I found this video by Juanito Moore while going down the youtube rabbit hole. A diy multieffects module (reverb and delays) based on a cheap DSP board from aliexpress.
Has anyone used this Aliexpress-Dsp before? Does anybody have some more information on it? How does it sound and so on... At this price point it makes for an easy order, I guess.
If anybody has any experience, I would love to hear that
cheers!
Self answer: I found some more stuff about the board. It itself is named dsp99-mk and seems to be based around a codec (cirrus logic cs4220-ks) and an one chip reverb (wavefront al3201bg). Would be interesting if the chips are authentic or clones, as they seem to be quite old.
All is controlled by an atmega mcu, reading the encoder, setting the display and controlling the reverb.
In the Coolaudio's V1000 datasheet there is a schematic of the stereo fx module using V1000 (AL3201), V4220 (CS4220) and Mega8 with 2-digit LED display. I think Chinese modules are based on it (but cutting out input/output buffers).
Attachments
StereoFXmodule_V1000_V4220.png (297.98 KiB) Viewed 2118 times
I've just build one of these on stripboard based on his schematic
(not including the optional CV'd clock).
At the moment the wet output is quite a bit quieter than the dry output, and that's with the trims set to minimum. As far as I know I've got the schematic right so I'm not sure how to correct it. I might try increasing the 10k resistors that lead into the trims from the dry side. Or try changing the 30k resistor. Sort of guessing here
FYI, I ordered one from Banggood ($22) and one from AliExpress ($15). The former arrived in about 2 weeks. The latter has been over a month, although apparently it did arrive in the UK a week ago.
I don't know what signal levels you are putting in to the module or expecting out of it, but these modules were made to 'plug' into the internal Effects Send bus of a mixing desk or music Amp.
So with reference to the datasheet for the main chip and the actual components used and the values on the module, you will need to work out the amplification and attenuation to add to the complete circuit. Which could be different for each board you have ordered - different manufacturers?
Also don't forget the low-pass filters for the module outputs, see the datasheet and the example in the previous post above.
I designed a interface PCB for this module a few months ago as a stand alone effects unit.
I might put up the circuit diagram, if you're interested.
smudge wiggle wrote: ↑Thu Oct 22, 2020 3:02 am
dylski - Step away from that circuit diagram!
I don't know what signal levels you are putting in to the module or expecting out of it, but these modules were made to 'plug' into the internal Effects Send bus of a mixing desk or music Amp.
So with reference to the datasheet for the main chip and the actual components used and the values on the module, you will need to work out the amplification and attenuation to add to the complete circuit. Which could be different for each board you have ordered - different manufacturers?
Also don't forget the low-pass filters for the module outputs, see the datasheet and the example in the previous post above.
Haha, possibly too late to pull out now as I have everything built so I'll see where I get tweaking some of the resistor values. At which point it might have to remain a slightly flakey DSP module for a while as other projects fighting for attention.
In the longer term it would be good to breadboard a better circuit for it.
smudge wiggle wrote: ↑Thu Oct 22, 2020 3:02 am
I designed a interface PCB for this module a few months ago as a stand alone effects unit.
I might put up the circuit diagram, if you're interested.
smudge wiggle wrote: ↑Thu Oct 22, 2020 3:02 am
dylski - Step away from that circuit diagram!
I don't know what signal levels you are putting in to the module or expecting out of it, but these modules were made to 'plug' into the internal Effects Send bus of a mixing desk or music Amp.
So with reference to the datasheet for the main chip and the actual components used and the values on the module, you will need to work out the amplification and attenuation to add to the complete circuit. Which could be different for each board you have ordered - different manufacturers?
Also don't forget the low-pass filters for the module outputs, see the datasheet and the example in the previous post above.
Haha, possibly too late to pull out now as I have everything built so I'll see where I get tweaking some of the resistor values. At which point it might have to remain a slightly flakey DSP module for a while as other projects fighting for attention.
With some experimentation I've changed the 2.2k resistor for 12k and the 30k for 20k and it works really well now!
Here's a really short test of the module. The second input is normalled to the left output for feedback.
Apologies for the sound quality - the whining is from my phone's crappy audio interface.
smudge wiggle wrote: ↑Thu Oct 22, 2020 3:02 am
dylski - Step away from that circuit diagram!
I don't know what signal levels you are putting in to the module or expecting out of it, but these modules were made to 'plug' into the internal Effects Send bus of a mixing desk or music Amp.
So with reference to the datasheet for the main chip and the actual components used and the values on the module, you will need to work out the amplification and attenuation to add to the complete circuit. Which could be different for each board you have ordered - different manufacturers?
Also don't forget the low-pass filters for the module outputs, see the datasheet and the example in the previous post above.
Haha, possibly too late to pull out now as I have everything built so I'll see where I get tweaking some of the resistor values. At which point it might have to remain a slightly flakey DSP module for a while as other projects fighting for attention.
With some experimentation I've changed the 2.2k resistor for 12k and the 30k for 20k and it works really well now!
Here's a really short test of the module. The second input is normalled to the left output for feedback.
Apologies for the sound quality - the whining is from my phone's crappy audio interface.
FWIW here's the stripboard layout.
I forgot to add space for the power connector and should have made space for the two trims but it works fine! You live and learn
I've also attached a PDF including the component list and trace cuts.
dylski wrote: ↑Mon Oct 26, 2020 2:04 pm
FWIW here's the stripboard layout.
I forgot to add space for the power connector and should have made space for the two trims but it works fine! You live and learn
100_DSP.png
I've also attached a PDF including the component list and trace cuts.
I have made the stripboard version, but would like to add the CV clock mod.
Would the optional 'CV clock mod' be +15v compatible?
I guess I would have to change the 470k resistor? Anything else?
tnx!
)
