Why are there no Mods to Satellite Receivers

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In the UK and parts of Europe, DAB digital compressed radio is very poor compared to FM. However, radio piped thru' satellite is much better.

Aky has such tight control that there is very little information about the digital audio streams in their boxes.

I have successfully tapped the Toslink output of the Sony VTX670 box to enable very good electrical spdif via 75R and a jitter buster.
However, this box is insensitive for fringe areas where I am.

But I just cannot find any technical info/service manual on the more sensitive Pace 26001 or DSN430 boxes.

Why? and why doesn't anyone modify satellite boxes-the standard analog output of the Pace boxes is DIRE, even though the dacs are 18 bit

:att'n:
 
Hi Fmak,

If you pop the lid and look at the chips inside, you should be able to get some info from silicon datasheets to work out I2S lines (although not all STBs use external DACs, most STB decoder chips do output I2S).
The best bet is probably to find the DAC, and then tap off I2S from there, it might be trickier at the stb chip - as it might be BGA.

That may well be the only mod I'd consider doing to a STB.

STBs are full of high frequency signals, typically cheap and with poor SMPS. I personally wouldn't spend too long modding one.
Also, don't think about reclocking them, as the clock signal is typically a drifting VCXO. This deliberate, and is used to ensure audio and video are in sync with each other. Reclocking that would lead to all kinds of problems. If you need to reclock, I guess you'd be able to use a free running clock to reclock the I2S (but I know little about reclocking like that, so check other forums for that).
Perhaps, the drifting clock is the main reason why people don't bother modding STBs?

Cheers,
Phil
 
philpoole said:
Hi Fmak,


STBs are full of high frequency signals, typically cheap and with poor SMPS. I personally wouldn't spend too long modding one.
Also, don't think about reclocking them, as the clock signal is typically a drifting VCXO. This deliberate, and is used to ensure audio and video are in sync with each other. Reclocking that would lead to all kinds of problems. If you need to reclock, I guess you'd be able to use a free running clock to reclock the I2S (but I know little about reclocking like that, so check other forums for that).
Perhaps, the drifting clock is the main reason why people don't bother modding STBs?

Cheers,
Phil


Hello Phil

Thanks for that. I

I have trouble relocking a Sony VTX 750 when I tapped the Tx pin of the Cirrus Chip. Yes only a coarse PLL works.

However, taking the digital out from the Toslink line of the VTX670, I have complete success and very good eye pattern. With twin PLL relock the sound is truly superior on and here I don't care about lip sync.

I shall try the I2S from the Pace units and see what happens.

Do you know where I can buy or download the schematic for a Pace 2600C1 or DSTN430?

Yes, dgiboxes are really nasty hf polluters. In a high end system using Hard Drive as transport, dCS upsampler and dac, I haer a difference when the Sky box and Plasma are switched on; subtle but affects tonality and spacial details!

Fred
 
Hi Fred,

I'm afraid I don't know where to find the schematics. However, if you take the lid off, and note down the chip numbers, you can probably find datasheets for at least some of them online - especially the DAC. From that, you should be able to work out which pins are I2S, and tap off of them and feed something else:)
Try www.datasheetarchive.com for the datasheets, you should hopefully find something that helps.
Sorry I can't be more precise.

Cheers,
Phil
 
Have you tried checking out some satellite-hacker forums? Someone reverse-engineered a bunch of North American satellite receivers and produced an impressive set of schematics. Maybe someone has done that for the European ones.

The Dish network in the USA used something like 128k to 160k bps for their radio channels in MP2 format. I don't suppose other broadcasters are any more generous with bits, so that has to limit the potential quality.
 
dangus said:
Have you tried checking out some satellite-hacker forums? Someone reverse-engineered a bunch of North American satellite receivers and produced an impressive set of schematics. Maybe someone has done that for the European ones.

The Dish network in the USA used something like 128k to 160k bps for their radio channels in MP2 format. I don't suppose other broadcasters are any more generous with bits, so that has to limit the potential quality.


Can you give me some urls?

In UK Satellite radio is 48k 16bit and better than digital audio broadcast which is terrible.
 
Hi,

fmak, I think dangus was referring to the compressed data rate, where I suspect you're quoting the sample rate.
DVB broadcasts for audio are very similar in europe as they are in the US. However, it is highly dependent on the broadcaster (shopping channels typically use far less bandwidth/lower bitrate than pay-per-view sport or movies).

Dangus, not that its important, but nearly all audio broadcast is MPEG1, only the video is MPEG2 (or MPEG4 these days). I think the only exception is AC3.
In fact MP3 audio is actually MPEG1, level 3.

Cheers,
Phil
 
This was MPEG 1 layer 2 audio, hence MP2. The radio channels I recorded were extracted directly from the transport stream and saved as MP2. MP2 files would play back with Winamp, and the occasional DVD player. Sound quality seemed inferior to MP3 at the same bitrate... deader somehow, less involving. OK for background music, though, until I got sick of the repetitive playlists.

http://www.audiocoding.com/modules/wiki/?page=MP2&PHPSESSID=

http://www.dvbapps.com/ for DVB radio tuner/recorder software, and FTA TV. (Broadlogic and Twinhan cards)
http://dvbn.happysat.org
http://www.id-discussions.com
 
Ive looked all over the net for mods to the Sky box and found nothing. Having looked inside my THompson its clear that significant improvements could be made. Especially the power supply. I reckon if I could find the audio output stage then a change of caps there would be worth it.


Anyone done this or any other mods to the sky box?
 
mikesnowdon said:
I just finnished the first mods to my Thompson sky box and got pleasing results

Thread with pics
here: http://www.diyaudio.com/forums/showthread.php?s=&threadid=119684&highlight=sky+box


I had a quick look.... I'll make couple of suggestions and it's up to you to try... if you want...

1. IEC connector needs much thicker mains wiring - I suggest solid core copper (you probably can't get your hands on silver ribbons?)

2. RCA connectors look good, but the choice of hook-up wiring could be better.... silver plated copper sounds harsh.... better try solid core copper from CAT5 cable (again, if you can't find silver ribbons...)

3. The embedded IEC filters are bad.... really bad! Try without the filter just for fun and see if the sound improves in definition and "spacial" ambient...


Boky
 
Thanks for the suggestions. I'll give the solid core copper a go cos your right about the sound being a little harsh, mainly in the top end. Theres a lot of detail but its not the smothest sound. Alot better than before, but could be better still.

Theres also an earth solder tag on the IEC but I'm not sure what to connect it to? Any ideas

I'm dubious about removing the IEC filter. I have 4 computers in my home, alot of crap on the mains. Why do you think these filters are so bad anyway?

By the way, Im not sure if I can get Silver ribbon but I know solid core silver wire is available in varying gauges. Which gauge would suit mains and which for the RCA'S?

Cheers for your input Boxy.
 
Extreme_Boky said:



3. The embedded IEC filters are bad.... really bad! Try without the filter just for fun and see if the sound improves in definition and "spacial" ambient...


Boky

I would say on no account should the filters be removed. Satellite receivers cause greater deterioration in the sound of my hifi systems than anything else.

I go for total satellite and video silence when I listen seriously. TEven the LNB downlead seems probelmatic.

And I have totally regenerated supplies for my hifi.

-----------------------------------------------------------------------------

On the question of mods, if you get a Sony 761, you can tap the spdif output from the chip and create a 48k digital output on 75R BNC. With the output relocked, the result is better than DAB!

I am still surprised that there are sp few mods to satellite recievers. The power of Sky??? May be BBC Freeview boxes offer more opportunities.
 
mikesnowdon said:
Thanks for the suggestions. I'll give the solid core copper a go cos your right about the sound being a little harsh, mainly in the top end. Theres a lot of detail but its not the smothest sound. Alot better than before, but could be better still.

Theres also an earth solder tag on the IEC but I'm not sure what to connect it to? Any ideas

I'm dubious about removing the IEC filter. I have 4 computers in my home, alot of crap on the mains. Why do you think these filters are so bad anyway?

By the way, Im not sure if I can get Silver ribbon but I know solid core silver wire is available in varying gauges. Which gauge would suit mains and which for the RCA'S?

Cheers for your input Boxy.

Using the IEC connector with embedded filter AND NOT connecting the ground pin probably means that you are using only about 50% of filter capability to "alter" the sound.... I say "alter" because that's what they do. They don't improve the sound - only change sound. Find the circuit diagram of a mains filter and see for yourself. Once you figure the above, ask yourself a question: “What if the mains ground is ALREADY polluted?”

The mains filters work ONLY if the mains supply is drawn from a sub-station via SEPARATE feed STRIGHT to the household. Many High Enders pay Energy Distribution companies a lot of money to obtain CLEAN mains (read: clean GROUND as well!!!)

In an ordinary every-day household, it all comes down to power supply sections and decoupling capability of individual Hi-Fi component’s to filter the rubbish from mains. If this is done correctly, the mains filters are not needed and will "alter" the sound in such way that the end result is a loss of space, definition and dynamics... and I have done a fair bit of modifications... proved this over and over again.

The catch is to improve the inner power supply, grounding topology and decoupling FIRST... and then try mains filters.

Anyhow, try it for yourself. If it works for you - GOOD!

They don’t work for me.

Boky
 
Fmak.

Im quite interested in the mod you suggest. Would it be possible with my skybox? Have you done it yourself and can you give more data?

Anyone.

I found some audiophile voltage regulators and opamps online: can these be used in a skybox?

Why isnt there any 'audiophile' set top boxes? Surley the AV fans out there would be interested?

PS: sound has become smother now from my modded unit. Its a little warmer too. Still lacking detail and upper bass definition. Top end sounds cleaner but it seems to roll off too soon. Could it be possible someone out there can re-design the sky box? The main boards are available, why not start from there and go all out for sound quality? Could be a winner £££££££££££!!
 
Interesting comments.

Im new to this so messing about with the skybox is like practice. I dont care too much if the thing explodes but I dont want to ruin my Hi-Fi so the Skybox is my first victim.

Fmak.
Excuse my ignorance here but ive no idea what you talking about. Are you saying the Sony already has a digital output? If not then youre talking about installing a DAC and running the SPDif(?) thingy into it? To be honest its over my head on the theory but I can solder and read schematics. If youve done this mod then posting some pics would be of great help to me.

By the way thanks for your input on this. Seems your the only one interested in gaining better sound from Sky.

Dangus.
I have no clue what the bitstream is over here.

Can anyone shed some light?

Still no reply on the earthing. Look at the pic here and tell me what to do with the earth pin on the IEC filter:

(the chassis is some kind of steel so its conductive. Do I just run a wire to the chassis?)
 

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