Firefox 0 Report post Posted January 25, 2004 (edited) Pictures for those who missed the last meet. The amp. Edited January 25, 2004 by Firefox Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 The power supply: The toroidal transfomer is a Nuvotem Talema encapsulated model. 2 x 15v, 30VA. I used Ultra-fast soft recovery diodes (HEXFRED's) for the bridge rectifiers. Film caps from Evox Rifa were used to bypass the diodes. +/- 15v, 1A via LM7815/ LM 7915 regulators 4,700uF pre-regulation capacitance per rail 3,300uF post-regulation capacitance per rail Tantalum caps bypassing regulators on the input and output pins Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 (edited) The rear of the amp: Chose those RCA's because there was minimal metal in the signal path. XLR connector for power input. Edited January 25, 2004 by Firefox Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 You can almost see the film caps used to bypass the opamps for transients and bass slams. Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 You can see the Noble potentiometer and Hovland Musicaps in the foreground. Not to mention the nice heatsink cooling the opamps. It's about 4" x 6" x 1" if ya need to grasp the size. Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 (edited) Brief details of the amp itself. The amp is of my own design using 2 opamps per channel. It's derived from experience and from combining certain aspects of other amplifier designs. The overall gain is approximately 9.5dB (3x gain). This was done so that the volume control can be turned up more, thus allowing better fine control. The gain was also more than sufficient for the purpose of driving headphones. The opamps (OPA627BP's) are biased into Class A at nearly 1/2 their rated current output and throw out quite a lot of heat. Hence, the large heatsink. Each channel also has two 6.8uF film caps providing high speed power to the opamps for transients and bass slam. Tantalum caps also bypass each opamp to keep them happy while under duress from the heavy biasing. There are 2 Neutrik Combo jacks for the output. Both accept the 1/4" stereo plug for normal headphones. In addition to that, the XLR portions are wired for left and right channel audio respectively. The potentiometer is a Noble potentiometer which I liked for it's build & the balance between the 2 channels at low volumes. Some cheaper potentiometers like the Alps Blue suffer from channel imbalance at low listening levels. Hovland Musicaps were chosen over their cheaper Solen and MIT/ Rel counterparts because of their speed. They cost $20++ a piece compared to the Solens at around $1.00+ a piece. They do sound slightly bright without burn-in but the sound smoothes out and becomes more neutral with burn-in. The whitish wires are actually specially drawn teflon insulated, 5N (99.999%) pure silver wire. Unlike cheaper (99.95%) 3N silver wires, this wire is very neutral sounding and not bright at all. Edited January 25, 2004 by Firefox Share this post Link to post Share on other sites
N@Z 0 Report post Posted January 25, 2004 Can both headphone outs be used at the same time & do they need to be used with the same impedance (Same type of headphones)? Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 25, 2004 Both headphone outs can be used at the same time. Headphones of different impedance can be used but I don't recommend it especially if you have 2 low impedance cans and listen at very loud volumes. Share this post Link to post Share on other sites
Q00 0 Report post Posted January 25, 2004 i have alot of good memories with this amp @ the meet.... it did very well with alot of headphones i tried... all the ath cans sounded good on this amp. Only comment is that i didnt like the cans that this amps was supposed to be tuned for... the dt-931. Maybe i just didnt like the cans? Share this post Link to post Share on other sites
cmk 0 Report post Posted January 26, 2004 Excellent piece of work. It would be better if you have the option of more than one input. Are you going to sell this commercially? Share this post Link to post Share on other sites
Rameish 0 Report post Posted January 26, 2004 Firefox is back in camp and no he's not going to sell this comercially - there's no market for it in Singapore. Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 27, 2004 Only comment is that i didnt like the cans that this amps was supposed to be tuned for... the dt-931. Maybe i just didnt like the cans? I didn't tune the amp for any cans in particular. I merely used my DT931's to tune the sound to my liking & type of music. Bear in mind that the amp was built more for speed, musicality & transparency... Even the DT931's are not fast enough to fully utilise the speed that the amp has. Low impedance cans like the CD3K's & Grado's actually benefit the most. I also designed the amp to drive almost any dynamic headphones with ease into Class A. With the exception of the K1000's of course, since the amp would then fall out of Class A at moderate to high volume levels. I think you don't have a liking for bright sound. I find my choice of sonics to lean towards the bright side. Share this post Link to post Share on other sites
Firefox 0 Report post Posted January 27, 2004 Excellent piece of work. It would be better if you have the option of more than one input. Are you going to sell this commercially? Having multiple inputs means adding a selector switch into the signal path and extra solder joints. I wasn't willing to sacrifice sonics for this as not everyone would need such a feature. Share this post Link to post Share on other sites
Q00 0 Report post Posted January 27, 2004 Oops, my bad! Lengcm gave me the impression that the amp was tuned for the 931 at the meet. One thing is for sure though. Its one hell of an amp. Share this post Link to post Share on other sites
N@Z 0 Report post Posted January 27, 2004 Besides the stunning sound, I think the amp looks great. I love the twin headphone sockets (gives it a headroom Max look to it) & the notched volume knob which feels superb to operate. Firefox's internal work would humble DIYers on Head-Fi. Share this post Link to post Share on other sites
