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Topics - smadin

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Schematics and Layouts / Electrosmash 1Wamp
« on: January 05, 2022, 09:47:55 AM »
Anyone familiar with this one? I came across it a little while ago, though judging by the forum posts it was published back in the early '10s. It's another LM386-based design, a bit more complex than the Honey, with a very thorough article breaking down the design and math for each section. The author even includes Teemu's book in the list of references at the end:

Kits and PCBs are no longer available for order, but the KiCad project, BOM, and layout transfers are hosted in the forum at, so I was thinking of it as a potential next project.

Honey Amp / Got my kit!
« on: May 02, 2021, 04:41:40 PM »
Hello folks,

I used to hang out on here, many years ago, though I lurked more than I posted, so when I got the email about the Kickstarter launch, I was thrilled to back it. My kit arrived yesterday — thanks @joecool85! — and I'm excited to start work on it soon. I'm curious what other folks are planning for enclosures!

The Newcomer's Forum / LM386 bypass
« on: May 30, 2008, 07:01:37 PM »
(I wasn't sure whether this should have gone in the main Amplifiers section instead, but I think it's a newbie-ish enough question...)

I've noticed that although the Ruby uses only a 100nF, and the Little Gem and Little Gem 2 don't use any at all, some cursory Googling suggests that a 10uF or so cap from pin 7 to ground on the LM386 goes a long way to reducing noise, and I see that (for example) n9voc tends to use them in his schems.  Is there any reason not to add those in to the Fetzer-Little Gem MkII I'm building?

Hello all, and apologies in advance for the high degree of redundancy to follow...

I've built a Ruby and am quite happy with it (modulo the limitations of the cheap little speaker it's driving currently), but I'm interested in moving on to a larger project.  So far, I think that's about the same as the majority of intro posts here :-)

I'm only in the very initial concept stages right now for what I'd like to do next -- after all, I'm so out of practice playing that I won't be able to make any amp sound its best just yet, and flubbed notes will only sound more jarring coming out of a big amp and a quality speaker.  I've been reading through a lot of stuff here, at runoffgroove, and occasional other places that come up on google, poking around GGG, AMZ and GEO, and reading through power- and op-amp IC datasheets, but although I know my way around a soldering iron and am beginning to get a feel for the functions of the various bits, my overall grasp of circuit theory is shaky at best.

What I'm thinking I'd like to do, roughly, is build a 1x10 cabinet, probably with a Jensen MOD10-50, and ideally design it so that the amp electronics are very modular: I'm thinking of this cab as more or less a platform for trying out different amp circuits as I build them, so I'd like to be able to swap them in and out without much trouble.  It needs some amp to start with, though; based on reading here, I'm inclined to think an LM1875, or a pair of them, would be a good approach.  (Unfortunately the pictures and schematic links for the LM1875 chipamp on the wiki appear to have gone 404, but there seems to be a good amount of information available 'round the net anyway.)  However, I'm also intrigued by the LM2876, which looks to have some better protective features built into it than the 1875.  Nothing on the 2876 came up with the search function here; has anyone had any experience with it, or does anyone know any particular reasons not to just work from the app note schematic?

Choice of IC isn't really my main concern, however; the part of the task I find most daunting is the power supply (a great advantage of battery amps...).  To drive an 8ohm speaker at 40W, it looks like the 2876 wants a +-30V supply, while for the 1875 (and presumably likewise for a dual 1875 setup?) I'd want +-25V; both chips have a pretty wide supply range, though.  Is building an adjustable PSU, so I could swap in, for example, an 1875 board at +-25, a 2876 board at +-30, or even a 3886 at +-35 (or a 386 at +-12), without changing out the power supply, liable to be prohibitively complex or difficult?

Thanks very much, and thanks also for all the information I've already gotten reading through these boards.

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