Marsh headphone amp from Linear Audio - Page 46 - 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 9th August 2012, 09:14 PM   #451
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by RNMarsh View Post
I found an eBAY low distortion sine wave signal source on pcb, loaded/built for $39. The fixed 1 KHz signal only has .00005% thd. That works for me. Ordered 2 of them. Look under electronics test equipment.
I measured the units -- 2ea of the 1Khz and found that only the even harmonics are very low. the odd harmonics are not so great -- -88-90db for 3rd and 5th and further down the road is still high. Not better than the AP. rats!

I'll contact the source of these and see what he says.

-RNM
  Reply With Quote
Old 10th August 2012, 01:00 AM   #452
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Jan,

I got the transistors today. Thanks! They arrived in great condition.
  Reply With Quote
Old 10th August 2012, 07:14 AM   #453
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by sonidos View Post
Jan,

I got the transistors today. Thanks! They arrived in great condition.
Actually you are one short. After unpacking box # 47 (or maybe it was # 55) from the move yesterday, one lonely 210 fell out. I'll get it to you for sure

I'd be curious how they match up, hope they are usefull for you.

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 10th August 2012, 02:55 PM   #454
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Jan,

I pulled out the Heathkit IT-18 last night and beta on the NPNs runs about 140 to 160, while PNPs run from about 160 to 180. I'll get plenty of useful ones from the set.

Maybe SY can toss that 1 lonely transistor in the mail when you come to the States for Janneman 2012 Chicagofest!
  Reply With Quote
Old 10th August 2012, 03:54 PM   #455
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Mr. Marsh,

I'll be checking for Vbe this weekend. Details to follow.

@jackinnj:

Coming up with a revision to my board will be cinch for those SMT fets..plenty plenty in stock at Mouser. I'll build a TO-92 version and an SMT version. Plenty of boards in my parts bin and plenty of etch solution.
  Reply With Quote
Old 10th August 2012, 05:27 PM   #456
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally Posted by sonidos View Post
Mr. Marsh,

I'll be checking for Vbe this weekend. Details to follow.

@jackinnj:

Coming up with a revision to my board will be cinch for those SMT fets..plenty plenty in stock at Mouser. I'll build a TO-92 version and an SMT version. Plenty of boards in my parts bin and plenty of etch solution.
For the F5 boards i had burned in China i allowed for use of SMT JFETs -- i should've thought of that when I did the headphone boards, but hadn't realized that there was a shortage of TO-92 parts...and as i mentioned previously, you could use GR rated 2sk170's or bf862.
  Reply With Quote
Old 10th August 2012, 06:35 PM   #457
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
On my part, it's a hard-headed approach to staying as faithful to the article.

But I'll shed no tears if I have to use the SMT parts.
  Reply With Quote
Old 12th August 2012, 05:03 AM   #458
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by RNMarsh View Post
I measured the units -- 2ea of the 1Khz and found that only the even harmonics are very low. the odd harmonics are not so great -- -88-90db for 3rd and 5th and further down the road is still high. Not better than the AP. rats!

I'll contact the source of these and see what he says.

-RNM
source says there is nothing wrong with them... must be my AP needs calibration... ??
  Reply With Quote
Old 13th August 2012, 06:24 PM   #459
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
yes, as a rookie, I was tempted to buy used stuff on ebay dirt cheap. Then I started to realize how will I know if it's defective? I later read somewhere to pay for a re-calibrated unit.

Update - the MOT fets I bought are junk. As soon as I put them on my breadboard to test Idss, they became extremely hot. Boy oh boy...

So I also worked on the SMT layout and I'll order some of those Fairchild SOT23 fets. But I bet I have close enough matching on those FETS I found in FLA and in Thailand. So on the fets, I'm good to go.
  Reply With Quote
Old 13th August 2012, 10:36 PM   #460
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Default SMT version

On the left channel, I laid it out for the smt versions of the jfets. I noticed on the Fairchild Semi datasheet that drain and source are inter-changeable. So it must be symmetric it seems.

Also note that I added film caps from rail to ground and also a film cap that goes from rail to rail. Mr. Marsh mentions this in the article. I lucked out and got the last of the Wima PPS box caps in stock. These are the Wima MKI series. Nice and small with 5mm lead spacing.
Attached Images
File Type: jpg marsh smt.jpg (138.4 KB, 443 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
FS: Meier Audio Corda Headphone Amp jtwrace Swap Meet 5 29th February 2012 11:34 AM
Histoically significant - Phase Linear audio pre-amp bobcul Swap Meet 0 21st February 2012 08:16 PM
Headphone amp with mixed-in telephone audio krfjr1965 Solid State 3 10th March 2010 03:50 PM


New To Site? Need Help?

All times are GMT. The time now is 01:35 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