Hi all,
I still have some Motu 24i Interfaces in use which are completely recapped and have already new OP-Amps and an upgraded Power Supply.
My question is now, there are still some Tantalum SMD caps in it which are now around 20 years old.
I'm specially thinking about the one who are used for the decoupling from the inputs to the OP-Amps and the DACS.
They are all 6.8uF 10V... is there any way to replace them with something better instead of just replacing them? Do you think it's necessary to replace them if they haven't any physical signs?
24i — ImgBB
Thanks,
Thomas
I still have some Motu 24i Interfaces in use which are completely recapped and have already new OP-Amps and an upgraded Power Supply.
My question is now, there are still some Tantalum SMD caps in it which are now around 20 years old.
I'm specially thinking about the one who are used for the decoupling from the inputs to the OP-Amps and the DACS.
They are all 6.8uF 10V... is there any way to replace them with something better instead of just replacing them? Do you think it's necessary to replace them if they haven't any physical signs?
24i — ImgBB
Thanks,
Thomas
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Unless these are known to give trouble in this model, I would leave them well enough alone. Aging tantalums may develop high leakage (not much of a concern here) and even short out and blow up with fireworks if subjected to excessive inrush currents long-term, but they do not generally degrade in the more predictable manner that wet electrolytics tend to.
Thanks for the reply. If i would to improve the sound quality, would it make sense to replace them with WIMA Film caps? Or anything else?
I don't think film caps are even an option here - they would be much, much bigger.
Please check what each of them do - by the looks of it, those next to the ADC may be supply / VREF bypass, I would leave those well enough alone. Those next to the 1/4" jacks I suspect are opamp power supply bypass (does the analog section run on +/-6..8 V or something?) but the picture is too blurry to tell - anyway, if so, I'd leave those alone as well. Yes, that would mean that the input is DC-coupled, and any offset would be taken care of by the ADC's digital highpass filter.
There's a few things I may be inclined to check:
1. AK5383 datasheet advises that a small [X7R] ceramic capacitor should be present between VREFL/R and GNDL/R pins as close as possible, but I see no such part. Please check.
2. Ideally you would trace out a whole input channel up to ADC input, with datasheet example circuits as a reference. Then we could check whether opamp type and output loading seem sensible enough and whether upgrading the capacitor at ADC input to NP0 may be an option.
3. Resistors in the ADC buffer circuit look utterly tiny, like 0402? I hope those are not thick film. You definitely want thin film types there.
Downsize-itis may make it difficult to achieve the kind of linearity that the components should be capable of here.
Please check what each of them do - by the looks of it, those next to the ADC may be supply / VREF bypass, I would leave those well enough alone. Those next to the 1/4" jacks I suspect are opamp power supply bypass (does the analog section run on +/-6..8 V or something?) but the picture is too blurry to tell - anyway, if so, I'd leave those alone as well. Yes, that would mean that the input is DC-coupled, and any offset would be taken care of by the ADC's digital highpass filter.
There's a few things I may be inclined to check:
1. AK5383 datasheet advises that a small [X7R] ceramic capacitor should be present between VREFL/R and GNDL/R pins as close as possible, but I see no such part. Please check.
2. Ideally you would trace out a whole input channel up to ADC input, with datasheet example circuits as a reference. Then we could check whether opamp type and output loading seem sensible enough and whether upgrading the capacitor at ADC input to NP0 may be an option.
3. Resistors in the ADC buffer circuit look utterly tiny, like 0402? I hope those are not thick film. You definitely want thin film types there.
Downsize-itis may make it difficult to achieve the kind of linearity that the components should be capable of here.
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