Fosi Audio V3 Mono Amplifier Review

[burkm]

There is no Info available, if anything "special" is provided for the V3 mono power supply, except the size of its connector.

 

[Deleted member 72219]

There is no Info available, if anything "special" is provided for the V3 mono power supply, except the size of its connector.

5.5mm external, 2.5mm internal DC.

-Ed

 

[antcollinet]

Is there a reason I need to turn the preamp volume up higher for the v3 monos to get the same loudness as a single ZA3?

Probably - most likely the gain of the two amps is different. Try the V3 mono on the higher gain setting.

If you are on the balanced input this is limited to 20dB which is on the low side - so not surprising you need more volts from the source. (ZA3 is about 26dB on XLR)

 

[antcollinet]

My intention: I just gather the temperature on the surface of the cabinet and try to get it => hotter (!),

That won't work. As has been pointed out, power into the case is the same. Case is "downstream" of the paste (In fact is the last component dissipating heat to the environment.

If power into the case is not changed, then case temperature will not change regardless of the paste. Only components upstream of the case will get hotter if it is not doing its job well.

 

[SMen]

I use a £30 mic from Dayton that has an ADC built into it that's perfectly capable digitalising analogue sound waves as a reference instrument. I think the device in the Ultra is inherently better than the majority of analogue phono preamps. Preserving the sound of an LP is a non issue, anything else is likely placebo.

Thank you for your reply. ADC's have improved over the last 40 years I believe, but we were told that digital measured perfectly and so was perfect back in the day.

My ADC is not expensive but very good. The 'anything else' you refer to is probably more measurable with phono stages than any (most) other piece(s) of gear these days.

To quote the wisest of members here (approximately) - why not do a blind test to be sure, with all these phono preamps!

No, what interests me most about these V3 monos, and a couple of other devices I am trying, is in fact related to your statement ... what is the point at which the measurements don't count because even the cheapest devices measure and perform so well? x distortion vs slightly worse distortion? The point of zero returns.

Historically measurements (it seems to me) have often been abused, and amazingly the equipment has got better (when it was of all perfect before). But these days, it does seem to be a very good time to be buying 'value' gear because it performs so well.

 

[antcollinet]

How quickly it reaches that temperature is telling you how good is the thermal coupling between chip and heatsink,

Not really - how quickly the case heats up will depend on how quckly heat is pumped into it. This is a result of the temperature differential between the chip/heatsink and case. The problem is the chip has very low thermal capacity - it will heat up very quickly - as will the transfer plate. So the rate of heat flow from chip to case will ramp up to full much quicker than the case will heat up. So the rate of temperature rise will not vary significantly with or without well performing paste.

 

[LSPhil]

I have the opportunity to get some 48V PSUs from work that are plenty big, Meanwell lighting switching power supplies, dimmable power supplies, industrial power supplies etc. Is there something special about the PSUs that Fosi provides or will any reasonable one suffice, even laptop PSUs?

there are no restrictions, you can use anything from 24V to 51V DC. Of course, the MW 600W 48V power supply will be very good. It will allow you to extract 2x250W at 4 Ohms or mono 500W from the system

 

[MCH]

Not really - how quickly the case heats up will depend on how quckly heat is pumped into it.

exactly

This is a result of the temperature differential between the chip/heatsink and case.

and the heat transfer coefficient, that is what we are trying to (roughly) evaluate here. h=q/ΔT

The problem is the chip has very low thermal capacity - it will heat up very quickly - as will the transfer plate. So the rate of heat flow from chip to case will ramp up to full much quicker than the case will heat up

most probably, but again, you are missing the different heat transfer coefficients. that "full heat flow" during warm up will be different in one case vs the other.

. So the rate of temperature rise will not vary significantly with or without well performing paste.

the rate of temperature rise, besides the heat transfer rate, will depend on many things, like for instance the mass and surface area of the case, but in any case, being alll other things equal, there will be a difference. How significant the difference is will only depend on how precise your measurement is.

 

[Killingbeans]

No, what interests me most about these V3 monos, and a couple of other devices I am trying, is in fact related to your statement ... what is the point at which the measurements don't count because even the cheapest devices measure and perform so well? x distortion vs slightly worse distortion? The point of zero returns.

Here's some qualified guessing:

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

 

[antcollinet]

Just come across this after replying to @courtesy ... at what date in the development of ADC's do you think that they became 100% audibly identical?

80s, 90s, 2000's, 2010's, 2020's

or have they been perfect since the 1980's in your view / measured performance?

I don't know - I don't have data on ADC performance over time.

If I were to guess I would say digital could audibly perfectly record vinyl probably from the early 80s. Some early CD players had 14 bit converters. 14 bits still has 84db of dynamic range - which matches or exceeds that of vinyl. Even if ADC's of the day only had 14 bit, they'd probably still be transparent to vinyl. But even by the Mid 70s, 16 bit 50kHz recording was in use in studios. By 1980 the redbook standard had been released in 1981 Sony released gear that could be used at home for recording redbook standard digital to VCR tape.

 

[antcollinet]

different heat transfer coefficients. that "full heat flow" during warm up will be different in one case vs the other.

Only until the chip heats up to the point where the heat is transferring through the thermal interface/resistance as fast as it is created. My expectation (though tests or calculations would be needed to verify) is that would be a very small time (a few seconds) compared to the temperature ramp up of the case. It would be difficult (or impractical if all you are using is a thermal probe and a stopwatch) to measure the difference.

 

[burkm]

But it will lower its internal temperature if the heat is been taken off faster. won't it ?

 

[SMen]

I don't know - I don't have data on ADC performance over time.

If I were to guess I would say digital could audibly perfectly record vinyl probably from the early 80s. Some early CD players had 14 bit converters. 14 bits still has 84db of dynamic range - which matches or exceeds that of vinyl. Even if ADC's of the day only had 14 bit, they'd probably still be transparent to vinyl. But even by the Mid 70s, 16 bit 50kHz recording was in use in studios. By 1980 the redbook standard had been released in 1981 Sony released gear that could be used at home for recording redbook standard digital to VCR tape.

Here's an interesting thing, I don't want to go off topic (but just in passing), but I am pretty sure that digital has taken a while to be better at recording sounds closer to silence.
Distortion goes up. So ironically the noise floor of analogue probably helped!

All I can say is that the ADC's on the market for doing anything like recording vinyl were pretty dire (subjectively).

It is only in the past couple of years I got one - actually the Audient Evo 4, where I would not want to walk into a room and say whether it was the record or the recording playing. Not expensive - a shade over 100 euros now.

But when one is talking about the recording itself ... 'I think I'll just do a little noise removal here or there' - just a 'smidgeon of processing' ... and generally the result is worse ... even if the noise measurements are better.

And then there is 'loudness' ... all the dynamic range measurements are rendered pointless by digital loudness (peak limiting) introduced into the recording. I've had some horrors come up on my screen looking at the wave form. So even if people criticize vinyl with it's dynamic range - the variation between peaks and troughs can all too often be much better.

All beautifully revealed by my Fosi V3 monos

Now if I have got my perceptions of dynamic range all wrong, I will stand corrected ... but I don't want cannons going off in my living room ...! Just the sense of them going off.

 

[antcollinet]

But it will lower its internal temperature if the heat is been taken off faster. won't it ?

Yes - anything upstream of the thermal interface material (TIM) will operate at lower temperature (steady state) if the TIM is working better (lower thermal resistance).

But anything downstream of the TIM won't (at steady state) change temperature. There will be a short term (very short if my expectations are correct) difference in rate of rise.

 

[antcollinet]

All I can say is that the ADC's on the market for doing anything like recording vinyl were pretty dire (subjectively).

But non subjectively - why on earth would that be. Dire Straits Brothers in Arms was recorded fully digitally in 1985 - with audio quality (including noise floor) vastly exceeding that possible on vinyl. So absolutely the ADCs used for that are easily capable of recording anything on vinyl without any audible degradation whatsoever.

Many other fully digital recordings were made much earlier, as mentioned above.

But when one is talking about the recording itself ... 'I think I'll just do a little noise removal here or there' - just a 'smidgeon of processing' ... and generally the result is worse ... even if the noise measurements are better.

And then there is 'loudness' ... all the dynamic range measurements are rendered pointless by digital loudness (peak limiting) introduced into the recording. I've had some horrors come up on my screen looking at the wave form. So even if people criticize vinyl with it's dynamic range - the variation between peaks and troughs can all too often be much better.

None of which has anything to do with the straight capture of a vinyl recording to digital and subsequent playback without any degradation.

 

[SMen]

Here's some qualified guessing:

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

A like is not good enough. VG. Take me off this thread a while!

 

[SMen]

But non subjectively - why on earth would that be. Dire Straits Brothers in Arms was recorded fully digitally in 1985 - with audio quality (including noise floor) vastly exceeding that possible on vinyl. So absolutely the ADCs used for that are easily capable of recording anything on vinyl without any audible degradation whatsoever.

I'm not sure that this is relevant. It's a great album though. There are just so many great recordings (and lousy ones across all technologies).

None of which has anything to do with the straight capture of a vinyl recording to digital and subsequent playback without any degradation.

It is very relevant to comparisons and sweeping statements - and also distortion rising the closer you get to recording silence. And, indeed, the dynamic range we hear.

Here's some qualified guessing:

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

Which makes this all the more interesting. I was banging on about left right channel balance a page ago! We are much more sensitive to this than I thought!
And about dynamic range...

 

[Lux_ury]

But it will lower its internal temperature if the heat is been taken off faster. won't it ?

A few points for people

Hot air will always follow into cooler air ambient is important. Lower the better.

The material will have differing coefficients like copper will have better absorption than aluminium.

The speed at which molecules excite varies according to environment.

 

[Sokel]

I'm not sure that this is relevant. It's a great album though. There are just so many great recordings (and lousy ones across all technologies).



It is very relevant to comparisons and sweeping statements - and also distortion rising the closer you get to recording silence. And, indeed, the dynamic range we hear.


Which makes this all the more interesting. I was banging on about left right channel balance a page ago! We are much more sensitive to this than I thought!
And about dynamic range...

Why not be a part of the equation and find out for yourself even better:

Listening Test

www.klippel.de

Puts the mind in rest once and for all,without guessing.

 

[SMen]

Why not be a part of the equation and find out for yourself even better:

Listening Test

www.klippel.de

Puts the mind in rest once and for all,without guessing.

Yes I know this. Will be delighted. I have also measured my hearing (used to pretty regularly, must do again).

But:

Taking balance between channels specifically rather than distortion. How consistent are the V3 monos outputs (for example) between units and batches of units? Measuring one in isolation does not measure this.

I think we are on page 173 ...

The two I have sound very well matched (subjectively) ... I have just bought a phono stage and a volume control where the emphasis is on very tight channel matching.
These work very well with the monos. Channel matching has often been an issue for me so +1 for my pair anyway - and my perception of far better balance with the new gear in this combination.

DAC's these days all seem to measure spectacularly well - nothing these days seem to come with balance controls! I suppose room correction can handle a fair bit.