Likely your amp is clipping. It is a well known design trade off of the O2. Either you need a source with less voltage swing or use low gain. The O2 clips from too high an input voltage for the gain used, not from the volume output.

Before you send them out the door to the next owner, you should try the James444 mod. It does improve the bass and confusion on busy music quite a bit. The mod is quickly and totally reversible and is very well documented by James444...

I'm looking forward to your impressions. I've been swapping between the XBA-Z5, MDR-7550 and HA-FX1100.   The FX1100 is a niche performer. It isn't an all-rounder, but it really shines with acoustic and close mic'ed vocals.

I'm been auditioning IEMs for the last week mostly at my desk, so:   PupDac > GS-1 > IEM   I'm lacking for portable sources, I have an HTC M8 and a Rockboxed Fuse, but I haven't been using those for auditioning over the last week. That is what I eventually will end up driving them with. I...

    Not yet. Untaped these have impressive enough bass. I actually think they have a bit more bass than the XB90ex. I also think the XBA-Z5 has equal bass to the XB90ex. I know that's a bit different from the opinions here in the thread. I'd rank the bass response and extension like this...

I don't know the mechanics of buying from overseas in the UK, but Amazon USA has 2 pair of the MDR7550 remaining, stocked in the USA, Amazon prime for $315 Amazon USA also lists 148 sellers of the EX800, almost all Japanese, starting at $207 w free ship.   It seems like USA availability is...

 I'm well into "new toy syndrome" with my Z5. I know enough about myself to know I can't give a good opinion about equipment until I've had it long enough for it be "old hat". There have been lots of examples of stuff that sounds great for the first week or two that I don't really care for...

Well, I gave in to the curiosity. My rationalization to myself was I haven't spent any money on audio toys in over a year. The two IEMs I have been wondering about are the XBA-z5 and the JVC HA-FX1100. On the JVC, I have a bit of expectation bias because I've listened quite a bit to my...

I've read this whole thread (and a couple others) and I'm interested in some of the source discussions as well. I only use my HTC M8 or a Sansa Fuse with a Pico slim for my portable rig. I have good balanced desktop gear - GS-X mk2 and DIY dynalo Mk2 - and I think I'll spend some time with new...

I've got a question for the Z5 crew here. I'm going to spend some $$$ on IEMs in the next few months, say $1000. I've been collecting mid tier IEMs for 10 years or so, so this purchase is more to add contrast to what I have, not as my only IEMs. I have my end game home set ups and only use...

What are you using to power the O2 ?   I wouldn't go so far as to call it a defect, but the O2's has unusual clipping that depends on rail voltage and input signal voltage. If you are sure you are clipping in the amp section, you have rails running too low for the input and gain. That is the...

I don't know of anyone with a build currently in progress. I've had one up and running since October. It's my grail headphone amp.   If you are considering doing a build yourself, I'd encourage it. The build, in and of itself, is no harder than the original dynalo or any of several other...

I ordered 1 as well. A nice option would be to offer the complete kit without the enclosure, like how the PuP was offered. I can see building several of these to integrate into one case with a PuP or O2/Odac. I'd be a buyer of a couple more without cases.   Thanks for another great, ready...

      Actually, this is a bit confusing. The O2 has very unusual clipping behavior and clips *only* based on the level of the input. The O2's volume control has no effect at all on clipping behavior. The 7v / the output voltage level of the source is a useful rule of thumb, but brings up a...

Very nice review, but it may cause some unintended spending on my part. Thanks very much for taking the time to post it up, it's useful. I currently use a x-sabre > GS-XmkII > HD800 as my dynamic set up. I'd be curious on the opinions of the three amps driving HD650 and using classical...