Hello
Please find some pics of my recently completed JLH class A headphone amplifier. The unit uses volume remote control, and all mains power wiring are hidden under the suspended chassis .. I done this to try and make the wiring more neater. I will be upgrading to burr dog agapters with better omp amps soon. The panel has been laser engraved on the back, the feet I made myself etc, the sound is 1st class.
all the best
JamesFeline
Please find some pics of my recently completed JLH class A headphone amplifier. The unit uses volume remote control, and all mains power wiring are hidden under the suspended chassis .. I done this to try and make the wiring more neater. I will be upgrading to burr dog agapters with better omp amps soon. The panel has been laser engraved on the back, the feet I made myself etc, the sound is 1st class.
all the best
JamesFeline
Hello
I was thinking of putting this unit on ebay if any one was interested? the volatge is 230v but I can convert to 110 or 120. The unit comes with a mini remote as well. I have been making DIY amplifiers for the last 25 years .. so practice makes purfect I suppose. The sound of this unit is amazing, watch this space for more builds from my log cabin ...
I was thinking of putting this unit on ebay if any one was interested? the volatge is 230v but I can convert to 110 or 120. The unit comes with a mini remote as well. I have been making DIY amplifiers for the last 25 years .. so practice makes purfect I suppose. The sound of this unit is amazing, watch this space for more builds from my log cabin ...
The version is the class a Chairria version single ended, the op amps will be the 627 version (metal can type) these are very expensive at £27 each. The remote pcb was purchased from Altronics. At the time I did not have a blue velvet alps pot so used the one that came with the kit .. sounds good to my ears and all who listened to the unit.
regards
Nick
regards
Nick
Hello
I will be putting this unit on ebay to make way for my next project, this unit is made to the highest standards. The start bid will be £100, trust me what ever the unit does sell for will still be well below the cost that it would be if you made the unit yourself. If anyone is interested in a special comission of the headphone amp (i.e I make the kit for you) please email me or send me a private PM
regards
Nick
I will be putting this unit on ebay to make way for my next project, this unit is made to the highest standards. The start bid will be £100, trust me what ever the unit does sell for will still be well below the cost that it would be if you made the unit yourself. If anyone is interested in a special comission of the headphone amp (i.e I make the kit for you) please email me or send me a private PM
regards
Nick
A little off topic but ....
I saw this a "JHL Class A headphone amplifier earphone AMP / preamp" in the ebay store of along1986090 from china. It looks like a normal JLH 10W amplifier with the bias current terned down for head phone use at least from the large picture. I will let you know when it arrives. For 20 UKP including shipping (approximately 25 euro) I thought it was worth a try anyway.
I saw this a "JHL Class A headphone amplifier earphone AMP / preamp" in the ebay store of along1986090 from china. It looks like a normal JLH 10W amplifier with the bias current terned down for head phone use at least from the large picture. I will let you know when it arrives. For 20 UKP including shipping (approximately 25 euro) I thought it was worth a try anyway.
Delighted with the sound quality!
Dear all,
The headphone amp I ordered from ebay the "JHL Class A headphone amplifier earphone AMP / preamp" has finally arrived from China.
I added little PCB pins to the cables to the PCB easier. Unfortunately I could not find a Headphone socket in electronics bits and bobs box. I connected it to my preamp power supply, (regulated +15V 0V -15V)I did not adjust the output voltage and it was a few millivolt from 0V.
So I could now test it, I found a pair of reasonable headphones with a broken cable so solder them to the board with some bell wire.
I was immediately very impressed with the sound. Although their was an annoying hum. When I disconnected the 0V supply the hum became inaudible, seems it was a ground loop.
Looking at the PCB it is first rate construction. The components are of cause not the highest audio grade at this price (20 Euro including shipping) and one of the electrolytic capacitor bypass capacitors was missing from one channel. I have not fixed this.
I don't keep my best headphones at home. Speakers are for home most of the time and these old headphones get a little hot on the ears, while I spent an hour or two enjoying "Rokia Traoré" latest album "Tchamantché" and the sound was so good I heard things that I had missed with my speakers (Quad ESL 63's). I would characterize the sound, by what is not present, the harsh treble I often find unpleasant, and common with many amplifiers is not present. The second thing to say about about this amplifier is it sounds very pleasant. The headphone amplifier still needs its own transformer and a box and headphone sockets, and wont get a AB comparison with my best headphones until it has these. I may later try driving it with a 32 Ohm and 300 Ohm resistor ands look at the output via my oscilloscope but thats for some time in the future. Playing into these headphones the headphones definitely distorted before the amplifier went into clipping and it was well above volumes that I should want to wear the headphones.
I feel convinced that this will become my main headphone amplifier. So box and connectors and transformer to finish the project off.
I will look into the amp a little more some time and check it is really a JLH amplifier variant, but at a casual glance it does look like it may be a scaled down variant of the 1969/1996 ETI class A 15W power amplifier with duel rail supplies at 15 V. Its heat-sinks get hot but not excessively so and idle or playing music their seems to be no difference in the heat generated.
I am sure jamesfeline's headphone amplifier is better built but if you want some of his amps quality this is a cheap and exceptionally option.
Even if its not 100% class A it is so good sounding that I will have to consider building a Class A power amplifier for my speakers again.
Regards
Owen
Dear all,
The headphone amp I ordered from ebay the "JHL Class A headphone amplifier earphone AMP / preamp" has finally arrived from China.
I added little PCB pins to the cables to the PCB easier. Unfortunately I could not find a Headphone socket in electronics bits and bobs box. I connected it to my preamp power supply, (regulated +15V 0V -15V)I did not adjust the output voltage and it was a few millivolt from 0V.
So I could now test it, I found a pair of reasonable headphones with a broken cable so solder them to the board with some bell wire.
I was immediately very impressed with the sound. Although their was an annoying hum. When I disconnected the 0V supply the hum became inaudible, seems it was a ground loop.
Looking at the PCB it is first rate construction. The components are of cause not the highest audio grade at this price (20 Euro including shipping) and one of the electrolytic capacitor bypass capacitors was missing from one channel. I have not fixed this.
I don't keep my best headphones at home. Speakers are for home most of the time and these old headphones get a little hot on the ears, while I spent an hour or two enjoying "Rokia Traoré" latest album "Tchamantché" and the sound was so good I heard things that I had missed with my speakers (Quad ESL 63's). I would characterize the sound, by what is not present, the harsh treble I often find unpleasant, and common with many amplifiers is not present. The second thing to say about about this amplifier is it sounds very pleasant. The headphone amplifier still needs its own transformer and a box and headphone sockets, and wont get a AB comparison with my best headphones until it has these. I may later try driving it with a 32 Ohm and 300 Ohm resistor ands look at the output via my oscilloscope but thats for some time in the future. Playing into these headphones the headphones definitely distorted before the amplifier went into clipping and it was well above volumes that I should want to wear the headphones.
I feel convinced that this will become my main headphone amplifier. So box and connectors and transformer to finish the project off.
I will look into the amp a little more some time and check it is really a JLH amplifier variant, but at a casual glance it does look like it may be a scaled down variant of the 1969/1996 ETI class A 15W power amplifier with duel rail supplies at 15 V. Its heat-sinks get hot but not excessively so and idle or playing music their seems to be no difference in the heat generated.
I am sure jamesfeline's headphone amplifier is better built but if you want some of his amps quality this is a cheap and exceptionally option.
Even if its not 100% class A it is so good sounding that I will have to consider building a Class A power amplifier for my speakers again.
Regards
Owen
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I have received it, and quickly hooked it up to test it out
Some quick notes in point form:
- You have to be VERY careful with DC offset - the pots let you adjust it, but they are FAR too sensitive - replace these with 10 or 25 turn 10k trimpots
- The DC offset takes a very long time to settle when it is first powered on - ~200mv initially, and over about 5-10 minutes, settles to what you adjusted it to, +/- 5mv
- The supplied schematics are not correct
It sounds really good, detailed, and the treble is better defined than most other amps i have played with. Very 'punchy' sound also
I think if i can fix the DC offset issue, it is definately a keeper
(I think it is one of the 100uF capacitors that needs to be reduced in size - will post up a schematic soon)
Some quick notes in point form:
- You have to be VERY careful with DC offset - the pots let you adjust it, but they are FAR too sensitive - replace these with 10 or 25 turn 10k trimpots
- The DC offset takes a very long time to settle when it is first powered on - ~200mv initially, and over about 5-10 minutes, settles to what you adjusted it to, +/- 5mv
- The supplied schematics are not correct
It sounds really good, detailed, and the treble is better defined than most other amps i have played with. Very 'punchy' sound also
I think if i can fix the DC offset issue, it is definately a keeper
(I think it is one of the 100uF capacitors that needs to be reduced in size - will post up a schematic soon)
A quick followup on that kit
The DC offset at the output varies by as much as 0.1v, and is entirely temperature dependant. The only safe way to keep using this amp is to build a DC servo, which got the DC offset down below 1mV
For more details, see here:
Rock Grotto Audio Forum - For Headphones - Headphone Amps - Amplifiers - X-Can V2 - Musical Fidelity - headphone Discussion - Amplifier Discussion - DIY - Amplifier Kits - Projects - SCHA - Sennheiser - Beyer - Grado - Audio Technica - Headphone amp
Great sounding amp, using it as my main amp now
The DC offset at the output varies by as much as 0.1v, and is entirely temperature dependant. The only safe way to keep using this amp is to build a DC servo, which got the DC offset down below 1mV
For more details, see here:
Rock Grotto Audio Forum - For Headphones - Headphone Amps - Amplifiers - X-Can V2 - Musical Fidelity - headphone Discussion - Amplifier Discussion - DIY - Amplifier Kits - Projects - SCHA - Sennheiser - Beyer - Grado - Audio Technica - Headphone amp
Great sounding amp, using it as my main amp now
You could just Email Geoff he’s you man on any of the JLH amps he is also a member here
The Class-A Amplifier Site - JLH Headphone Amplifiers
The Class-A Amplifier Site - JLH Headphone Amplifiers
I disagree with the suggestion to use an output capacitor. Very few capacitors are transparent sounding.
A properly implemented offset corrector,connected at the other side of the 68 ohm output resistor as shown in the amended circuit will also be transparent sounding.
I fail to see the need to contact anybody else on this subject.
The solution given will work well, and for no more than the cost of a high quality output capacitor. The poster is obviously more than happy with the results of his efforts, but perhaps the PSU area could now be investigated to obtain further gains ?
SandyK
A properly implemented offset corrector,connected at the other side of the 68 ohm output resistor as shown in the amended circuit will also be transparent sounding.
I fail to see the need to contact anybody else on this subject.
The solution given will work well, and for no more than the cost of a high quality output capacitor. The poster is obviously more than happy with the results of his efforts, but perhaps the PSU area could now be investigated to obtain further gains ?
SandyK
Well it was just a suggestion you dont have to but take a proper look at the site and you will see why i posted the link i also have the original builders manual for this JLH headphone amp you Will also find the JLH schematic i posted is likely the better amp the Little brother to the JLH speaker Amp