Greetings friends, I hope you are doing well!

I really love my A-V system that's based on vintage Altec A5 Voice of the Theatre loudspeakers.

There's just something really fun about watching a movie with actual movie loudspeakers from the early days of movie theaters. 

My Altec A5s have crossovers based on Jean Hiraga’s superb 16-Ohm crossover circuit, but with a few modifications recommended by Yazaki-san that allowed me to blend the drivers for room boundary positioning (room corners), in my relatively small A-V room.

If you look closely you'll notice the vintage Western Electric 16GA used to wire the components in the crossovers together. Another Yazaki-san discovery. 

The crossovers work magnificently to give me superb sound quality for listening to music or watching films. 

You might have noticed in the system photo at the top of the page the SPEC RSA-M3 EX Real Sound Amplifier, which was designed & voiced by Yazaki-san to sound similar to his personal single-ended-triode amplifier.

The RSA-M3 is a really nice match to my Altec A5 VOTT loudspeakers, and it does a remarkably good job of sounding like an SET amplifier, which is exactly what my A5s love to be driven by. 

One of the benefits of the RSA-M3 is that it runs so cool it doesn't heat up my room at all, which comes in really handy with the increasingly hot summers we've been getting where I live.

We hit 115F and 118F during the summers over the last couple of years, so it's nice to have a cool running amp in the summers.

I've got an Acoustic Revive Power Reference power cord connecting the RSA-M3 to the AC, which is a really nice match for it, and Duelund DCA16GA tinned-copper speaker cables connecting it to my A5 VOTTs. 

The real story here - and the subject of this article - is the impressive little Improved U4 Bluetooth DAC - modified by Yazaki-san - that allows me to stream music from my iPhone in impressive fidelity (you can read previous articles in this series HERE and HERE).

I'm connecting the Improved U4 to the SPEC RSA-M3 with Belden 8402 tinned-copper microphone cable interconnects. Another Yazaki-san recommendation. 

The Improved U4 in this system setup is impressing the heck out of me.  

I am huge fan of Jazz24 out of Seattle. They have superb taste in jazz, and they stream a jazz playlist 24-7 that always impresses.

What's particularly nice is that Jazz24 has an app for the iPhone (below) which is perfect for streaming to the Improved U4.

Oh, and it's a free app, which really appeals to my frugal nature. 

What's really fun is that jazz streaming from the Jazz24 app on my iPhone to the Improved U4 sounds so good it's scary.  

The sound is big, rich, liquid, nuanced, dimensional, beautiful, and extremely musical.

No glare, no hardness, or other digital nasties of any sort at all when playing Jazz24, the Improved U4 just sounds extremely natural and musical. I can just feel the tension drain out of my body as I listen.

If I brought you into my A-V room blindfolded, sat you down, and streamed Jazz24 over the Improved U4 over my iPhone, and then asked you how much you thought the DAC cost that you were hearing, I'm guessing you'd say somewhere around $5-$10K USD.  Or maybe more. 

The fact that you can buy a U4 off AliExpress for between $42 and $73 USD makes it even more amazing.

Now that's before the modifications, of course, but even when you go through and add in all the DIY modifications that Yazaki-san has developed to bring the U4 to this level of performance, you are still talking less $ than a nice dinner & cocktails out on the town. 

It's all rather mind boggling. Beautiful tone, natural timbre of instruments, a soundstage as wide as my room, lots of nuance, terrific imaging, and a huge sense of ambient space.

Honestly, the Improved U4 over-performs to such an extent that I can't really find anything to criticize about its sound quality when streaming Jazz24.  

The music is simply gorgeous, full of emotion, and life.

This is what happens when world class audio engineers like Yazaki-san and Honda-san turn their attention towards maximizing the performance of a humble and inexpensive DAC like the U4. 

I completely understand why Yazaki-san and friends are so excited about the Improved U4, and I really appreciate Yazaki-san inviting me to join in their iPhone Adventure with the Improved U4.

I'll be telling you more about the Improved U4 in the not too distant future.

I'll explore more about how it does streaming Amazon & YouTube music and report back. (Hint: YouTube & Amazon music streaming quality is much more variable than Jazz24).

I'll also give it a try in my main music system with my Tannoy Westminster Royal SE loudspeakers and the exotic and superb Audio Note (UK) kit that is in residence, and let you know how that works out. 

I'll do a little tube rolling and let you know the results.

Ok, that's all for now, but much more to come.

A huge "Thank you!" to Yazaki-san for sending me an Improved U4 so I could join in this adventure - what fun!

As always, thanks for stopping by, and may the tone be with you!