31/01/2025
𝗥𝗲𝗺𝗲𝗺𝗯𝗲𝗿 - 𝗧𝘂𝗿𝗻𝘁𝗮𝗯𝗹𝗲𝘀 𝘀𝗵𝗼𝘂𝗹𝗱 𝗡𝗘𝗩𝗘𝗥 𝗯𝗲 𝗶𝗻𝘁𝗲𝗿𝗻𝗮𝗹𝗹𝘆 𝗴𝗿𝗼𝘂𝗻𝗱𝗲𝗱!! Whoever carries out this modification should not be opening up these turntables as this alone proves they are not qualified, and dont know what they are doing.
Reason is simple: Unlike line level signals where the screen and chassis can be commoned at source, Phono level signals need the audio and chassis ground to remain separate from source because the phono (RIAA) signals operate at a much lower voltage and have a lot more sensitivity. Otherwise static (electrical interference) will be induced within the very sensitive audio signals, because the turntable chassis acts as a large antenna with some capacitance which constantly needs to be electrically drained (through the separate ground wire). This must be kept separate until it reaches the RIAA preamplifier (eg dj mixer) and only then can the connection be made between chassis and audio ground to create whats known as a grounding star point. (Electricians will appreciate this regarding the difference between electrical earthing, grounding and bonding.)
Be careful when some people say 'Internal grounding is fine if done correctly' - this is very misleading, because there is no 'correct' way to do something which should not be carried out in the first place!
Many people will be under the illusion that they have never had a problem with internal grounding, but listener fatigue will be masking the capacitance effect as to why they are experiencing reduced/muddy audio quality. Plus its like driving a car with faulty brakes - everything seems fine until something goes wrong!
I am seeing an increasing number of turntables come to me which have retrofited audio PCBs that have an internal ground link. These are NOT a genuine Technics part and are a very poor aftermarket design.
𝗕𝘂𝘁 𝗱𝗼𝗻𝘁 𝘄𝗼𝗿𝗿𝘆 - 𝗜 𝗵𝗮𝘃𝗲 𝗴𝗼𝘁 𝘆𝗼𝘂𝗿 𝗯𝗮𝗰𝗸!! 𝗔𝗹𝗹 𝘁𝘂𝗿𝗻𝘁𝗮𝗯𝗹𝗲𝘀 𝘄𝗵𝗶𝗰𝗵 𝗰𝗼𝗺𝗲 𝘁𝗼 𝗺𝗲 𝘄𝗵𝗶𝗰𝗵 𝗵𝗮𝘃𝗲 𝗮𝗻 𝗶𝗻𝘁𝗲𝗿𝗻𝗮𝗹 𝗴𝗿𝗼𝘂𝗻𝗱 𝘄𝗶𝗹𝗹 𝗵𝗮𝘃𝗲 𝘁𝗵𝗲 𝗼𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝘀𝗲𝗽𝗮𝗿𝗮𝘁𝗲 𝗴𝗿𝗼𝘂𝗻𝗱 𝗿𝗲-𝗶𝗻𝘀𝘁𝗮𝘁𝗲𝗱 𝗮𝘀 𝗽𝗮𝗿𝘁 𝗼𝗳 𝗮 𝘀𝗲𝗿𝘃𝗶𝗰𝗲.
Remember - only ever allow formally qualified engineers to service your turntables. You have the best, lets keep them that way. Watch out for social media 'idiots' who try and convince you otherwise. They dont know what they are talking about.
For more information please read the following document:https://www.technics-service.co.uk/app/download/15133899/Internal+Grounding+Info.pdf
Richard Talmage, LCGI EngTech TMIET
Engineer
UK Engineering Council Registration No: 590664.
IET Registration No: 1100173589
