Hydra 2 Sync Testing
We often get asked to recommend a quality SCART switching solution other than the GSCART and the only other contender is the Hydra Switch by Lotharek, however, there where some reported compatibility issues with first Hydra Mark 1 when using some CSYNC RGB SCART cables, therefore, I decided to purchase a Hydra for testing. We did not test for picture or audio degradation, this was purely a sync compatibility test.
For this test a set of custom cables with switchable sync outputs where constructed. For example the sync types on the Playstation cables where switchable in real time between CVBS, LUMA, CSYNC, the NTSC Super Famicom between CVBS, CSYNC and TTL CSYNC, the PAL Super Nintendo between CVBS, LUMA and CSYNC, the Original XBOX between CVBS and CSYNC and the Sega Mega Drive 2 between CVBS and CSYNC. Please see model numbers below.
|Console||Region||Model Number||Serial Number|
|Mega Drive 2||PAL||MK-1631-50||151167645|
|Super Nintendo||PAL||SNSP-001A (UKV)||UP13373133|
|Original XBOX||PAL||X01263-001 (Label part number)||1147251 32405|
Table 1. Console model and serial numbers
Various Cables with toggle switches to select various sync types
Test cables inserted into Hydra 2
The test setup consisted of mentioned consoles above, a male to male SCART extension lead, female SCART to BNC adapter, 4 x BNC T adapters, a 4 way BNC cable, Rigol DS1054Z Oscilloscope and a Sony PVM-20L2MD monitor. This enabled us to intercept the sync signals before they reached the monitor.
Test rig whereby the signals where captured by the scope before entering the monitor
Before connecting any consoles through the Hydra 2 we measured each consoles peak to peak values for various sync types. The only exception being for the Super Famicom whereby we favoured TTL CSYNC rather than sync over luma as it would have introduced another toggle switch to the cable and it already had two switches on there! The reason we tested TTL on the Super Famicom cable is because these cables are also sometimes used on modified N64 consoles which can output attenuated CSYNC (which means the 470 resistor is inside the console) when using particular RGB modification boards, therefore the 470 ohm resistor inside the cable is not required, hence the reason for offering the cable without the resistors inside the cable.
|Mega Drive 2||266||422|
Table 2. Original sync values under load direct to monitor, mV Peak to Peak AC coupled.
The Hydra 2 has a built in sync cleaning function labelled as CSYNC on the duel SCART outputs. We measured an "out of specification" sync amplitude for every console we tested whenever the CSYNC was activated on the Hydra 2 no matter what the original sync source was, which is unsuitable for use on regular consumer grade SCART televisions and also analogue to digital converters like the OSSC and Framemeister which operate around the half volt mark or below. But you can however use this CSYNC function safely on professional CRT monitors which can handle sync signals up to 5 volts, like the range of Sony PVM and BVM monitors.
|Console||CVBS||CVBS + HYDRA CSYNC ON||CSYNC||CSYNC + HYDRA CSYNC ON||TTL||TTL + HYDRA CSYNC ON||LUMA||LUMA + HYDRA CSYNC ON|
|Mega Drive 2|