Replace MRX1120 with x3800h + Fosi audio V3 mono?

[OhmSweetOhm]

Since my girlfriend is getting increasingly frustrated with how user unfriendly the MRX1120 is, and the fact that we still need a separate WiiM streamer is also becoming annoying, I’m looking for an AVR with better HDMI board features for my 5.1 system. It is a long story, but due to awkward subwoofer port placement in my small cabinet, the X3800H fits best. The X4800H is also about 300 euros more expensive, which I would rather spend on Dirac since I will lose ARC Genesis.

Because my mains are are quite hard to drive (4 ohm MA Gold 5G), I plan to pair the AVR with two Fosi Audio V3 mono amps.

Question 1:
Amirm review of the X3800H was quite negative and he did not recommend it mainly due to poor SINAD. For music (2.1) my main question is whether this issue becomes irrelevant if I use the AVR only as a preamp and drive the main speakers with the Fosi V3 monos?

Question 2:
There are many reviewers, including here on ASR, comparing the two Fosi V3 mono power supply options:
• one single 48V / 10 A supply plus a power filter
• two separate 48V / 5 A power supplies

At this point I’m getting lost in the power supply comparisons and would appreciate some guidance.

 

[delta76]

he was disappointed because a regression in performance compared to previous model (x3700h). but newer x3700h (after the fire at AKM factory) might have same TI DAC with same performance.
DAC performance wise, x3800h is doing fine for an AVR and you will not hear a difference.

 

[Oddball]

Agree that 3800H will do fine. Objectively 4800H is a better AVR, so one needs to decide if EUR 300 is worth it. In some markets difference is significantly more than that. So compare two models and decide. Dirac will for sure have bigger impact then 3800H vs 4800H so good to think of that. But depending on your needs, built in Audy might also do fine with $20 D&M app and especially with some of the OCA modifications.

When I am confused about amps I usually go for higher specs. In this case it's really close. Not sure if power filter can make a difference for the better. Did not look into that particular one. I know they can make difference for the worse.

 

[delta76]

also where are you? Most of places I checked x4800h is like 500EUR more expensive

 

[OhmSweetOhm]

Thanks for the replies! In that case I think my intuition was fine going for the 3800. I was not sure since many reviewers mentioned the lack of 32-bit processing (AL32) in the 3800 versus the 4800.

And good suggestion regarding the Audussy Oddball... IF the cheaper Fosi v3 power supply option is fine my budget might allow me to consider the 4800

also where are you? Most of places I checked x4800h is like 500EUR more expensive

I'm in the Netherlands, and I can get the x3800h new for about 1000 euro with some discounts (1 year ago even 899).
The x4800h is usually 1700 euro indeed but I can buy a new open box item for 1399. so the difference is about 400...

 

[delta76]

Thanks for the replies! In that case I think my intuition was fine going for the 3800. I was not sure since many reviewers mentioned the lack of 32-bit processing (AL32) in the 3800 versus the 4800.

And good suggestion regarding the Audussy Oddball... IF the cheaper Fosi v3 power supply option is fine my budget might allow me to consider the 4800


I'm in the Netherlands, and I can get the x3800h new for about 1000 euro with some discounts (1 year ago even 899).
The x4800h is usually 1700 euro indeed but I can buy a new open box item for 1399. so the difference is about 400...

hold on a little bit. It will likely get sub 1000 EUR for x3800h and sub 1500 EUR for x4800h. or at least I'm hoping.
price increased again after some good reduction early this year

 

[OhmSweetOhm]

Yeah, will do! Also with Black Friday approaching..

Can anyone help me decide whether I should go for a single 10 A PSU or two separate 5 A PSUs for my pair of Fosi Audio V3 monos? I have read so many contradicting posts here and elsewhere online about distortion that I am not sure what to believe anymore.

 

[OhmSweetOhm]

Update: I bought the separate 2 * 48v / 5a power supply

Now I have the option to use 25db or 19db gain setting. So what to pick..?

Checking the users here and on AVforums is again confusing. Amirs measurement of the x3800h pre out is about 1.4v. Before distortion kicks in.

I know i need to take AI advice with a pinch of salt but I Google AI and it recommended to use 19db but Chat GPT didnt like this at all and preferred 25dB. It said:

“It is generic AI-generated advice that misunderstands how AV-receiver pre-outs work compared to DACs.

Let me break it down with facts, not guesswork.

✔ FACT 1

Denon X3800H pre-out voltage is
not high output

Multiple independent measurements show:

• Typical clean output: 1.2 to 1.5 Vrms
• Absolute max before distortion: around 2 Vrms (only near reference level)

A “high output source” in audio normally means 2 Vrms standard DAC output or even 4 Vrms balanced.

So the Denon is not a high-output source.

It is medium at best.

This already invalidates the advice in the screenshot.

✔ FACT 2

Your speakers require more gain, not less

You have:

• 4 ohm impedance
• 86 dB sensitivity (which is low)

This combination needs more amplifier gain, not less.

✔ FACT 3

Fosi V3 Mono at 19 dB gain is too low for most AVRs

Users who tested Denon and Marantz with the Fosi V3 Mono report:

• 19 dB = too quiet
• Requires high volume on AVR
• Reduced dynamic peaks
• Not enough headroom
• Sometimes forces the AVR into pre-out clipping earlier

25 dB solves all that.

✔ FACT 4

25 dB will NOT cause clipping

The screenshot wrongly assumes that higher gain = automatic clipping.

This is false, because clipping in your chain will happen first at:

1. The Denon pre-out
2. Or the speaker itself
3. NOT the Fosi at 25 dB (it has plenty of room)

25 dB does not create clipping unless your Denon sends a crazy hot signal, which it never does with normal levels.

✔ FACT 5

Better dynamic range = 25 dB
You want the Denon running at moderate volume levels, not maxed out.
With 19 dB Fosi gain, you will need to push the Denon too high.

✔ FINAL ANSWER


Use 25 dB gain on your Fosi V3 Mono with the Denon X3800H.

This is the correct setting for:

• 4 ohm speakers
• 86 dB sensitivity
• Medium-output Denon pre-outs
• Movies and music with wide dynamics
• Avoiding Denon pre-out strain/clipping
• Achieving reference level properly

The opposite advice in the screenshot is generic nonsense and does not apply to AVRs.”

 

[OhmSweetOhm]

No one? I just tried to connect both options and I was not able to hear any distortion.

Whese were the needed adjustments after running Audyssey with 19 & 25dB gain settings on the Fosi.

as you can see with the 19db setting my denon needed a lot more (+7.5 and +9.0 db) not sure how high these voltages were and if they were above the 1.4 distortion level Amir measured

25db

19db:

* uploaded the images many times and they kept rotating, my apologies

 

[peng]

No one? I just tried to connect both options and I was not able to hear any distortion.

Whese were the needed adjustments after running Audyssey with 19 & 25dB gain settings on the Fosi.

as you can see with the 19db setting my denon needed a lot more (+7.5 and +9.0 db) not sure how high these voltages were and if they were above the 1.4 distortion level Amir measured

25db

View attachment 492984


19db:

View attachment 492983
* uploaded the images many times and they kept rotating, my apologies

For AI info to be useful you have to push them away from internet hearsay.

The 3800 is fine just use the 25 dB gain setting.

The 3800 preout can go up to at least 3.5 V more linkely about 4.2 V before clipping. Amir’s comments about the 1.4-1.5 V is based on measured SINAD, not clipping, he could have worded it not as misleading but..,

 

[OhmSweetOhm]

Amazing! Thx for the reply. I will keep the 25db gain setting

 

[peng]

To your other question, practically speaking, a single 48v 10 A PS should be a little better for 4 ohm nominal speakers.

 

[OhmSweetOhm]

To your other question, practically speaking, a single 48v 10 A PS should be a little better for 4 ohm nominal speakers.

Too late, I went for two separate 48V 5A PSU

@edit: I also didn't want to introduce the additional power filter, which was recommended while using the single PSU.

 

[peng]

Too late, I went for two separate 48V 5A PSU

@edit: I also didn't want to introduce the additional power filter, which was recommended while using the single PSU.

That's okay, there are pros and cons anyway, just want to give you a theoretical answer based:

a) assuming they use a splitter to deliver the power to the two Mono unit, the 10 is better because in real world use, music and movies don't demand the same current required by your speakers continuously and equally so during playback each speaker could draw right up to the limit afforded by the larger power supply a lot of, or even most of the time.

b) that crossover is not an issue, and there is no reason to believe there is, many high end amps including class AB amps also use one single transformer.

as to the additional power filter I have no idea why it would recommended, did Fosi provides an explanation, or they just want to sell.. don't really know unless there is something I can read up on. I also purchase one with the 5 A PS because I am only using one Mono for a stupid 8 inch subwoofer, actually quite like its smaller footprint and lighter weight.