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Fosi Audio V3 op-amp rolling, has anyone tried it? Snake oil? Or are there actual differences?

bgravato

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Disclaimer: I'm fairly new here and with so many forums, it wasn't easy to decide which one to post this...
If this is not the best one please let me know or (if you're a mod) feel free to move it.

TL;DR: I've recently order a Fosi V3 (should get it next week or so).
I'm not sure I'll keep it, so I will have only a few weeks to try it out before returning if I don't like it... and I've been wondering if it's worth getting some op-amps and try some op-amp rolling.
I'm usually a bit skeptic on these, but curious if anyone tried and what results they got...

Here's some background on what I've tried before and why I'm looking into this...

The speakers I have are the DALI Spektor 2, currently driven by an old Philips FA950 amp.

When I bought the DALI (a few months ago), I originally ordered an Aiyima T9 Pro (because I wanted something small and also needed an USB DAC).
My father had an old Philips amp in his garage collecting dust, so I decided to pick it up and see if it still worked and how it sounded with the new speakers.
I honestly was expecting the T9 Pro to be better, because it was newer and I thought technology would have made significant advances in the past decades... (but apparently this was a wrong premise)

There were significant differences between the T9 Pro and the vintage amp... with the Aiyima, it sounded kind of veiled as if the sound was coming from the end of the room, behind a thick curtain. Soundstage/imaging wasn't the best...
With the Philips amp soundstage was much more forward. There seemed to be better instrument separation too. Acoustic instruments sounded more "natural". Everything was more "alive".
I ended returning the Aiyima and kind of lost my faith in these tiny chi-fi amps...

In the meanwhile I got a Topping E30 II to use with the vintage amp and I've been happy, except for the fact the Philips amp is huge and I'd really like to get something smaller that would actually fit in my current furniture... (and make other half a bit more happy about the aesthetics...)

Fosi V3 has been released and after so many people raving about it, I decided to give it a try...
No high expectation and I'm actually a bit afraid it might be another big disappointment like the T9 Pro was... So I was wondering if replacing the op-amps could somehow improve soundstage (in case it needs to be improved) or other aspects... or if this op-amp rolling thing is just snake oil marketing...

No way I'm going to spend €80 or €170 for a pair of MUSES02 or Sparkos op-amps... I was thinking more about something like OPA2134, OPA2604 or AD712...

Any thoughts on this from someone who actually tried rolling the op-amps on the Fosi V3?
Did it impact soundstage or any other aspect?

TIA
 

Joe Smith

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What I hear is that the op-amp sockets on the Fosi are "grabbier" than on, say, the Aiyima A07. Unless you have good tools, looks pretty easy to destroy the stock ones in there... So I have not made any change to mine.

I did try swapping for low cost on the Aiyima A07 and A04 amps I own, no difference that I could perceive between the stock 5332s and the other "genuine" ones I ordered from Mouser - I'm with you, maybe the Sparkos are magic, but I prefer not to find out as I'm perfectly happy as it sits.

You're going to get divergent opinions on here about swapping op-amps in these Class D amps...I'm in the camp of, if you're feeling experimental, try it, but you are unlikely to hear a difference.

The main plus of the V3 is the taper volume pot - much more control than some of the other small amps when playing at softer volume levels.

If you are thinking you might return it, removing the stock op-amps might be an issue for you. It was really simple on the Aiyimas, I was surprised to see how some were having to mangle the pins to get the 5332s removed in the V3.
 
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bgravato

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What I hear is that the op-amp sockets on the Fosi are "grabbier" than on, say, the Aiyima A07. Unless you have good tools, looks pretty easy to destroy the stock ones in there... So I have not made any change to mine.

I did try swapping for low cost on the Aiyima A07 and A04 amps I own, no difference that I could perceive between the stock 5332s and the other "genuine" ones I ordered from Mouser - I'm with you, maybe the Sparkos are magic, but I prefer not to find out as I'm perfectly happy as it sits.

You're going to get divergent opinions on here about swapping op-amps in these Class D amps...I'm in the camp of, if you're feeling experimental, try it, but you are unlikely to hear a difference.
Thank you for the reply.
I'm electronics/IT engineer, so replacing op-amps in a socket is not something that scares me...

I need to put up a list of things that I may need to order from Mouser to try to reach the "free shipping" limit. If I can do that, I'll probably add some op-amps to the order and give it a try... They got the OPA2134 for €5.49, so basically €11 for two, which isn't crazy expensive... I think I can live with that "loss" if it turns out to be just snake oil...
 

bargainguy

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You're making a couple assumptions: 1. You won't like the "stock" sound of the Fosi, assuming you can hear a difference between it and the Phillips. 2. That if you don't like the stock Fosi, you can make it sound "better" with different op-amps.

If you hadn't already ordered the Fosi, I'd suggest you take the total amount you want to spend - say, the Fosi + op-amp upgrade - and then spend that amount on a different amp you don't have to "upgrade."

But since it's already on order, might as well listen to it for awhile. Then decide which direction. No need to get ahead of yourself here. Trust your ears and see what happens.
 
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bgravato

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You're making a couple assumptions: 1. You won't like the "stock" sound of the Fosi, assuming you can hear a difference between it and the Phillips. 2. That if you don't like the stock Fosi, you can make it sound "better" with different op-amps.
Regarding 1, partly true. After my disappointing experience with the Aiyima T9 Pro, I don't have high expectations, but I'm giving it the benefit of doubt... If I was "sure" I wouldn't like it wouldn't order at all... but I have some hope it will be good enough for me to like it.

Regarding 2, I'm not assuming anything... I don't know if it can be made better with a different op-amp or not, that's exactly what I'm asking here and the main reason why I started this thread...

If you hadn't already ordered the Fosi, I'd suggest you take the total amount you want to spend - say, the Fosi + op-amp upgrade - and then spend that amount on a different amp you don't have to "upgrade."
You got me wrong, that's exactly my point when I say I'm not interested in expensive op-amps like MUSES02 or Sparkos. If I'm spending a bit over €100 in an amp and then I'm spending another €170 in a pair of op-amps, it would make more sense to just get a €300 amp in the first place... right? So I totally agree with you on that point...

That's also why I'm putting a cap at about €10(ish) for a different pair of op-amps (and I'm willing to buy only one pair for now, not a bunch of them to try all possible combinations... if one pair sounds different then I'll know it's not pure snake oil... if it sounds the same, I'm not buying any other models).

But since it's already on order, might as well listen to it for awhile. Then decide which direction. No need to get ahead of yourself here. Trust your ears and see what happens.
It's just a timing issue... I'll probably have to order the op-amps online, which means some days (or weeks in a worst case scenario) to get them delivered... so I need to fit that window into the trial period for which I'm able to return the Fosi for a refund...

That's the only reason why I'm trying to get a bit "ahead" of time, it's just to give me a more comfortable time window for trial.
 

MaxwellsEq

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What I hear is that the op-amp sockets on the Fosi are "grabbier" than on, say, the Aiyima A07. Unless you have good tools, looks pretty easy to destroy the stock ones in there... So I have not made any change to mine.

I did try swapping for low cost on the Aiyima A07 and A04 amps I own, no difference that I could perceive between the stock 5332s and the other "genuine" ones I ordered from Mouser - I'm with you, maybe the Sparkos are magic, but I prefer not to find out as I'm perfectly happy as it sits.

You're going to get divergent opinions on here about swapping op-amps in these Class D amps...I'm in the camp of, if you're feeling experimental, try it, but you are unlikely to hear a difference.

The main plus of the V3 is the taper volume pot - much more control than some of the other small amps when playing at softer volume levels.

If you are thinking you might return it, removing the stock op-amps might be an issue for you. It was really simple on the Aiyimas, I was surprised to see how some were having to mangle the pins to get the 5332s removed in the V3.
Op-amps have a generic character, which is why they are brilliant for teaching purposes at college. To a first order, any generic op-amp from the 741 onwards should have similar "behaviours"

But in reality, they need care and attention. Some have different sensitivities regarding DC rails and ground; some are designed to only work optimally when compensated; some have loading sensitivity etc. When you take a real-world op-amp out of a circuit designed to get the most from that op-amp and put in an op-amp that is only optimal with a different circuit design, you will downgrade the circuit, even if the new device is a much better op-amp. This is why so much professional gear uses optimally designed circuits based on the 5532.

You may get audible differences that you prefer, but that doesn't mean the results are measurably better. In fact there's a better than even chance that it will measure less well (especially if you look at very high frequency behaviour on a scope).
 
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bgravato

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Op-amps have a generic character, which is why they are brilliant for teaching purposes at college. To a first order, any generic op-amp from the 741 onwards should have similar "behaviours"

But in reality, they need care and attention. Some have different sensitivities regarding DC rails and ground; some are designed to only work optimally when compensated; some have loading sensitivity etc. When you take a real-world op-amp out of a circuit designed to get the most from that op-amp and put in an op-amp that is only optimal with a different circuit design, you will downgrade the circuit, even if the new device is a much better op-amp. This is why so much professional gear uses optimally designed circuits based on the 5532.

You may get audible differences that you prefer, but that doesn't mean the results are measurably better. In fact there's a better than even chance that it will measure less well (especially if you look at very high frequency behaviour on a scope).
Yes, the magic of audio pleasant distortions that make tubes still so popular these days... ;-)

I'm looking at the AD712 datasheet and it seems to have two (main) variants AD712J and AD712K with slightly different specs...
By the numbers I'd say the K variant seems better, but I'm no expert... Any thoughts on that?
 

MaxwellsEq

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Yes, the magic of audio pleasant distortions that make tubes still so popular these days... ;-)

I'm looking at the AD712 datasheet and it seems to have two (main) variants AD712J and AD712K with slightly different specs...
By the numbers I'd say the K variant seems better, but I'm no expert... Any thoughts on that?
You probably are unlikely to notice any difference between the two - since the real world characteristics of the circuit will be dominated by NFB. The slightly wider BW is probably going to be irrelevant
AD712.png


But this was my point earlier on - you start with a set of design criteria and then you can tell whether the K is the one for you. There is simply no way of knowing whether one, both or either will work properly/stably in the Fosi circuit.
 

Joe Smith

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The ones I subbed were LM4562's, which work fine with the Aiyimas. But no perceptible sound difference from the stock 5532's.

Nothing really magic about the sound or performance of the V3, but it is a good inexpensive class D amp particularly good for lower volumes and where the small form factor works. Identified internal components and better heat dissipation, but when used at lower volume levels, case never gets very hot. But it is IMO an improvement over the Aiyima A04 and A07 amps, which I use and like.

I think all the folks pushing these small amps to the highest power levels they are capable of are kind of chasing rainbows...if you need Hypex-amp-level power, get a Hypex amp (or Purifi).
 
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bgravato

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You probably are unlikely to notice any difference between the two - since the real world characteristics of the circuit will be dominated by NFB. The slightly wider BW is probably going to be irrelevant
View attachment 310302

But this was my point earlier on - you start with a set of design criteria and then you can tell whether the K is the one for you. There is simply no way of knowing whether one, both or either will work properly/stably in the Fosi circuit.
Thanks. That would be my most likely guess too. I believe this opamp rolling feats are more of a marketing trick than anything else, but I thought I'd ask to get some feedback of people who might have actually tried it and proved it one way or the other...
 
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bgravato

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The ones I subbed were LM4562's, which work fine with the Aiyimas. But no perceptible sound difference from the stock 5532's.

Nothing really magic about the sound or performance of the V3, but it is a good inexpensive class D amp particularly good for lower volumes and where the small form factor works. Identified internal components and better heat dissipation, but when used at lower volume levels, case never gets very hot. But it is IMO an improvement over the Aiyima A04 and A07 amps, which I use and like.

I think all the folks pushing these small amps to the highest power levels they are capable of are kind of chasing rainbows...if you need Hypex-amp-level power, get a Hypex amp (or Purifi).
I listen to low levels. I live in an apartment and I like my neighbors and I like my ears too.

When I tried the Aiyima T9 Pro, my problem was never lack of volume (I never ever got the volume level past 50% at most), it just sounded kind of dull/veiled compared to the vintage Philips amp on the same speakers. I suspect the tubes on the T9 Pro might be hurting it more than helping. Anyway, I was curious and willing to give another shot at a non-tube chi-fi amp and see the differences... I actually thought about getting an A07 at some point, but then Fosi V3 got released with all the fuss about it, so I thought... why not?

Worst case scenario it goes back like the T9 Pro did. I may have to pay the shipping on this one though, since I ordered it directly from Fosi, rather than from Amazon, but it's a small price to pay for some peace of mind.

If I can find some of the "recommended" op-amps for under €10 for the par I might try it just for some extra peace of mind, but judging from the comments so far, seems like op-amp rolling doesn't make much of a difference.

Hypex should be nice, but not €100 by any means. My point here is just to confirm whether that T9 Pro was a bump in the road, or if "all" chi-fi cheap amps have the same issues and all the people raving about them don't know what they're talking about :)
 

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I'll be interested in your thoughts. I tend to use mostly vintage & restored receivers and integrated solid state amps, but dipped my toe in with SMSL many years ago with their original SA-50 small amps. (I never bought one of the cheap Lepai Tripath amps, that moment had come and gone.) The SA-50 is a decent amp with a 24 V power brick that I used off and on for many years. Then when the 3116 chip boards came out but SMSL was slow to adopt, I did a couple home builds of those. They sounded pretty good. Cut to the present with the newer TI 3251 and 3255 chips and all the praise for the Aiyima A07, so I got interested again. Like Aiyima, Fosi is throwing a lot of variations at the wall and seeing what sticks, but the overall design of the V3 is pretty nice and well thought out. SMSL has some good things now too (I have and like the AO100, which uses the Infineon chip), but again, so many variations from that maker it's hard to keep track.

The main issue for me with the V3 at softer levels is that I kind of miss tone controls. I like being able to just slightly accentuate bass and treble at low volume, like the standard "loudness" circuit on older equipment. I can get that by adding an older preamp into the chain, or by buying one of the new analog EQs from Schiit etc., or using the EQ in streamers. But not a big deal, just depends on your listening preferences.

I think the next opportunity for the Chinese makers, and for the folks building with Hypex/Purifi, is offering integrated amps or amp / preamp matching components for a nice pairing. I think someone will get that done and pitch into the $300-500 zone soon. Fosi is aiming to develop some modular components based on the V3 form factor.

Tubes aren't my thing and from what you've said, yeah, the T9 was probably not something you were going to like....
 
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bgravato

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Like Aiyima, Fosi is throwing a lot of variations at the wall and seeing what sticks, but the overall design of the V3 is pretty nice and well thought out. SMSL has some good things now too (I have and like the AO100, which uses the Infineon chip), but again, so many variations from that maker it's hard to keep track.
They're companies trying to make money, so I guess a wider variety of offers will attract a bigger audience...
"Audiophiles" have all sort of "audio fetiches". Some have the tube fetiche (here's a tube amp for you), some have the modding fetiche (here's an amp where you can swap some parts...) and so one...

I think the T9 is there just for those tube freaks... I never had anything with tubes so I thought I'd give it a try. It looked neat too. Got me sold initially... Sound wise? meh... So it went back (thank you Amazon for the great 30-day no-questions-asked return policy).
I'd like to try some "good" tube amp some day, but T9/T9 Pro definitely doesn't make the cut...

I also agree that tone control would be nice... But on the other hand I like the minimalism of it... hopefully means they had more time to focus on fewer design decisions and had more money to spend on fewer, but better components...
The T9 Pro was a hell lot of things in just one package... not surprising that it's not good at any of them...

I'll post back my thoughts on the Fosi V3 when I get it...
 

burkm

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Human hearing (anatomy of the ears, personal preferences etc.) is/are quite individual to ones person. That probably is the reason, why each has his own impression and personal preferences considering this. All OP amps seem to have at least some sort of "audio" character of their own, allthough measurements don't seem to show this, but at least they give a hint. My personal OP amp preference for the Fosi V3 are Ti OPA1656 but others have different preferences.
I would check the amp out, if its character is basically to your liking (incl. the default NE5532 OP amps supplied) and have - alternatively - a look at some of the rather "cheap" integrated OP amp alternatives, which fit the V3 sockets from their specs. The rest is up to you...

Hint: An OPA1656 (dual OP amp) in his needed adapter (Fosi V3) costs around 5 - 6 $.
 
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bgravato

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Human hearing (anatomy of the ears, personal preferences etc.) is/are quite individual to ones person. That probably is the reason, why each has his own impression and personal preferences considering this. All OP amps seem to have at least some sort of "audio" character of their own, allthough measurements don't seem to show this, but at least they give a hint. My personal OP amp preference for the Fosi V3 are Ti OPA1656 but others have different preferences.
I would check the amp out, if its character is basically to your liking (incl. the default NE5532 OP amps supplied) and have - alternatively - a look at some of the rather "cheap" integrated OP amp alternatives, which fit the V3 sockets from their specs. The rest is up to you...

Hint: An OPA1656 (dual OP amp) in his needed adapter (Fosi V3) costs around 5 - 6 $.
How would you describe the differences you hear between the stock opamps and the OPA1656?

Different soundstage? Imaging? Detail? Bass/treble balance? etc...
 

MaxwellsEq

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Human hearing (anatomy of the ears, personal preferences etc.) is/are quite individual to ones person. That probably is the reason, why each has his own impression and personal preferences considering this. All OP amps seem to have at least some sort of "audio" character of their own, allthough measurements don't seem to show this, but at least they give a hint. My personal OP amp preference for the Fosi V3 are Ti OPA1656 but others have different preferences.
I would check the amp out, if its character is basically to your liking (incl. the default NE5532 OP amps supplied) and have - alternatively - a look at some of the rather "cheap" integrated OP amp alternatives, which fit the V3 sockets from their specs. The rest is up to you...

Hint: An OPA1656 (dual OP amp) in his needed adapter (Fosi V3) costs around 5 - 6 $.
If there is a difference it will be measurable. It will most likely be caused by removing an op-amp from its optimised circuit and putting in an op-amp that requires a different optimisation approach. So, potential always a downgrade (e.g. in DC behaviour, RF behaviour, real (not theoretical) noise behaviour, distortion).
 

burkm

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Will see (or actually hear) myself :cool:

The "problem" is, that several factors intermingle, which might influence ones personal impression.
I don't know, if everything of those stated "sonic" characteristics of the chosen OP amp are really exist, but many seem to believe in it, imagined or not.
Neither "school" can prove their points ultimately, so you have to setup your mind yourself, because no one can share his own impression as ears are no measuring instruments, which can be "objectively" traced and be aconsidered as a "reference".

That same situation seems to hold true for other sonic characteristics of their units, which some seem to "hear" and others are classifying as pure "imagination", because they can't measure it nor identify it in a blind test.

All what finally counts is your own satisfaction with whatever you gathered yourself, imagined or not.
 
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SIY

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Human hearing (anatomy of the ears, personal preferences etc.) is/are quite individual to ones person. That probably is the reason, why each has his own impression and personal preferences considering this. All OP amps seem to have at least some sort of "audio" character of their own, allthough measurements don't seem to show this, but at least they give a hint. My personal OP amp preference for the Fosi V3 are Ti OPA1656 but others have different preferences.
I would check the amp out, if its character is basically to your liking (incl. the default NE5532 OP amps supplied) and have - alternatively - a look at some of the rather "cheap" integrated OP amp alternatives, which fit the V3 sockets from their specs. The rest is up to you...

Hint: An OPA1656 (dual OP amp) in his needed adapter (Fosi V3) costs around 5 - 6 $.
There is almost nothing there which is correct.

Opamp rolling will keep one busy and entertained, but will not improve the sound in any way. At best, no actual (as opposed to imagined) sonic changes. At worst, increased noise, offset, and oscillation.
 
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