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Topics - UsableThought

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Schematics and Layouts / Anyone using the latest CircuitMaker on Windows?
« on: February 02, 2016, 02:26:55 AM »
[NOTE: I thought I could answer this question for myself by searching the forum for "CircuitMaker" - but the search mechanism gave me zero hits, so either I did it wrong or it's balking for some reason. So I'm posting this question instead.]

I saw CircuitMaker recommended by many folks as an alternative to LTSpice or other programs. A link was given to an old, XP version, but I'm running Windows 7 (via Parallels on a Mac) and the program installer is 16-bit and refuses to work.

So I Googled and they are still around - web site at which has a "community" aspect of course - and still offering a free version - there may be paid options as well, I don't know. I've installed and the exe is DXP.EXE, version 11 something-or-other, for Windows 7.

So far it seems very slow - which is not my usual experience with Windows 7 via Parallels - and not brilliantly designed. From the look of it they are running it on a browser platform of some sort and those can often be rather clunky.

Is anyone using this? Thumbs up or down?

My alternatives are:
- iCircuit, Mac only - very pretty & works well for simple analog circuits, but the component library is way too small for anything more than that
- LTSpice on Mac - terrible interface!
- Fritzing, which is a neat newish layout program, also browser-based but better built it seems. You can lay out a schematic, then "breadboard" it, then do a PCB, both manual and autorouting available. However I can't see that it runs simulations. It seems strictly layout.

iCircuit works very well but is too limited. What I just realized I ought to do is download LTSpice for Windows, which looks to have a much better interface than the Mac version (e.g. a toolbar, amazing!).

The Newcomer's Forum / Disappointed by Ruby chip amp from RunOffGroove
« on: February 01, 2016, 11:49:01 PM »
Having built only pedals before, my first venture into something that could be called a solid state "amp" was the Ruby from RunOffGroove. It is one of a family of related little 9V or 12V chip amps - Little Gem, Smokey, Noisy Cricket, etc. - all built around an LMN386 or similar. The Ruby differs from the Little Gem by having a buffer & some other minor tweaks.

I found the instructions helpful; they included some minor mods, a few of which I tried out. Also since at one point I was contemplating an 18V version of the LMN386, I started wondering whether the bias for the buffer transistor's gate would need improving rather than just having the bias resistor go to ground. I know nothing at all about this but a lucky Google brought me to AMZ's page on simple buffers, and I added the "reference voltage" tweak at the top of that page to the Ruby's buffer. Along with that I raised the value of the bias resistor to 10M, again as suggested by AMZ. I ended up staying w/12VDC, but even then the changes to the buffer circuit seemed to make the amp sound moderately better to my ear.

And that's about all I can find to really like about the Ruby - the slight improvement in sound from fiddling with the buffer. While tweaking, I have been running it on a breadboard with a 12" speaker from a Yamaha combo. The circuit is not noisy at low gain despite all the jumpers. But the amp suffers from what I would consider a rather crude breakup (if that's the right term) - it sounds similar to but not quite as appealing as the AMZ dirty boost pedal I built some time ago. The buffer moderates this breakup making it a bit more constant and fizzy, with which low gain at 12VDC is OK; but it is still very inconsistent, e.g. more breakup the higher up the neck you go, which is frankly weird.

The next step in my various little projects has always been to build a finished version - and I was all set to do that, when I stopped & asked myself, why? This amp is anything but versatile. If the tone could be moderated with pedals that might help a bit, but the Ruby doesn't seem to like pedals much: RunOffGrove warn you in their FAQ that anything but unity out of a pedal will overdrive a 386-based amp, and I can tell you from experiment that the result is unpleasant. Putting a passive tone pedal on, followed by just enough boost to get back to unity, didn't work work at all. A reverb pedal worked OK so long as I kept the volume low to minimize breakup.

So probably I will not build it, but disassemble it. I am starting to accumulate so many parts that at this point I really need to organize them better - right now I have "big box of caps" and "big box of resistors" plus "other box of resistors" plus "bigger boxes here & there that I just throw hardware into," etc. You get the picture. But with as many parts as I've got, it is becoming slowly easier for me to build small circuits here or there without having to order absolutely everything fresh. Just a question of what circuits.

I didn't have super high hopes but after reading the glowing descriptions at RunOffGroove for the Ruby and elsewhere for the Noisy Cricket, it seems apparent that some guitarists are able to take pleasure from a simple amp more easily than I can. My only consolation is that from what I read, should I keep muddling my way along w/ SS, apparently this is the lowest level of circuit, and other amps and preamps can sound a lot better.

Crude schematic below with my minor changes from stock Ruby - also I included polarity protection w/parallel diode plus fuse in main branch.

There's a discussion over on The Gear Page about what "rail" or "power rail" means - the OP asked what aspects of a tube power supply it referred to. In responding I cited some pages defining it in terms of computer PSUs, op amps, and SS audio amps, where basically it seems to be shorthand for "a DC supply voltage."

So now the further question has been raised, does it even make sense to talk about "rail" with a tube amp? After all for a typical tube power supply - let us say for HT - yes, there is a transformer & rectifier & reservoir cap; but thereafter there is also additional smoothing w/ the filter caps for each stage. So is the power supply in a tube amp too distributed for "rail = supply voltage" to be useful? 

I guess another way of asking the question is, are SS and tube power supplies that different in nature? Or is it just historical accident that "rail" gets used more in SS, just because of how op amps evolved or some such?

Trying to decide which way to lean in learning about SS amp design. And it may seem silly but I am wondering how the availability of the different kinds of silicon affects this.

- E.g. I read somewhere recently that transistors of the kind used in older amp & pedal designs are no longer even made - and that the ones we buy are old stock. I don't know whether this is crazy Internet rumor or sober truth nor how I could find out. This might affect for example delving very far at all into adapting any of Nelson Pass's DIY designs, or even one or two of Rod Elliott's.

- And how about op amps - are they still being made in plenty?

- Also, I read in my out-of-print edition of "Art of Electronics" - but can't find the reference verbatim at the moment - that a hazard of designing with ICs is that the particular IC you built your idea around has abruptly gone out of manufacture. As a possible example, DigiCom no longer stocks the 18V version of the LM386 and though Mouser has a few, they're end-of-life.

I'm VERY far from actual designing - a couple of light years out - but if I am going to go through the trouble of learning, well OK I understand that learning about the transistor comes first regardless; but even so I would like to know whether new building is being affected by the above questions.

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