Hi to all the people here
I bought the old preamplifier,i remember it as pretty silent,and the "apparent" S/N ratio is further increased by the proprietary noise gate called "H.U.S.H." This is a good pic of the board ,found on a website
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tei1daqvapl3ygx.jpg I'm finding it a bit too noisy,and this noise sounds as "digital noise",more than white noise..it sounds like the frequencies composing the noise are related to the activity of the segments digits of the display.Adding a piece of wire as antenna to the resistors between IC driver and display increases some particular frequency to the heared noise,confirming my impression . I tried shorting ground points with good cables,it does not change anything. I tried adding some metallic shield with minimal or null impact. I ask your opinion about the decoupling capacitors,they are 1uF ceramic capacitors,with relatively long leads.Do yout think that it is worth replacing them?Maybe with SMD capacitor directly to IC VDD and GND? Another idea is to replace the displays with new ones more efficient,needing much less current,and then ,to increase the resistor values,less current=>less noise,but i still dont know if such display exists. I would like to know your opinion. Thanks for your time Diego