This is a review and measurements of the "biosciencegeek" CMOY headphone amplifier. The CMOY is named after its designer, Pow Chu Moy. It is built out of myriad of IC (dual) opamps with the circuit so simple that just about anyone can put one together. I probably built mine 20 years ago and helped my son build one about 8 years ago. I remember being shocked how much better it sounded compared to the native output of my laptop.
The specific version loaned kindly to me by a member was prebuilt in a beautiful Altoids box (trademark of the Cmoy builds):
Went to look for this Altoids enclosure and only found one on ebay for $65! Apparently it is a collector's item now due to its rarity.
As noted, the circuit is quite simple:
It powers on when you plug in the headphone which is nice. A red LED indicates it is on. There is no volume control. You would use the one in the source for that.
CMOY Audio Measurements
Let's start with our usual dashboard:
That's quite a bit of gain at 15 dB. Anything more than 0.35 volts input would cause it to severely clip.
Signal to noise ratio running on batteries was very good:
Frequency response is nice and flat:
With just 2 volts output, there is not a lot of power there into 300 ohm load:
As you see, I also measured it using 12 volt power supply as the owner indicated the unit is rated to work better. Indeed it does. Distortion is markedly reduced and power increased.
Strangely, the reverse happened with 33 ohm load:
Conclusions
It is trivial to beat this specific CMOY with just about any headphone amplifier. Heck, even a phone dongle may produce more power. But that is not the point of CMOY. It is great "first electronic project" that should fit right in to the needs of a young person wanted to build something and use it immediately. I suggest building one using a breadboard as you don't even need a soldering iron.
So despite horrible objective results, I am going to recommend the CMOY portable headphone amplifier. It should started my journey into headphone amps.
------------
As always, questions, comments, recommendations, etc. are welcome.
Still without a working septic tank. Technician came, took a look and told me what I already knew: "your tank is full -- needs to be pumped first." Then asked for $200. Pumping will happen tomorrow. Meanwhile my wife is all unhappy and we are having to keep running outside to use the toilet in our RV.
The worse part is that I can't process any fruit. Here is a small sampling of harvest waiting pretty:
Please wish me success in getting our septic tank fixed by donating as much as you can using:
https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The specific version loaned kindly to me by a member was prebuilt in a beautiful Altoids box (trademark of the Cmoy builds):
Went to look for this Altoids enclosure and only found one on ebay for $65! Apparently it is a collector's item now due to its rarity.
As noted, the circuit is quite simple:
It powers on when you plug in the headphone which is nice. A red LED indicates it is on. There is no volume control. You would use the one in the source for that.
CMOY Audio Measurements
Let's start with our usual dashboard:
That's quite a bit of gain at 15 dB. Anything more than 0.35 volts input would cause it to severely clip.
Signal to noise ratio running on batteries was very good:
Frequency response is nice and flat:
With just 2 volts output, there is not a lot of power there into 300 ohm load:
As you see, I also measured it using 12 volt power supply as the owner indicated the unit is rated to work better. Indeed it does. Distortion is markedly reduced and power increased.
Strangely, the reverse happened with 33 ohm load:
Conclusions
It is trivial to beat this specific CMOY with just about any headphone amplifier. Heck, even a phone dongle may produce more power. But that is not the point of CMOY. It is great "first electronic project" that should fit right in to the needs of a young person wanted to build something and use it immediately. I suggest building one using a breadboard as you don't even need a soldering iron.
So despite horrible objective results, I am going to recommend the CMOY portable headphone amplifier. It should started my journey into headphone amps.
------------
As always, questions, comments, recommendations, etc. are welcome.
Still without a working septic tank. Technician came, took a look and told me what I already knew: "your tank is full -- needs to be pumped first." Then asked for $200. Pumping will happen tomorrow. Meanwhile my wife is all unhappy and we are having to keep running outside to use the toilet in our RV.
The worse part is that I can't process any fruit. Here is a small sampling of harvest waiting pretty:
Please wish me success in getting our septic tank fixed by donating as much as you can using:
https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/