I received a letter from Walt a few weeks ago... he was disappointed that so few people were into DIY audio any more.... and so was going to consolidate everything and drop the blog.
-RM
Is he consolidating it on DIY audio? I'm really suprised that he said that so few people were into DIY, hard to tell here.. Mind you a lot of cheap chinese hardware doesn't help.
Walt,
Great to see you here!
But unless I am missing something, this is what I get when I on anything pointed to by your opening page ...
Forbidden
You don't have permission to access /PDFs/Walt's_Blog_2014_About_This_Blog.pdf on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Appears it was cached. I just got that page too and I went to his home page and clicked the link from there. Try that and it should work.
Walt, If I go to Waltjung.org and click through to the Archived "Sitepages" link I get the following on all of the PDF links:
Forbidden
You don't have permission to access /PDFs/Walt's_Blog_2014_Classic_Articles_Page.pdf on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Pls try it again, starting from the home page (as noted in the signature line below), and click on Site Pages as indicated. Then click on whatever link you wish. They should all work.
I did see it work OK, then I also saw the 404 msg, etc.
However it seems to be all A-OK now. FWIW, this is what I am aiming for in terms of operation.
I did see it work OK, then I also saw the 404 msg, etc.
However it seems to be all A-OK now. FWIW, this is what I am aiming for in terms of operation.
why is there links on a PDF? why not just put the links to the archives on the page. some pdf viewers dont let you click on links from within a PDF.
just sayin.
just sayin.
There's a wealth of information on Walt's site. Highly recommended !
Something to make anyone's DIY project better.
-Richard Marsh
Something to make anyone's DIY project better.
-Richard Marsh
It was mentioned before but if you do not like to do matching of transistors, you can buy a complete matched set of all transistors from Tech-DIY LLC. This takes a lot of the work/time out of the project. The output devices supplied are 2 each of the -649/669 types.
http://tech-diy.com/Store/MarshHeadphone.htm
THx-Richard
http://tech-diy.com/Store/MarshHeadphone.htm
THx-Richard
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Recently, I tried this package of matched transistors and tested it. The results are excellent: All harmonics were well below -100dB. depending on PS voltage and load, the harmonics were typically in the -110-130db areas. Again, using only 2 diode bias; two diode produce 100mA ouput current draw while 3 diodes will double that to 200mA idle in OPS.
So,you can use the matched semiconductor package from Tec-DIY LLC. without worry about the results not being as good. Plus, you can use +/-24vdc PS for greater load driving ability at very low distortion as the output devices are rated for higher voltage. However, the drivers (Vas stage) and OP stage will need greater heat sinking if you do.
THx-RNMarsh
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So, when do you need to use 3 diode bias string? Well, if your headphones are <100 Ohms, the thd will be higher with 2 diodes and <100 Ohms.
Use three diodes for <100 Ohm headphones to keep the thd at minimum.
THx-RNMarsh
Use three diodes for <100 Ohm headphones to keep the thd at minimum.
THx-RNMarsh
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Nice article Mr. Marsh.
His test circuit matches by Vbe.
Should BJTs also be matched by Hfe, like for the input stage of an amplifier, for minimum offset or is Vbe the preferred way to match them?
Thanks...