Another thread about the classic noise problem when using various dc-dc converters for powering different modules and audio noise that you get and how to avoid this problem?
I’m having this problem with my battery powered setups.
I’ve just realised that mains ac 240v to dc PSU are isolated by there nature 🙂 because other wise mains ground would be connected to dc gound and so audio signal ground which would electrocute the user, urrgh!
Where's dc-dc converted don’t need to be isolated for safety. Being previously used to mains power supply's as ive grown up, i’ve taken for granted not having this noise problem.
I am trying to have connected together (battery or single mains psu powered):
tpa3250 (use tor browser to view if doesnt load): TPA3250-2CH-50W | 3e Audio
tpa3255 amp TPA3255-2CH-260W | 3e Audio :
I power the (12v OPA2604 tone board) pre-amp via buck dc-dc converter powered from the same dc-dc boost converter of the amp. Which seams to help with noise a lot... Well preamp powered this way seams to not have problems, works fine 🙂. The other +/- 15v dc tone board seams to be ok too. Been changing the dc-dc convert setup ive used for it as the previous module i used kept getting blown up in accidents 🙁 so i need to try out the new one to see if its ok.
Adding the 5v vu meter is new and where i am having noise problems.
I have a suspicion that having a 2x audio isolator transformers in parallel isn’t going to work. one for the vu meter and other one for audio source.
I have been using diy audio isolators. Using cheap yellow 1:1 ratio little transformers from china, in my tpa3116 battery powered setups/boxups. However in my higher end amps im putting together i would like to not use them to preserve fertility
So what about isolated dc-dc converters?
like https://www.tracopower.com/products...etail/dc-dc-converters/reinforced-insulation/
looks like there are aimed at medical and are quite expensive: £27 for 6w:
https://www.rapidonline.com/tracopo...onverter-18-36v-dc-in-5v-dc-600ma-out-57-6063
There are these ones for £18 but i’m not sure if there isolated? :
https://www.rapidonline.com/tracopo...nverter-18-75v-dc-in-5v-dc-1500ma-out-57-5509
There’s also this digital audio isolator board :
https://www.ebay.co.uk/itm/Car-PC-N...121N-Eliminate-Common-Mode-Noise/312052536970
Datasheet: https://media.digikey.com/pdf/Data Sheets/Rohm PDFs/BA3121_F_N.pdf
Ordered it, waiting for it to come.
Some progress reports of my TPA3255 project
I’m having this problem with my battery powered setups.
I’ve just realised that mains ac 240v to dc PSU are isolated by there nature 🙂 because other wise mains ground would be connected to dc gound and so audio signal ground which would electrocute the user, urrgh!
Where's dc-dc converted don’t need to be isolated for safety. Being previously used to mains power supply's as ive grown up, i’ve taken for granted not having this noise problem.
I am trying to have connected together (battery or single mains psu powered):
tpa3250 (use tor browser to view if doesnt load): TPA3250-2CH-50W | 3e Audio
- 30v amp powered by Sure 300w boost Sure Electronics' webstore 300W BOOST Converter for CAR Audio - TL494
- 5v led digital VU meter 5v Aiyima 5PCS 5V RGB LED level indicator VU Meter Amplifier Board DIY MCU Adjustable Display Pattern Dual Channel Dual 24 -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
- 12v-15v OPA2604 preamp tone board: https://www.ebay.co.uk/itm/preamp-S...olume-Treble-Bass-Super-LM1036/181936831248ai
- handheld gadget source (usb charged/powered 5v. aka phone, DAP, laptop, etc)
tpa3255 amp TPA3255-2CH-260W | 3e Audio :
- 48v amp powered by Sure 500w boost http://store3.sure-electronics.com/ps-sp12148
- 5v led digital VU meter 5v
- +/-15DC preamp tone board https://www.aliexpress.com/item/Upd...er-Volume-Tone-Control-Board/32730560110.html Currently Powered By but subject to change: https://www.ebay.co.uk/itm/30W-DC-D...-15V-3A-Dual-Power-Supply-Module/172924866165
- handheld gadget source
I power the (12v OPA2604 tone board) pre-amp via buck dc-dc converter powered from the same dc-dc boost converter of the amp. Which seams to help with noise a lot... Well preamp powered this way seams to not have problems, works fine 🙂. The other +/- 15v dc tone board seams to be ok too. Been changing the dc-dc convert setup ive used for it as the previous module i used kept getting blown up in accidents 🙁 so i need to try out the new one to see if its ok.
Adding the 5v vu meter is new and where i am having noise problems.
I have a suspicion that having a 2x audio isolator transformers in parallel isn’t going to work. one for the vu meter and other one for audio source.
I have been using diy audio isolators. Using cheap yellow 1:1 ratio little transformers from china, in my tpa3116 battery powered setups/boxups. However in my higher end amps im putting together i would like to not use them to preserve fertility
So what about isolated dc-dc converters?
like https://www.tracopower.com/products...etail/dc-dc-converters/reinforced-insulation/
looks like there are aimed at medical and are quite expensive: £27 for 6w:
https://www.rapidonline.com/tracopo...onverter-18-36v-dc-in-5v-dc-600ma-out-57-6063
There are these ones for £18 but i’m not sure if there isolated? :
https://www.rapidonline.com/tracopo...nverter-18-75v-dc-in-5v-dc-1500ma-out-57-5509
There’s also this digital audio isolator board :
https://www.ebay.co.uk/itm/Car-PC-N...121N-Eliminate-Common-Mode-Noise/312052536970
Datasheet: https://media.digikey.com/pdf/Data Sheets/Rohm PDFs/BA3121_F_N.pdf
Ordered it, waiting for it to come.
Some progress reports of my TPA3255 project
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hmm what about these audio isolator transformers??
A187A12C | Ground Loop Isolation Transformer 600Ω | OEP
Vigortronix VTX-101-007 PCB Audio Transformer | Rapid Online
A187A12C | Ground Loop Isolation Transformer 600Ω | OEP
Vigortronix VTX-101-007 PCB Audio Transformer | Rapid Online
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Perhaps a sketch would be better to show each device, and the power supply used for each device, and the signal connections. That should remove any uncertainty of what is connected to where.
You appear to have a ground loop circulating around the 30V supply, through the amp, out to the VU meter module, back through the buck to the 30V.
You could check by adding ground resistance (eg. 100 ohm) between amp and VU module (as that connection should have negligible current flow).
You could check by adding ground resistance (eg. 100 ohm) between amp and VU module (as that connection should have negligible current flow).
hmm it was still a bit noise with portable cd player.
With headphone amp/usb dac connected to laptop it was ok.
Need to learn to measure with scope... i guess ill try audio isolators next? For the vu meter i don’t mind so much if its missing some frequencies.
Thanks
With headphone amp/usb dac connected to laptop it was ok.
Need to learn to measure with scope... i guess ill try audio isolators next? For the vu meter i don’t mind so much if its missing some frequencies.
Thanks
Is the portable cd player the 'audio source' in your sketch, and is it powered by its own batteries?
Is the laptop the 'audio source'?
How is the headphone amp powered?
There also appears to be a ground loop around the tone board and its power supply and back through the other two ground paths.
How much current does the VU board take? Can it be powered from the 15V supply via a 5V linear reg?
There also appears to be a ground loop around the tone board and its power supply and back through the other two ground paths.
How much current does the VU board take? Can it be powered from the 15V supply via a 5V linear reg?
headphone amp as its own built in battery.
i have noise with and without the tone board. both the tone and vu meter with "100ohm" (test meter measures as 70ohm~)
not much current hmm less then 100ma i expect. theres an idea, yea ill try it.
i have noise with and without the tone board. both the tone and vu meter with "100ohm" (test meter measures as 70ohm~)
not much current hmm less then 100ma i expect. theres an idea, yea ill try it.
Isolate the audio before/after the tone board. (Puts it on its own island because of the +/- needs) Isolate the audio at the amp input. Don't use those powered isolators! It adds another ground loop on the inputs.
This type are the best isolators I've found. Trust me..
3.5mm Aux Audio Noise Filter Ground Loop Isolator Eliminate Car Electrical Noise-in Bluetooth Car Kit from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group
This type are the best isolators I've found. Trust me..
3.5mm Aux Audio Noise Filter Ground Loop Isolator Eliminate Car Electrical Noise-in Bluetooth Car Kit from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group
Lets generalise and say that ALL audio equipment is to be fed from an isolated supply. An SMPS supply or a conventional mains transformer achieves this. They isolate the circuitry the from the live/neutral connections by means of Galvanic Isolation:
Galvanic isolation - Wikipedia
The mains ground connection may (or may not) be carried through to the DC ground (as you call it). This is a pure design choice and depends on the individual equipment in question. There is no safety hazard or electrocution risk. Many commercial amplifiers and source components do indeed have direct continuity by design from mains ground to both chassis and the audio ground.
Mains ground is at zero potential relative to the floor you stand on, the walls you touch and so on.
ok thanks, isolation it is. thx for the link to that audio isolator. different looking transformers from the yellow cheaps one i’ve prev used. 🙂
maybe i can get them without the case?
would you say isolated dc-dc converters are worth trying?
How do products that include pre amps, avoid ground loops? They include dc-dc converts or lin regs. Careful detailed technical design?
I am prepared to splash on fancy things in order to get a good, higher quality job done. as i would like to finish these projects and move on.
maybe i can get them without the case?
would you say isolated dc-dc converters are worth trying?
How do products that include pre amps, avoid ground loops? They include dc-dc converts or lin regs. Careful detailed technical design?
I am prepared to splash on fancy things in order to get a good, higher quality job done. as i would like to finish these projects and move on.
DC-DC convertors have their uses, however the DC rails they produce will have more high frequency noise on them than will a conventional power supply.
As you mention, careful detailed technical design is what it is all about. A preamp for example should be constructed not just that it is silent in its own right, but also that it is silent when confronted with differing scenarios in use... such as being partnered with other equipment that is or that isn't mains grounded.
One technique is to ensure that the audio ground is slightly 'lifted' from mains ground via a low value resistor but these are all things that have to be 'designed in' to a product.
As you mention, careful detailed technical design is what it is all about. A preamp for example should be constructed not just that it is silent in its own right, but also that it is silent when confronted with differing scenarios in use... such as being partnered with other equipment that is or that isn't mains grounded.
One technique is to ensure that the audio ground is slightly 'lifted' from mains ground via a low value resistor but these are all things that have to be 'designed in' to a product.
arr, if only there was a ready made product with the features i want...
I guess if i was starting from scratch again to day, with what i leant and wanted something easy and quick to do. i would get the new fx-audio tpa3250 (ready made, pre amp, bofxed) + sure boost dc-dc into a box (unless this other 150w one i ordered is any good [1]) and use my Fiio-317k:
Digital controlled, bass, treble, balance controls, pre amp, usb dac. its all in one:
Fiio E17K ALPEN 2 USB DAC Headphone Amplifier | Reviews | Head-Fi.org
Just wish it had mid tone control as well.
would mean a bunch of boxes tape together and feature scarifies :| which is why i went for diy. build it all into one nice unit, in this case, a robust cheap 2rd hand peli case 🙂
arr it ant easy.
thanks again, now to try some stuff.
[1] Aliexpress.com : Buy Aiyima For Car Bluetooth Amplifiers Power Booster Module DC DC 10V 32V Step up 15 35V Adjustable Power Supply Module 150W PC from Reliable amplifier for pc suppliers on AiyimaTechnology Store
I guess if i was starting from scratch again to day, with what i leant and wanted something easy and quick to do. i would get the new fx-audio tpa3250 (ready made, pre amp, bofxed) + sure boost dc-dc into a box (unless this other 150w one i ordered is any good [1]) and use my Fiio-317k:
Digital controlled, bass, treble, balance controls, pre amp, usb dac. its all in one:
Fiio E17K ALPEN 2 USB DAC Headphone Amplifier | Reviews | Head-Fi.org
Just wish it had mid tone control as well.
would mean a bunch of boxes tape together and feature scarifies :| which is why i went for diy. build it all into one nice unit, in this case, a robust cheap 2rd hand peli case 🙂
arr it ant easy.
thanks again, now to try some stuff.
[1] Aliexpress.com : Buy Aiyima For Car Bluetooth Amplifiers Power Booster Module DC DC 10V 32V Step up 15 35V Adjustable Power Supply Module 150W PC from Reliable amplifier for pc suppliers on AiyimaTechnology Store
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heh they have a even more fancy version of that audio isolator
HIFI ground loop isolator for Audiophile-in Bluetooth Car Kit from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group
Whats the diff between there normal version and audiophile versions transformers? they don’t post any test data.
i give faith to OffGridKindaGuy’s recommendation about the normal one. i just wonder about this one.
HIFI ground loop isolator for Audiophile-in Bluetooth Car Kit from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group
Whats the diff between there normal version and audiophile versions transformers? they don’t post any test data.
i give faith to OffGridKindaGuy’s recommendation about the normal one. i just wonder about this one.
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Those yellow isolation transformers are junk! Lot of fidelity loss. The units I suggest are fantastic and much cheaper than an isolated output power supply..
Same units without the case. You can get complete units cheaper and take the case off. That's what I do..
which is why i had a by-pass switch to use most of the time and used them on cheap little amps on with not the best speakers.
but this tpa325* amps deserve better 🙂
interestingly you can use audio isolation transformers to make a stereo to mono converter. found old wring diagram. been quite useful.
yea, I think i will buy the ones ones you linked to 🙂 but the one i linked to sold by rapid, how do they compare? Are they the same sort of audio fidelity but more expensive markup?
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