Dub Optimiser convertor for U-matic VCRs


INPUT: U-Matic dub

OUTPUT: Full specification S-Video.

Configurable for PAL and NTSC machines

As used by national archives, broadcasters, universities, police forces and many more organisations who require the best quality


KS U-Matic dub to S-Video convertor

Universal power supply

Dub cable assembly with 7-pin connector

Premium quality S-Video 4-pin mini-DIN double ended cable



Time is running out for video material stored on U-Matic format tapes. The tapes are deteriorating and the equipment is nearing end of useable life. Now is the time to digitise your precious media.

Digitising U-matic tapes can be as simple as connecting the composite video out from the machine into a digitiser card but the results are often disappointing.

A much better way is to use the component (Y/C) signals from the dub connector. These component signals differ from the Y/C required for S-Video connection but can be converted using the Keystrobe Dub-optimiser U-matic to S-Video convertor.

Developed specifically for archival work, the convertor achieves the best possible pictures.

Dub-optimiser uses precision active filtering for the Luminance and Chrominance components to optimise quality.

Dub-optimiser will work with most Sony front-loading U-Matic machines. We do not recommend it with the BVU series. In any case a full refund will be given if Dub-optimiser does not suit your purpose.

Terminology note:

S-Video is a component video interconnection standard for Y/C (component luminance and chrominance), it should not to be confused with S-VHS (SVHS) which is a videotape format.

The terms are frequently mis-used in literature and descriptions.

Theory of operation:

Component connection gives better performance than composite. This is because the VCR playback video Luminance and Chrominance are no longer coherent – where they were originally spectrally interleaved, the colour-under recording process has introduced some spectral and “smear” meaning that if the components are re-mixed to create composite video, Luminance resolution is reduced and unwanted pattering occurs. By keeping them separate, we can avoid this and optimise quality.

Some notes about U-matic picture quality:

U-matics use primitive (by today’s standards) video noise reduction techniques. The effects can be seen on the regular composite output as smearing, loss of resolution and a general flattening of fine detail. These are severe artefacts for a relatively small amount noise reduction. The Dub output precedes this destructive “noise reduction” and gives a pure output which can be much more effectively “noise reduced” in the digital domain if deemed necessary.


The dub connector was intended to connect a player to a recorder for a minimal loss transfer. It carries two signals for baseband Luminance and encoded Chrominance. The Chrominance can be at 686KHz for low-band or 984KHz high-band (PAL only). The Chrominance signal at this point has phase and frequency instability. This instability is corrected during playback of the dubbed tape.

The 4.43MHz or 3.58MHz we tap off is stable.

Further reading:

Keystrobe have no connection to this article but link to it because it explains the reason for going component and the spectral difficulties of U-matic very well.