I've just finished my first BH kit - the Crack - and had to jump on here immediately to say thanks for making this possible guys. I got the kit for Christmas and I've taken my time building it, not wanting the fun to end really. And it really has been so enjoyable. Great manual to follow, too. I'm not entirely new to electronics, but it's been a while, and getting into the audiophile hobby has rekindled my passion.
It all went together well and tested fine. When I plugged my HD650s in, which I bought to pair with the Crack, and set Corrine Bailey Ray playing on my old iPod, I had goosebumps within seconds. Such a great sound! I had lots of upgrades in mind, but even though nothing is burned in yet (headphones included) it's got me wondering why I should bother, although I know I will. That's what the audiophile journey is about after all.
In case you're not yet tired of seeing Crack build photos, here are some of mine. The only variations I made were the wire colour choices from the IEC to the mains transformer primary, as being in the UK red is a hot/live colour and never used for Neutral. And I twisted the ground wires from the pot along with the signal wires to continue the common mode rejection. I have to say that I was amazed at how quiet this amp is, with zero audible hum or hiss even at max volume.
Another thing I was particularly impressed with was how close the HLMP LEDs matched one another in terms of forward voltage drop. Do you match them, or did I get lucky? They measured exactly the same.
On my resistance and voltage readings I did get a channel discrepancy.
Resistance checks:
Right Channel RCA centre pin - 97.6
Left Channel RCA centre pin - 92.9
Voltage checks:
1 - 76.9V (Right CH.)
5 - 80.7V. (Left CH.)
The voltage readings correlate with the higher resistance on the right channel, which tells me I should expect some level of channel imbalance in my headphones. Could the resistance difference between channels be due to the wiper on the inexpensive the stock pot? Thoughts on that and how best to get the readings closer would be appreciated. Or does this somehow not affect channel amplification and therefore not matter? Or perhaps it's too small a difference to hear in a headphone system.
Anyway... Thanks again for developing these kits and supporting them as you do. I've really enjoyed the build and now have a great headphone amp too.
-- Steve