Fosi Audio V3 Mono vs BT20A Pro A/B sound comparison question

[geauxwandering]

FYI, I am a total novice in the world of hi-if audio. Having had the BT20A Pro since it came out and loving it. Based on reviews, I decided to give the V3 Mono’s a try. I’m noticing a bit more detail, but that’s about it. The Pro seems to have more punch and volume. I’m thinking maybe I am doing something wrong out of ignorance.

My setup is a Topping D50iii feeding both amps. The mono is connected by TLR and the pro by RCA. I maxed the volume on the topping as well as the BT20A Pro. I also set the tone controls on the Pro to the middle detent. My speakers are Sony SCCs5’s. My iPhone is the source and controlling the volume.

When switching between the 2 set ups. The Pro is noticeably louder by a wide margin. I even dialed the tone controls all the way back and still louder. I reached out to Fosi and got the following response:

V3 MONO Specifications: Gain:
RCA: 25dB, 31dB
XLR: 20dB

BT20A PRO Gain: 29.5dB
Please note that the BT20A PRO and V3 MONO have different gain levels and designs. The BT20A PRO includes volume control, making a direct comparison between the two not applicable.

And Amir’s tests showed the following:


Based on this, I would expect the V3 Mono to be on par or slightly louder.

As I said, I’m new to all this and trying to understand. Any input would be greatly appreciated.

 

[staticV3]

The Pro has 9dB higher gain but is working with a 6dB quieter input signal.

With its volume set to max and neither Amp clipping, it will therefore play 3dB or about 25% louder than the Mono.

The maximum output power is not a good indicator for loudness in an A/B scenario.

I highly recommend you purchase a basic multimeter to double-check the gain of your Amplifiers and perform proper level matching.

To do this, set the Pro to max volume (Tone off) and turn down the D50III a lot.

Play a 60Hz test tone on the D50III on loop, then measure the voltage at each Amp's speaker output.

The Pro should have higher voltage.

Slowly turn down the Pro until both match.

Now leave the volume knob there, maybe fix it in place with tape, and you can start paying music and comparing the two Amps

 

[geauxwandering]

That is my next step. I have an O-scope and DMM.

My question more centers around how did Amir get the above measured output and what am I missing to get that output. It appears the Mono is capable of greater output wattage than the Pro. Is the issue that rated wattage doesn’t necessarily translate to volume? Like I said, I’m new to this and trying to better understand some of the concepts.

 

[staticV3]

My question more centers around how did Amir get the above measured output

Is the issue that rated wattage doesn’t necessarily translate to volume?

It's all simple Ohm's Law type stuff.

(input voltage * gain) ^ 2 / load impedance = output power

 

[geauxwandering]

It's all simple Ohm's Law type stuff.

(input voltage * gain) ^ 2 / load impedance = output power

Gotcha, so there is a higher input voltage on the pro vs the mono?

They are being supplied signal from the same DAC. Shouldn’t an amp capable of 240w be louder than the 180w amp?

Where I’m lost is the test figure results of 240w for the Mono vs 180w for the pro.

Thanks again for answering my questions.

 

[staticV3]

Gotcha, so there is a higher input voltage on the pro vs the mono?

The Pro is working with a 6dB quieter input signal.

Shouldn’t an amp capable of 240w be louder than the 180w amp?

Not inherently.

Loudness is dictated by gain, headroom by rated output power.

 

[MaxwellsEq]

Shouldn’t an amp capable of 240w be louder than the 180w amp?

No. A 6000W amp with a gain of 15 will always be quieter than a 200W amp with a gain of 30 at normal domestic listening levels.