I purchased the iBasso PB5 portable nutube amp and just received it. It’s a new portable amp made to pair with the iBasso DX320MAX DAP and their matching iBasso D16 1-bit DAC/Amp.
Copy paste from the “Whats in the Box” thread:
It’s been a very long time since I got a chance to review the Cayin C9, but from memory, I don’t remember the C9 having such a distinct flavor change as this PB5 does. This thing really emphasizes dynamics and adds mid-bass to my Subtonic Storm IEM and my Sony MDR-MV1 headphones, while also making things very clearly euphonic and holographic. I don’t want to state that in stone yet though since I’ve had barely any hours on these tubes and who knows what it’ll sound like when it’s more broken in, but from what others have stated who have used it much longer, it doesnt sound like those attributes will change that much.
My initial listen was crazy bloomy, but that’s settled down a lot, so I think it’s becoming more clear.
“Tracking.” 
Appreciate this. Anytime you’ve got something to say about Mr. Osprey you’ve got a friend who will listen.
Used Kiwi Ears Allegro portable DAC/Amp as the source since it had 4.4mm and was easy to use and compared it with and without the PB5 Osprey with two IEMs
Subtonic Storm (With PB5 in green)
Dunu Zen (with PB5 in green)
My impressions of the additonal bass boost are quite measurable. It’s actually kind of funny because I was doing a PEQ set for the Subtonic Storm and it was almost the same exact result…
Anyway, I can’t imagine its the Korg Nutubes doing that effect and it must be the amp system adding that bass shelf above and beyond the distortion the nutubes add (which is also very present and pleasant)
I’ve used the PB5 for a few hours now and some things I like and may be not like.
First off, it looks great and feels nice. The sound quality is really nice for my needs. I wouldn’t recommend this probably for something that is already overly warm and bassy, but for a neutral or bright IEM, this is a really nice compliment. I gives a great fun sound with additional bass response, and a holographic soundstage, with a bit of a reverb thrown in. It’s quite tubey, at least so far. (possibly, still in the burn-in stage)
What I don’t like so far?
- I know the stepped attenuator has advantages, and just like the 320Max, I just don’t like using it as much as a normal smoother pot. The cut-in/cut-out and the accidental ability to leave something between steps is a bit annoying. It’s not a deal breaker, but I’d prefer a normal smoother pot. Other stepped pots arent as annoying as this one is to me.
- The included 4.4mm bullet looking plugs are really cool looking but its too close to the volume knob and it makes it harder to use. Again, not a deal breaker.
- It doesn’t do PD charging, which is a tad annoying for me given that most of my already available USB-C connectors on my desk are all PD since I use them for a variety of devices and they work with devices that aren’t PD capable so I was a bit surprised these don’t take them. Not the end of the world either, but just a strange caveat.
- I don’t know if this is factual or not, as there’s not real good battery indicator on this device, but it doesn’t seem to charge the battery while in use, or if so, the charging does not keep up with the battery drain, as the battery will eventually die even while plugged in. It’s happened twice in the 2 days I’ve had the device.
Very good points of interest. Buyers need to know this. Thank you so much. That issue with the battery seems very odd and could be a deal breaker for me.
Appreciate your insight and experimentation, @antdroid
I got some tips on the head-fi thread for this amp. It looks like if you use it for a little bit, then unplug and replug the usb-c cable back in, it will resume charging the battery while playing. This seemed to work for me.
The iBasso circuit is designed to shut off charging completely when it’s full, and won’t resume until its reinserted and not full. Kind of a quirky design.
In recent years I’ve purchased electric devices that will either charge or discharge, but that cannot be charged when in use. This never happened to me with old nickel cadmium (NiCd) batteries, but those went away per the toxicity of cadmium. I took the change to mean newer battery technologies have limitations, there may be a risk of overheating, newer long-lasting designs seek to maximize battery life, or they saved money by cutting the combo usage circuitry.
Oh I see now. Well then that isn’t so bad and I get the point of it.
Also, what is the expected battery life using a balanced input?
Thanks again for all this.
They state it’s 10.5 hours avg playtime. it has 6 individual 900mAh batteries in it.
Decent. Very reasonable time. Much better than the WA-8 eclipse that’s for sure