Hey Now,
Just finished up my Crack and was listening to it with my HD650s. Yep, just like everyone else says, it sounds terrific. I forgot I had another 300 ohm headphone, the MB Quart QP805HS. I plugged those in and woo-hoo, what a difference the Crack makes with this headphone. The bass is more pronounced, tighter and well defined, the mids are very nice and sweet. I listened to them for several hours last night.
I also tried some AKG601s (120 ohm) and it sounded nice, not as good as the HD650 or QP805s. I am gonna give the Crack a good listening too before I do the Speedball upgrade. I'm liking it very much so far.
I only had one cold solder joint on the right channel. Easy peasy re-solder fix. Thanks Bottlehead, love this amp.
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Finest kind,
Chris