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Old 3rd January 2013, 10:41 AM   #531
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Thank you Georg but no gif appears at all - just blank .
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Old 3rd January 2013, 11:49 AM   #532
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A Paul Kemble web page - John Linsley Hood preamp designs.
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Old 12th January 2013, 07:14 PM   #533
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by RNMarsh View Post
here is the original JLH headphone amp circuit --- RNMarsh

??
I bought about 2 yrs ago a JLH headphone amp being promoted on this DIYAudio site.... it doesnt measure as well, either. What else can i say. I even paid about $450 for a finished product off a headphone only site and wasnt pleased with the results, either. Now that one also sits unused as more wasted money. :-( It was all IC based.... but couldnt drive low Z headphones well... even with a buffer IC after the opamp. The sound matters. Measurements matter. Seemingly small changes matter.

Thx-RNMarsh

Last edited by RNMarsh; 12th January 2013 at 07:18 PM.
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Old 12th January 2013, 10:18 PM   #534
Telstar is offline Telstar  Italy
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JLH amp IC based? the sold u a fake.

A real JLH circuit is in my do do list (after yours, yay!)
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
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Old 13th January 2013, 03:17 AM   #535
Guiness is offline Guiness  United States
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Adding this to my ever going collection of headphone amps!
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Old 13th January 2013, 11:14 PM   #536
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Default PCB's Pls

Quote:
Originally Posted by jackinnj View Post
After the turn of the year I will put together batches of parts (including the matched transistors.)

In the interim, I'll put together a BOM with the device sizes.
Hi Would be intrested in pcb and / or parts pls let me know when they become avaliable, even the pcbs would help.
thanks
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Old 13th January 2013, 11:19 PM   #537
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Quote:
Originally Posted by jackinnj View Post
After the turn of the year I will put together batches of parts (including the matched transistors.)

In the interim, I'll put together a BOM with the device sizes.
would be intrested in the pcb and bits when they are avaliable pls pm me
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Old 14th January 2013, 12:46 AM   #538
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by Telstar View Post
JLH amp IC based? the sold u a fake.

A real JLH circuit is in my do do list (after yours, yay!)
I just looked at my comment - some of it didnt come thru.... the JLH was bought off this forum/dyiaudio headphones here. Not IC. Others tried were IC based. There are many to choose from. Some are copies of others work- like JLH. Some are improvements on others work. I am here only to help with my headphone amp... its dirivation is discussed in detail in Linear Audio publication.
In another forum here in dyiaudio I am working on measuring the thd and harmonics and trying to come up with a signal source and thd meter to measure the headphone amp. each time I get something better to test with, the number drops. My older Audio-Precision wasnt up to the task. I now use a ShibaSoku AD725D which can measure directly, to -135db re 1 volt. Then I can add FFT and notch filters to drop that further. Now I need a better signal source and modifying an HP339A as a better (lower distortion) source. All started because I couldnt get an accurate number for my own headphone amp design with the A-P. Its been expensive but fun, too.

Thx-Richard Marsh

Last edited by RNMarsh; 14th January 2013 at 12:50 AM.
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Old 18th January 2013, 02:27 PM   #539
sonidos is offline sonidos  United States
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Update -

Working on the psu using LM317 as a pre-regulator per jackinnj's input.

Thanks to one of our DIY mod's I picked up a TEK 475 scope on ebay for $235 and it arrived in great shape. The itch gets more serious! hehehe
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Old 19th January 2013, 07:14 PM   #540
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I've put together some kits of parts for the Marsh headphone amplifier -- you've got two choices: 1) Semiconductors and active components = $54;
2) Semiconductors = $27.50.
This will be sufficient for a pair of amplifiers -- one for each ear.

The JFETs are matched for Idss (that is you get a 2N5460 and 2N5457 which are matched for Idss +/- 0.1mA), bipolar output devices for hfe.

Click the image to open in full size.

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