# Current Head Units w/ Digital Output (Coaxial Preferred)



## illgorilla (Feb 28, 2015)

Hello DIYMA members -

I just bought a Helix DSP Pro (from a DIYMA member) and I am interested in optimizing the SQ possibilities of my setup. To do this I would like to utilize one of the DSP Pro's digital inputs, preferably the coaxial input over the optical due to the improved specifications (12-96kHz optical; 12-192kHz coaxial, as per the manual). Does anyone know of a currently produced head unit that has digital outputs?

I am collecting equipment now and nothing is installed, but I will have two Brax MX4 amplifiers with six of the eight channels actively running a Focal Utopia 7 kit in front and the other two channels running a Utopia 7 kit through the Crossblock for the rears. An MX2 will be running two JL Audio 12TW3 subwoofers under the rear seats. This will be in a 2015 Ram Crew Cab Longhorn (the truck currently has the 8.4 Uconnect system).

So far my research has produced the Alpine x009 series, of which the universal version is the one that would work in my Ram. It has an optical output. I feel that I would be happy with this unit, but I would appreciate having more options to choose from before making a decision.

Thanks.


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## kustomkaraudio (Jun 20, 2009)

The current Alpine 7", 8", and 9" AV units are the only thing that I know of currently having digital (toslink) out.


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## t3sn4f2 (Jan 3, 2007)

And you'll need to move master volume control down to the processor if you decide to go digital from any head unit out there.


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## teldzc1 (Oct 9, 2009)

I don't know of any Car Audio components which used a coaxial digital output. That being said, in this case I don't see value in it. The DSP section of the DSP Pro operates in 24bit/96khz max. Anything above that will be downsampled in order for the DSP to process the signal.


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## t3sn4f2 (Jan 3, 2007)

teldzc1 said:


> I don't know of any Car Audio components which used a coaxial digital output. That being said, in this case I don't see value in it. The DSP section of the DSP Pro operates in 24bit/96khz max. Anything above that will be downsampled in order for the DSP to process the signal.


There's probably a few, and at least one. Though likely all old school stuff. 

MINT Denon DCT-Z1 for sale!!! - diyAudio

I think also Pioneer DVD Double Din of a few years ago came with a Coax digital output via a 3.5mm socket in the rear.


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## illgorilla (Feb 28, 2015)

Thanks for the information. I will be using the Helix URC-2A controller until the "Director Controller" is released (six weeks out still according to Brax this morning).

teldzc1: where can I find data like this? I only skimmed the manual of the DSP Pro, but I didn't see anything about downsampling. It's not that I don't believe you, I just want as much information as I can get my hands on.

I will look into the Denon. I am looking for current units due to the extra features that they might offer, but if I can't find what I am looking for I will get into older SQ decks.


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## teldzc1 (Oct 9, 2009)

I asked them directly via Facebook Messenger. They responded with that information. I posted that in the Helix DSP Pro thread. 

Sent from my SAMSUNG-SM-N900A using Tapatalk


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## t3sn4f2 (Jan 3, 2007)

teldzc1 is correct. The spec listed for the digital inputs are resolution limits for the particular input. The 96kHz is the sample rate the processor runs at. DSP works by sampling the incoming signal, analog or digital, then manipulating it however. It does that at a given sample rate. Everything out there does it at 24bit/48kHz, The DSP pro is the first to move this up to 96kHz. You can see it in the specs where normally the frequency response limit of a processors is ~20kHz (ie the limit for 24/48). The DSP pro should show something into the 40kHz range. That's around where that sample rates limit is. It's not quite the digital limit because of the inherent degradation from the analog outputs.

Edit: 

http://www.audiotec-fischer.de/lng/en/helix-dsp-pro.html

"The signal processor for all those, who are only satisfied with the best! The new HELIX DSP PRO raises the bar to a new level, not only in terms of sound quality. Due to the implementation of the latest generation of ultra-fast Audio DSPs with enormous 64 Bit resolution, this device provides more calculating power than every other signal processor available on the market today. In addition, it is the first of its kind which performs the full signal path with a sampling rate of 96 kHz, resulting in an extended audio bandwidth up to more than 40 kHz."


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## Picaro (Feb 18, 2015)

There have been relatively few head units with any sort of digital output, let alone coaxial ones. Careful about Denon as I thought those were only digital input, not output.

You can still get a couple of Nakamichi models (if you really look around) that had digital coaxial output though, the MB-X and MB-100. They both used an outboard processor for the D/A conversion, but it could be bypassed for that.


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## Niick (Jun 3, 2015)

HELLLLPPPPP!!!

We've installed an alpine x009 "restyle" H.U. in my bosses Jeep, we ran the optical out to a Rockford 3sixty.3, but no sound. 

I tested the optical out of the alpine and discovered that it runs at 44.1kHz, and the 3sixty.3 wants a 48kHz input! 

What to do? Is there a way to select a higher sample rate on the alpine skiing digital out? Probably not!! Arggggg!


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## crackinhedz (May 5, 2013)

Only accepts 48kHz? Thats strange.


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## Babs (Jul 6, 2007)

Currently the big hole in the market.. Which is bad because folks have to improvise, but good because folks are improvising.  Tablet installs on the rise, and other signal converters being tried with much success to feed DSP's. Reason I'm in defiance and revolting against the head unit makers and doing an iPad build in the truck, whenever I ever get around to it, with some wired method or maybe wireless.. Depends on what's out by then for digital signal options. But the doggone tablet (iPad in my case) will do anything and everything a crazy head unit will do, except play a disk or have a sure-enough local radio tuner.

I should add, if you can do a 2-din, there is the option possibly of an E3io (PC-based) head unit, with whatever output you can have them hang off the back of it. I imagine they've had quite a few folks requesting a hi-def audio "SQ" based build. Prepare to shell some coin for one, but having seen them in action in Req's car, they're bad to the bone.


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## InstantCrush (Sep 2, 2015)

crackinhedz said:


> Only accepts 48kHz? Thats strange.


Yeah, it would be quite strange if that were true. CDs are 44100Hz... CDs aren't the only thing that people listen to but one might think that rate would be supported...


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## subwoofery (Nov 9, 2008)

Babs said:


> Currently the big hole in the market.. Which is bad because folks have to improvise, but good because folks are improvising.  Tablet installs on the rise, and other signal converters being tried with much success to feed DSP's. Reason I'm in defiance and revolting against the head unit makers and doing an iPad build in the truck, whenever I ever get around to it, with some wired method or maybe wireless.. Depends on what's out by then for digital signal options. But the doggone tablet (iPad in my case) will do anything and everything a crazy head unit will do, except play a disk or have a sure-enough local radio tuner.
> 
> I should add, if you can do a 2-din, there is the option possibly of an E3io (PC-based) head unit, with whatever output you can have them hang off the back of it. I imagine they've had quite a few folks requesting a hi-def audio "SQ" based build. Prepare to shell some coin for one, but having seen them in action in Req's car, they're bad to the bone.


...or wait for Sony Hi-Res HU: 
Sony Hi-Res Audio For Car Due This Year | ceoutlook.com 

Kelvin


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## Niick (Jun 3, 2015)

InstantCrush said:


> Yeah, it would be quite strange if that were true. CDs are 44100Hz... CDs aren't the only thing that people listen to but one might think that rate would be supported...


Oh, it's true all right. I have the ability, (it's quite easy really) to measure the sample rate and bit depth coming out of the Alpine H.U.

Plus, I have the ability to generate whatever bit depth/sample rate digital signal I want from 8k to 96k and from 8bit (I think, it's either 8 or 16) to 32bit. AES/EBU or S/PDIF. 

Even when I play a DVD disc in the alpine, the digital out is 44.1k, which I thought DVD was 48k. maybe I didn't try enough DVDs. I seem to remember reading that they can be different sample rates, depends on the recording/disc?

Also, I can generate 44.1k audio (S/PDIF) and the RF 360.3 makes no sound. 
Which, after looking into it, isn't that strange apparently, the bit one is the same way, according to the documentation. (Or so told me a co-worker yesterday, I was troubleshooting this for him)

What seems strange to me, is the Alpine running at 44.1 k regardless of source. I haven't tried any sources other than USB, CD, DVD, Tuner. So maybe HDMI would work. Who knows.

Even when I play 48k out of my iPad (I'm not talking iTunes here) into the alpine via USB, the digital out of the alpine is STILL 44.1k


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## InstantCrush (Sep 2, 2015)

Niick said:


> Even when I play a DVD disc in the alpine, the digital out is 44.1k, which I thought DVD was 48k.


DVD does not have one set sample rate. I know for a fact that it can be 48kHz, 96kHz or 192kHz, and am fairly sure that it can also be 44100Hz, 88200Hz (yes, it exists). Maybe even 32kHz, 16kHz, 8kHz, but hopefully nobody ever actually uses those ones.


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## t3sn4f2 (Jan 3, 2007)

It looks like too save money they did not add a sample rate converter to the 360. So it can only accept its native sample rate of 48kHz. Using an external converter like and Audison SFC or a Mini DSP Minidigi should fix the problem.

miniDIGI | miniDSP


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## Niick (Jun 3, 2015)

InstantCrush said:


> DVD does not have one set sample rate. I know for a fact that it can be 48kHz, 96kHz or 192kHz, and am fairly sure that it can also be 44100Hz, 88200Hz (yes, it exists). Maybe even 32kHz, 16kHz, 8kHz, but hopefully nobody ever actually uses those ones.


Right, that's what I thought, so maybe the choice of DVD disc is a factor, BUT, why no 48k output when running 48k input from iPad via USB?


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## InstantCrush (Sep 2, 2015)

Niick said:


> Right, that's what I thought, so maybe the choice of DVD disc is a factor, BUT, why no 48k output when running 48k input from iPad via USB?


Your HU may resample things to 44100 because maybe Alpine's DSP expects 44100... But I don't understand why they'd resample on the HU side rather than on the DSP side.


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## Niick (Jun 3, 2015)

t3sn4f2 said:


> It looks like too save money they did not add a sample rate converter to the 360. So it can only accept its native sample rate of 48kHz. Using an external converter like and Audison SFC or a Mini DSP Minidigi should fix the problem.
> 
> miniDIGI | miniDSP


AWESOME sir, thank you very much! This is exactly the kind of info I was looking for.

One more question, let's say I play a DVD that is KNOWN to be 48kHz, but the alpine outputs digital audio that's STILL 44.1k? What do we make of that? Or is that not possible?

I'm at work now, so I'll try this out as soon as the boss opens the shop.


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## Niick (Jun 3, 2015)

I checked out the audison SFC, it looks like it can DOWN sample the signal from a HIGHER sample rate to a lower 48k, but not the other way around. Is this right? 

The miniDSP thing looks promising, MAYBE? unless it's the same way?


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## InstantCrush (Sep 2, 2015)

Niick said:


> The miniDSP thing looks promising, MAYBE? unless it's the same way?


In the datasheet it says it can both upsample and downsample.

It probably supports any rate that its DAC does (which can probably handle anything you would encounter) and converts it to 48kHz which is what MiniDSP (and almost all DSPs) run(s) at.

I've no experience with miniDIGI, but for what it's worth, I really like MiniDSP.

I would like it more if it ran at 96kHz, but I guess I can't have everything.


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## Niick (Jun 3, 2015)

InstantCrush said:


> Your HU may resample things to 44100 because maybe Alpine's DSP expects 44100... But I don't understand why they'd resample on the HU side rather than on the DSP side.


Now THATS precisely what I was thinking, see, I can live with CDs not being an input option in this scenario, but everything else, things that SHOULD be 48k, STILL coming out as 44.1, well that to me seems more like the Alpine is the funny one here, not the RF. 

everyone else seems to think the processor is the one behaving strangely. Hmmmm.....

I'm gone try to send 44.1k into the bit one and see if it will play, then I'll know if the RF is the oddball or not.


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## Niick (Jun 3, 2015)

InstantCrush said:


> In the datasheet it says it can both upsample and downsample.
> 
> It probably supports any rate that its DAC does (which can probably handle anything you would encounter) and converts it to 48kHz which is what MiniDSP (and almost all DSPs) run(s) at.
> 
> ...


AWESOME sir! Thank you very much for the info!


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## InstantCrush (Sep 2, 2015)

Niick said:


> Now THATS precisely what I was thinking, see, I can live with CDs not being an input option in this scenario, but everything else, things that SHOULD be 48k, STILL coming out as 44.1, well that to me seems more like the Alpine is the funny one here, not the RF.
> 
> everyone else seems to think the processor is the one behaving strangely. Hmmmm.....
> 
> I'm gone try to send 44.1k into the bit one and see if it will play, then I'll know if the RF is the oddball or not.


Personally I think it's strange of both. I don't think a HU should ever need to resample anything for any reason, and I think that any DSP should accept any reasonably common sample rate.

Of these two "issues," I'd call the DSP the worse one.


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## t3sn4f2 (Jan 3, 2007)

Niick said:


> AWESOME sir, thank you very much! This is exactly the kind of info I was looking for.
> 
> One more question, let's say I play a DVD that is KNOWN to be 48kHz, but the alpine outputs digital audio that's STILL 44.1k? What do we make of that? Or is that not possible?
> 
> I'm at work now, so I'll try this out as soon as the boss opens the shop.


I would think they re-sample to 44.1Khz to make it compatible with more products out there. It's counter intuitive being that pretty much every DSP out there has always run at 48kHz, but they aren't looking at it from the DSP or DAC side of thing. They are just concerned with making the output be like most other device outputs out there. And since most are CD transport outputs, then they went with 44.1.

Years ago when the only source outputted digitally was the transport, it would have probably switched between 44.1 and 48kHz. Depending on the media. But now that all sources are starting to be sent out digitally they just went back to fixed 44.1Khz.


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## Niick (Jun 3, 2015)

InstantCrush said:


> In the datasheet it says it can both upsample and downsample.
> 
> It probably supports any rate that its DAC does (which can probably handle anything you would encounter) and converts it to 48kHz which is what MiniDSP (and almost all DSPs) run(s) at.
> 
> ...


Ok, great, so......how do I buy one, I need this thing NOW!! I looked on their website, but?
Edit:never mind, I'm retarded!! Found it!


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## InstantCrush (Sep 2, 2015)

miniDIGI | miniDSP

add to cart link right on there


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## t3sn4f2 (Jan 3, 2007)

Niick said:


> Ok, great, so......how do I buy one, I need this thing NOW!! I looked on their website, but?
> Edit:never mind, I'm retarded!! Found it!


Don't forget the power supply for it.

miniDC Isolator | miniDSP


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## InstantCrush (Sep 2, 2015)

t3sn4f2 said:


> Don't forget the power supply for it.
> 
> miniDC Isolator | miniDSP


That is rarely necessary, though at least the price is very reasonable.


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## t3sn4f2 (Jan 3, 2007)

InstantCrush said:


> That is rarely necessary, though at least the price is very reasonable.


Yup, I'm thinking it's cheap so why not. Beside you never know if a noise electrical input could be messing with the digital signal. Something that might be so subtle that it can't be noticed without some extensive testing. Yet is there degrading signal quality.


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## Niick (Jun 3, 2015)

t3sn4f2 said:


> Don't forget the power supply for it.
> 
> miniDC Isolator | miniDSP


Ok, but, doesn't the sample rate converter need 3.3VDC?


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## InstantCrush (Sep 2, 2015)

Niick said:


> Ok, but, doesn't the sample rate converter need 3.3VDC?


Most likely but the MiniDIGI will handle that part of the power supply. Actually, it has its own power supply built in. The other product that was linked is not actually a power supply, but rather an isolator and filter to help ensure that the power is clean. I haven't looked into it very much but it's probably a charge pump design which is pretty effective for low power devices. It basically charges up those capacitors which then power the MiniDSP, but there is isolation between charging them and providing the power. The isolation can help prevent noise and ground loop problems from contaminating your system.

That's why I said it wasn't usually necessary.


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## t3sn4f2 (Jan 3, 2007)

InstantCrush said:


> Most likely but the MiniDIGI will handle that part of the power supply. Actually, it has its own power supply built in. The other product that was linked is not actually a power supply, but rather an isolator and filter to help ensure that the power is clean. I haven't looked into it very much but it's probably a charge pump design which is pretty effective for low power devices. It basically charges up those capacitors which then power the MiniDSP, but there is isolation between charging them and providing the power. The isolation can help prevent noise and ground loop problems from contaminating your system.
> 
> That's why I said it wasn't usually necessary.


Yes, an isolator, my bad.


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## Niick (Jun 3, 2015)

I'm copy/pasting this from the original post since a lot of people have helped me with this on this thread:

UPDATE:

My apologies to everyone who may have read this original post! 

The Rockford Fosgate 3sixty.3 DOES seem to be able to play 44.1k 16 bit optical input signal no problem. There is something wrong with the alpine deck or cable we're using. 

Originally, I analyzed the audio (the signal that wouldn't work) coming into the Rockford 3sixty.3 FROM the Alpine HU, and found that when it was plugged into my TASCAM US-1800 digital in, the resulting audio format was 44.1kHz, 16bit S/PDIF, and I could analyze the signal, and it worked perfectly. 

However, when I fed that SAME EXACT optical input into the the 3sixty.3.....no sound. 

So I grabbed my iPad with CCK and a cheap little Behringer UCA-202 connected via USB, ran the optical out from there into the RF 3sixty.3, opened AudioTools Generator, selected sine, set to arbitrary frequency, and turned on the output, and I got sound immediately. The iPad with CCK and $20.00 cheap ass-Behringer interface with optical out worked like a champ, but this big expensive alpine deck didn't! "What the f**k?!" I thought.

I then thought "there must be something different about the two signals"

Since I knew that I was getting 44.1k digital out of the alpine, I decided to see what my iPad was giving thru the behringer interface, so I fed it into the same analyzer input that I had previously just fed the alpine signal, and it showed 48k. 

Ok, I thought, this must be the reason. So I ordered an miniDIGI sample rate converter from miniDSP and it arrived yesterday. Still no luck. So I got the bright idea to just generate my own 44.1k signal using the iPad and AudioTools (in settings, general/global settings, select "limit sample rate to 44.1k"). 

So I fed the 44.1k signal into the RF3sixty.3 and immediately got sound! So I checked the signal JUST TO BE SURE that it was 44.1k, and it sure was, so then I generated a DIFFERENT 44.1k signal using my TASCAM US-1800 digital output and also got sound. 

So, YES, THE ROCKFORD 3sixty.3 DOES ACCEPT A 44.1k signal. 

Now I just have to figure out what is it about the alpine deck's output that isn't working with the Rockford, but that allows me to see the signal with my analyzer. The only thing I could so far find different was that the Alpine optical signal, when you look at the light at the end of the cable, isn't as bright as the test signals, it's dimmer, like, half as bright. 

And because the alpine uses a proprietary cable for optical, WHICH THEY DONT MAKE ANYMORE!! (We got ours from our alpine rep who had a small supply of them at his warehouse), I can't just try a different optical cable. So stupid, there is NOTHING ok about the way this alpine deck does its optical out. (Alpine X009)

BTW, the miniDIGI is awesome. Totally works like a champ. Super easy to use, at least for what I was wanting it for.


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## Babs (Jul 6, 2007)

That's more than a few times I've read that little Behringer unit with the camera kit works well. 


Sent from iPhone using Tapatalk


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## Niick (Jun 3, 2015)

Babs said:


> That's more than a few times I've read that little Behringer unit with the camera kit works well.
> 
> 
> Sent from iPhone using Tapatalk


Oh it's awesome, stone cold reliable. AWESOME troubleshooting/signal injection tool.


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## tru tech99 (Jan 3, 2011)

subwoofery said:


> ...or wait for Sony Hi-Res HU:
> Sony Hi-Res Audio For Car Due This Year | ceoutlook.com
> 
> Kelvin


it call the sony RSX-GS9 (google it ) ..... was in the market looking for a headunit with optical out put that will hook to iPad also .... thanks Kelvin for post it...


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## tru tech99 (Jan 3, 2011)

but hoolllllllllyyyyy **** it cost 1500$$$$$ 

Sony RSX-GS9 (rsxgs9) Single DIN In-Dash Hi-Resolution Audio


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## Niick (Jun 3, 2015)

UPDATE: turned out to be the optical cable itself was crushed by the seat bracket when it got installed. My Tsacam US-1800 was able to make sense of the signal while the 360.3 couldn't.

But just as soon as we loosened the seat bolt that the optical cable ran behind, that was it. No more signal on the analyzer screen. Once we could remove the seat completely, we saw the crushed optical cable, and holding it and wiggling it at the point of the crush would cause the signal to drop in and out.

So, anyways, that was the deal.


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## fcarpio (Apr 29, 2008)

Sooo...

Any other head units with optical out? So far it looks like Alpine and e3io only. For Alpine it seems you need a proprietary cable that is not made anymore, is that correct? I want to go digital ONLY to my PXA-H800. The head unit is that last piece of the puzzle for my install.


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## BlackHHR (May 12, 2013)

I have a cable for the Alpine optical output. Not using it anymore.

Sonic electronics has one in stock.
https://www.google.com/shopping/pro...J-GMKHTjUA3cQ2SsICw&ei=SsaLVt_iJ4nwjwO4qI-4Bw


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