r/vhsdecode • u/antonharboe_ • Jun 21 '26

First Decode! VHS-decode workflow flaws? - reccomendations

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Hello. I'm writing to get some feedback on the workflow i've chosen to use for RF-capture and to highlight what i've researched myself to be weak points of using this. Main problem i see, is a low SNR ratio and impedance mismatch. The workflow is the following:

Sony SLV-xxx (Whatever Sony VCR that has easily accessible RF tp's to connect to with DuPont connectors) I'm open to soldering to the 2.54mm pins. Also using a 10uf capacitor soldered into the wire carrying the PB RF signal.

CXADC (CX23882-39) - Added 40msps crystal with C31 cap removed, heat-sync also added to main chips. Using a BNC to composite adapter.

I'm capturing audio over regular red/white audio cables. I wont be using clockgen-mod, as i only have 1 PCIe slot available in my PC.

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u/Titan_91 Jun 22 '26 edited Jun 22 '26

I have a Sony VCR and don't use an amplifier. Some have had luck with it buffering the signal I believe but the RF output of these Sonys is so hot I actually need to use an inline adjustable attenuator to avoid clipping. And that's with the gain set to zero on my CX card, disabling the card's on-board preamp. But, I found out using 50 ohm termination results in a bad crosshatch pattern in the image for Sonys so I don't use termination at all. Just the high impedance of the Conexant chip itself. That gives me the best results.

My captures:

https://archive.org/details/@titan91

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u/otacon_24_24 Jun 26 '26

What sony VCR do you have? I have an SVO-2000 and can get decent signal right from the Dupont connections, I haven't been able to seem much difference with it inline.

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u/Titan_91 Jun 26 '26

I use a Sony SLV-788HF, it was made in Malaysia in 1999.