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.

Quote from: J M Fahey on January 25, 2016, 07:11:25 AM
Don't overthink it, it's exactly the same, power rail is newspeak , +B is oldspeak, +V or -V is midspeak, if you allow me to make up that word.

Either I've just got a glimmer of understanding or I'm deeper in the mud than ever.

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?

Quote from: Loudthud on January 22, 2016, 06:42:29 PMSome of the new parts that get designed are never made in through hole versions. There are little adapter boards that you can solder surface mount IC's to for prototyping.

Thanks, also useful to bear in mind. I had read about the adapter boards on someone's blog recently & didn't quite get it - now it makes sense.

Quote from: Enzo on January 22, 2016, 05:42:56 PMThe transistors that are no longer made are the old germanium ones.  silicon works much better and more reliably.  The place germanium shined was in old fuzz tone pedal circuits.  If you want to specialize in that, then start collecting old Ge transistors.  That is, germanium, not General Electric.

Thanks, all that info is very helpful.

I realize now that what I read about transistors going away must have been a comment exclusively about germanium & it would have been obvious in context had I known. If I remember it was an old fuzz tone being discussed.

Also I'm remembering too (my memory is like an electron, it moves slowly, not at speed of light) that with the "Art of Electronics" comment, they were talking only about extremely esoteric ICs and saying that it was safer to design with those that were a bit more generic.

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.

Quote from: bazmusicman on January 08, 2016, 06:30:35 AMAs I am about to embark on making one of these,  on the first diagram on how to make one, it only shows 2 wires. Shouldn't there be an earth wire

If by "first diagram" you mean the diagram in post #1 of the stickied thread on this forum, it is actually two diagrams & the lower of the two does show earthing.

This is not trivial by any means nor does it seem wise to say it is just a light bulb circuit. Mains voltage and domestic appliances, including lamps, have certainly killed far more people than the high voltage inside a tube guitar amp.

To add to the list, something I found out that did not seem obvious:

Don't assume (as a beginner like me did) that the "hand in pocket" rule is adequate for personal safety when working on a live amp. The hand that you extend toward the amp, e.g. when holding a scope probe, has lots of surface area - so be very careful not to, for example, unthinkingly use the heel of your hand to push something else out of the way (e.g. a cable, smaller sub-PCB not fastened down, etc.) so as to get the probe into a tight spot. Easy to get a painful zap this way - won't kill you, but can burn a small hole in your flesh, etc.

Instead, always keep pencil or chopstick or other non-conductive pusher/poker handy. Or better yet turn off power, unplug, drain filter caps if need be, and use blue painter's tape or whatever works to hold back the cable or object (so long as this is safe to do). I use up a LOT of blue painter's tape, taping things down like small temporary cable connections, meter probes, etc., prior to actually starting a task with voltage. I don't want anything to slide, drift, get pushed, etc.

I have sometimes wondered if rubber gloves would be helpful. Not sure.

Note, I like the section on safety procedures in teemuk's amp book because he not only describes what to be careful of but why, e.g. why you want to take your wedding ring off before working with high voltage, etc. I often recommend the book to people just for that section.