keng Posted January 9 Posted January 9 (edited) If i put a 47k ohm resistor at the output of 1:15 SUT ( same as input to phono) inorder to half the impedance load to 23500 ohm . So i can get a effective reflected load impedance to the cartridge of 23500/225 = 104 ohm. Is this OK. So can i just solder 47k resistors across the outputs of both RCA (left & right channel) inside the SUT. So total i need to get two piece of 47k ohm resistors? Can i solder across the 47k ohm resistor to the RCA pins in that circled area? Edited January 17 by keng Just an update, decided not to add the resistor instead I had rewire n using very thin tiny wires this time with minimum solder see updated picture, result spectacular exactly what I was aiming for
e83cc Posted January 9 Posted January 9 (edited) Short answer is yes - but I would question whether this is wise. The most important criteria for a SUT is getting the gain right - loading is not important for most modern cartridges. Transformers have ringing/overshoot, altering the loading can from the load (47k) that the designer assumed, might have unpredictable outcomes. The solder joints on that unit are awful and are probably degrading the sound. You need to trim the wire so there are no protruding wires and/or sharp pieces of solder hanging off. For an optimal electrical connection you want smooth solder joints - think of a gently rounded knoll. I sometimes use a fine file to grind solder joints to their optimum shape - no sharp edges. Coming back to loading, if you must - use bulk foil vishay resistors - they are pricy but make a huge difference when used in a loading application. Edited January 9 by e83cc 1
aussievintage Posted January 9 Posted January 9 1 hour ago, e83cc said: The solder joints on that unit are awful and are probably degrading the sound. You need to trim the wire so there are no protruding wires and/or sharp pieces of solder hanging off. For an optimal electrical connection you want smooth solder joints - think of a gently rounded knoll. I sometimes use a fine file to grind solder joints to their optimum shape - no sharp edges. Sorry, but this is overkill, almost OCD. The shape of the joint has zero effect, and using a file on it is cosmetic at best. 2
bob_m_54 Posted January 9 Posted January 9 4 hours ago, e83cc said: The solder joints on that unit are awful and are probably degrading the sound. You need to trim the wire so there are no protruding wires and/or sharp pieces of solder hanging off. For an optimal electrical connection you want smooth solder joints - think of a gently rounded knoll. I sometimes use a fine file to grind solder joints to their optimum shape - no sharp edges. I agree that the joints look very agricultural. But they do appear shiny, which indicates correct temperature at least. Pointy solder joints, or protruding wires have no effect on the electrical properties of the joint. For an optimal solder joint, you should be able to see the wire protrude through the solder pad, and a shiny concave fillet of solder between the wire and the pad, with the tip of the wire also tinned. Which means clipping the tip off the wire after soldering is not best practice. 1
e83cc Posted January 10 Posted January 10 Quote a shiny concave fillet of solder between the wire and the pad, with the tip of the wire also tinned. Yes that's correct 1
cafe latte Posted January 10 Posted January 10 On 10/01/2025 at 5:07 AM, e83cc said: Short answer is yes - but I would question whether this is wise. The most important criteria for a SUT is getting the gain right - loading is not important for most modern cartridges. Transformers have ringing/overshoot, altering the loading can from the load (47k) that the designer assumed, might have unpredictable outcomes. The solder joints on that unit are awful and are probably degrading the sound. You need to trim the wire so there are no protruding wires and/or sharp pieces of solder hanging off. For an optimal electrical connection you want smooth solder joints - think of a gently rounded knoll. I sometimes use a fine file to grind solder joints to their optimum shape - no sharp edges. Coming back to loading, if you must - use bulk foil vishay resistors - they are pricy but make a huge difference when used in a loading application. Those solder joints are fine, sharp edges do nothing that affects the signal or sound. Chris 2 1
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