เข้าร่วม: 25 Feb 2008
ที่อยู่: BKK. Thailand
|ตอบเมื่อ: Tue Jun 17, 2008 1:22 am เรื่อง: มาดูเครื่องในแอมป์หูฟังชื่อดังราคาร่วม 2 หมื่นกันครับ
|Modding the Grado RA-1
This project started as a joke. I had a Grado RA-1 that I traded some cables for. I never really liked the amp, even with RS-1's, and thus never really treated it very well. The Grado got dragged around a lot, and eventually broke due, I assume, to power being hooked up backwards (I was running it off of two wall warts that connected to the 9V tabs, but didn't have any inherent direction.) Having heard that the Grado was very simple, I thought I'd open it up and fix it myself.
Grado, however, had gone to great lengths to keep anyone from opening their amp. The wood screws holding the bottom on have non-standard hex heads that require a special tool. Not having a special tool, I used a wrench and scratched up the bottom pretty badly. Further, once the amp is open, one finds that Grado has stuffed all of the parts into wells in the wood, and dumped epoxy on top. It took me hours to get through the epoxy.
Once inside, I found what Grado was hiding -- a $0.40 opamp, 6 $0.10 resistors, 2 tiny capacitors, and 2 (unnecessary, it turns out) input caps. These parts, combined with the switch, potentiometer, and jacks, make this a $30 knockoff of Chu Moy's super simple headphone design. (Grado did change how the voltage divider works, but not by much.)
The former Grado insides The thing that amazed me the most was not the low quality of the parts in the amp (everyone knows about the cheap parts in the amp, but no one ever remarks at how terrible the wire is), but was instead the terrible build quality. Solder joints where ready to come apart in places (particularly the wires soldered to the RCA jacks). The opamp pins were bent like it was crushed at some point, the small caps on the board were bent and cracked, and there were burns in the case around the RCA jacks where someone had trouble with a soldering iron.
I always knew that the Grado sounded like crap, but after opening it I knew that it was crap. Thus, I decided that rather than trying to modify a poor circuit, I would build a decent amp and put it inside the Grado case. The amp I decided to build is the Pimeta. It is a pretty common DIY design, and there are tons of threads on it at Head-Fi.
Front view with a new blue LED
อ่านต่อได้ที่ link ด้านล่างครับ
ข้อมูลจาก :- http://www.ecp.cc/ra1.html
ต้องขออภัยผู้ที่ใช้ แอมป์ GRADO RA-1 ด้วยครับ แต่ผมคิดว่าข้อมูลเหล่านี้น่าจะเป็นประโยชน์สำหรับนักเล่นนักฟังส่วนใหญ่ครับ.... ส่วนตัวผมเองเห็นแล้วหนาวครับ.....