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★★Free JLH Hifi Headphone Amp PCB, 0.008% THD★★

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Try pf range caps across C,B of the output BJTs to slow them down, or one across the 2K7 resistor. Making the input filter more drastic by raising its cap (C2) some times is a solution also. Start in the hundreds pf and see how it goes. Those suggestions come from general amps compensation practice bodging. Watching the scope and having some ceramics handy may do the trick.
 
Sorry for the late response
I was on vacation and just after my last post my laptop died on me.
Got home yesterday only to find out my desktop is dead to... :(
Got a new laptop now I just need to get my stuff from my old laptop and desktop.
Will report back as soon as possible.

Ric
 
Keep on offering free audio PCBs..

Free JLH Headphone Amplifier Boards

This board is following JLH2005 design. Transistors used are: BC550, BC560 and MJE3055. Works excellent for 32, 120, 300 and 600 Ohm headphones. The THD is only 0.008%. Feel free to get 2 now, happy listenning!

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.

Hi silicon ray
Received the JLH Headphone pcbs today UK
Thank you very much :D
Is this the latest schematic you are at as I see some components changes to the original Geoff Moss Schematic I posted on here some time ago any updates to this Headphone amp would be appreciated pleas thanks;):)
 
HI Davy
Which cloud are you living under? Not the big tartan one is it thats comming my way:umbrella::)
Very good of silicon ray to put the boards up for the members

my build my take a little time as I have a valve amp too finish and some other pre amps on the go
But having heard its big brother running speakers this little fellow should have no problems with some good cans hooked up to it The JLH amps do have a big following on here:) and the world wide web
 
A tartan cloud would make a interesting change to the black versions I am accustomed to ;)

I tried to look up the associated power supply silicon ray has on his site but the link does not seem to work. Maybe the capacitor suppliers could not keep up with demand :D

I also looked for info on postage costs to the UK but could not find anything, I wonder how much the complete kit's would cost including p&p.
 
HI Davy
Yep I have seen that psu here’s another one available on eBay

68pcs 80V150UF matrix Power supply kit for L20 L15D L20D L25D Power amp board | eBay
[pt=US_Amplifier_Parts_Components&hash=item1c25cc03ad]68pcs 80V150UF matrix Power supply kit for L20 L15D L20D L25D Power amp board | eBay[/url]

Also if you want the same psu as I am planning to build for this amp here’s the schematic
the new link to the class an amp site and the speaker version plus the other headphone amp and psus is here The Class-A Amplifier Site
 

Attachments

  • JLH-HPhoneAmp-PSU.gif
    JLH-HPhoneAmp-PSU.gif
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Yep the link works and the item is still listed :confused:
It looks rather like this forum is blocking the eBay links not helpfully for Diyers looking for parts if this is whats happening

I also find this forum very bad for dead or broking links very annoying when you spend time reading through a thread only to find the link you want is dead :mad:
 
I don't think it's deliberate but it is annoying, something to do with ebay rover compatibility but I am not interested enough in computers to find out what. If you set your posts per page to 50, it helps with links to other posts on here but ebay remains a problem. Other than that, I find this a very good forum for us diy fanatics. There are some great group buys going on as well as the commercial section and of course the forums own online store.
 
Hi Ray,

I have one of your JLH Headphone kits. In the kit there are two variable resistors, one is 500 ohm and the other 5k ohm. Which is VR1 and VR2?

Also the two supplied R15 resistors are different values, one is 10 ohm and the other is 20 ohm. Which is correct so I can try and find another in my parts box.

Thanks
Mark.
 
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Hi Ray,

I have one of your JLH Headphone kits. In the kit there are two variable resistors, one is 500 ohm and the other 5k ohm. Which is VR1 and VR2?

Also the two supplied R15 resistors are different values, one is 10 ohm and the other is 20 ohm. Which is correct so I can try and find another in my parts box.

Thanks
Mark.
Oppps..Both should be 500 Ohm.

Both 10 and 20 works for R15. For low impedance headphone 10Ohm is better. Just keep them the same value.

Sorry for the inconveniences.
 
Hi, I finished soldering all the parts to the PCB but when testing I found that both boards oscillate at about 4Mhz. 10Vp-p

I traced the oscillations around the circuit with my oscilloscope, here are the results.

Q1 collector,
Q2 Emitter 10v and Base 5v
Q3 collector
Q8 collector
Q6 collector 1V p-p
Q5 emitter 1V p-p
Q4 collector 1V p-p, base 102mV, emitter 1V p-p

voltage across R10 (0.47ohm) is .028V

anyone know what the problem could be?

Thanks
Mark.
 
I dont have any images to post.

These are the areas in the circuit where the oscillations were present. I only noted the voltage of the oscillations at a few points.

Q1 collector,
Q2 Emitter 10v and Base 5v
Q3 collector
Q8 collector
Q6 collector 1V p-p
Q5 emitter 1V p-p
Q4 collector 1V p-p, base 102mV, emitter 1V p-p

Thanks for taking a look.
 
Q6's collector impedance should block normal amplifier activity
and abnormal amplifier oscillation from reaching through to Q5.
The pair is intended to be a constant current, ignoring what the
rest of the circuit is doing.

You measure 1VPP voltage swing on Q5, should not be possible...
Therefore my first suspicion would be something not right about
that current source pair.
 
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