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

[jEDGEc0m]

Small tip:
in REW do Trace arithmetic -> A/B.
That will show just the frequency response difference between the two measurements (much easier to read).

Live n Learn! Thx. Much more readable indeed. I'd ignore the almost 1dB diff down at 23hz, cause that's almost certainly noise floor from the real world. speakers had a highpass at 25 for the test anyway.

Yeah, some difference. not much. We have no impedance graph that i know of for these JBL S26 speakers, if that would assist interpretation.
i gotta say, they seem like pretty darn good speakers, considering. picked them up a few years ago when previous main speakers had a tweeter die that could no longer be sourced for replacement.

 

[ViperDom]

OP,
Any reason you havnt ran a freq sweep with REW to visualize the difference in freq response that you are hearing?
This is where i would have begun.
You can literally overlay the measured frequency response all four setups to present how they differ rather than relying on........@^&#$

+1

Could you make some measurements to confirm the difference? I bet many in here would be interested in the results.

+2

... and I just got a pair of Fosi V3 monos today. previously had and was using Fosi v3 stereo.


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.


f

Kudos for illustrating how to do this.

 

[dcolak]

I think I know why I don't like Fosi V3 mono compared to Topping LA90 discrete mono:

vs

Look at that THD + N over 5Khz. Play it loud and it sounds... wrong. I still owe recording the same song on a couple different amps

 

[staticV3]

I think I know why I don't like Fosi V3 mono compared to Topping LA90 discrete mono:

View attachment 479641

vs

View attachment 479642
Look at that THD + N over 5Khz. Play it loud and it sounds... wrong. I still owe recording the same song on a couple different amps

G

'Is SINAD around 5-15 KHz relevant?'

Jul 19, 2024

I’m trying to build some active 3-way bookshelves. At this point, I need to decide for amp selection for my high frequency >2.5 KHz. I love Hypex products and will be powering the low end and midrange with hypex modules.

I’m a bit hesitant about the tweeter amplification. Most newer class D amps from Hypex and Purifi are great with power and low distortion, until they get to >10 KHz, where they suck. There are a few clas A/B amps out there that have better SINAD than the new class D amps above 10KHz. Would like some insight, am I overthinking it? Is it possible that some of the high...

• gags11
• Replies: 39
• Forum: Audio Power Product Reviews and Discussion

 

[dcolak]

What other explanation could it be there? I hate FOSI's playing loud, it sounds unnatural. There you have it, the measurement. Now we're not taking that measurement into account? I'm not buying it.

 

[staticV3]

What other explanation could it be there?

Cognitive bias.

Using a loosely related measurement as supposed proof for a shaky claim is textbook pseudoscience. Flat earth kind of stuff.

First establish that there actually is a difference outside of cognitive bias, and then you can look into where that difference might stem from.

 

[norman bates]

Intermod distortion isn’t the best, not the worst though……

 

[jEDGEc0m]

I think I know why I don't like Fosi V3 mono compared to Topping LA90 discrete mono:

View attachment 479641

vs

View attachment 479642
Look at that THD + N over 5Khz. Play it loud and it sounds... wrong. I still owe recording the same song on a couple different amps

I feel like that distortion level is still low enough that I wouldn't "hear" it. and I also feel like a lot of music production has a lot of saturation applied too, which would probably blend and mask. But yeah, if you've found a preference, maybe you don't need to quantify it more. Listen to what makes the music enjoyable to you.

But if you can do some kind of recording and measurement, and blind comparison, could be interesting.

I found this, but only just did a very quick try, and don't think I can hear the difference, so I didn't bother trying the ABX foobar tester more, as I'd just be guessing.

'Blind test - can you tell the class D amp from original loop in ABX'

Nov 13, 2021

This is the test of the looback file vs. the file recorded through a class D amplifier. The files for download are here:

Dropbox

www.dropbox.com

If you are interested, please download the zip file, unzip it and listen. Dropbox account is not needed, just click somewhere outside the login box and it will disappear. I would like for you to support your result by a protocol from the ABX test, like provided in Foobar plug-in, e.g.

P.S.: the music in the test is not an "Easy listening". It is from the Beethoven Violin Concerto, movement 3.

• pma
• Replies: 61
• Forum: Amplifiers, Phono preamp, and Analog Audio Review

• 

 

[dcolak]

I feel like that distortion level is still low enough that I wouldn't "hear" it. and I also feel like a lot of music production has a lot of saturation applied too, which would probably blend and mask. But yeah, if you've found a preference, maybe you don't need to quantify it more. Listen to what makes the music enjoyable to you.

But if you can do some kind of recording and measurement, and blind comparison, could be interesting.

I found this, but only just did a very quick try, and don't think I can hear the difference, so I didn't bother trying the ABX foobar tester more, as I'd just be guessing.

'Blind test - can you tell the class D amp from original loop in ABX'

Nov 13, 2021

This is the test of the looback file vs. the file recorded through a class D amplifier. The files for download are here:

Dropbox

www.dropbox.com

If you are interested, please download the zip file, unzip it and listen. Dropbox account is not needed, just click somewhere outside the login box and it will disappear. I would like for you to support your result by a protocol from the ABX test, like provided in Foobar plug-in, e.g.

P.S.: the music in the test is not an "Easy listening". It is from the Beethoven Violin Concerto, movement 3.

• pma
• Replies: 61
• Forum: Amplifiers, Phono preamp, and Analog Audio Review

• 

This is ridiculous. Borderline flat earthing here.

They sound bad, measurements are bad, no, I'm imagining it. Because... because... I somehow decided I don't like Fosi Lol...

 

[jEDGEc0m]

I'm not sure I understand what I said that was deemed ridiculous. If could be that we're misunderstanding each other.

But I think I understand that you have an amp you like to listen to, and one(s) you don't - so all is well - Listen to the one that makes the music sound good to you.

 

[JSmith]

I'm imagining it.

What makes you think you're not?

Best to level match and compare without peeking. If you can so easily identify them then, come back and post your results. Members will then be very interested, some may perform the same comparison and if confirmed further investigations will be done.

If you just come in with "trust me Bro"... that won't fly here.


JSmith

 

[Audionaut]

But I think I understand that you have an amp you like to listen to, and one(s) you don't - so all is well - Listen to the one that makes the music sound good to you.

That's it.
That's all you need to say about the whole thread, that's all you need to know.

 

[dcolak]

Last night I did something different.

First round of listening - NAD M51 -> FOSI V3 monos -> JBL ARRAY 1400

Bass is there but... it's not omnipresent, it's not engaging the room, resolution is okeish.

Second round of listening - NAD M51 -> Left channel TOPPING LA90 DISCRETE bridged -> Right channel FOSI V3 mono -> JBL ARRAY 1400

I've matched the levels so that the singer's voice was dead center as always.

Music was from the album We Cut the Night by AaRON, songs Ride On, Invisible Stains, We Cut the Night.

I highly recommend the album, those songs are great to check the resolution of the system, the soundstage...

Listen to them, you'll understand.

People, the bass, it was on a whole new level, whole room was full of the bass, it was part of the soundstage, not "something coming out of speakers."

The clarity went up, resolution, all those sounds you usually don't notice, they were back.

So, my bias is... what... only in the right ear but not in the left ear?

 

[jEDGEc0m]

Last night I did something different.

First round of listening - NAD M51 -> FOSI V3 monos -> JBL ARRAY 1400

Bass is there but... it's not omnipresent, it's not engaging the room, resolution is okeish.

Second round of listening - NAD M51 -> Left channel TOPPING LA90 DISCRETE bridged -> Right channel FOSI V3 mono -> JBL ARRAY 1400

I've matched the levels so that the singer's voice was dead center as always.

Music was from the album We Cut the Night by AaRON, songs Ride On, Invisible Stains, We Cut the Night.

I highly recommend the album, those songs are great to check the resolution of the system, the soundstage...

Listen to them, you'll understand.

People, the bass, it was on a whole new level, whole room was full of the bass, it was part of the soundstage, not "something coming out of speakers."

The clarity went up, resolution, all those sounds you usually don't notice, they were back.

So, my bias is... what... only in the right ear but not in the left ear?

View attachment 479974View attachment 479975

I know you said it was in phase with Fosi pair, but this still sounds like maybe you have one Fosi that is the older model with reversed polarity, and when you use both of 'em together, they're out of phase.

The Fosi you used with the LA90 - was it the one that has gain switch of 19 - 25dB?

 

[Talisman]

What makes you think you're not?

Best to level match and compare without peeking. If you can so easily identify them then, come back and post your results. Members will then be very interested, some may perform the same comparison and if confirmed further investigations will be done.

If you just come in with "trust me Bro"... that won't fly here.


JSmith

Not to mention that we've been waiting for a month for some phantom measurements that never arrived to justify a dull bass... then they pull out these diagrams of Amir's measurements that POSSIBLY could show something at high frequencies and certainly not at low frequencies.
In short, I never make these statements lightly, but I firmly believe he could be a troll.

 

[jEDGEc0m]

Not to mention that we've been waiting for a month for some phantom measurements that never arrived to justify a dull bass... then they pull out these diagrams of Amir's measurements that POSSIBLY could show something at high frequencies and certainly not at low frequencies.
In short, I never make these statements lightly, but I firmly believe he could be a troll.

It does seem kind of odd! We have put in a lot of chat into it. We might be suckers!

They are correct though, that the AaRON songs they mentioned have a lot of bass, having put them some on just now.

 

[staticV3]

Last night I did something different.

First round of listening - NAD M51 -> FOSI V3 monos -> JBL ARRAY 1400

Bass is there but... it's not omnipresent, it's not engaging the room, resolution is okeish.

Second round of listening - NAD M51 -> Left channel TOPPING LA90 DISCRETE bridged -> Right channel FOSI V3 mono -> JBL ARRAY 1400

I've matched the levels so that the singer's voice was dead center as always.

Music was from the album We Cut the Night by AaRON, songs Ride On, Invisible Stains, We Cut the Night.

I highly recommend the album, those songs are great to check the resolution of the system, the soundstage...

Listen to them, you'll understand.

People, the bass, it was on a whole new level, whole room was full of the bass, it was part of the soundstage, not "something coming out of speakers."

The clarity went up, resolution, all those sounds you usually don't notice, they were back.

So, my bias is... what... only in the right ear but not in the left ear?

View attachment 479974View attachment 479975

Still no recordings?

 

[dcolak]

I know you said it was in phase with Fosi pair, but this still sounds like maybe you have one Fosi that is the older model with reversed polarity, and when you use both of 'em together, they're out of phase.

The Fosi you used with the LA90 - was it the one that has gain switch of 19 - 25dB?

If it was not in phase singer would never end up dead center ;-)

I know I know, I owe the recording! Too much work these days :-(

I have the microphone, but the ADC, you will not like, it's this one:

 

[dcolak]

It does seem kind of odd! We have put in a lot of chat into it. We might be suckers!

They are correct though, that the AaRON songs they mentioned have a lot of bass, having put them some on just now.

No trolling here JBL S36's... I was looking for those, my S38 share the mid and high, still going strong, almost 20 years now.

I'm sad I didn't purchase the S412Ps, I got me S312's

Greg Timbers was behind them!

 

[joeg26er]

Does anyone have the circuit diagram for the Fosi V3 Monoblocks?
What are the decoupling capacitor values used on the input voltage rails?

as far as reducing the rising distortion in these at high frequencies, what about 48 V rail cleanup

would this typically be the largest, most reliable reduction in apparent HF THD(+N) rise?

because it removes the source of intermod (SMPS HF energy) before the power stage?

[48 V SMPS brick]
│ (+) --------------------------.
│ (–) ---------------------. │
│ │
[DC CM choke (bifilar)]
│ │
After CM choke: +----' '----+
| |
0.1u 0.1u 0.1u 1u (ceramics close to amp jack)
| |
+---+-------------+---+----> to amp 48 V (+)
| |
[1.5uH] [Bulk 2200uF 63–80V]
| |
+----------[0.18Ω]----+
| |
[1.5uF film] GND ----> to amp 0 V (–)