On Monday, 1 July 2019 16:36:27 UTC+1, blisca wrote:
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
https://images.reverb.com/image/uplo...aqvapl3ygx.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

The simple way to find out if replacing a cap will help is to bridge it with another cap. If the original is ok, it makes no difference. If the original is bad, it solves the problem. Sometimes you can just hold the 2nd cap & touch it onto other caps one after another to dx a fault.


NT