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Old 20th April 2012, 05:25 PM   #211
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So this thread is still alive ! But no Jap transistors in sight ?
I've been wanting to do this for a long time but couldn't. So now I'll build the JLH using Jap transistors and see what comes out of it. Maybe I'll build the split supply version with relay protection in case of a large dc offset. No dc servos or output coupling caps. I think tripping can occur under about 30 to 40 mV dc which is still over 10dB below the 1mW rating. So the dc will not burn out the coil.
Might take some time as I'm not completely 'free'. However I've collected all the parts. Need to work out the supply and protection and build a prototype pcb. Lots of other changes here with a better source etc. Hope it turns out well !
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Old 20th April 2012, 05:56 PM   #212
Telstar is offline Telstar  Italy
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You got the pcb from siliconray?
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Old 21st April 2012, 05:09 AM   #213
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Who are you asking ?
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Old 21st April 2012, 09:28 AM   #214
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by ashok View Post
Who are you asking ?
I was asking to you. Which PCB are u using?
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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 21st April 2012, 03:13 PM   #215
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OK.
I don't have a pcb yet ! I will be making one for this project. Remember that I wanted to include a protection relay which isn't there on any of the current boards. Besides that I want to mount the power transistors so that they all sit on a sheet of aluminum that I want to use as the base. Currently most boards require individual heat sinks.
I don't want to talk too much about it. If I do, then I might never get it done !
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Old 24th June 2012, 11:14 AM   #216
oz7aff is offline oz7aff  Denmark
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Hello

My first post to this list and please excuse my lack of proper English.

I have build the JLH Headphone Amp on PCB's from Enjoy in your hi-fi project, diy tube amp, amplifier diy, amp diy

And I must say that the results is disapointing, it is a weak amplifier with no power to match my old Koss HV/1a Headphones.

I have done some of the modifications recomended in this tread, but it made no change that is worth talking off.

I have been building several Headphoneamplifieres, but only one design has found place in my heart and I have build many of them in defferent versions since 1980.

You can have idea of the design here, it is also Class A

http://www.sandcastle.dk/artikler/HP%20Amp.pdf

I am building on a tube amp, I hope that it will do me good

Click the image to open in full size.

Click the image to open in full size.

Regards from Denmark

Max
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Old 23rd July 2012, 06:02 PM   #217
xslavic is offline xslavic  Moldova
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Default JLH JHL ebay headphone preamp amp amplifier Dont buy it!!

attention-amp is fake,yo will have A very big background noise,can't be repaired without
-- removing some tracks and adding components --
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Old 24th July 2012, 05:45 AM   #218
mkusan is online now mkusan  Croatia
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Quote:
Originally Posted by oz7aff View Post

I have build the JLH Headphone Amp on PCB's from Enjoy in your hi-fi project, diy tube amp, amplifier diy, amp diy

And I must say that the results is disapointing, it is a weak amplifier with no power to match my old Koss HV/1a Headphones.

Max
Hi Max,
something is amiss here, if anything this amplifier has power.

I can easily drive both pair of my headphones (32&600 Ohms) to levels that can cause hearing damage.
I am not familiar with your headphones but I presume they are an easier load than small 2-way bookshelf speakers that I also tried on this amp, I beleive someone else in this topic successfully tried that too.

Hope you will get it sorted
Marko
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Old 27th July 2012, 04:55 PM   #219
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I also built this JLH using PCB from ebay, but I change the part based on Miles's advice. I hardly use any part that come with the kit. All in all, with around 30 hours of burn-in, the result is satisfied.

BTW, I adjust the trimpot and get around +-5mV by average during used.
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Old 3rd August 2012, 02:25 AM   #220
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Default JHL to JLH the hard way

Hi everyone,

Looks like this thread has now pretty much dried up now but i will add to it just to thank milescampbell, hotiron, badgerboy and others for their previous very informative postings. I also bought the Chinese JHL Headphone Amp fully assembled kit around xmas 2012 and have just got round to setting it up. However, i did this before i read this thread and although the amp sounded OK, it was dull and flat sounding. Armed with all the info on this thread, i stripped out all the bad/duff components and turned it into the JLH version that sounds far far better. I dont have any specialist audio test equipment but it sounds pretty good to me, i can listen to it as a headphone amp for my Sansa Clip+ MP3 player and also use it as a pretty decent Class A Pre-amp. I incorporated most of the changes but used replacement components that i had available, as near to the recommended values as possible. I did not change the feedback gain setting because i want to also use the headphone amp as a pre-amp and the existing 20dB gain was fine for that. Besides, the original reason for buying the kit was although the Sansa is a pretty decent multi-format music player, it struggled to drive my 32 Ohm Koss PortaPro headphones to a decent listening level.

I cant really add anything instructive to the original thread but at least i can share my pics of the headphone amp and the seperate PSU. I built the seperate PSU because i like to re-use parts for other audio equipment i might build in future and it seemed strange to take a very high quality, low noise headphone amplifier and stick it in a box with a humming mains transformer. OK, the real reason was the case i bought was too small Everything bought cheap from Ebay and Maplin (the case was only 13 inc post) Enjoy!
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