Fun with amp comparison

[davmol]

I recently picked up a bargain pair of Fosi Audio v3 monoblocks and decided to compare with my class-A Musical Fidelity A1 clone (MFA from here), which I bought a year or two ago from Aliexpress. I was using the WiiM Ultra's line-out, along with a 4-way RCA switching box that I've used previously when testing DACs with headphones. Given that this time I would be listening with speakers (Wharfedale Diamond 9.1) I also employed the use of the ET30 Vu-Meter/amp/speaker switching box. This combo allowed me to have simultaneous output from the RCA switching box and then I could use the ET30 remote to seamlessly change between the amps while listening. As a bonus, I could also hook up the Fosi with both RCA and XLR inputs (using RCA to TRS cable for the latter), so I could listen for any differences, given various comments that XLR input "sounds better", supposedly in the case of the V3 due to not needing the additional op-amp employed by RCA input.

Summary of results:

• V3 (RCA at 31db) vs MFA: The V3 sounded way better, with "more of everything", more bass, fuller in the mids and more detail up top.
• V3 (RCA at 25db) vs MFA: Results were reversed, the MFA sounded better than the V3.
• V3 (XLR) vs MFA: As per 25db RCA, the MFA wins, again, just "more of everything".

It was clear to me then that my preferences were simply due to the volume differences between each amp (and inputs). The V3 at 31db RCA input is slightly louder than the MFA, and with XLR or 25db RCA inputs, the V3 are quieter than the MFA. Given that the V3 and MFA are both power amps, it's not that simple to level match, but after listening a while longer I decided that V3 (RCA at 31db) was about "1 notch" louder than the MFA (with volume being controlled by the WiiM Ultra). So, with WiiM and ET30 remotes in both hands, and calling on my youthful motor skills from many years playing California Games on the C64, I started to simultaneously switch up the volume as I moved to the MFA, and back down again when I moved to the V3. The night-and-day differences I originally heard, with the V3 being better in all areas, simply vanished. Now, this wasn't really a surprise to me anymore after doing the DAC tests (much more rigorously than this) but it still brought a big grin to my face to once again see (or hear in this case) how much my brain plays tricks on me, and how much volume can dictate our perception of how good (or bad) something sounds.

Again, this is just a bit of fun, and to be sure that I hear no differences at all I would have to level match exactly, but this simple test was enough for me to decide that I can remove the MFA from the setup and keep the compact Fosi V3 monoblocks. I'm grateful that I found ASR, as it has taught me to really question what I am hearing and why I am hearing it, and doing these little tests is quite simple and a lot of fun, which has the side benefit of helping me to make informed decisions about what I am buying. Amp, DAC and streamer sorted, now I need to start saving the pennies for a UMIK-1 and a pair of Wharfedale Linton 85th!

I did also compare the XLR vs RCA inputs but as this is a physical switch on each V3 it was not as easy to compare without relying on memory. I would say that I didn't recognise any notable differences, but that the XLR is quieter than the 31db RCA, and similar volume to the 25db RCA. Again, take it with a big pinch of salt, because I'm not even able to stay seated when switching between the inputs so it's difficult to offer anything reliable. Lastly, I should point out that this is not a criticism of the Musical Fidelity A1 clone, it's beautifully built inside and superb value for a well regarded class-A design, so I would recommend it to anyone wanting to scratch their musical space heater itch, without breaking the bank.

 

[joeg26er]

Interesting - what volume levels did you listen at? Source materials? What power supplies did you use with the V3s?
How hot are yours running?

I ordered 4 of these Mono V3 with separate 10A supplies. So I am interested in setup tips

Can you post pics of the inside of that MFA Clone? Or link to past posts?

 

[davmol]

Volume was about half (50) on the WiiM Ultra preamp, so reasonably loud but not deafening. I usually listen to soundstage / "hifi show-off" type playlists on spotify when comparing devices (I listed a few on this DAC testing post). I was using the 48v/10amp supply and the splitter to power both of the Fosi V3 Monos. They run warm, but nothing crazy, I can still rest my hand on them for a while and it never gets uncomfortable, although I don't stack them so maybe that helps.

Here is a youtube link to the MFA1 clone that I bought, and he opens it up and shows the internals.

 

[Dumu]

Next step to try is hooking a volt meter or oscilloscope to speaker terminals and check how much power you are actually using. When I did that first time I was sure I was doing something wrong when I got hardly one volt while listening quite loud. Since it seemed that 1Wpc is already loud enough to bother neighbours and shake windows I have never again had to care about amp power ratings.

 

[joeg26er]

Fosi's newest V3 (V4?) have 19/25db gain switches instead. They said they did it because the 31db setting could cause issues (praphrasing)

 

[DVDdoug]

with "more of everything", more bass, fuller in the mids and more detail up top.

It's not unusual to hear other differences with volume changes and some of those changes are normal. The sound is often described as "more dynamic" and more details do become more audible when turned up. And the Equal Loudness Curves show that when you turn up the volume it sounds like you've turned up the bass even more.

And there is another reason for level matching - When you do a blind ABX test the "goal" is to determine if you are really hearing a difference by reliably identifying X. If A or B is louder and you can hear a difference, that's a "give away" and you can identify X every time.

to compare with my class-A Musical Fidelity A1 clone

FYI - Class A isn't better. It's class A because it was the first. It was the first type of amplifier invented and after class A/B was invented it required one less tube so it was more economical. That continued into the transistor days and almost all tube and transistor amplifiers and TVs were class A. Now the electronics are cheap and once you need more power the cost-per-Watt is lower with class A/B, even with the extra transistor/MOSFET. The electronics for class D are WAY more complex but with all the extra electronics in a chip the cost-per-Watt goes down even more.

Also see Controlled Audio Blind Listening Tests (a video by Amir) .

 

[joeg26er]

I guess mine are Fosi V4 Monos with the 19/25db gain settings. Or should we call these V3.5?

In talks with Fosi to get the defective pair swapped for the 19/25 versions