I am a manufacturer and I usually dont do headphones, but I have been invited to a local high-school to exhibit for their science fair. I am excited to teach a little here and encourage more students to pursue science and math careers. I plan to demonstrate the differences in SQ between MP3, .wav, ALAC and AIFF files. Also highlight differences between digital and analog out on an iPod, which will be my source. I will reclock it of course in order to reduce jitter to the point where I can hopefully hear these differences using my DAC.
Anyway, I purchased a Lyr Headamp based on some of the reviews I've read here and the fact that I will likely need the power for HE-400's. Really nice looks and build quality.
After a day or two of audition, I am impressed with the Lyr for the price-point, but being a long-time modder (I dont mod anymore), I wanted to see if I could make it a world-class contender using some of the left-over parts from my modding days. I thought I would share some of the mods with the world because they do add more life, extension and better top to bottom dynamics to this little headamp. These are not too difficult for the skilled DIYer.
1) Changed the two bridge rectifers to 8 individual 600V rated HEXFREDs, half soldered on the bottom and half on the topside - use kapton tape to prevent shorting to chassis. There is plenty of room for these because of the tall standoffs. Put a strip of solder on all leads of the bridge rectifiers and use two soldering irons and they will just fall out. Suck the solder from the holes with solder-wick and you are ready to add the HEXFREDs.
2) Added one Black Gate 350V 22uFd cap to the point where the high voltage splits to two 27K resistors to each tube (4 resistors in total connect to this spot). I scraped the soldermask off on the trace between these resistors and put a lump of solder on there. Did the same with the groundplane for the other pin of the capacitor. Then carefully drop the cap on and solder each pin to the board. Make sure the polarity is right.
3) Added .1uFd 250V film caps to the bottom side of the tube sockets, one each. Connect on end to ground and the other end to the opposite side of the 27K resistors. Same resistors and location as the (2) cap. These are soldered essentially to the same place, but grounded at the tube sockets.
4) You can upgrade the two 860uFd 35V caps to low ESR Panasonics. Just pull them out and replace them.
5) Replace the two red rectangular film caps with .22-.33 versions at 250VDC rating. I used a custom teflon cap that I had made for my older tubeDAC, but you can use Mundorf, V-Caps or others. I recommend a teflon cap with tin film or copper film. Avoid plated Mylar. Make sure that any excess leads are insulated and will not short to anything. High voltage here.
6) Cut the two long traces from the center contact of the input RCA connectors to the volume pot. Use X-acto and cut out a short piece of trace right at the RCAs and then right at the Pot. 4 cuts total. Then on the bottom, wire these to the same places using cotton-insulated pure silver wire from VHAudio. Twist two wires, one signal and one ground from connector to pot. One pair for left and one pair for right. 4 total wires.
7) Replace the fuse with a fast-blo solid wire type with a higher rating. I used to do this on all of the Benchmark DAC-1s that I used to mod. Makes a big difference in dynamics.
8) There are some other caps you can add to improve the power to the FETs, but these are trickier to get in. I would need photos to explain.
9) One last thing - replace the tubes with NOS Siemens CCA grey-plates. This is the most expensive part, about $400-$500. More than the DAC cost, but worth it.
Good luck, and dont hurt yourself!! Make these mods at your own risk.
Edited by audioengr - 2/1/13 at 5:38pm