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Post by dmcrimson on Jul 9, 2016 18:11:10 GMT
Ok, so I recently ordered a CmoyBB clone *2 and a RA1-clone - they've now both dispatched For the CMOY-clones I have the enclosures - other one will go into Barklays Liquorice tin (similar to Altoids, measures the same as Adafruit-tin) and other one will go to plain black plastic box which is the same size. That RA1-clone I would love to get a decent desktop enclosure - toss me links, ideas, DIY-tips and so on
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Post by dmcrimson on Jul 22, 2016 21:57:43 GMT
Ok, the RA-1 -clone arrived and it suffers from the same error as the one discussed at RG... At least on silkscreen. Also components reflect silk. 6*1003, 6*4640 (instead of 4643) and 6*1213 - also, the led has no resistor... there's a spot labeled XK, nad if nothing is soldered there, led will not light Also, where the volume pot is placed, reads 100km but the pot appears to be dual 50k. Blech. Other two amps are waiting at post, I'll pick them up tomorrow.
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Rabbit
Administrator
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Post by Rabbit on Jul 23, 2016 7:30:33 GMT
I think the RA-1 is a CMoy as well. It was a right rip off really considering the price that it sold at.
There's something really nice about the simplicity of Cmoys that I like.
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Jul 23, 2016 8:18:52 GMT
Yes the RA1 is a C'Moy
50k is better than 100k. Would prefer a 10k or 20k myself. lower resistance = lower noise floor. Is it a double sided PCB ?
I have NO idea why it was decided to use such high resistance values in the feedback path as there are no capacitors inline.
I would recommend to replace the 464k feedback-R with 4k7 and replace the 121k resistor with a 1.2k resistor. This will lower the noise level measurably.
The resistor value for the LED could be anywhere between 2k2 and 47k depending on which LED is used (efficiency) and how bright you want it to be.
I would replace the input electrolytic caps for 1k resistors myself when I was certain the source does not contain a DC component. A non biased polar cap is not ideal here.
Are there markings on the cap stating 'Bp' ? In that case they are at least better suited than if they have a + and -.
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Post by dmcrimson on Jul 23, 2016 9:40:43 GMT
Caps are bipolar. I'll take pics of the pcb later today. I'd have expected a bom with the kit...
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Post by dmcrimson on Jul 23, 2016 20:08:11 GMT
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solderdude
Administrator
measureutternutter
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Post by solderdude on Jul 23, 2016 21:19:47 GMT
Xk is indeed for the LED. It is probably marked Xk because it is unknown which resistor value'X' is to be used in 'k'Ohm. As said before it can be anywhere between 2.2k and 47k
Personally if you had to buy SMD resistors anyway I would also buy 1k2 and 4k7. That is if you want a gain of 5x if you want a smaller or higher gain you can change the 4k7 to a higher value (more gain) or a lower value (for less gain)
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Post by dmcrimson on Jul 23, 2016 22:15:38 GMT
Well, I can get the resistors next month, as work begins again... The SMT-machines spit them out a plenty Once they hit the reject bin, they're trash. Only those components that are limited in amount get picked and put to tape or tray again...
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Post by dmcrimson on Jul 24, 2016 11:43:55 GMT
Oh, did some research on RA-1 clones in general and those values popped up again. Better gain and lower noise with them... Now I just need to source a suitable enclosure for it.
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Post by dmcrimson on Oct 9, 2016 13:10:32 GMT
Hmm, I no longer need that RA-1 -clone... Salvaged a Logitech X3 2.1 set from our dumpster, took it home for further inspection. Turns out the connector to subwoofer-unit (mini-DIN) suffered from bent pins (kids, too much force?) and a broken input cable. Easily fixed
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