yashsingh1/xdaforums huggingface dataset:
[Android Head-Units] ExtremeMOD:
All great points. Now let me respond to some of them.

1. I believe you missed the core point of it all - we build Android head units for audiophiles on budget. This essentially means all the people looking to have great sound at the smallest cost while keeping full functionality of an Android device.

2. Your comment on "500W RMS" and "tiny tiny cables" is irrelevant. Why? Because your sound will only be as good as the source. An Android Head unit will often output very poor sound from pre-outs. We therefore maximise the internal amp and surrounding electronics, advising folks not to use external amps and DSP's. Most of the cars we build for use 18 AWG speaker cables already, same as in the ISO harness. We do however use 16 AWG power cables with proper grounding.

3. I'm sorry but I'm yet to see a DSP processor that offers what Viper4Android does. Especially within feasible cost range.

4. The units we build have their TDA7850 amps running at 18v, not 12v - obviously with bespoke cooling to support the high temps. In most cars, true 200W output will be more than enough.

To summarize, we started this project to build all-in-one Android Head Units that offer everything an audiophile would want without spending thousands of dollars, while keeping all that an Android can offer. We had a good look around and found absolutely nothing in the Android Head unit space that did not require the user to sacrifice at least something, whether it's the sound, the handsfree quality, the UI, Android apps limitations etc.

The real reason for why no manufacturer is building units such as this - is the cost. In mass-production, it would simply be too expensive. Luckily we can work with what we've got and replace components with much better ones, hardware and software alike.

We are also looking into optimizing these units specifically for people that want to use external amps and DSP's. This too requires quite a lot of modding to ensure the pre-outs deliver as high quality output as possible. We'll be looking for audio pro's to test them and give us feedback. You can apply on our site if you're interested and located near London, UK.
[Android Head-Units] Bob_Sanders:
I didn't say it can't be done. I said it's not worth it. There is a difference.

If you want to mod and improve, then start with a good quality base. This head unit is not that.
[Android Head-Units] Bob_Sanders:
Replacing (and using) internal amps is a useless and fruitless endeavor. There are far more options available in external amps, quality and ease of installing when going with external amps. Indeed, if you are on a budget then external amps (and dsp's if need be) are the better way to go because you can upgrade a bit at a time.
[Android Head-Units] theog11:
Does an external amp increase audio quality ?

I think if source is not very good, external amp will just allow more power output, but what about quality ?

How to check if head unit has DSP ? Mine is supposed to have but I want to verify
[Android Head-Units] Bob_Sanders:
An internal amp does not increase audio quality any more or less than an external amp does, so it is a moot and irrelevant question. If you have bad audio quality going into an internal amp, then the outcome is exactly the same. Regardless of what amp you use (internal or external), if the audio quality is bad going into the amp, then it will be bad going out of the amp too.

What an external connection with external amps does is allow more flexibility in the

quality of amps used

, the number of amps used, and the power involved. You can also add external dsp's if you wish.
[Android Head-Units] ExtremeMOD:
It is a charity project so :) Besides, we're focusing on 8227L units primarily. They are cheap and pretty much made for low-cost modding with more than respectable outcomes.
[Android Head-Units] ExtremeMOD:
But then I would go back to the point 1 I made - the bottleneck is the Android Head unit itself. If it doesn't deliver good output at pre-outs, no point in investing in external gear. Today you pretty much forced to choose - either good sound or an Android Head Unit. This is what we're trying to remedy, while keeping the cost in the lower brackets.
[Android Head-Units] Bob_Sanders:
That has nothing to do with the choice of amp (internal or external) you use. The output of the RCA's is the same input for either amp. It is simply delivered internally to the internal amp and through RCA's for the external. If it is not clean audio from the RCA's then it also won't be for the internal amp. The only difference is that the internal amp is cheap and under powered so it can't emphasize the crappy audio as well as a cleaner and more powerful external amp can

Internal amps are crappy.... always have been... and with the cheap price of external amps these days and the large selection of them, it doesn't make sense to upgrade an internal

And with that, I go back to my original point.... modding and improving a cheap head unit is not worth it. You are better off starting with a good quality base model first.

This particular head unit is clearly a sub par unit with bad sound quality, low screen resolution, and insufficient memory, so all of that would have to be fixed first before anybody worries about an output amp to begin with.

The long and short of it is that the OP is going to be spending probably twice as much as the head unit is worth trying to make it into what he wants.
[Android Head-Units] ExtremeMOD:
I have to respectfully disagree. In these units, there is little to no correlation of the sound output between the internal amp and RCA's. This is why there are 2 different directions that modders take - one focused on the internal amp and one focused on the RCA output. Both mods cannot exist in the same unit by the way.

The RCA's have poor electronics behind them as well as poor shielding, resulting in the equally poor audio output. What you will be amplifying is just that - poor sound.

I would agree to a point but many "hi-end" android head units are very difficult if not impossible to mod and it's also a matter of price. As this is a charity project, we're looking to keep the cost low while maximizing the value.

Yes many of these units are honestly not worth touching. As for CPU and memory - the use of these can be considerably optimized with Android programming skills, making them very much usable in day-to-day scenarios. As an example, you can check out the video in my signature and fast forward to where we show the Google Maps loading times on a 1Gb RAM unit.

This is probably true. But then again, he as many others are always faced with a choice of what to prioritize: sound quality or a fully-fledged Android onboard computer.

Finally, I think anyone can improve their head units if they would really want to as there is so much information out there and guides. It would cost time but not much money. This is, I guess, why XDA also exists - for everyone to share knowledge :)
[Android Head-Units] Bob_Sanders:
Yes there are.

The output from the fm chip (just for example) does not have separate outputs for rca and internal. It has only one (L&R) output set which is fed to an input selector which is in turn fed to a preamp. That preamp output is fed to the internal amp with what basically amounts to a tap off to the rca's. Aside from a few decoupling caps and such, along with a filter and output set for the sub, the RCA signal is virtually the same as what is being fed to the internal amps.

"poor shielding" amounts to a crappy set of rca output cables which can be replaced for a couple of bucks if you have shielding issues.

BOTH the internal and external amps get their signal from the same preamp and filter stages. Not only that, but the internal amp also gets its power from the same internal power supply as the rest of the head unit does, so if that power supply is not clean then it affects the internal amp too. Drive any power supply too hard then you start getting dirty sound. An external amp has it's own dedicated power supply, which means you don't have to drive the head unit's power supply very hard at any time. That leads to a cooler running head unit with lots of power to run its other components.

Internal amps are IMO... a crappy way to go.

Well... you mention "charity" not the OP, but the point is that the cost is

NOT

low when you start talking about having to purchase higher res screens (complete with driver), new memory and dsp boards. Your pretty much replacing more than half of the head unit's essential electronics. Heck... if you're going to be replacing that much.... you may as well start from scratch and build one from the ground , up
[Android Head-Units] ExtremeMOD:
Ah, I see now what you're trying to say. Okay so yes, you are correct on a number of points, however, as I mentioned before - we are driving the internal amp with a separate 18v 15A power supply (we only need 10A but there you go). A power supply that is custom-built using a step-up DC-DC converter with temperature-controlled cooling (at 8A+ it starts to get pretty warm).

The internal amp is completely disconnected from the internal 12V power, while still being connected to everything else. We improved the audio output quality by quite a staggering 40%.

Internal amps will never be able to compete with external equivalents, but when you put it in a perspective of an Android - it's a totally different comparison. Like comparing cars with trains. Sure, both are means of transportations but quite different in themselves.

By the way, the "RCA" mod actually removes the internal amp altogether from the circuit.
[Android Head-Units] Allan_Hun:
I will agree that 200 true Watts is probably enough for most people -If they also have a powered sub. Check the recommend amps for popular subs like alpine and JL. Deep bass require some muscle. And 200W feeding a sub, two (mid)woofers + two tweeters ain't much. Heck my woofers sounds notably better @2x150W compared with 2x75W.

Most modern car subs are mostly optimized for low frequency production in small boxes. This is achieved with a stiff suspension and big motors. -Not a very efficient in therms of db/W.

I also think your definition of true watts is quite different than mine...

In my book true watts means continuous 20-20khz 1% THD.

I just checked the 7850 specs, and it is actually quite impressive for it's size. With 18V input it delivers almost 90W. BUT at 30W the distortions increases and at 40W it skyrockets!

Regardless of budget I don't think many "audiophiles" would appreciate >10% distortion...

For a budget android car hifi experience I believe HU, USB DAC + external amp would be the way to go.

IMHO Viper is by far the best sound mod app but it can't replace a DAC. Does Viper have auto tune? Automatic input selection ? Autoand programable turn on/off?Hardware volume control? Ground isolation? Logic 7 centerchannel? Fully costume covers?

Viper and a standalone DSP is two rather different things.

My DSP also have high level inputs so maybe I should try if the 7850 output vs the preamp RCAs. You do seem to know the HU's internals quite well. Can you explain why internal amp sounds better compared to the preamp output?

Isn't the 7850 recurving same signal as the preamp plugs?
[Android Head-Units] ExtremeMOD:
You're absolutely correct. While this unit will drive some of the passive subs (thanks to all the additional cooling), we do highly recommend using an active subwoofer for the best sound experience. Even an underseat sub like Kenwood KSC-SW11will make enough of an impact as many people don't want to use the extra space for a sub.

You're absolutely correct on the distortion part. I haven't experienced it driving 4 Ohm speakers in various cars but all of them had active subs.

On USB DACs - totally correct. However these head units have fairly unreliable internal electronics to effectively drive them (surprise surprise). Hardware modding is required and we haven't been able to get any good results. The internal hardware is too weak to drive DAC's. Drivers are unstable as well. External DAC's was one of the first things we tried.

As for internal vs RCA output - what you're mentioning is correct when it comes to most devices out there. This is how it should be. On these head units however, it's a bit of a mess. In fact, we tried to "rewire" it internally but it resulted in an even worse output from RCA's.

The internal electronics are many times completely removed and we install an internal preamp microchip with separate power supply (step down DC-DC converter) and redo the capacitance as well as internal shielding.

We haven't had any requests yet for RCA-only projects so it's still very much an area of testing and development for us.
[Android Head-Units] Allan_Hun:
My DSP is connected through usb and it works fine with USB audio player pro. For anything else I use the optical output. Do you think the speaker output would improve the soundquality compared to the optical output?

Also tried a I had a 8227L I also tried a E1DA 9038D DAC and it worked except I could not control the volume, so it would play at full volume. So I guess a DAC with a volume dial could work.

Your statement about only needing 10A at 18V don't match your claim about 200 true watts. The 7850 is class AB so efficiency is probably about 75% . 10x18x0.75=135W...
[Android Head-Units] ExtremeMOD:
We're trying to keep as much as possible "inside" the head unit itself so we only looked at internal DAC's such as PCM5102a that we too need to mod to properly integrate with the circuitry inside. The goal is to make it part of the head unit, with all the functionality in place, such as internal volume control. This is where the drivers come into play.

Optical output is an interesting idea. Gotta look into that.

As for the wattage, I should have said "up to 200W". You can increase the efficiency and the output of TDA7850 with surrounding electronics.

We use electrical test equipment to calculate wattage. We've been able to come very close to 200W in some of the setups. But yes, those were pretty much perfect conditions and we pushed the voltage to 20v. With an active sub, even the 2 Ohm speaker set up will not exceed 150W but the sound level is very high in a car, even a large SUV.

As for DSP - I noticed, I forgot to comment on your previous reply. Truth to be told, Viper would've been awesome if it also came in a hardware version. I wouldn't call DSP's from manufacturers like Audissey - true DSP's. Why? Because coming from an audio engineering background, a DSP should not just balance the sound but also offer options to customize to the listener's liking. This is done by the means of EQ, dynamics controls and frequency-specific tweaks (such as stereo imaging and expansion). Viper4Android does offer delay controls as well to get you that smooth audio experience in all of your car.

Many audiophiles on budget will try to make the most of factory speaker setup or perhaps invest in smaller upgrades. So for them, Viper is by far the only alternative if you look at the options for sound control
[Android Head-Units] Bob_Sanders:
You are not making a lot of sense. Running the TDA7850 at 18 or 20volts with a 2ohm load pins it at its MAXIMUM output, both in terms of heat and power. Not only do you MASSIVELY increase distortion levels, but you also shorten its life with all the heat. Any "audiophile" knows you don't run an amp at its maximum level if you want clean sound. For clean sound if you want to run at 200 watts then you should be using a 500watt amp (just as example). This gives the amp comfortable head room in terms of heat and power

Can you do what you are claiming? Yes you can... but it is no longer, efficient, effective, or low cost. The 7850 is a good and reliable chip, but it was not meant for that kind of abuse.... and neither is the head unit's power supply. Most of them are fused at 10 amps, and with that, the average alternator puts out 14.7 volts, so at the end of the day the TRUE output (assuming 100% efficiency... which nothing is) you will only ever get

14.7 x 9amps = 132 watts of reasonably clean audio (I say 9 amps because the rest of the unit needs power too). Anything beyond that for the 7850 in the REAL world..... is a simple pipe dream
[Android Head-Units] ExtremeMOD:
We call it "stress-test" conditions. Also to be fair it's 18v x 9amps leading to 162W as we run it at 18V with the external power supply that steps up the voltage and while it pulls 14A to do that, the car battery can manage that just fine. We limit the output of the power supply to 18v / 9.5A just to be on the safe side.

To be honest we're talking about max conditions - which is what the market focuses on when pitching their products.

The "real world" scenario would heavily depend on whether the HU has to drive a passive sub or whether an active one is present instead. You can come up to 9A with a passive sub at volume levels of 90%+ but with an active sub you'll struggle to come up to even 6A at max volume level.
[Android Head-Units] Bob_Sanders:
Well... I'm now completely confused as to what your end goal is here. You talk about clean sound, then you start talking about driving a chip at pretty much its limits. You talk about charity, then you start talking about replacing power supplies and a whole pile of other stuff. It matters not though.... I'm not what you would describe as an "audiophile" but I do appreciate clean sound and I wouldn't in a million years take the approach you're taking to get there.

I use RCA's out to an Axxess AXDSP-X DSP then to 3 amps... 400 watts to the front, 750 watts to the rear and 1200 watts to a set of dual 10" subs and it's perfectly clean sound. No hiss, no whining, no groundloop noise.... just clean sound.

IMO... if you want REASONABLY clean sound at a cheap price then what you SHOULD be doing cleaning up the RCA outs and supplying a 4 channel external amp. At the prices they are these days it doesn't make sense to go any other way. Heck... if you are stuck for money, you can pick up a Blaupunkt 4 channel amp (79W x 4 at 2ohms) for $59 plus shipping.

Amazon.com: Blaupunkt 1600W 4-Channel, Full-Range Amplifier AMP1604 : Electronics

Buy Blaupunkt 1600W 4-Channel, Full-Range Amplifier AMP1604: Multichannel Amplifiers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Anyway... WAY off topic here. OP asked if he can rebuild his unit into something that he actually wants, and again I stress, you can rebuild anything if need be, but it's not worth it for that unit. OP is better off selling what he has and buying something which won't require spending twice what its worth to rebuild it.
[Android Head-Units] ExtremeMOD:
Any piece of equipment needs to undergo a proper stress test as part of the QA process.

You also normally advertise maximum performance indicators

This is a charity project - something we do on the side, without making any money and the little money we do make, we give to charities.

Bear in mind that it takes about 340 man-hours to build just one unit. We'd charge thousands of dollars for it if we made this for profit, using much better base hardware (4Gb RAM and better CPU) as we're the only ones that deliver units such as this, so pretty much an open market. Android Auto makers charge up to 5 figures for their devices and they aren't even real Androids, as a comparison.

The goal is to deliver a "one-in-all" product without the need for external gear other than an active sub (not required, but very much preferred)

Don't forget the huge aspect of the Android itself, in addition to car sound

The RCA direction is currently under development as we haven't had much demand for it, yet.

Clean sound is great and I'm happy it works well for you. If it is possible for you to compare your sound with your stock amp and it sounds at least the same, then you're all set.

In our experience, even if you manage to get a clean sound out of RCA's, it is the depth and spaciousness, that often feels reduced. The bigger the external rig, the greater is that difference felt.

Bottomline - you can get RCA's to produce something you would accept, but it would require additional investment in external hardware and some skills in balancing the sound.

I'm sorry to say this, but this amp is not a real BlauPunkt as that German company went out of business a number of years ago. The brand name was acquired by an Indian company that uses the cheapest Chinese components in its hardware. The amp you linked to has poor man's TDA7388-like amp microchips running at miserly 2,2k and 3,3k mf caps (compared to 10k mf in that feeds our TDA7850). It's so bad, it'll make your ears bleed. I wouldn't pay $10 for such an amp. It'll run up 200W before starting distorting at 4 ch 4 Ohm. Not even going to go into the lack of dynamic range...

Then you need to add DSP module to it - and you still will be struggling with getting the sound compared with the output of our units (for standard car speakers). Even if you could get away with a $100 external amp you'd still need to spend around $1,000 on DSP to get the same results as you get from our units, plus the external dynamics processor unit that goes for thousands of dollars. It all quickly adds up :)

We've done at least a year of research into everything you and I are talking about before starting this project. We believe we have found a good balance between value and quality while offering something fairly unique, at least for now.
[Android Head-Units] marchnz:
This was/is so confusing to follow, it seems like the statements might be based on a large number of false assumptions, so unpicking these...

The discussion switches from operating a integrated power amp IC at/beyond *absolute* max ratings - something a designer would never do, the amp *will* fail - to discussing 'Android head units for charity.'

Did I read correctly, modifying a head unit [Chinese non-standard/non-google-sanctioned/certified kanged OS/greybox knockoff] as 'charity'. Also, mixing charity and market - that's confusing. So selling without any margin or financial reward? Which charities do the proceeds go and how much of the profit goes to charity?

No, one does not need to spend $1000 on a DSP, amps with DSP can be had for half of that, well exceeding the power output at much lower distortion than pushing a TDA7850 over the cliff.

On that, modifying a power amp power supply to push it closer to distortion is not anywhere near the ball-park. It's plainly flawed, bordering on nonsense - sorry, but it is exactly that. "Clear sound" - definately not!

Some data, based on manufacturer data sheet.

At 18v, 4 Ohm load (typical aftermarket and OEM fitted fullrange speaker) 10% distortion - power output is up 18w, resulting in slight/negligible SPL increase (How loud it is perceived.)

@18v, to remain below 1% THD/distortion, output power must not exceed 30w RMS. Into a 2 Ohm load, it's 50w rms. Distortion is likely around 0.5-0.7%.

There is almost no increase in dynamic headroom.

The capacitor incorrectly assumed to 'make your ears bleed' - unless there is a real supply issue, increasing C7/decoupling cap by a factor of 5 is unlikely to yield any improvement. The manufacturer recommended value is 2200uf, at which the tda7850 achieves its maximum rated power output.

Sound level/SPL doubling requires an increase of 4x power output.
[Android Head-Units] Bob_Sanders:
You are the one who mentioned "charity". Personally speaking, I wouldn't buy an amp that cheap if my life depended upon it. It was a mere example of how cheap they are now if you are stuck for dollars.

As for cheap Chinese parts... what the heck to you think is inside a Chinese made android head unit?!?!