Some other Source Follower COnfigurations - Page 11 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 26th July 2010, 04:22 PM   #101
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
Hi Patrick,

Thanks for the reply.

Quote:
Originally Posted by EUVL View Post
.... If using EI, it is better to mount the transformer away from the amplifier to minimise magnetic disturbances.
Either a toroidal (if not too expensive) or a separate PSU case, then... No problem.

Quote:
4. If you want to put a buffer upfront, you might as well add a proper line stage with gain instead.
But this depends on what headphone impedance you intend to drive with.
The reason for thinking about a headphone amp is an upcoming sabbatical leave, which will leave me without music while away unless I do something about it... (No way can I ship all my stereo and speakers...) So my idea was to build a headphone amp and buy a good (OK, self-indulgent ) pair of headphones when I get up to the US, since they cost a fortune down here. I've been looking at Grado or AKG, which appear to mostly have impedance around 32R, although I'm open to other suggestions. I presume when you said a gain stage "depends" on impedance that you meant a higher impedance than this would need one (say 300-600R or something) Right??

If I need gain juma's BF862 preamp (gain of 2) springs to mind, since I've made two and found them to be excellent. On the other hand it might be simpler not to bother, and just take one of them with me. Unless, of course, you meant something with more gain than that?

Cheers

Nigel
  Reply With Quote
Old 26th July 2010, 04:52 PM   #102
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
DAO is perfect for AKG701 or 702.
No need for voltage gain if you have a source with 2Vrms output, IMHO.
Gain of 2 does not bring much if you have 600R phones and you still want a volume control somewhere.

Whether you need a buffer (e.g. Curl Follower, otherwise known as B1) or not depends on your source (if it can drive a load of say 10k or less).


Happy building,
Patrick
  Reply With Quote
Old 26th July 2010, 05:32 PM   #103
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Quote:
Originally Posted by EUVL View Post
... a buffer (e.g. Curl Follower....
I'm afraid it's older than Curl - CCS loaded Cathode/Source/Emitter Followers are known since the dawn of time...
  Reply With Quote
Old 26th July 2010, 06:01 PM   #104
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
True.

But to use a pair of matched JFETs on a small common substrate (e.g. 2SK389) so that they track each other thermally, I first came across in Borbely's article, where the name Curl was mentioned.


Best Regards,
Patrick
  Reply With Quote
Old 27th July 2010, 08:12 AM   #105
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Quote:
Originally Posted by EUVL View Post
... I first came across in Borbely's article, where the name Curl was mentioned....
Yes, it's the Borbely's article: "JFETS: The New Frontiers, part 2"
That article mentions Mr. John Curl's JC-2 module, where he used complementary, push-pull JFET buffer (fig. 16b) but not the JFET CCS loaded SE buffer (fig. 15c) we are talking about. It's treated as generic, classic circuit...
  Reply With Quote
Old 27th July 2010, 02:40 PM   #106
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Nigel, if your volume control output impedance is not too large (and hence does not cut high frequencies when feeding the LU1014 gate capacitance), then you might not need the buffer. Just the volume control and the DAO stage.

1.225 V RMS (which most sources can supply) will get you 50 mW into 30 Ohm headphones. So if using modern high sensitivity 'phones you will likely get in excess of 110 dB. Most folks seem to listen in the range of 70 - 80 dB, so you will have plenty in reserve.
  Reply With Quote
Old 29th July 2010, 02:44 AM   #107
diyAudio Member
 
Join Date: May 2010
Location: Santa Fe, New Mexico
Default Crossfeed for headphone amps

Six or seven years ago I was playing with DIY headphone amps, based on Chu Moy's "headwize" website. It's a controversial subject, but my various fiddlings and listenings convinced me that headphone amps with crossfeed are better than those without for extended listening. Some of the folks from headwize went off and formed head fi about the time I turned attention to other topics, and that has since become huge. There is a lot of information on headphones, portable headphone amps, tube headphone amps, buffers, power supplies, you name it, at these sites, and if I were going to be without my stereos for a sabbatical year I would want to get the latest word and DIY accordingly.
  Reply With Quote
Old 29th July 2010, 04:23 AM   #108
diyAudio Member
 
Join Date: Feb 2005
Recordings vary and the amount of "required" amount of Xfeed will also vary to your taste, from none at all to quite a bit (very precise, yes!) - there are a number of ccts around but are fairly consistent about the freq points and attenuation and Xfeed levels.

As bd mentioned above, both "headwize" and head-fi" contain a lot of useful information, and links to some of the newer developments - suprising.

From my #81 post, you can see that I'm slowly playing around with the input stages to the unit - the amp itself is Patrick's standard Taylored design (280mA), and I just replaced the zener with a "string of leds" and tried different caps - I have simplified the power supply to basic Shottky diodes, R-C-R-C smoothing into a beefed up Salas Shunt Reg (Version 1) that replaced the previous Cmultiplier method - this, too, required the output delay/dc detect cct as the +/- rails don't come up together, unfortunately.

I have concentrated on a "tilt" control (HeadWize) plus a version of Rane tone controls but have a long way to go yet - Xfeed is a mixture of the J Meier and Ohmon ccts, adjustable and the type of caps here make a bit difference - I use styrene generally, but many other readily available good caps - fancy bits are not always best choice here, IMO.

Some of the newer commercial headamps are worth a look, too.

my 2 cents, regards
__________________
... jh
  Reply With Quote
Old 29th July 2010, 10:41 AM   #109
njepitt is offline njepitt  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: Maine
Hi Guys,

Thanks for all the replies.

Quote:
Originally Posted by Gordy View Post
Nigel, if your volume control output impedance is not too large (and hence does not cut high frequencies when feeding the LU1014 gate capacitance), then you might not need the buffer. Just the volume control and the DAO stage.
Actually, it seems that the heatsinks will make the chassis a good deal bigger than the basic DAO circuit needs, so there should be plenty of space inside - I will probably do it first with no buffer, and pop one in later if it seems to need it.

Quote:
Originally Posted by bdbender View Post
Six or seven years ago I was playing with DIY headphone amps, based on Chu Moy's "headwize" website. It's a controversial subject, but my various fiddlings and listenings convinced me that headphone amps with crossfeed are better than those without for extended listening.
Yes, I've been looking through the sites you mention, and I'm fascinated by the crossfeed idea. I'm not usually a big headphone user, but since there's no way I can ship speakers I'm trying to learn up.

Quote:
...if I were going to be without my stereos for a sabbatical year I would want to get the latest word and DIY accordingly.
Amen.

Quote:
Originally Posted by jameshillj View Post
From my #81 post, you can see that I'm slowly playing around with the input stages to the unit - the amp itself is Patrick's standard Taylored design (280mA), and I just replaced the zener with a "string of leds"
Are you using the J511? I'm having trouble finding where to get them. (Just pricing things out for the moment)

Quote:
I have simplified the power supply to basic Shottky diodes, R-C-R-C smoothing into a beefed up Salas Shunt Reg (Version 1) that replaced the previous Cmultiplier method - this, too, required the output delay/dc detect cct as the +/- rails don't come up together, unfortunately.
I'm thinking of either the Salas reg (by "first" you mean without the "R6 mod" that's discussed in the thread?) or the zen v3 supply that Steenoe used in the DAO. What delay/dc detect circuit are you using?

Quote:
...I have concentrated on a "tilt" control (HeadWize) plus a version of Rane tone controls but have a long way to go yet - Xfeed is a mixture of the J Meier and Ohmon ccts...
OK, I have some reading to do....

The other issue with planning the amp is its size and weight. Taking a family of six abroad for six or seven months means an incredible amount of luggage, so with flight weight restrictions I may need to make something more portable and leave the DAO for when I come back. Not really clear yet, but I can almost hear my wife now ("You're taking WHAT??") The headwize and head-fi sites have loads of info, but does anyone have a recommendation for something lighter (but maybe not as small as an Altoids tin)?

Thanks for the help

Nigel
  Reply With Quote
Old 29th July 2010, 12:33 PM   #110
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
J511 is obsolete from Vishay, but available from Linearsystems.

http://www.linearsystems.com/datasheets/J500.pdf

But any JFET with Idss of around 5mA will do.
You just need to short gate and source together to make a CRD.


Patrick
  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
Source follower and common source output stages slogan2112 Pass Labs 2 9th October 2008 08:19 PM
Bootstrapped FET source follower ? ash_dac Solid State 11 14th November 2006 08:19 PM
Aleph-type current source, but source follower this time tschrama Pass Labs 4 29th July 2005 12:55 PM
Source follower electret mike -> use with current source? capslock Solid State 1 28th February 2003 12:54 PM
Source Follower Enlightenment SteveS Pass Labs 3 20th June 2002 09:58 PM


New To Site? Need Help?

All times are GMT. The time now is 12:18 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