Gain is ~11dB (~3.5x) and max output is no more than 10Vpp (3.5Vrms) to stay in reasonable distortion range. Being single ended Class A with a resistive load, it can’t swing much. It’s more of a headphone amp, a preamp input of 2.8Vrms will clip. The 150mV amplitude test case is 1/2 of the amplitude of the peak to peak input for about 1Vpp output, a typical listening level amplitude for average headphones.
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I have a plan , i don't know if it looks good,
I will call it Hakuin Integrated Preamp.
OPA1642 Phono Pre-amp Passive RIAA --> Selector Switch (To Take other input like Aux, CD, Tape) --> Hakuin (to add beautiful sound signature) --> OPA1656 for Baxandall Volume Control.
OPA1642 is chosen for Phono Stage to add bit of bite and flare which OPA1656 lacks.
Is it look good to you , X?
For me , no hurry now , i will take it up in Autumn of next year as i have things like Entrance exams to handle until then.
I will call it Hakuin Integrated Preamp.
OPA1642 Phono Pre-amp Passive RIAA --> Selector Switch (To Take other input like Aux, CD, Tape) --> Hakuin (to add beautiful sound signature) --> OPA1656 for Baxandall Volume Control.
OPA1642 is chosen for Phono Stage to add bit of bite and flare which OPA1656 lacks.
Is it look good to you , X?
For me , no hurry now , i will take it up in Autumn of next year as i have things like Entrance exams to handle until then.
I decided to build my first ever headphone amplifier and after a thorough search on diyaudio, this looked like the ideal candidate. I had an enclosure that I wanted to use for the amp, so I started from the wrong end of the build and tried to fit everything to that enclosure. It was a real 3d puzzle and it even shaped the layout of the boards. This is also the reason why I could not use the Hakuin DBs unfortunately...
I went with 5s lipo battery as the power source. While the initial idea was to use a LDO regulator, I could not wait for the delivery and used a switching regulator that I had. I placed the battery charger into the case as well, so I only connect a power cable when I want to charge it. There are 3 switches, first one connects the charger to the battery as I thought I can disconnect the charger while listening, but I cannot hear any difference when it is connected so it may always stay on. The second one turns on/off the amplifier and the last one connects/disconnects the headphone socket to address the power-on thump issue.
I am listening to this amplifier with Sennheiser HD6XX and a non oversampling dac (tda1387). I do not have anything to compare it against but it sounds amazing. Thank you xrk971 for the design!
I went with 5s lipo battery as the power source. While the initial idea was to use a LDO regulator, I could not wait for the delivery and used a switching regulator that I had. I placed the battery charger into the case as well, so I only connect a power cable when I want to charge it. There are 3 switches, first one connects the charger to the battery as I thought I can disconnect the charger while listening, but I cannot hear any difference when it is connected so it may always stay on. The second one turns on/off the amplifier and the last one connects/disconnects the headphone socket to address the power-on thump issue.
I am listening to this amplifier with Sennheiser HD6XX and a non oversampling dac (tda1387). I do not have anything to compare it against but it sounds amazing. Thank you xrk971 for the design!
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Thank you Andersonix! Yes it is the DAC. Sorry if it is a bit off-topic but here is how it looks inside. I had originally built it with a power supply that has the standard AC transformer, diode bridge, capacitor filtering followed by a linear regulator. I was happy with it until I built this headphone amplifier. Then I started hearing the hum from the transformer at maximum volume. So I tested powering the DAC with batteries as well. Now the background is totally silent even at maximum volume.
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Super work, DP! Bravo.
Love the repurposed vintage boxes!
Glad the sound is to your liking. My personal opinion is that this circuit is one of the top 3 headphone amps that I have ever heard. So not surprising you like it.
It may not have the power of those big amps, but for a high impedance can like the HD6xx, not too many amps can touch it. Especially for quietness and resolution.
You have Aksa to thank for the circuit. Hugh is a genius with the CFP topology.
Love the repurposed vintage boxes!
Glad the sound is to your liking. My personal opinion is that this circuit is one of the top 3 headphone amps that I have ever heard. So not surprising you like it.
It may not have the power of those big amps, but for a high impedance can like the HD6xx, not too many amps can touch it. Especially for quietness and resolution.
You have Aksa to thank for the circuit. Hugh is a genius with the CFP topology.
X,
You seem to have lost momentum on this amp? I had been using my ESS headphones on my bedroom amp and really enjoying them but upgraded to a pair of Hifiman Anadas for my portable and will need a new portable amp as well. Of course I have at least 3-4 projects ahead but just making sure the pump never looses prime. Just letting you know there is interest.
Bill
You seem to have lost momentum on this amp? I had been using my ESS headphones on my bedroom amp and really enjoying them but upgraded to a pair of Hifiman Anadas for my portable and will need a new portable amp as well. Of course I have at least 3-4 projects ahead but just making sure the pump never looses prime. Just letting you know there is interest.
Bill
Thanks for the show of interest. Actually, I did lose momentum for the lack of interest by people. It’s a lot of work to do these projects and I move on if it doesn’t seem to gather the steam needed. The amp works fine - I ran into issues with the fuel gauge feature. It required reconfiguring all of the resistors to get it to work.