Hello not sure if this is the right forum I do apologize, I know the title is a bit weird but I will try my best to explain it. I have been using this tone control from Aiyima ( I know tone control is not very popular here) and I happen to like the sound of it very much, I swapped out the ne5532 op amps for some OPA2134's and it sounds very good. The issue is that this preamp is mounted in the chassis of an amp I built and I made some extensions (roughly max length is 12in) for the potentiometers like this for example so I could mount the pots to the front plate. In doing so I encounter a lot of buzzing noise that is audible when ears are very close to the tweeters on my speakers. I used this 6 conductor twisted pair shieled wire to extend the pots and tied the shield to common which did decrease the amount of noise greatly but wondering what else I can do to get rid of the rest of the buzzing noise. The does also persist when the preamp board is not in the chassis aswell. Any help would be greatly appreciated.
Attachments
I would try to connect the shields to the earthed chassis, instead. The goal here is to shunt the noise that’s picked up away from the audio circuit ground. Having wires in the vicinity to that other board with the fans may be a major contributor to the audible buzz.
Unfortunately, needed a quick way to step down 48V to 12v don't know of a linear regulator that could accept that high of a voltage input.
I'll trying grounding to the chassis and let you guys know if there is any change,also try grounding the Pot bushings
Redid the chassis grounding and it is WAY quieter now. what got rid of a large amount of the noise is making sure the front where the potentiometers were mounted was also grounded.
Yes the pot's frame needs to be grounded typically (it depends mainly on the impedances inbvolved - higher impedances, more pickup. Modern design tends to choose say 5k rather than say 100k pots where possible, which helps with Johnson noise as well.
If you want good "offness" (high attenuation when using log pots when turned fully anticlockwise), run separate screened cables to the pot and back again. This screens incoming from outgoing signal.
If you want good "offness" (high attenuation when using log pots when turned fully anticlockwise), run separate screened cables to the pot and back again. This screens incoming from outgoing signal.
the difference is 36v, an ordinary LM317 can handle that, its max in-out being 40v
at first power up there will be 48 volts across the LM317 as the output cap charges up the voltage across the LM317 will decrease to 40. A typical workaround is to put a 40 volt zener across the LM317. That is what I did for a 70 volt regulator using a LM317
With this scenario being so close to max. spec, and 36V available for regulation, a simple power-resistor, then connected to a fairly large capacitor
that will have charge time can help + reduce the heat of the regulator. It would be described as 'two step voltage reduction' 🙂
None really.
Remove cabling, solder in new potentiometers and redrill chassis/front cover to accept the board being mounted like intended. Also the potentiometers nuts may keep the board at its place and worst case (due to weight) is to use an aluminium bracket with long standoffs with the PCB mounted on it. Even if the front cover is too thick extension axles would be a better choice. Keep electrical connections short (with some slack) and tidy definitely with sensitive signal connections. Keep input/line level stuff far away from power supplies and away from class D amplifier circuits outputs.
Correct errors at the root and correct your own made errors even more strictly. It will make the quality of your projects better. If you allow yourself errors like these and also to accept them then things will not improve. Swapping opamps is then a futile action.
A tiny PCB with a tiny linear PSU will solve the self inflicted issues of the bucket converter.
Remove cabling, solder in new potentiometers and redrill chassis/front cover to accept the board being mounted like intended. Also the potentiometers nuts may keep the board at its place and worst case (due to weight) is to use an aluminium bracket with long standoffs with the PCB mounted on it. Even if the front cover is too thick extension axles would be a better choice. Keep electrical connections short (with some slack) and tidy definitely with sensitive signal connections. Keep input/line level stuff far away from power supplies and away from class D amplifier circuits outputs.
Correct errors at the root and correct your own made errors even more strictly. It will make the quality of your projects better. If you allow yourself errors like these and also to accept them then things will not improve. Swapping opamps is then a futile action.
A tiny PCB with a tiny linear PSU will solve the self inflicted issues of the bucket converter.
Last edited:
I actually took the whole thing apart last night and I am doing some reconfiguration, I built a linear regulator circuit with the lm317 and used a very nicely sized heatsink to replace the noisy buck converter I lowered the voltage to around 44v so I can get the voltage difference around 32v. I moved the pre-amp very close to the front, and redoing all the grounds in the chassis. I don't have it 100 % back together yet but enough to test and its worlds more quiet now. I'll be going through and making sure all of the current carrying / signal cables are twisted. Thanks everyone for the suggestions I am learning alot and taking notes.