This is a tear down of the Neurochrome HP-1 High performance Headphone amplifier. My review of HP-1 showed exemplary distortion and high power handling. With kind permission from its designer, here is a look at what is inside.
Here is a lower resolution shot of the PC board:
For 4X higher resolution, click on this attachment:
You may have seen my tear down of massdrop THX AAA 789 amplifier which had plenty of empty space. Not so here. As you see, nearly every inch of space is used.
Unlike the massdrop THX 789, the power supplies for the HP-1 are internal. We have two switching supplies from the reputable Mean Well Taiwanese company. I am assuming one provides positive and the other, negative supply rail. If an external switcher is used as in THX 789, then you have to generate the negative rail internally which can be of lower quality. I am happy to see the two thermistors (red and black) for surge protection together with fuse protection. Nice bank of capacitors and inductors clean up the output of the switchers. To adjustable regulators (LM337 and LM317) provide lower output voltages (?).
Looking at the block diagram, we nicely see the instantiation of the same on the PC board:
The only difference is that the DC servo (feedback) loop is implemented using OP2197 rather than OPA2140 as noted above. Or else my eyesight has gone down the hill more than I think they have.
Normally the feedback loop around an amplifier is passive (resistors and capacitors). Here, an active "DC servo" is used in the form of OP2197 (2140 on block diagram) to null the output DC. I believe this is a similar circuit to what is used in my Audio Precision analyzer.
Everything is doubled here to get more power by paralleling the two amplifier stages (OPA1611 and LME49600).
The OPA1612a opamp is used both for differential input, and the gain stage.
Nice to see proper protection circuit to guard against DC into headphones.
Since Tom is here, I am going to stop pretending I have fully reverse engineered this unit from just a picture and let him explain more.
Here are specs for some of the key ICs used:
LME49600: http://www.ti.com/lit/ds/symlink/lme49600.pdf
Notice the incredibly low THD+N rating (of course the challenge is to make it perform this well in a real circuit).
OPA161a: http://www.ti.com/lit/ds/symlink/opa1612.pdf
OPA2197: http://www.ti.com/lit/ds/symlink/opa197.pdf
Note how nicely lined up and organized the parts are. Quality of assembly and soldering is high. Likewise, happy to see top brand capacitors (Nichicon).
Here is a lower resolution shot of the PC board:
For 4X higher resolution, click on this attachment:
You may have seen my tear down of massdrop THX AAA 789 amplifier which had plenty of empty space. Not so here. As you see, nearly every inch of space is used.
Unlike the massdrop THX 789, the power supplies for the HP-1 are internal. We have two switching supplies from the reputable Mean Well Taiwanese company. I am assuming one provides positive and the other, negative supply rail. If an external switcher is used as in THX 789, then you have to generate the negative rail internally which can be of lower quality. I am happy to see the two thermistors (red and black) for surge protection together with fuse protection. Nice bank of capacitors and inductors clean up the output of the switchers. To adjustable regulators (LM337 and LM317) provide lower output voltages (?).
Looking at the block diagram, we nicely see the instantiation of the same on the PC board:
The only difference is that the DC servo (feedback) loop is implemented using OP2197 rather than OPA2140 as noted above. Or else my eyesight has gone down the hill more than I think they have.
Normally the feedback loop around an amplifier is passive (resistors and capacitors). Here, an active "DC servo" is used in the form of OP2197 (2140 on block diagram) to null the output DC. I believe this is a similar circuit to what is used in my Audio Precision analyzer.
Everything is doubled here to get more power by paralleling the two amplifier stages (OPA1611 and LME49600).
The OPA1612a opamp is used both for differential input, and the gain stage.
Nice to see proper protection circuit to guard against DC into headphones.
Since Tom is here, I am going to stop pretending I have fully reverse engineered this unit from just a picture and let him explain more.
Here are specs for some of the key ICs used:
LME49600: http://www.ti.com/lit/ds/symlink/lme49600.pdf
Notice the incredibly low THD+N rating (of course the challenge is to make it perform this well in a real circuit).
OPA161a: http://www.ti.com/lit/ds/symlink/opa1612.pdf
OPA2197: http://www.ti.com/lit/ds/symlink/opa197.pdf
Note how nicely lined up and organized the parts are. Quality of assembly and soldering is high. Likewise, happy to see top brand capacitors (Nichicon).