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Budget DC-DC Step-Down Converter for MB6582


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I love using the Recom DC-DC Step Down converter (r-78b5.0-1.5) in place of a standard 7805 5v regulator, with Power Supply Option E: http://www.midibox.org/dokuwiki/doku.php?id=wilba_mb_6582_psuopte

 

It's super efficient @ ~94%, so it doesn't require a heat sink, but it's a bit expensive @ ~$10.23 USD: https://www.mouser.com/ProductDetail/919-R-78B5.0-1.5

 

I noticed that you can find super cheap DC-DC converters on AliExpress for only a couple bucks: https://bit.ly/36LB0q9


Clearly, they're not quite as efficient @ 76-90%, but they look like they should do the trick.

 

Any thoughts on these?

 

  

5f7fbe139dc2e_ScreenShot2020-10-08at9.05

5V

Description: 
 
Input voltage 6.5~40V,output 5V
 
Maximum output current 1A
 
DC-DC Step-Down Converter module working frequency 550KHz. efficiency is 76-90% .
 
Quiescent current: about 1.5MA
 
Overtemperature shutdown, input under-voltage protection, BS-voltage protection, and short circuit protection.
 
2.54mm pin pitch,Can directly replace the L78XX  LM78XX  TO-220 IC
 
Edited by dwestbury
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I think the only thing to consider is the switching frequency, although 550KHz seems pretty high. I would expect worse filtering performance if ordering from AliExpress but I mean who knows ;) That's part of the fun of using AE. 

 

In my case, I'm trying to decide if I should keep with my external PSU option as I had before, going with the C64 PSU option or trying Option E as you noted above. I built an external linear PSU previously using a 7805 and 7809 and some power resistors to dissipate the heat before going into the 7805. It was a heater as you can imagine, and NOT UL listed :) But did the trick. I think I can improve that though. I like the idea of an external PSU because it keeps the heat out of the case gives me plenty of room for filtering (if using switchers) or a huge heat budget if I wanted to use linear regs.

Switchers vs Linear was, at one point, pretty hotly debated on these forums but it sounds like in practice it's just not that big a deal anymore. The SID itself is noisy enough in ideal conditions so yeah I think the switcher at least on the 5V rail makes a lot of sense.

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1 hour ago, m00dawg said:

Switchers vs Linear was, at one point, pretty hotly debated on these forums but it sounds like in practice it's just not that big a deal anymore. The SID itself is noisy enough in ideal conditions so yeah I think the switcher at least on the 5V rail makes a lot of sense.

Yeah, I read through some of the older forum debates, but decided to give PS Opt. E a go, with the Recom SREG and haven't looked back.

My ear doesn't pick up on any discernible noise, above what a standard 8580 SID would produce on it's own (not that I'm any kind of expert on the subject).

I went ahead and ordered some of AliEx converters, which I'll plan to take for a spin in a couple weeks :-)

 

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I kinda went down a bit of a rabbit hole today while looking at these. I think I still favor an external option since that's how my MB6582 is currently setup. But I also like the idea of embracing the switchers so busted out an external board that would replacing my ugly and probably dangerous breadboard I was using previously. This would use a 12VAC transformer (might be able to get away with 9VAC perhaps - I can't remember what I used to use). And then, much like Option E, has the Recom switcher with a linear 7809.

Since it's external to the MB6852 mainboard I've got some room to add protection diodes, a choke, and some caps per the spec sheets. I thought about adding fuses too but will settle for one on the AC side I think.

I originally had a crazy 5, 9, +/- 12 design that was all linear. I still have the schematic for it but for now am not going to worry about adding any analog filters or anything. That might be better done as an MBCV project anyway where I could use the filter for other things, not just the SID.

 

Screenshot from 2020-10-16 15-40-28.png

Screenshot from 2020-10-16 15-35-34.png

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The only step down converter I have is the 360 Mini which I bought very cheap some years ago but I never considered them to use in Audio Setups especially for the SiD because I don't know if I could thrust them and I think they produce some unwanted Noise.

It's okay to use a 7805 with 9V but 12V would make him pretty hot.

The next things I will buy for my Midibox SID is an 12V and 5V Meanwell AC/DC Converter. 

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