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Author Topic: Low audio volume with composite modded G7000  (Read 3807 times)
emuola
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« on: June 18, 2014, 02:06:46 PM »

I got me a "silver" G7000 from Netherlands. I then modded it for outputting composite with this very easy mod:

http://www.ebay.com/itm/Magnavox-Odyssey-2-Philips-VideoPac-G7000-A-V-Composite-Video-Mod-Kit-DIY-/181078338355

Otherwise the mod works fine, but the audio level is really low. Audio works fine with games, but the level is just very low. Although I have to raise the volume from the tv/amp much higher compared to my other retro stuff, the audio is surprisingly "clean" meaning no hiss etc. Picture quality is very acceptable Smiley Is this a known problem? How could I get the audio level higher?
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VideopacBelgium
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« Reply #1 on: June 18, 2014, 06:02:45 PM »

Hi,
Could you post here the "Wire labelling guide"?
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emuola
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« Reply #2 on: June 18, 2014, 07:31:06 PM »

Ok,  here's the page from the wiring guide and a picture from my G7000. My mobo is totally different, and there are only 3 wires from the mb to the modulator. The modulator had the ground directly from the mobo with a metal "plate". I measured the levels of the 3 wires with a multimeter and got values 4.8v (-> 5v), 1.2v (-> video) and 0.2v (-> audio). Like I said, works ok, but audio level is really low. Thanks for the help in advance guys Cheesy I'm just a newbie regarding G7000 although I have a looong history with other consoles/computers from 70's/80's/90's.

Guide:
http://1drv.ms/1r83rRt

My G7000:
http://1drv.ms/1kgLQkP


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Rene_G7400
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« Reply #3 on: June 19, 2014, 01:37:10 PM »

If you take a look at the schematic of the G7000 (see below) you'll see that there is a 33k resistor (R766) is series with the sound output. To get a higher output level you could solder another resistor in parallel with R766 (for example 10k).

http://home.kpn.nl/rene_g7400/vp_info/G7000_2.jpg
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emuola
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« Reply #4 on: June 19, 2014, 01:45:19 PM »

If you take a look at the schematic of the G7000 (see below) you'll see that there is a 33k resistor (R766) is series with the sound output. To get a higher output level you could solder another resistor in parallel with R766 (for example 10k).

http://home.kpn.nl/rene_g7400/vp_info/G7000_2.jpg


Ok, thanks Rene_G7400 for the tip Smiley I might just do that Smiley Just being curious, is the audio level particularly low with G7000? Is it by design, or is there something missing now, because the modulator has been removed? I'm asking this, because If I compare the audio level to (standard) Atari 2600, MSX, C64, Amiga, Amstrads, Spectrums, TurboGrafx etc, it's something like 1/2 or even lower.
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Ozyr
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« Reply #5 on: June 19, 2014, 02:05:51 PM »

I've got one of those board (have not used it yet). Make sure to use the G7000 instructions, not O2 (but guessing you have done that).
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emuola
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« Reply #6 on: June 19, 2014, 03:32:58 PM »

I've got one of those board (have not used it yet). Make sure to use the G7000 instructions, not O2 (but guessing you have done that).

Yes, I used the instructions for G7000 Smiley
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Rene_G7400
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« Reply #7 on: June 19, 2014, 11:01:27 PM »

With the RF modulator the level might be higher (don't know for sure, I never use a modulator). It also depends on the input of your TV, if it has a low impedance, the 33k resistor of the G7000 is too high. (Assuming that the A/V mod doesn't change the level.)
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emuola
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« Reply #8 on: June 20, 2014, 08:51:29 AM »

With the RF modulator the level might be higher (don't know for sure, I never use a modulator). It also depends on the input of your TV, if it has a low impedance, the 33k resistor of the G7000 is too high. (Assuming that the A/V mod doesn't change the level.)


Thanks for the explanation Rene_G7400 Smiley Actually the mod seller told me to bypass the audio section of the mod, meaning I connect the audio directly from the mb to the rca connector I added to the back of the case. I'll try that asap Smiley I know only little about electronics so I don't know what the audio section does to the audio signal. We'll see how it goes.
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emuola
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« Reply #9 on: June 23, 2014, 07:56:06 AM »

Thanks for the explanation Rene_G7400 Smiley Actually the mod seller told me to bypass the audio section of the mod, meaning I connect the audio directly from the mb to the rca connector I added to the back of the case. I'll try that asap Smiley I know only little about electronics so I don't know what the audio section does to the audio signal. We'll see how it goes.

Actually it helped a lot Smiley I bypassed the mod routing the audio directly from the pin to the output (rca) and the level is now on the same level (pun intended) compared to my other retro gear Smiley

However, I noticed that there's actually some interference? in the video. I did not notice this before, because I was so thrilled to get the mod working in general :/ With interference I mean some random white (where there's black) pixels flashing on the screen here and there. It's really no big deal, but I was wondering if this is something usual? Noisy psu?
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Rene_G7400
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« Reply #10 on: June 23, 2014, 09:43:37 AM »

However, I noticed that there's actually some interference? in the video. I did not notice this before, because I was so thrilled to get the mod working in general :/ With interference I mean some random white (where there's black) pixels flashing on the screen here and there. It's really no big deal, but I was wondering if this is something usual? Noisy psu?

Does this happen with all games?
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emuola
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« Reply #11 on: June 23, 2014, 10:42:56 AM »

However, I noticed that there's actually some interference? in the video. I did not notice this before, because I was so thrilled to get the mod working in general :/ With interference I mean some random white (where there's black) pixels flashing on the screen here and there. It's really no big deal, but I was wondering if this is something usual? Noisy psu?

Does this happen with all games?


I only have 2 games atm: Freedom fighters and Pickaxe Pete. The "interference" happens with both games, but It's more apparent with freedom fighters (there's more black on the screen).
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Rene_G7400
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« Reply #12 on: June 23, 2014, 01:38:40 PM »

I only have 2 games atm: Freedom fighters and Pickaxe Pete. The "interference" happens with both games, but It's more apparent with freedom fighters (there's more black on the screen).

If I remember correctly both of these games have a bug: the background color is updated lots of times which causes little dots. With an RF signal these dots are hardly visible, but with an A/V output or better (RGB) they become visible because the picture is sharper.
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emuola
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« Reply #13 on: June 23, 2014, 02:25:34 PM »

I only have 2 games atm: Freedom fighters and Pickaxe Pete. The "interference" happens with both games, but It's more apparent with freedom fighters (there's more black on the screen).

If I remember correctly both of these games have a bug: the background color is updated lots of times which causes little dots. With an RF signal these dots are hardly visible, but with an A/V output or better (RGB) they become visible because the picture is sharper.


Ok, that would explain it Smiley Thanks!
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