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Marsh headphone amp from Linear Audio
Marsh headphone amp from Linear Audio
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Old 15th July 2019, 05:26 AM   #1651
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by DualTriode View Post
Hello,

Apologies

I posted results in error.


I pushed the wires into the incorrect location on the breadboard. Corrections are made.
Using Figure 10 in the Linear Audio article the Drain current measures 0.61196mA much closer to the 0.8 mA Drain current discussed by Dr. Marsh in his article.

Including the 1K resistor in the test jig reduces the Drain current (IDSS) from 2.37462mA to a Drain current of 0.61196mA. See the attached photo of the test schematics and breadboard.

Thanks DT





-RNM
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Old 22nd July 2019, 01:52 AM   #1652
jhead is offline jhead  United States
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I am looking for a Mouser bill of material to order all my part's from there. Has anyone done one up for this project? Please share would give me one less thing to get done to make this build.
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Old 22nd July 2019, 02:00 AM   #1653
MarkS is offline MarkS  United Kingdom
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Marsh headphone amp from Linear Audio
Quote:
Originally Posted by jhead View Post
I am looking for a Mouser bill of material to order all my part's from there. Has anyone done one up for this project? Please share would give me one less thing to get done to make this build.
Have a word with https://www.diyaudio.com/forums/members/jackinnj.html
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Old 22nd July 2019, 02:03 AM   #1654
rsavas is offline rsavas  Canada
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min order of 2500 for
610-2N5460 at Mouser, same for Digi-key, off to ebay? polida2008 has some, I have bought from them, seem to be okay
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Old 22nd July 2019, 06:38 AM   #1655
jan.didden is offline jan.didden  Europe
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Jameco has the originals, still. Probably a good idea to snap up 100 or so.

Jan
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File Type: png jameco.PNG (119.6 KB, 241 views)
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Old 22nd July 2019, 01:39 PM   #1656
jackinnj is offline jackinnj  United States
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Marsh headphone amp from Linear Audio
The second set of boards I burned can accomodate SMT devices, as well as the pinout for J74/K170
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Old 24th July 2019, 06:36 PM   #1657
Mark Johnson is offline Mark Johnson  United States
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Marsh headphone amp from Linear Audio
Quote:
Originally Posted by jan.didden View Post
Jameco has the originals, still. Probably a good idea to snap up 100 or so.
Thanks for the heads-up, Jan. I ordered 100 pieces of each (2N5457, 2N5460) and they were delivered this morning.
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Old 25th July 2019, 01:32 PM   #1658
jackinnj is offline jackinnj  United States
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Marsh headphone amp from Linear Audio
Quote:
Originally Posted by Mark Johnson View Post
Thanks for the heads-up, Jan. I ordered 100 pieces of each (2N5457, 2N5460) and they were delivered this morning.
Check them out with a curve tracer and some Fairchild or OnSemi (Motorola) originals.

The batch of 2N5457 I bought from them were rebranded --
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Old 25th July 2019, 03:09 PM   #1659
jan.didden is offline jan.didden  Europe
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That is strange, Jameco is a bona fide outfit. Maybe they were ripped off too ...

I would actually go to their store when they still had one, must have been last century.

Jan
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Old 25th July 2019, 11:46 PM   #1660
DualTriode is offline DualTriode  United States
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Hello,

A couple of months ago I renewed the effort looking at the magic of FET’s and Dr Marsh’s headphone amplifier.

A month or so ago I bought 100 of each 2N5457 and 2N5460 from Jameco. These JFET’s labeled “Fairchild” did not look right when tested on the bench. If I recall correctly it was the 2N5460 that was way off and not looking like the datasheet. The IDSS was well below the 1mA minimum called out on the datasheet. The Id Vg curves (Drain current and gate Volt curves) did not look like the datasheet either. These JFET’s from Jameco are set aside on the bench top for later.


Too much fun!
DT
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