Hi
Just to let you all know that my JLH headphone amplifier will be going on ebay today. Full working order with remote. I will even guarantee my work !
I have a another unit that I am making. also you may be interested (watch this space) a pair of stan curtis 60w class A mono blocks nearly completed .. remember those from the 1980's
best regards
Nick
Just to let you all know that my JLH headphone amplifier will be going on ebay today. Full working order with remote. I will even guarantee my work !
I have a another unit that I am making. also you may be interested (watch this space) a pair of stan curtis 60w class A mono blocks nearly completed .. remember those from the 1980's
best regards
Nick
Hello
The mains connection looks like a speakon connection, as they look the same. The mains connection is a Neutrek connection (same company that makes the speaker connections) this is the correct mains connection version that they make hence blue .. a speaker plug will not fit the blue mains connection. I have the correct mains lead made for the unit.
The Blue mains Neutrek connection also complys will all relavant safety directives .. have a look in Farnel or RS
all the best
Nick
The mains connection looks like a speakon connection, as they look the same. The mains connection is a Neutrek connection (same company that makes the speaker connections) this is the correct mains connection version that they make hence blue .. a speaker plug will not fit the blue mains connection. I have the correct mains lead made for the unit.
The Blue mains Neutrek connection also complys will all relavant safety directives .. have a look in Farnel or RS
all the best
Nick
OK "Neutrik Powecon", fine but what's wrong with the standard IEC mains inlet that we've all got already?
Does a headphone amp really need a 20A rated connector?
Not been super-critical (am I?, sorry) but just don't see your reasoning for the choice of connector for a low power CE device.
Frank
Hello
Thanks for the feedback and I don't think you are being super critical at all, its important for me to accept all feedback.
The main reason I use this type of connector is that it is easier to mount when making the units, as all I have to do is drill a hole and then make sure the socket is straight then fix the screws.
The normal IEC mains plug needs a whole punch, and sometimes I get panel damage. So the choice of this connector is purely on the grounds of ease of construction .. well for me anyway.
all the best
Nick
Thanks for the feedback and I don't think you are being super critical at all, its important for me to accept all feedback.
The main reason I use this type of connector is that it is easier to mount when making the units, as all I have to do is drill a hole and then make sure the socket is straight then fix the screws.
The normal IEC mains plug needs a whole punch, and sometimes I get panel damage. So the choice of this connector is purely on the grounds of ease of construction .. well for me anyway.
all the best
Nick
I have all the bits of my JLH Amp sitting on my desk but still waiting for the box and bigger heatsinks.I have wired it up anyway but am using 3 fans to keep it cool as the 15V 2A Toroid is giving it lots of power so heating is till a problem.The amp has no hum or noise whatsoever unless I turn up the volume to about 3/4's then I can hear a bit of hiss.I can also turn over half way(I don't wanna try to much in fear of overheating) but it seems to have no distortion at these levels and the sound seems to increase with volume steadily and proportionally to the frequencies...in other words the sound remains the same throughout the change.I'm running it with my MDR-V500 Sony Headphones(16ohm) and even though they are less popular among fans they do carry a great tolerance to overpowering, they are also really good sounding and it would be much to the surprise of the critics..until of coarse you hear them. Like I have said I have worked in a production studio of a radio station and with what I'm listening to now I must say I have never heard these headphones like this before and can easily compete against the best headphone setups. If this is what the JHL sounds like with cheap headphones....I'd like to hear what they sound like on the big boys!!!
I am really impressed with this amp.
I am really impressed with this amp.
Definitely a good move.
I've just received this kit from Hong Kong - my first instinct is to drop all the caps in the bin and go buy some better quality ones, my second instinct is to cut the board in two to separate the rectifier and regulators from the amplifier itself - looking at the layout this seems do-able, but not as neat as it could be. One thing that does strike me as worth changing is are the two 2200uF smoothing caps between the rectifier and the regulator inputs - that's too much capacitance and will result in massive (and very fast) instantaneous current (at 100Hz) flowing through thee rectifier diodes - in theory these could be 10's of amps lasting a few microseconds which could be the source of the hum that some people have experienced. Just removing one of the two caps will help - the regulators are quoted at 62dB ripple-rejection so smaller caps on the input will be fine. Therefore the 'extra' caps would be better placed on the regulator outputs where they can act as reservoirs for any instantaneous current the amp will ever need.
Certainly getting the 15-0-15 ac off the amplifier board is not going to make it worse
The value of C13 on the pcb artwork is 1uF, but they've supplied 0.47uF with kit I've just received. At this stage trial and error (sorry... select-on-test) is as good a solution as any.
I also note that the value of C9 (in the Zobel network) on mine is 100nF, not 33nF that you have.
First guess is it's simply an impedance matching issue - the AKG's are 120ohm while the HD650's are 300ohm so they will behave differently. I'd check the value of R7 (2R2) as it could be a damping problem. Also the value of C9 in the Zobel network (mentioned above) could be having an effect - this circuit should/could be tweaked to match the headphones, which may change the sound. Wikipedia has a short (not too helpful) paragraph on Zoble network matching circuits:
Zobel network - Wikipedia, the free encyclopedia
What I suggest is using one capacitor.
I suggest you adjust the DC offset to be as large as you can make it, ideally above 0.5 volts, then note if it positive or negative, do this at initial start up and leave it for 30 mins or when the offset stops drifting. If its still more than 0.5 volts and also remains the same polarity as you started with your in the right settings region.
If the DC offset is positive then put the positive connection of the capacitor on output and negative to the headphone.
If the DC offset is negative then put the negative connection of the capacitor on output and positive to the headphone.
Regards
Owen
I suggest you adjust the DC offset to be as large as you can make it, ideally above 0.5 volts, then note if it positive or negative, do this at initial start up and leave it for 30 mins or when the offset stops drifting. If its still more than 0.5 volts and also remains the same polarity as you started with your in the right settings region.
If the DC offset is positive then put the positive connection of the capacitor on output and negative to the headphone.
If the DC offset is negative then put the negative connection of the capacitor on output and positive to the headphone.
Regards
Owen
Hi
I think I have solved the DC offset problem with my amp.
I have adjusted the offset pots and both channels now hover around 0.0mV on all volume levels.I agree with the other chap who said these pots are flimsy and they are also touch sensitive.I think a combination of this pot and a bit of lossy from my multi-meter causes the values to drift somewhat ever so slightly(Energy +- =Heat)
I think if those pots were better quality the DC would not be a problem.
This is also how I have built my amp but I will post pics later as I'm not finished yet.
For the input I am using high grade thick jack to RCA cables with ferrite cores but I have cut the RCA plugs off and soldered the wires directly onto the PCB so I have a direct input which is also shielded from my power supplies and all the other wires.I have also like I mentioned used 15Vx2 2A Audio Toroid Coil which is high quality and low noise.This gives me more Headroom at 60W rather than 30W(Min recommended)
The second power supply is a regulated 12V 1A and that is for the 2 high powered IMB Thinkcenter CPU fans...one on each heatsink.The seller says that the factory recommends 2-3times the size heatsinks for this amp if using more than 12V 1A.....this maybe the heat drifting problem you guys are having.My heatsinks run in ambient temp. a constant 23-24deg.C and never more.
For my output I cut short lengths off my Jack input coax for the female headphone jack.Like I said they are nice and thick coax cable so it works like a bomb on the output also.For the volume I drilled a hole directly in front of the box and left the pot untouched on the PCB.I have no hum or hiss problems only very slight hiss at 3/4 volume but I think that is my noisy soundcard as I can hear the motherboard working at the same levels.I plan on buying an Asus Xonar soundcard to get rid of that and a bit of decent input for the amp.
I would like to(And will) replace the caps with Elna Silmic II caps of all the same values.The seller said this shouldn't be a problem but I would like to hear any advice on this.
This is my first ever electronic build but I hope that the research I did can help anyone else in the future.I recommend this amp to anyone who wants a decent headphone amp(And it sounds amazing on my MDR-V500 headphones.....cant wait to hear it on a better set of phones!!)
I think I have solved the DC offset problem with my amp.
I have adjusted the offset pots and both channels now hover around 0.0mV on all volume levels.I agree with the other chap who said these pots are flimsy and they are also touch sensitive.I think a combination of this pot and a bit of lossy from my multi-meter causes the values to drift somewhat ever so slightly(Energy +- =Heat)
I think if those pots were better quality the DC would not be a problem.
This is also how I have built my amp but I will post pics later as I'm not finished yet.
For the input I am using high grade thick jack to RCA cables with ferrite cores but I have cut the RCA plugs off and soldered the wires directly onto the PCB so I have a direct input which is also shielded from my power supplies and all the other wires.I have also like I mentioned used 15Vx2 2A Audio Toroid Coil which is high quality and low noise.This gives me more Headroom at 60W rather than 30W(Min recommended)
The second power supply is a regulated 12V 1A and that is for the 2 high powered IMB Thinkcenter CPU fans...one on each heatsink.The seller says that the factory recommends 2-3times the size heatsinks for this amp if using more than 12V 1A.....this maybe the heat drifting problem you guys are having.My heatsinks run in ambient temp. a constant 23-24deg.C and never more.
For my output I cut short lengths off my Jack input coax for the female headphone jack.Like I said they are nice and thick coax cable so it works like a bomb on the output also.For the volume I drilled a hole directly in front of the box and left the pot untouched on the PCB.I have no hum or hiss problems only very slight hiss at 3/4 volume but I think that is my noisy soundcard as I can hear the motherboard working at the same levels.I plan on buying an Asus Xonar soundcard to get rid of that and a bit of decent input for the amp.
I would like to(And will) replace the caps with Elna Silmic II caps of all the same values.The seller said this shouldn't be a problem but I would like to hear any advice on this.
This is my first ever electronic build but I hope that the research I did can help anyone else in the future.I recommend this amp to anyone who wants a decent headphone amp(And it sounds amazing on my MDR-V500 headphones.....cant wait to hear it on a better set of phones!!)
I haven't got all my caps yet but I will be using Nichicon FG for the 2200uf caps and Elna's on the small ones...I will also order Nichicon KZ for the small ones to see if they sound better than the Elna's.
I now also have the Asus Xonar STX Soundcard and the amp is now running off the Analog side....I'm also now using Beyer Dynamic DT-770's as too many of my producer friends say that these headphones sound EXACTLY the same as speakers so very good for mixdowns and mastering also.
Now let me tell you about this amp from my view...Heliguy says this amp has no applicable value....YEAH RIGHT!!!
I tested my Xonar headphone amp that is supposed to be so good and even better than the Analog output of the same card.Well have I got news for you.This JLH Amp SOUNDS BETTER ON THE ANALOG OUTPUT THAN THE SOUNDCARDS HEADPHONE AMP!!!! (THE HIGH END IS ONLY "VERY VERY SLIGHTLY" LESS CRISPY)
The other thing is that I also heard a difference when changing from Onboard HD to Xonar STX with my same DT-770's it went from trying to "Push" the headphones at around 3/4 power from the onboard HD, down to only 1/4 with the input of the Xonar...UNBELIEVABLE SOUND RIGHT ACROSS ALL FREQUENCIES AND DIFFERENT MUSIC TOO.
This amp powers my DT's with GREAT AUTHORITY And I will liken it to the best radio station equipment costing thousands of dollars AS I USED TO WORK IN ONE.
THIS IS WITH STANDARD CAPACITORS!!!!
SURELY THERE "IS" NOTHING TO COMPARE THIS AMP TOO, as the other gentlemen said!!!
Amazing stuff and I will keep you posed on the caps and when I'm finished I will upload the pics AND THANK YOU FOR THIS THREAD!!!!!!
I now also have the Asus Xonar STX Soundcard and the amp is now running off the Analog side....I'm also now using Beyer Dynamic DT-770's as too many of my producer friends say that these headphones sound EXACTLY the same as speakers so very good for mixdowns and mastering also.
Now let me tell you about this amp from my view...Heliguy says this amp has no applicable value....YEAH RIGHT!!!
I tested my Xonar headphone amp that is supposed to be so good and even better than the Analog output of the same card.Well have I got news for you.This JLH Amp SOUNDS BETTER ON THE ANALOG OUTPUT THAN THE SOUNDCARDS HEADPHONE AMP!!!! (THE HIGH END IS ONLY "VERY VERY SLIGHTLY" LESS CRISPY)
The other thing is that I also heard a difference when changing from Onboard HD to Xonar STX with my same DT-770's it went from trying to "Push" the headphones at around 3/4 power from the onboard HD, down to only 1/4 with the input of the Xonar...UNBELIEVABLE SOUND RIGHT ACROSS ALL FREQUENCIES AND DIFFERENT MUSIC TOO.
This amp powers my DT's with GREAT AUTHORITY And I will liken it to the best radio station equipment costing thousands of dollars AS I USED TO WORK IN ONE.
THIS IS WITH STANDARD CAPACITORS!!!!
SURELY THERE "IS" NOTHING TO COMPARE THIS AMP TOO, as the other gentlemen said!!!
Amazing stuff and I will keep you posed on the caps and when I'm finished I will upload the pics AND THANK YOU FOR THIS THREAD!!!!!!
I forgot....I can now also turn my amplifier to MAX and it is DEAD SILENT because the Xonar STX has shielded components therefore I cannot hear any interference from my pc whatsoever and obviously I'm using very high quality coax input soldered Directly to the board...no joins no connections to any female RCA's just right on by all those wires directly to the board and volume pot same story...left it right were it's supposed to be. 
))
))
A little up date to this ! I would have said a similar thing after I built one except that I didn't want to get flack !
Yes, a cowardly act of course !However I've just heard a lot of 'cans' with various amps at Canjam held at the RMAF. Plenty of tubed ones and many solid state ones at various price points and most not approachable by an average DIY audio guy, me included.
I am happy to say that the JLH amp built properly can match up with the best over there ! I have no doubt about it. Maybe next year I should carry one along with me for direct comparison !
So for those hesitating to build one , go right ahead and you will have a hp amp that's as good as some of the best.
You have hum, hiss and dc offset issues ? Something you have done must be wrong. Find the problem and fix it , it isn't because the circuit is poor or defective !
If you really want to be a purist , build the split supply one , it does noticeably sound better without the output capacitor if your headphone can resolve the fine difference. Might add that those who want the protection of a capacitor and use the single supply version, it still sounds excellent even with a standard electrolytic capacitor.
Enjoy. Thank JLH !
Cheers.
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