Fosi v3 Mono - User Impressions | Owner's Thread

[SMen]

I am switching between the amplifiers to power a pair of Klipsch Forte II speakers, and the Fosi ZA3 is sitting on top of the Pass DIY Class A amp using complementary pairs of Sony VFETs. This was the first Pass DIY amp I ever built and. It is a keeper. The Sony VFETs are near-unobtainium and the amp has that beautiful, warm sound that First Watt amplifiers are known by. However, this amp gets hot and can be a space heater.

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Great pics and great project! Impressive. So the Fosi's do fill in duty. VG!

 

[gwing]

Thank you Fosi, received mine today nicely packed and undamaged.

My chain is Wiim pro+ | Optical | DAC/Preamp | XLR | 2x Monos | Speakers. Sounds very clear and with good dynamics, basically how you would hope a decent amp sounds, effortlessly goes louder than my ears can take and has gain to spare.

The monos do run a bit warm, in standby still warmer than my pre-amp even though that has a strong class A headphone amp in it. Bottom of case is noticeably warmer where the chip is, side vents are noticeably hotter than the case surrounding them so it seems both the chip/case coupling and ventilation are working as designed.

Very happy punter here. One day I'll get round to fitting the 2 Muse02s that came with it but at the moment I'm just listening

 

[Miser_Audioman]

Ok think i have this confirmed. Verified polarity on receiver, wires, speakers. Unless hk has it wrong inside, should be gtg

 

[Miser_Audioman]

If i switch the polarity on the fosis, they match

 

[Miser_Audioman]

Fosi in orange. Can someone else verify this result? If the HK230 is correct, the Fosi is reversed.

 

[EddNog]

Fosi in orange. Can someone else verify this result?

Sorry, I don’t have the ZA3 on-hand anymore. I really should have tried flipping one to see the effect before I sent my dad back his ZA3.

-Ed

 

[Sokel]

If i switch the polarity on the fosis, they matchView attachment 381887

Yep,it was clear by the measurement.
Now we have to find who to blame.

 

[EddNog]

I feel massively vindicated here because clearly there was no damn bias involved when I reported this in the first place, yet ASR members decided it was necessary to hound me and blame my report on some mental bias when I made it clear that it was IMPOSSIBLE to NOT hear it.

-Ed

 

[Sokel]

I feel massively vindicated here because clearly there was no damn bias involved when I reported this in the first place, yet ASR members decided it was necessary to hound me and blame my report on some mental bias when I made it clear that it was IMPOSSIBLE to NOT hear it.

-Ed

That's why the best investment in this hobby is couple of measurement gear,one for acoustics and one for electric measurements.
One is literally blind without them,they worth it 100% even for sanity reasons only.

For $300-400 everything can be in the right place.

 

[EddNog]

That's why the best investment in this hobby is couple of measurement gear,one for acoustics and one for electric measurements.
One is literally blind without them,they worth it 100% even for sanity reasons only.

For $300-400 everything can be in the right place.

Whose sanity? I can sit here and share nothing. It costs me nothing to trust that I’m not insane and my ears function like they should. $300 to $400 for the privilege to share my results and not get refuted? Sorry, I have better places to put that like my sons’ 529s.

-Ed

 

[spandy]

So there is in fact thermal compound supplied by Fosi? Getting mixed reports on this...

 

[EddNog]

So there is in fact thermal compound supplied by Fosi? Getting mixed reports on this...

No thermal interface material from the factory between the heat plate and the casing interior for V3 or V3 Mono. ZA3 does have it.

-Ed

 

[Sokel]

Whose sanity? I can sit here and share nothing. It costs me nothing to trust that I’m not insane and my ears function like they should. $300 to $400 for the privilege to share my results and not get refuted? Sorry, I have better places to put that like my sons’ 529s.

-Ed

This has nothing to do with the "others".
It's our own sanity such gear can preserve.

I can show you (with measurements) how many things can go wrong in a chain that can be avoided just by common sense or with some rearrangement.
But will never be sure unless you have the visuals.

Even for the most practical reasons,for example nothing gets in my chain without measuring if it's working fine first.And after that if it's working fine with in the chain.
Basic stuff really,there's no need to know much,evn by presenting them people can tell you.

Just like the above polarity issue.
It was more than evident but since you didn't know you could easily take it as "character",voicing",etc. when is just a grand fail.

So...

 

[Petrushka]

I feel massively vindicated here because clearly there was no damn bias involved when I reported this in the first place, yet ASR members decided it was necessary to hound me and blame my report on some mental bias when I made it clear that it was IMPOSSIBLE to NOT hear it.

-Ed

I’m here to say you can hear out of phase speakers without realizing the cause of the trouble. I wonder how often it happens.

I never thought it could happen to me, so I just assumed something was broken, maybe a tweeter blown.

Doesn’t help to have old ears.

 

[spandy]

No thermal interface material from the factory between the heat plate and the casing interior for V3 or V3 Mono. ZA3 does have it.

-Ed

post #426 says otherwise, unless I'm reading that incorrectly. @rhing could clear this up.

 

[SMen]

I feel massively vindicated here because clearly there was no damn bias involved when I reported this in the first place, yet ASR members decided it was necessary to hound me and blame my report on some mental bias when I made it clear that it was IMPOSSIBLE to NOT hear it.

-Ed

It does get out of hand this whole 'must be bias' thing, or 'must be levels' . I do understand though when it is relevant, but in your case it was not...

Sometimes what one hears is so 'darn' obvious it is time to check the equipment - or love the equipment without messing around.

I plugged in a switch relay attenuator upstream of my new Fosi V3 monos. No I am not going to blind test!

I'm going to enjoy it.

VG Monsieur @EddNog West Coast USA (I think)!

 

[EddNog]

…It was more than evident but since you didn't know you could easily take it as "character",voicing",etc. when is just a grand fail.

So...

It is obvious that despite all my attempts to communicate it, I was not talking about those types of things. I specifically said that it appears something was out of phase when using the two different amps on opposite channels. This is not something that can be up for misinterpretation. I wasn’t talking about character, voicing, texture, soundstage, etc. etc. which are topics I have long ago decided to leave outside the door when walking into ASR. Out of phase is impossible to not hear. It also has a very specific way of sounding. Regardless, since, once again, my advice has proven inadequate due to lack of testing procedures and equipment that meet the mighty standards of this establishment, I will reiterate that I am done providing any form of advice other than, “it makes sound,” or, “it does not make sound.”

Seems perfectly evident to me that nobody here will miss my contributions, anyway.

-Ed

 

[SMen]

It is obvious that despite all my attempts to communicate it, I was not talking about those types of things. I specifically said that it appears something was out of phase when using the two different amps on opposite channels. This is not something that can be up for misinterpretation. I wasn’t talking about character, voicing, texture, soundstage, etc. etc. which are topics I have long ago decided to leave outside the door when walking into ASR. Out of phase is impossible to not hear. It also has a very specific way of sounding. Regardless, since, once again, my advice has proven inadequate due to lack of testing procedures and equipment that meet the mighty standards of this establishment, I will reiterate that I am done providing any form of advice other than, “it makes sound,” or, “it does not make sound.”

Seems perfectly evident to me that nobody here will miss my contributions, anyway.

-Ed

Well speaking personally my contributions won't be missed either / or will be , as in literally missed

I hope those sunnies are polarized. You realize you can't actually see any difference with polarized sunglasses.

 

[Sokel]

It is obvious that despite all my attempts to communicate it, I was not talking about those types of things. I specifically said that it appears something was out of phase when using the two different amps on opposite channels. This is not something that can be up for misinterpretation. I wasn’t talking about character, voicing, texture, soundstage, etc. etc. which are topics I have long ago decided to leave outside the door when walking into ASR. Out of phase is impossible to not hear. It also has a very specific way of sounding. Regardless, since, once again, my advice has proven inadequate due to lack of testing procedures and equipment that meet the mighty standards of this establishment, I will reiterate that I am done providing any form of advice other than, “it makes sound,” or, “it does not make sound.”

Seems perfectly evident to me that nobody here will miss my contributions, anyway.

-Ed

Nothing is evident as no one is at your MLP when you listen to stuff.
The only way to know is to measure.And ok,let go the electrical measurements,they are more difficult to learn.

But for the acoustic ones as the above,a UMIK at the price of couple boutique opamps is enough.
Even for testing these very opamps if you do it right!

 

[GPJ]

Seems perfectly evident to me that nobody here will miss my contributions, anyway.

-Ed

Take it all in stride ..... water off a duck's back .... most established forums have their elite clique that like nothing better than to beat down innocent replies. Been true on EVERY forum I've frequented over the past decade. There's no room for innocent reply's. Really sad you have to think if your going to get jumped or not before hitting the submit reply button.