Mr. Samuels is right, "You really have not heard the amp properly & have never experienced what it was designed to accomplish... The 650 needs the balanced termination to really shine also. Please get your self the proper cable for your phones to enjoy the Protector properly." Mr. Samuels espoused the above in reply to some comments I made about the Protector in single ended mode, esp. when used with AKG701 phones.
Soon after I received my amp, I sent out my HD650's Stefan AudioArts cable to be a bit shortened / reterminated with XLR connectors, and had built a Protector plug-to-XLR adaptor using a piece of the Stefan AudioArts cable. Both items arrived two days ago (total cost = $60
- I can't say enough about the person who did the retermination / custom adaptor build for me, but that's another story.) I brought the pieces into work with me yesterday. I did only about an hour of balanced burn-in with the Isotek disc at work yesterday morning plus some more hours today. Yesterday and today I put some rock, classical, and Alison Krauss into play. Latest (nicely mastered as always, it seems) Peter Gabriel disc got playing time today, too.
It is a truthful comment that my HD650s have never sounded better. Great pairing between amp and phones, for sure, in balanced mode. More air around and improved positioning of voices / instruments, improved midrange, gobs of detail, tuneful bass, more realistic orchestral instrument sound-presentation-presence, etc. I know it is only a limited amount of time running the amp balanced v. tons of single-ended burn-in time that I did previously, and that more burn of the reterminated Stefan AudioArts cable and custom adaptor as well are to come. However, I cannot help but like very much what I heard over a few hours of work yesterday and today. I note that things also have improved from yesterday's listening session, too. I look forward to some more 24/7 burn-in over the weekend with the Isotek disc, coupled with listening using even better sources. I note the amp has no problem holding its charge, too. I anticipate it will now be most unsatisfying to listen in single-ended mode to my other headphones - darn hobby.
I think my questions about this amp are being answered with each balanced listening session. I'm going to have to see if I can get those AKG701s balanced, too.
[FYI - I used to own a Xin SMIV, and kept it safe during use and transit in a quite small, well padded digital camera case. The Protector amp, which is certainly smaller than the Xin amp, easily fits into the same case; I imagine a personal player would fit, too. A few well placed snips in the back of the case made flaps that allow me access to the amp's recharging plug plus the gain switch. Furthermore, the rear sides of the case each have small openings, which allows me to readily use / snake out a right-angled 3.5mm adaptor from the Protector's rear input. I think the digital camera case ran me approx. $12 at Target some years ago. Just a thought for those who need a case.]