A while back I got the headphone bug and purchased a pair of Grado SR80 headphones. I am very pleased with these headphones and consider them to be great bang for your buck. The Grado SR80 headphones have an impedance of 32 ohms, so I built a CMoy Headphone Amplifier in an Altoids mint tin to drive the demanding headphones. The results were surprisingly good, especially when you consider that one can easily build a CMoy Head Amp for about $20. The CMoy easily outperforms the built-in headphone amplifiers on my NAD C162 and NAD 1020 preamplifiers.
A while back, I was showing off the Grado SR80 headphone / CMoy combination to a friend. He is the Walkman, Discman and now iPod type who typically lives with the factory supplied headphones until they die, replacing them with similar light travel headphones. He was stunned with the amazing sound quality, so I let him live with the Grado / CMoy combo for a while. Not surprising, he loved the sound quality, but found that the Grado headphones were too bulky and leaked too much sound for use on public transit.
While he found that the combo was not suitable for his daily commute, he was in love with the amazing sound quality and decided to spoil himself. He purchased a pair of Grado SR225 headphones and a Grado RA1 headphone amplifier for use at home.
For those of you who are not familiar with the Grado RA1 headphone amplifier, it is well regarded, runs off of two 9V batteries, is housed in a beautiful mahogany enclosure and retails for about $350US. A stock photograph the Grado RA1 is shown below.
Recently I had the opportunity to visit and listen to his Grado SR225 / RA1 combination. Of course I brought along my CMoy headphone amplifier! :)
We both did some blind listening and in the end we pretty much had the same listening impressions. We thought that both the CMoy and RA1 amps sounded excellent and fairly similar, but we both gave a slight edge to the DIY CMoy amplifier. We were both a little surprised, considering you can build a CMoy for about $20 or buy an already built one for about $40 on eBay, yet the Grado RA1 rings in at $350.
What I found interesting was the similarity in sound between the two amplifiers. Of course I was itching to take the RA1 apart and have a peak inside (why not, it’s not my amp?). After a few Google searches, we found that others had reported similar listening impressions between the two amps. That being, they both sound very good, with similarities between the two and the slight edge going to the CMoy. But what I found most interesting were these sites, one which showed the dissection of a Grado RA1 headphone amplifier and the other which also took apart and upgraded the Grado RA-1. The sites provide pictures of the inner details of the RA1 and also a schematic for the amplifier section. It was immediately obvious why the CMoy and RA1 sounded fairly similar … they essentially use the same circuit! The schematics below show the both the Grado RA-1 and CMoy headphone amplifiers.
Schematic - Grado RA1 Headphone Amplifier (above)
Schematic - CMoy Headphone Amplifier (above)
As you can see, both of these designs are based around a operational amplifier (opamp). For my CMoy, it is a OPA2132PA (Burr-Brown) which retails for about $5 and for the RA1 it is a JR4556 that retails for less than $0.50!!! Despite the fact that the JR4556 is a low cost opamp, the RA1 sounds pretty good. Not as good as a properly implemented CMoy headphone amplifier, but it should keep most people happy.
While I consider most Grado headphones to be a great purchase, $350 for a Grado RA1 gets you a $20-$40 headphone amplifier in a $300+ mahogany case.
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