Shanling M8 Android Portable player

[SMOoth Operator]

Any ideas where most of the heat is coming from? More from the DAC or the amp?
More with high bit rates, respectively turbo mode or in general?

I believe this was extensively covered earlier in the thread by another poster. The M8 has very advanced heat dissapation inside of it, the amp stage looks pretty killer too for its size. I have no idea if its the DAC's or amps heating it up, I suspect it is both, but this is the way it is designed on purpose. Other DAP'S just dont have the same use of thermal conduction that M8 uses and IMO the AMP section appears to be allot beefier than other DAP's. I do not see the heat as being a bad thing, it is because the M8 was designed well, with a solid amp section.

 

[szore]

This stuff gets confusing really quickly, and not all vendors reveal all the info in order to make the comparisons properly.

An amplification circuit is able to produce a specific amount of voltage and current into a specified load. The maximum voltage is determined by the power supply rails feeding the amplifier. Current is related to the capacity of the parts, the load impedence, and the power supply as well.

An amplifier has a designed amount of (voltage) gain (dB are confusing, so let's just use how many X higher V-out is compared to V-in.) let's say 3X. So, if you put 1v in, you get 3V out, if you put 2 in, you get 6 out. Let's say you have an 7V power supply. So, if you try to put more than 3.5V in the amp clips, since it can't go higher than 7V power supply gives it. (A buffer is an amp that typically "adds" current output capability but does not change voltage, by definition, unity gain Vin=Vout).

Most dac chips need some circuitry between them and the actual (power) amp, so those are what supply the voltage to the amp section. If there is digital volume control then turning the volume up or down raises or lowers that voltage. (The amount of current that flows is dependent on the impedance of the load being driven, the wilder the impednce curve, the more of a moving target the iem or headphone is)

If you set the device to Line Oout, vs Headhone Out, it may simply set the volume at max. It may reroute the signal to a different jack and bypass the power amp section--depends on how it is designed/built. Given the bit above about cliping, it is generally regarded as best-practice to have more rather than less voltage available- so maybe M8 just has LO=full blast turbo output (perhaps with or without the current capability of the power amp section there or not. Power amp input is much higher impedance than iems, so more voltage-concerned than current (10s or 100s of ohms for iems, 1000s or 10s of thousands of ohms for line level inputs)

So, it comes down to implementation- is the LO signal path different than the HO output, where is the volume control implemented, and overload margin of the external amp input.



All of the above is straight off the top of my head, so please be kind.....

Epic post...

 

[RTodd]

This stuff gets confusing really quickly, and not all vendors reveal all the info in order to make the comparisons properly.

An amplification circuit is able to produce a specific amount of voltage and current into a specified load. The maximum voltage is determined by the power supply rails feeding the amplifier. Current is related to the capacity of the parts, the load impedence, and the power supply as well.

An amplifier has a designed amount of (voltage) gain (dB are confusing, so let's just use how many X higher V-out is compared to V-in.) let's say 3X. So, if you put 1v in, you get 3V out, if you put 2 in, you get 6 out. Let's say you have an 7V power supply. So, if you try to put more than 3.5V in the amp clips, since it can't go higher than 7V power supply gives it. (A buffer is an amp that typically "adds" current output capability but does not change voltage, by definition, unity gain Vin=Vout).

Most dac chips need some circuitry between them and the actual (power) amp, so those are what supply the voltage to the amp section. If there is digital volume control then turning the volume up or down raises or lowers that voltage. (The amount of current that flows is dependent on the impedance of the load being driven, the wilder the impednce curve, the more of a moving target the iem or headphone is)

If you set the device to Line Oout, vs Headhone Out, it may simply set the volume at max. It may reroute the signal to a different jack and bypass the power amp section--depends on how it is designed/built. Given the bit above about cliping, it is generally regarded as best-practice to have more rather than less voltage available- so maybe M8 just has LO=full blast turbo output (perhaps with or without the current capability of the power amp section there or not. Power amp input is much higher impedance than iems, so more voltage-concerned than current (10s or 100s of ohms for iems, 1000s or 10s of thousands of ohms for line level inputs)

So, it comes down to implementation- is the LO signal path different than the HO output, where is the volume control implemented, and overload margin of the external amp input.



All of the above is straight off the top of my head, so please be kind.....

Awesome long answer.

Still need @Shanling to explain.

What you say though helps a little to understand why the L&P P6PRO line out still allows the volume adjustment on the player, since they are using relays.

 

[SMOoth Operator]

How does it sound, what transducer and music are you listening to?

Need more time to give an accurate answer. So far I have only listened to the Class A in Transistor mode. I am typically a tube guy, listening to transistor out of curiosity. So far it sounds good, the treble sibilance is tamed on the C9 compared to the CDM. I need more time with the C9 in tube mode, going toe to toe with the CDM to give you a better comparison. Currently listening to heavy metal, nu metal and just metal in general.

 

[Whitigir]

Lineout mode can have the gain level adjusted. The max volume out can not be adjusted unless switching back to phone out

 

[FooFighter]

How do you guys work around the heat issues and how much of a pain is it in reality when on the go like sitting in the back of your jeans?
e.g. specific protection case or some add ons usually used for CPU cooling etc?

 

[Ojisan]

This stuff gets confusing really quickly, and not all vendors reveal all the info in order to make the comparisons properly.

An amplification circuit is able to produce a specific amount of voltage and current into a specified load. The maximum voltage is determined by the power supply rails feeding the amplifier. Current is related to the capacity of the parts, the load impedence, and the power supply as well.

An amplifier has a designed amount of (voltage) gain (dB are confusing, so let's just use how many X higher V-out is compared to V-in.) let's say 3X. So, if you put 1v in, you get 3V out, if you put 2 in, you get 6 out. Let's say you have an 7V power supply. So, if you try to put more than 3.5V in the amp clips, since it can't go higher than 7V power supply gives it. (A buffer is an amp that typically "adds" current output capability but does not change voltage, by definition, unity gain Vin=Vout).

Most dac chips need some circuitry between them and the actual (power) amp, so those are what supply the voltage to the amp section. If there is digital volume control then turning the volume up or down raises or lowers that voltage. (The amount of current that flows is dependent on the impedance of the load being driven, the wilder the impednce curve, the more of a moving target the iem or headphone is)

If you set the device to Line Oout, vs Headhone Out, it may simply set the volume at max. It may reroute the signal to a different jack and bypass the power amp section--depends on how it is designed/built. Given the bit above about cliping, it is generally regarded as best-practice to have more rather than less voltage available- so maybe M8 just has LO=full blast turbo output (perhaps with or without the current capability of the power amp section there or not. Power amp input is much higher impedance than iems, so more voltage-concerned than current (10s or 100s of ohms for iems, 1000s or 10s of thousands of ohms for line level inputs)

So, it comes down to implementation- is the LO signal path different than the HO output, where is the volume control implemented, and overload margin of the external amp input.



All of the above is straight off the top of my head, so please be kind.....

First thing to keep in mind is that phone out and line out have different load expectations, thus different designs. Line out is, as already mentioned, usually 2V peak-to-peak with low current requirement since the expected load is typically around 10K ohms. This is often impedance matched around 10K ohms and you don't expect wild impedance/current/voltage swings like you do with phone out.

M8 manual says 3.5mm socket is the only line out. With previously published diagrams, it's not clear if any of the amps are bypassed for line out. They probably have not done this to save routing space and extra components needed for a dedicated line out circuitry. Instead, they probably have a fixed gain stage setting that would closely imitate line out stage to drive the 10K ohm load. This may still include the switchable gain of the active gains stages, resulting in some volume control.

It just so happens that with home audio, line level signals usually don't have volume adjustments. But in pro audio, there are plenty of line drivers to adjust levels to maximize SNR. So volume control is no indication of "line out" implementation.

Ok, so we still need explanation from Shanling

 

[szore]

Lineout mode can have the gain level adjusted. The max volume out can not be adjusted unless switching back to phone out

OK, but 'adjusted' by what? The DAC or the Amp? (or neither?)

 

[Ojisan]

Happy to report that my update went smoothly OTA in 20min. I think it's more responsive now. Thanks @Shanling !!!

 

[SMOoth Operator]

How do you guys work around the heat issues and how much of a pain is it in reality when on the go like sitting in the back of your jeans?
e.g. specific protection case or some add ons usually used for CPU cooling etc?

I do not know, as I am always using a seperate tube amp and do not carry it around. But I suspect the heat is not going to burn you or anything, if that is what you are worried about.

 

[SMOoth Operator]

Lineout mode can have the gain level adjusted. The max volume out can not be adjusted unless switching back to phone out

Are you referring to the M8 or C9?

 

[Whitigir]

Are you referring to the M8 or C9?

The M8

OK, but 'adjusted' by what? The DAC or the Amp? (or neither?)

The Volume attenuations is likely coming from the DAC as 4499 has the ability to digitally attenuate. The gain level by DAC or Amp ? I don’t know

 

[fzman]

First thing to keep in mind is that phone out and line out have different load expectations, thus different designs. Line out is, as already mentioned, usually 2V peak-to-peak with low current requirement since the expected load is typically around 10K ohms. This is often impedance matched around 10K ohms and you don't expect wild impedance/current/voltage swings like you do with phone out.

M8 manual says 3.5mm socket is the only line out. With previously published diagrams, it's not clear if any of the amps are bypassed for line out. They probably have not done this to save routing space and extra components needed for a dedicated line out circuitry. Instead, they probably have a fixed gain stage setting that would closely imitate line out stage to drive the 10K ohm load. This may still include the switchable gain of the active gains stages, resulting in some volume control.

It just so happens that with home audio, line level signals usually don't have volume adjustments. But in pro audio, there are plenty of line drivers to adjust levels to maximize SNR. So volume control is no indication of "line out" implementation.

Ok, so we still need explanation from Shanling

True. Fixed vs variable output is a different consideration than line out vs headphone output. In the olden days of 2 channel speakewr audio, line level was usually your tuner or cassette deck and was fixed level, 100mv into 10k or higher ohms. Most power amps were 1v input for full rated output power. Post cd-playter world, line level is 2v or more, into the above-mentioned 10k or higher load. My friend John Iverson from Electron Kinetics used to say that a proper preap should be able to drive Klipschorns loudly-ie, a good line stage could produce a decent amount of current.

 

[szore]

The M8


The Volume attenuations is likely coming from the DAC as 4499 has the ability to digitally attenuate. The gain level by DAC or Amp ? I don’t know

I assumed it was DAC and you confirmed, thanks!

 

[Ojisan]

True. Fixed vs variable output is a different consideration than line out vs headphone output. In the olden days of 2 channel speakewr audio, line level was usually your tuner or cassette deck and was fixed level, 100mv into 10k or higher ohms. Most power amps were 1v input for full rated output power. Post cd-playter world, line level is 2v or more, into the above-mentioned 10k or higher load. My friend John Iverson from Electron Kinetics used to say that a proper preap should be able to drive Klipschorns loudly-ie, a good line stage could produce a decent amount of current.

I've heard arguments like that. A good line-level receiver should be sensitive enough and not draw so much current to cause problems. I think what your friend is saying is that there are poor line-out and receiver implementations out there such that a stronger driver will give you a more consistent SQ result. It's not an enforced standard (I don't think...) and with the variety of products we see today, you get all sorts...