I've been listening to the Allo Volt+D
https://volumio.org/product/allo-volt-d/ for about a month now alongside a cheapo TPA 3255 amp
https://www.ebay.com/itm/DC30-48V-T...798167?hash=item3b08bee317:g:iTEAAOSwJN9ayusO
Here are my impressions:
background:
For roughly a year, my main amplifier has been the Allo Volt+ board. I'd been quite happy with the older Allo, but the layout of that board's connectors made it really hard to put the thing in a box. When I heard that a new board with a conventional layout was on its way, I started communicating with Allo to find out when I could order one. It took a while and when the Allo Volt+D came out, it wasn't initially available in board form. Instead it was nicely packaged in a futuristic acrylic box with a stepped potentiometer. Where the Volt+ board was $39+ shipping, the Volt+D was closer to $150 after shipping through Volumio (for some reason, the shipping from Volumio is much less than it is from Allo, even though the amp was shipped from Bangalore). The amp got here quickly and it was very nicely packaged.
In addition to changing the connector layout, Allo went from a single chip to a dual chip design with the TPA 3118 and changed out several capacitors and the coils for more audiophile parts. They also told me that part of the delay was due to repeated tweaking and testing of the final production design. I'd say this attention to detail paid. There's a noticeable difference between the Breeze Audio tpa 3116 and the Volt+. I'd say there's also a noticeable difference between the Volt+d and the Volt+.
Due to my various audio neuroses brought on by reading positive comments about TI's TPA325X series, I thought I'd try it. For that reason, I wound up ordering the TPA 3255 amp and an FX3250 amp that I happened to find use on E-bay for cheap. I'm not sure why Allo stuck with the TPA311x series, btw. While I have, over the years, had a variety of amplifiers from a Richard Marsh-Bill Westerfield Amp from the 80's , a 300 B tube amp with Western Electric tubes, a weird Luxman amp with liquid cooling, a couple versions of the Pass 40 Class A amp, a Lang class A amp, Marantz8, Audio Research D50, LM 3886, and various EL34 amps, to a variety of t-Amps, it's been years since I've had anything other than Class D at home. It's not that I think Class D is superior to all others. It's more that it's fun to fool with it and it's pretty darn close to the best the more traditional amp realm has to offer (at least at what I can afford).
system:
My system's a little unusual. I mostly listen through a pair of 6.5 inch two way speakers, Scanspeak fiberglass woofer, Scanspeak revelator tweeters. The crossovers were designed by Brian Smith. I don't use a CD player, records, or a preamp. My music is mostly flacs ripped from CDs though I also have some 24/192 files, all stored on a hard drive on a Lenovo i5 computer that feeds a Hifemediy ESS9018 DAC that has an its own volume control. I doubt that this is a reference quality system, but I like it a lot. I also listen mostly in a 12x11 bedroom/study.
While I do my share of track a vs. track b listening, I mentioned here earlier that I think the most effective test of audio equipment comes from casual listening. If you're listening to a lot of music suddenly, something you've done to your system was probably a good idea. I do it this way, because I easily fall prey to confirmation bias.
In the last month, I've been listening to a lot of music.
What my ears tell me:
I'm listening to a Pierre Boulez conducted recording of Bartok's Concerto for Orchestra. While full orchestra is never going to be the forte of 6.5 Inch woofers, the Volt+d does a surprisingly good job of giving the listener the sense of distinct sections. Strings don't sound like woodwinds when playing in the same register. The brass choirs at the end snap at the bottom end and blend without sound like a big splat. The strength of the Volt+D and the TPA 311x is a kind of midrange purity matched with the ability to reproduce detail well. In complex tutti passages, the music held together without homogenizing.
There are some things that are missing. The kettle drum goes low, but it doesn't really thump. The bass violins maybe don't resonate the way they should, though you can definitely hear the notes. There's also a slight sense that instrumental attacks are rounded off just a bit. These could be my speakers and source as much as the amp, but the TPA 3255 does do better with these sorts of details.
With smaller scale classical, the Volt+D is predictably a true pleasure. I've listened to a mixture of Brahms, Barber, Mozart, Haydn, and Elliot Carter string quartets and the Volt+D's ability to make you feel like you're listening into the music really shines in this sort of repertoire. It also does very well with solo classical and jazz piano, especially with relatively spare music. Kenny Drew's Everything I Love and Jean Yves Thibaudet's Bill Evans album not only let me hear the notes, but the pedaling technique and the dynamics, that brought on a terrific sense of immediacy.
Small scale folk and soft rock are similar. Things like James Taylor Live, Joni Mitchell's Blue, and my various Jennifer Warnes albums have this haunting quality. The simpler and the sweeter the music, the more I found myself wanting to listen through the Volt+D. You become very aware of things like the blend of voices and instruments, the individual sounds of instruments, etc. My 24/192 versions of Muddy Waters Folk Singer and Simon and Garfunkel's Bridge Over Troubled Water were filled with detail (fingers on the guitar strings type stuff, taps on the body of the instrument) and a really alluring sense of resonance/decay as notes came and retreated.
I'm not a hard core rock kind of guy, but if I were I'm not sure the Volt+D would be the best choice. My test albums are things like Joni Mitchell's Wild Things Run Fast, lots of back wall detail, the voice is incredible, and even that long bass note that starts Unchained Melody on the opening track does give a very strong sense of foundation to the song. It's a similar thing with Dire Straits Telegraph Road and Brothers in Arms. There is something missing, however. The Volt+D doesn't really do pace well. You hear drum solos, but you don't exactly feel them below the waist. Al Green also didn't make me want to jump up and dance. fwiw, I had the same issue with my 300B amp. There are certain things that require big woofers and lots of watts. When you get the front end of the waveforms right, I find you want to dance to the music. When you get the overtones and stuff, you want to listen. Sometimes, a system manages both, but even with bigger more efficient speakers, I have a feeling that the Volt+d or any tpa311x will tend to fall on the listen side of the reproduced music spectrum. fwiw, that's not a bad thing. In any case, played at bother the wife on the other side of the house volume, I did notice some distortion with my medium-efficiency speakers.
The higher power (I mostly use a 24 volt power one linear regulated supply for both amps. It works, but may not be ideal for either) of the TPA 3255 does imo make it the better amp for electric beat-driven music. It's very clean and, as might be expected, there's a greater sense of ease with the TPA 3255.
I'd say the Volt+D is sweeter sounding and has a somewhat fuller sound. Both are quite detailed. The TPA 3255 seems to have greater extension both in the treble and bass, but it's a little more distant sounding. It's not just a tpa311x with a lot more power; there are some differences in the sound. An old audio friend once told me that if you like different things about two systems, it's a sign that neither one is fully right. I actually like both amps quite a bit, but given my listening habits and speakers, I prefer the Volt+D. At the same time, I like having the TPA 3255 around and have listened to it for several days in a row without saying, "Damn, need to hook that other amp back up." This happens even when I'm listening to small scale acoustic or vocal music.
fwiw, I also prefer the TPA 3255 for movies.
conclusion:
The Volt+D is a terrific choice if you're into harmonic purity, detail, and very close listening. The simpler the music, the richer the thing sounds. It helps to have reasonably efficient speakers. If you like things like single-ended tube amps, low wattage class A, or the T2020-2024, The Volt+D is a terrific choice. In fact, it's my choice for my system and usual listening preferences.
If you want something that thumps and makes you want to dance around the room or play air drums while listening with your eyes closed, I'm not sure that the Volt+D is for you, though I don't want to give the impression that it's bad at these sorts of things, though I don't think it's macro fast. It's just that there's better. I might consider a well executed class AB amp instead. You might want to hear from someone with bigger more efficient speaker than mine though. My system's not really set up for that sort of thing.
Right now, I'm very curious to see what a tricked out TPA 325x might be able to do. The one issue is that the TPA325x requires higher voltages and the one thing about the Volt+ amps sounding great with laptop power supplies isn't going to be a possibility. Instead of spending $10 on an e-bay power supply or even running down an Astron linear supply, you'll probably have to spend $80 or more on a power supply which starts pushing all this fun above $200 (still amazingly cheap), but that gets me out of the I can buy 3 of these at once just for the heck of it realm. I suspect my next step will be to try one of the 3e audio boards for the 3251 or 3255 and picking up a 36 or 48 volt power supply. If and when I do that, I'll likely check back with a comparison to the Volt+D. In the meantime though, I'm listening to lots and lots of music.