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.
Related Post:
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13 comments:
Hi, Most interesting, will it drive 8 ohm phones? I have a pair of vintage Koss that run close to 8 and lots of headphone circuits have problems supplying the needed current
Good listening
Bruce
gofar99@hotmail.com
Hi Bruce, no, the opamp cannot drive that load.
However, a LM386 (not to be mistaken with a LM3886) could be used to drive 8 ohm headphones.
Here is a link to the Headbanger Headphone Amp which uses the LM386:
http://www.minidisc.org/headbanger.html
Cheers,
Gio
Gio
Thanks for the Grado/DIY can's amp shoot-out. The Brr-Brown chips are meant to be the very best so not surprised the DIY amp gave good performance. As you know I stuffed my head phone DIY amp so i'm keen to have another go. Maybe I can come up with a nice cigar box (cedar)to put it in and get the best of both worlds. You know how I love my case-work!
i guess you can try using a audio Hi-fi preamp to drive ur 8 ohm phone. An tutorial guide for Gwado Ra1 can be found at http://williamneo.blogspot.com
@anonymous 23 March, 2008 05:36
Those OPA opamps will NOT drive 8 ohm headphones! You need something like the LM386.
Looks nice... but I'm looking for a solution which will drive a 4Vrms output, I doubt this is capable of it. Any ideas or designs you may know of? Thanks.
Anthony, what are you trying to drive?
Want to take my MP3 player (Sansa e260) and pipe it into my head unit which has a 4Vrms input IIRC. I have it set up, but volume on both devices has to be set rather high to get good signal. I'm guessing a simple headphone amplifier will get the job done well.
With the CMoy you can adjust the gain so this should not be a problem.
Daniel, from what I can tell in the schematic it looks like the Grado RA1 is the one which has adjustable gain via the 100k pot. And actually now that I think about it, it was the output of my headunit which was 4Vrms, not the input. I think any sort of amplification on the input beyond what my Sansa can drive will be a great help. I'm going to try building one of these powered off of the car 12V with a LM7809 or something. Thanks a bunch!
Hi Anthony,
The gain is set using the resistors in the circuit. In the case of the RA1, the gain is 465/122 + 1 = 4.8. In the case of the CMoy I built, it is 8.2 / 1 + 1 = 9.2. The 100k pot is used to attenuate the input signal. If your source is an IPod, you can skip the pot as the IPod has a built in volume control already.
Cheers,
Gio
The Grado engineers are smart - the 4556 is a good chip that is designed to drive low impedance loads, like Grados. A higher quality part like the Burr Brown chip is overkill for the audio frequency range and just hurts their profit margin. The cMoy needs an output resistor to increase the load impedance to a suitable range, which results in volume attenuation, but this can be compensated for by increasing the gain of the amplifier by adjusting the feedback resistor. I seriously doubt that there is really much of a sonic difference between these two amplifiers - you would need some very sensitive test equipment to actually compare them. People build these esoteric amplifiers that distort on the order of tenths of a percent, but even the best speakers or headphones distort 5-10%!
Take a look at the National Semiconductor LM4562 op-amp. These are very quiet and work great followed by an LH0002 buffer.
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