connected to it as they will be outside the case (probably).
Cheers,
Steve
Attached Images
File Type: jpg untitled-6.jpg (55.1 KB, 339 views)
  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
<WTA>Tube biased by LED arwan_zoel Tubes / Valves 1 24th October 2008 02:33 PM
12AU7/EL84 Headphone Amp sorenj07 Headphone Systems 8 5th February 2008 04:44 PM
The Importance of Being Biased Nelson Pass Pass Labs 74 26th July 2007 01:58 PM
OLT Headphone amp useing two EL84's & a 12ax7? ak_47_boy Headphone Systems 3 24th December 2006 07:58 AM
#19 biased class A Joel Tubes / Valves 33 20th December 2002 05:38 PM


New To Site? Need Help?

All times are GMT. The time now is 09:22 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