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Old 19th March 2006, 07:04 PM   #1
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Default Improving Sky Digibox for Audio

Frustrated by the poor sound of my Pace 430 on satellite radio, I changed two output coupling capacitors from the dac to Black Gate C and, presto, I have much improved sound.

Taking an spdif out from the AK chip is going to be hard, but I wish other diyers will try. Dissembling the pcb is much more difficult and reminescent of classic British mechanical designs. Why they should crimp the pcb onto a chasis that just fits is beyond me. Even the flexible cable to the front board os fragile.
My Sont VTX 750 has optical out, but not as good a picture as the Pace. The ouput is so bad that my twin pll dejitter won't lock on the 2nd pll!
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Old 19th March 2008, 12:50 AM   #2
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Default Sky box mods?

I intend to do some upgrades to my Sky Digi box.

Firstly I should tell you that my keenest intrest/hobby is DIY Hi-Fi upgrades all in the quest for the best sound.

I understand that the quality of the mains supply to AV equipment can affect the sound/picture quality.

So, I plan to replace the figure 8 mains inlet with a IEC unit with built in filtering. Its basicly a chassis choke filter built into the rear of the IEC socket. I have read that simply changing the fig8 to IEC has good results.

I also plan to upgrade the phono sockets to gold plated insulated types. Ive had a look inside the unit and the above looks easy to do.

Its an oldish Thompson box so its not under warranty anymore.

One of the most common upgrades to HI-FI is changing the capacitors in the power supply to 'audiophile' grade. Another common mod is to do the same in the output stage (audio)

Im interested in doing this to my Digi box but have no idea where the audio output stage is? This is usually easy to find in HiFi. There are a bunch of Caps near the phono sockets, but which ones to change?

I have a simmilar problem with the power supply Caps, where are they? There are a bunch of them of different sizes near the Transformer.

One final consideration is the the Transformer. Im pondering changing this for the Tordial type found high end Hi-Fi. It would require more space so I may even re-house the internals of the box into a nice alluminium chassis. These can be found online and the facia can be macined to accomodate the car slot buttons etc.

Im mostly concered with improving the sound quality, and in improving the power supply I should get better picture also.

Does any of this make sense to you and can you help me finds answers?

I would be very appreciative of any help you can give.
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Old 21st March 2008, 09:24 PM   #3
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Default First mods complete!

Finnished the first mods today and the results were great.


First I removed the crappy phonos for the audio out. They were PCB mount so I needed to solder in some lead wires to connect to the new Gold plated Phonos. I used some Silver plated Copper wire from some old QED Sliver anniversary speaker cable. Obviously this was quite thick so I stripped it back and took out 3 of the twisted cores.

This was very tricky, I had to take my time on this and there was limited space. I only just got them in as the bottom Phono was fouling the PCB.

Next up was to remove the FIG8 mains outlet. Again this was PCB mount so I had to install some lead out wires. Probably the worst part of this project was making the hole for the IEC. I couldnt open up the original hole as the IEC would then be too low and foul the PCB. I had to make a new hole above the old one which meant I also needed to make a blanking plate. In the end I made up a 'flashing' from an old DVD case to go around the IEC and cover the old opening. I used hot glue to hold this in place.

The mains lead was easy. Screen attatched to earth at the Hot end. Heatshrink applied to the Lead out of the Screen and more Heatshrink outside to tidy it all up and give a Pro look.

Results: Picture has more depth and better contrast, edges sharper, better Blacks, better colour. Very pleasing results, even on my cheap CRT. Soundwise I'm very happy! The detail is in a different league to before, and the bass.....Prior to this mod bass was 'one note' and quite loose. It was also a little overpowering. Now its tight, tunefull and it goes really deep. I have TDL RTL2's and youd be mistaken for thinking there was a sub in the room! The best thing is that the bass dosent drown out or affect the midrange like it did before. Overall clarity is much better, accoustic guitar sounds realistic and un coloured. Treble is still a little cluttered but there is less distortion. When I can find out where the output stage Caps are I'll upgrade them and that should sort the Treble.

Listening to Planet rock via Sky (which was the main reason for this project) is quite astounding compared to before. The seperation of different instuments is much better. I just watched 'Eragon' with the kids and it was really great!

To be honest I wasnt sure if there would be any improvement but the results are really good. A good value project with rewarding results.

See pics here: http://www.23hq.com/receive/2969313/B1DA4FCD5A28C3F35
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Old 25th March 2008, 10:41 PM   #4
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Any ideas?

Anyone?
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Old 27th November 2008, 10:21 PM   #5
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Its been awile since I started this thread (since then I have learnt a little bit).

Well the Thompson sky box gave up recently so rather than repair it I decided to get a new one. I wanted to have the best available as a good base for some future modding. After reading several reviews I decided to go fo the Sony VTX-S760U as by all accounts has the best picture and most importantly has good sound quality.

Most of my attention will on improving the audio output stage with better op-amps and improved caps. I would also like to seperate the audio section off with its own trafo and PSU. For the digital sections I plan to replace supply caps (and local decoupling) with oscon caps.

The fig-8 mains inlet will be replaced by a Schaffener inline filter and the chassis will be dampened. Output RCA's will be changed to gold plated ones.

I will post some internal pics soon.

Please feel free to make any suggestions before I start.
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Old 27th November 2008, 10:49 PM   #6
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Hi fmak.

Looking to do the same fella.

Posted a thread a while ago, since then the Thompson gave up so I've ordered a Sony off eBay.

Have you ever had yours open? What kind of opamps were in the output? DIP8 I hope, makes upgrading easier.

I dont have a DAC so I plan to tweak the audio section and upgrade a few caps.

http://www.diyaudio.com/forums/showt...hreadid=119684
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Old 28th November 2008, 05:07 AM   #7
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Quote:
Originally posted by mikesnowdon
Hi fmak.

Looking to do the same fella.

Posted a thread a while ago, since then the Thompson gave up so I've ordered a Sony off eBay.

Have you ever had yours open? What kind of opamps were in the output? DIP8 I hope, makes upgrading easier.

I dont have a DAC so I plan to tweak the audio section and upgrade a few caps.

http://www.diyaudio.com/forums/showt...hreadid=119684
I now have the vtx760, tappping into spdif out. Changing opamps is goinr to be very difficult.
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Old 28th November 2008, 08:24 AM   #8
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SMd
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Old 28th November 2008, 09:30 AM   #9
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Quote:
I now have the vtx760, tappping into spdif out. Changing opamps is going to be very difficult.
Surface Mount?
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Old 28th November 2008, 04:22 PM   #10
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Click the image to open in full size.

Just found this image, Looks like theres space for a seperate PSU for the audio output stage. No luck with the service manual yet.
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