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

[Svend P]

Am I allowed to say it? Change the op-amps!

No, that is only something you recommend to someone who doesn't want the sound to change.

IME these amps sound a lot better with MUSES02 op-amps which lean warm. Maybe you should try them before abandoning ship?

It doesn't make any difference except to your expectations

'Does Op-amp Rolling Work?'

Mar 16, 2025

When I post my last video on review of Douk A5 amplifier, I mentioned that rolling (changing) op-amp ICs in there is fruitless. I got have a dozen comments under that video in youtube asking why so I thought I experiment again with the A5. Note that I have done the same testing with both DACs and Power Amplifiers and found the change to not make a difference. But let's see if the results are different this time.

The Douk A5 makes this job both easy and hard. It is easy because you can just lift the plexiglass and replace the op-amps. The difficulty was...

• amirm
• Replies: 1,149
• Forum: Stereo and Multichannel Amplifier Reviews

• 

 

[dcolak]

There you go, I'm imagining things Fosi sounds good like all my other amps...

There must be a measurement we are not measuring...maybe a damping factor, if we are talking about the lack of bass with Fosi?

But, what would explain the "metallic" sound of male voices through Fosi and not through Dayens Ampino?

Dayens Ampino sounds "liquid" while Fosi sounds like "why is everything so... dead?"

 

[norman bates]

6:36+ (jbl L100 classic I think)

“…. experience to you if you pair with $1,000 to $500 price range of speaker. They should do well up to 85 DB range after that it may not be their best in terms of sound quality. It has a good amount of power output but to control this 4 ohm 12 inch driver I don't think it has enough power to give me satisfyingly deep and rich with nice dynamic attacks with very chest thumping bass quality. So, that is uh not doable with this V3 monos in my system. When I try with this Pioneer TAD S-1EX towers same thing, V3 mono with TPA 3255 chip based amps of good sounding for the price and price is very very good. But you need high efficient speakers to get the best out, meaning you know effortless bass quality with articulated notes with the chest thumping immediacy and attack that if you want to hear that, that is at least 95 DB above sensitive speakers to get the best out, so I took it up to like 96-97 DB Max with probably like above 100 DB Peaks. If you don't push that loud you will be totally fine.”

 

[Svend P]

There you go, I'm imagining things Fosi sounds good like all my other amps...

There must be a measurement we are not measuring...maybe a damping factor, if we are talking about the lack of bass with Fosi?

But, what would explain the "metallic" sound of male voices through Fosi and not through Dayens Ampino?

Dayens Ampino sounds "liquid" while Fosi sounds like "why is everything so... dead?"

You are not testing level matched and blind. You should read this:

'Master Thread: Are Measurements Everything or Nothing?'

Nov 18, 2020

Seems like so many review threads get challenged with:

1. Measurements are not everything.

2. You all never listen.

3. I trust my ears, not graphs.

4. I don't listen to graphs. I listen to music.

5. You all must not listen to music at all.

6. Why don't you all buy the best SINAD gear?

7. I have heard your best SINAD gear and they sound terrible. I don't like any of this Chinese stuff.

8. You don't trust your ears. I/we do.

9. All these reviewers/youtubers/audophiles say these amps, DACs, etc. sound different and you say they don't. They can't all be wrong.

10. Surely designers...

• amirm
• Replies: 17,445
• Forum: General Audio Discussions

• 

 

[dcolak]

I used more volume with Fosi, did not change a thing.

I love other amps (NAD M3, Topping LA90 Discrete, Yamaha P3500S, Dayens Ampino, TRENDS TA10.1, Virtue Audio TWO), it's just Fosi that sounds terrible.

You must be right, I must have something against Fosi, I spent money on it just to not like it.

Maybe it's speaker connectors that have a problem? Something must be wrong, or... all class-d amps sound like this?

Now I'm afraid buying Apollon Audio Purifi 1ET9040BA DM Dual Mono. I had my eyes on it.

 

[Ropeburn]

I used more volume with Fosi, did not change a thing.

I love other amps (NAD M3, Topping LA90 Discrete, Yamaha P3500S, Dayens Ampino, TRENDS TA10.1, Virtue Audio TWO), it's just Fosi that sounds terrible.

You must be right, I must have something against Fosi, I spent money on it just to not like it.

Maybe it's speaker connectors that have a problem? Something must be wrong, or... all class-d amps sound like this?

Now I'm afraid buying Apollon Audio Purifi 1ET9040BA DM Dual Mono. I had my eyes on it.

Look mate, it's one thing to not like one particular model for whatever reason, real or imagined, whatever.

It's a completely different thing to then go and project that onto the whole technical category. It's like getting a cheap "my first Sony" kind of amp, not liking it, and then concluding that class AB must be bad.

Don't be stupid. You can do better.

 

[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........@^&#$

For Example:

 

[dcolak]

Look mate, it's one thing to not like one particular model for whatever reason, real or imagined, whatever.

It's a completely different thing to then go and project that onto the whole technical category. It's like getting a cheap "my first Sony" kind of amp, not liking it, and then concluding that class AB must be bad.

Don't be stupid. You can do better.

So you are saying not all class-d amps are as bad as Fosi?

 

[dcolak]

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........@^&#$

For Example:

I have a better idea, I will play the same song through two amps and then do a null test between the two ;-) As soon as I find my microphone :-D

 

[norman bates]

Anyone run the v3 monos with a big speaker ?

Using a 12" or a 15" in a 3-way speaker ?

Anyone leave their v3 monos on all the time ?

 

[dcolak]

Anyone run the v3 monos with a big speaker ?

Using a 12" or a 15" in a 3-way speaker ?

Anyone leave their v3 monos on all the time ?

I did. Used them with JBL Array 1400's and JBL S312II's.

They run out of steam when you go loud. Bass never sounds right. Male voices have a "metallic" sound to them.

Topping LA90 Discrete in bridge mode is FAR FAR better.

 

[Svend P]

Male voices have a "metallic" sound to them.

There is nothing in the measurements that supports this claim. You need to test blind and level matched.

 

[dcolak]

There is nothing in the measurements that supports this claim. You need to test blind and level matched.

That means we're not measuring something that needs to be measured.

 

[Ropeburn]

That means we're not measuring something that needs to be measured.

It can mean that, but you can't know until you properly test your perception.

 

[Talisman]

As you can see, you're not spreading hate at all, just doubts about your subjective assessments, which are respectable to you but have no value to others.
If you want to support your argument, bring measurements. Such an audible difference in bass as you claim to hear would be extremely evident in a frequency response scan measured with a microphone.
If you keep talking about your sensations, none of us can help you.
I have two Mono V3s, and they sound exactly like my Yamaha AS 501 and my Hypex NC252.

 

[voodooless]

Anyone run the v3 monos with a big speaker ?

How does the amp know how big the speaker is?

 

[dcolak]

When Erin listens to speakers or amps, before measuring them, do you think he starts doing "blind tests" between them or he simply takes a note and then goes into measurements, to see if what he heard is what the measurement shows?

We're putting too much emphasis on "was it blind" and discarding observations that might as well be valid.

If I was a professional reviewer, I might have done "blind tests" but we all have lives to live, I shared my experience with you guys, for what it's worth.

I've had many different amps, this is the first time I heard the sound like that of the Fosi amp.

 

[Svend P]

When Erin listens to speakers or amps,

He doesn't give subjective impressions of amplifiers. Because they all sound the same!

 

[voodooless]

When Erin listens to speakers or amps, before measuring them, do you think he starts doing "blind tests" between them or he simply takes a note and then goes into measurements, to see if what he heard is what the measurement shows?

He did test the V3, and did an ABX vs the ZA3

He could not reliably tell them apart.. oops

 

[dcolak]

He was not impressed with them either.