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2 x Fosi V3 + 2 x 10A 48V psu - what the hell?

white noise said:
I am using v3 monos with a 2-way 96 dB bass reflex - 15" Beyma 15LX60V2 + 1" Beyma Cd10Nd in a Seos15 waveguide (2-nd order xover with passive CD equalization) - and I am happy with. Listening position at about 2.8 meters from speakers. Two other friends use V3 Mono to power up their 15" speakers, both different than mine, with success. The only problem I had was that initially these Fosi V3 Monos sounded thin, which is not the case now (but I do not want to be 'crucified' here for broken-in , as not scientifically proved yet :)) As for leaving the V3 Monos ON all the time: no way. I prefer switching them on/off for each session, especially they get hot just on idle, with no music program (at 22-24 *C room temperature, the outer case temp reaches 43 * C in about 2h). I am using one big heatsink for both monoblocks. Power wise, I never get out of steam with large scale classical orchestra music, electronica, avantgarde jazz or progressive rock/metal . My room is 20 sq meters.
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Sounded "thin" - exactly my experience. Still sound thin. :-)

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dcolak said:
I just checked, I ordered two, one is 31/25 the other is 25/19... Pffffff.

I don't use RCA inputs but still...

So 25/19 is a good one sq wise?

I ordered them as a part of a bundle, why would they want to ship two different ones :-( ppfffffffff

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Just set them both for 25. For example, my amplifiers are only 22dB, but they are also intended for my specific pre-amp, that has 2-3 times the output of most pre-amps.
Basically, when you have a higher output from your pre, and a lower sensitivity on the input of your power amplifier = lower dB gain. Then you should get better signal to noise ratio.
I run a fully active system, where the amplifiers are directly connected to each driver, which is why I need more attention to low noise.
With your system - running passive speakers - you often get a lower sensitivity and therefore do not hear any potential hiss from the tweeter, like I can with my active system.
So in essence, you should be fine with 25dB gain and a bit more volume on your pre.
 
dcolak said:
Yes, phase is ok. It's just that they run out of steam and bass is never blooming, just... dry... boring... I'll record it soon.
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Amplifier running out of steam means that you are either running out of gain (not loud enough), or you are running out of power (distortion). If you have less bass than some other amplifier, but neither of the above, then most likely the amplifiers do not have flat frequency response, which would be easy to prove by simple recording or sine sweep.
 
Dude, what you're doing is a real typical case of judging audio gear just by ear. A lot of audiophiles are like this. They go on and on about the sound produced by some old - school Japanese amps. But if you look at the actual measurement results, it's really bad.

I once posted something about Class D amps losing high frequencies. And yeah, that's what the measurements showed. A bunch of people thought I was some kind of bat that could pick up ultrasonic waves! Hahaha.

To be honest, I feel that with Class D amps, the loss or distortion of high frequencies makes the high - pitched sounds harsh. It just doesn't have that smooth and sweet sound like Class AB amps do in the high frequency range.

But dude, when I first heard someone say that Class D amps lose low frequencies, that's just crazy talk. The best thing about Class D amps is the bass. You know, most of those big subwoofers out there are definitely powered by Class D amps.
 
Let's not forget. Class D is sold as efficient, cool, small and light.
They are also a ton cheaper to produce. Big caps, cooling fins and transformers are expensive and heavy... No matter how good they potentially can be.
And all this benefits transportation worldwide, size, design and price.

I would stop all this debate forth and back, and then take a piece of paper, sit down and define what you want. Then you can actually seek help and guidance. But randomly/ignorant throwing things together and expecting perfection, because of one isolated review/test... Don't... It's not helping anyone, especially not your wallet.
 
dcolak said:
Why can't they be matched? I don't use RCA, I use XLR, they are not out of phase :)
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It’s nothing to do with the choice of connection, but the gain. I thought you said your amps had different gains, due to them being from different production runs. I was simply checking if you’d got good channel balance, as that would give a poor impression unless you realised what was going on.

Although I didn’t mention speaker phase, others have. That is usually the first place to check if you perceive lack of bass. But you seem to have decided you don’t like the Fosi monos, so I wish you luck with a replacement choice.
 
jayapple said:
Dude, what you're doing is a real typical case of judging audio gear just by ear. A lot of audiophiles are like this. They go on and on about the sound produced by some old - school Japanese amps. But if you look at the actual measurement results, it's really bad.

I once posted something about Class D amps losing high frequencies. And yeah, that's what the measurements showed. A bunch of people thought I was some kind of bat that could pick up ultrasonic waves! Hahaha.

To be honest, I feel that with Class D amps, the loss or distortion of high frequencies makes the high - pitched sounds harsh. It just doesn't have that smooth and sweet sound like Class AB amps do in the high frequency range.

But dude, when I first heard someone say that Class D amps lose low frequencies, that's just crazy talk. The best thing about Class D amps is the bass. You know, most of those big subwoofers out there are definitely powered by Class D amps.
Click to expand...

I can give you another example: YAMAHA P3500S vs YAMAHA P5000S.

P3500S uses classic power supply, it's very heavy, P5000S uses switching power supply.

I have both amps, I got P5000S after long time having P3500S, thinking I might get more of everything.

Was really surprised with the sound of the P5000S, it sounded boring, highs were muted, lows were no longer "blooming" it sounded artificial.

I keep using P3500S because it has MUCH MORE bass, much nicer, "cleaner, more natural" highs.

1756818911281.png
 
Nopiano said:
It’s nothing to do with the choice of connection, but the gain. I thought you said your amps had different gains, due to them being from different production runs. I was simply checking if you’d got good channel balance, as that would give a poor impression unless you realised what was going on.

Although I didn’t mention speaker phase, others have. That is usually the first place to check if you perceive lack of bass. But you seem to have decided you don’t like the Fosi monos, so I wish you luck with a replacement choice.
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The gain setting works only for RCA inputs, it does not work for XLR inputs.
 
Please take the test.

pma

'Do all amplifiers sound the same? Level matched listening test'

Do all amplifiers sound the same? Level matched listening test

One more to this neverending discussion. Two very different amplifiers are tested, however both with very flat frequency response in the audio band. The test level is set such that 0dBFS of digital data corresponds to THD = 0.9% for both amplifiers under test (that means close to clipping). The music sample has maximum digital amplitude of -0.1 dBFS and DR = 12. Outputs of both amps are recorded via Cosmos ADC, time aligned and level matched (to average RMS). The ADC recorded music samples have maximum amplitude of...
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dcolak said:
Was really surprised with the sound of the P5000S, it sounded boring, highs were muted, lows were no longer "blooming" it sounded artificial.
Click to expand...
Yet again, have you measured the response to know that you are not affected by bias?
 
jayapple,

very interesting what you posted.

"To be honest, I feel that with Class D amps, the loss or distortion of high frequencies makes the high - pitched sounds harsh. It just doesn't have that smooth and sweet sound like Class AB amps do in the high frequency range."
 
Or, it could be because the 'test' was done with a less good speaker, where a so-called 'smoother' amp would cover up its flaws.
With less information, we're left to guessing ;)
 
dcolak said:
The gain setting works only for RCA inputs, it does not work for XLR inputs.
Click to expand...
Ah, I see now, so despite being from different batches the gain via XLR is identical. And hence you have no balance issues, just the perceived lack of bass. Thanks for clarifying. (Mine aren’t currently in use, but I did used XLR connection, and I thought I’d tried different gain - but I think memory is failing me!)
 
Digital_Thor said:
Or, it could be because the 'test' was done with a less good speaker, where a so-called 'smoother' amp would cover up its flaws.
With less information, we're left to guessing ;)
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Wharfedale Elysian 4, JBL Array 1400, do you think those are a "less good speakers?" :)
 
dcolak said:
Wharfedale Elysian 4, JBL Array 1400, do you think those are a "less good speakers?" :)
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No, maybe... haven't seen precise measurements of them. But you aren't really particular happy with them ;)
dcolak

'Wharfedale Elysian 4'

I would so like to see the AudioScience review of the Wharfedale Elysian 4's.

There is no bass under 80Hz, there are no highs above 15Khz.

Here are the measurements I did of my pair.

The two 7" drivers play well above their crossover point at 340Hz.


Screen+Shot+2025-02-23+at+18.03.26.png




Screen+Shot+2025-02-23+at+18.03.37.png
...
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OP does seem to be perceiving massive difference in sound. Surely they don't wanna hate the amps they bought. Something might be up. Sorry to hear it.

My first thought was that they're out of phase with each other. Does it sound like turd when playing just one channel?
they said one has the 19-25 gain, and the other 25-31? might have old model and new model mixed in their delivery. if using balanced input, gain should be fixed and near enough between them, but might mean one was from older batch with reverse phase issue? if both have the issue, would sound ok if not combining with subs/other speakers. but if one is wrong, and one is right, would sound out of phse. and horrible. kind of describing what they are reporting.

though they did say they're not out of phase... still, gotta try switch speaker connections on just one amp, and listen if it's much worse, or much better... ideally with music playing mono.

Hopefully they find a solution - if nothing else, they have other amps they are satisfied with.
But the V3 monos should be a good amp, to say the least, and thus make speakers make sound, and it should sound like what you're playing them.

rather than a long rambling post, this one ends, and another begins...
 
... and I just got a pair of Fosi V3 monos today. previously had and was using Fosi v3 stereo.

the models delivered i have are both 19-25 dB gain switch on the RCA in. i first installed a V3 mono on just one channel, and played music in mono, with a V3 stereo on one side, and V3 mono on the other. with gain on 25 RCA input, there was still a little gain/volume difference. not unexpected. but it sounds fine. phase is correct with the new amps/consistent with the v3 stereo, and plays correctly with subs.

testing 32v power supply and the 48v, sounds the same, and obviously gain/volume is unchanged. no surprise. i'm not likely anywhere near power limits, so most likely will just run them with 32v 5A.

now I have both of the V3 monos connected with balanced source/input (source is MOTU ultralite mk5).

once output level from MOTU adjusted to the V3 monos to match subs, all is fine. The same. I got the monos somewhat on an impulse, and for peace of mind of PFFB freq response, and balanced line in is nice to have, if your source has it.

ps: similar speakers to OP - JBL Studio S26. older USA made ones ~1999 with bronze coloured woofers.

I also did this, as a crude, perhaps practical test to see whether PFFB was making any freq response difference with those JBL S26:

UMIK-1 in a mic stand. position fixed. sweep measured with V3 stereo amp.
changed amp to V3 mono, adjusted output of test sweep to make it close to SPL match. Some minor consistent difference in higher frequency if you zoom in enough. i would say that'd be inaudible to me with real music content. maybe even measurement variation? though i did do several sweeps and for a fixed amp, the lines overlayed better than this, so some confidence that the difference might be "real".

Anyway, amps seem fine. they do amping. music plays. and i can have placebo of so much magical SINAD, and superior balanced connection, and PFFB :-P veils! nights! days! (not.) but it sounds the same. it sounds fine. it sounds great. just like it did before.
Currently listening to Pineapple Thief's "Versions of the Truth" - nice sounding recording, with great drummer and great sounding drums.

REW UMIK Graph...
We;re very very zoomed in folks - note the dB scale to the left.

Yellow is the V3 mono.
Blue is the V3 Stereo.

1757416968089.png
 
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