Build report: Retro style Ruby miniamp

[Foxpaw]

I have just finished a half watt Ruby miniamp. (Thx for the guys at runoffgrove.com!) It's really sweet sounding, suprisingly loud and if you try it with an OD/DIST it almost blows your head off... I installed a DC jack so I can use an adapter, that will save some battery life... The speaker is a really old (about 25 years?) Tesla speaker. (Not so HI-FI, but not that bad at all!) Installed within a wooden box, so it really looks like an old-old radio or something like that...

Pictures:
http://kep.tar.hu/foxpaw/50225423

Cheers,
Foxpaw

[Mark Hammer]

A VERY nice case, and one that looks like it will not rattle, no matter how loud.

If you want loud and long battery life, I suggest you use 6 or 8 C-cells.  This will involve two "clips" of either 3 or 4 batteries wired in series.  The pictures show that you have plenty of room inside.  As long as the speaker impedance is not too low (i.e., below 4 ohms) the 386 should be able to comfortably handle a 12v supply voltage.

The picture also shows that you have plenty of room on the piece of perfboard for additional circuits, so if you decide that you want to add something like an EQ section to fine-tune the cabinet/speaker, or any other effects, the extra battery power will provide plenty of current for that.

Finally, with such a beautiful finish to the case, the longer you can wait in between openign it up and changing batteries, the longer it will stay that beautiful.

[Foxpaw]

Wow. Thank you for the nice advices... I will consider to build in some sort of EQ and a headphone jack later...

Now I am going to build some onboard guitar electronics to my cheap Samick guitar. (Sustainer maybe...) And I am designing my first own distortion box at the moment...

[royzic]

keep up the good work !

[Quackzed]

cool wood cab!!! awesome   i put my ruby in an old Victor speaker box... its like 60 years old... but it looks it!!!  yours looks new and cool!!! what was that wooden box originally? or did you make it from scratch? i love the look of the rounded corners and the clear finish!!! awesome job, now get down to the corner with your tip cap!!!! aren't these little 1/2 watt suckers LOUD?  i read that derek trucks has used car speakers too!!! And i feel he's got a great ear for guitar tone!!!

[syndromet]

That is the most beautifull ruby I have ever seen. Congratulations!!!

The ruby is the next ting to build on my list, and I went out and bought the parts for the cabinett today. I'm gonna build two rubys into a suitcase. I'm gonna start on it tomorrow, so let me know if you are interested in some pictures from the making...

[Quackzed]

Yes! thats a great idea for an amp cabinet... like an old tweed suitcase or something? That would be perfect for any bluesman.... you could use it as a suitcase AND an amp!!! btw i used an old 12" organ speaker and it's pretty loud with a 12", louder than any acoustic, i did the bassman mod and it sounds good! it starts to break up at around 10 oclock and is pretty high gain at 100%
maybee ill post a pic of my victor,  i like how it looks  but i'd love to see it when it's done!

[343 Salty Beans]

SLICK.

[Foxpaw]

I bought the wooden box. It was just a wooden box ( ), but big and strong enough to hold the speaker.
And it was wonderfull to "close the box"... While I tested the circuit, the speaker was just sitting on the table, but after I installed it to the box and closed the box It got some really beautiful tones. I realized that the speaker's cab takes a really great part in shaping tones... It just come out right, so I am very happy...

I like this wooden boxes. They look good and easier to work with than metal boxes...

I used this kind of wood box for my Lava Rim 2:
http://www.elixant.com/~stompbox/smfforum/index.php?topic=42102.0

The only bad thing is that I can't find a normal DPDT or 3PDT or any useable footswitch here in Hungary...   

Thank you for the nice comments!

[Quackzed]

yeah, enclosure size and stiffness definately have alot to do with tone...and especially bass content. i bet it sounded a little thin out of the box, i know when i close the back of my ruby/victor box it sounds fuller and has more bass...i like to leave it open sometimes for a more mid/highs like an open back cab!! other times i close it for more bass thats my tone controll , hey it works for me!
so convinient to just grab my ruby and go jam with my acoustic playing friends...

[Foxpaw]

Right, the same tone thing noticed with my ruby case.

Sometimes it makes weird clipping... (Maybe battery low, I haven't measured it yet...) The guitar signal is just suddenly lost some volume. With adapter, it sometimes does the same, but when I use a distortion box in a front of it, there are no clipping. Maybe the output of this cheap guitar are too low?  Or the battery are low and the adapter is a little bit too much? (12 V rated adapter but I measured 9 V from it.) It is more difficult to get out some clean sounds while I am using the adapter... The speaker is a 4 ohm speaker. Maybe speaker impedance too low for the opamp? Anyway, this thing is really awesome, these are the biggest problems I ever noticed, and with an distortion box, these AREN'T problems... Maybe I should try a booster...

[Quackzed]

I know that when i had a 4 ohm speaker hooked up i got this (fizz) underneath the guitar signal..it was especially noticable as a note decayed or with soft playing, using an 8ohm cleared THAT up...i think the little 386 n-1 chip i have in mine(radio shack) had some trouble tring to drive the lower ohm speaker...(a lower 4 ohm speaker will be louder(x2) than an 8 ohm speaker of the same efficiency-but will also make the chip work harder sometimes with bad side effects like distortion(not the good kind). also they go through batteries kinda fast...when my batteries dying it starts to produce this constant buzzy note if i crank the volume...the deader the battery, the lower i have to turn the volume to avoid this...
   you could try a resistor in series with the + speaker lead if its the fizz issue like a 10ohm-100 ohm as it might be hard to find an 8 ohm car speaker.
  also i've read that more voltage ie 12v gives more clean headroom but yu have to make sure your chip is rated for it...so if the adapter gives less cleen it's probably because it puts out 9.0 and not 9.6...you could try to find an adapter that puts out a little more @10v ? or try the resistor trick..

[Foxpaw]

OK. Thx. I see what can I do. I found a 4,7 Ohms Carbon Resistor.... (Or I must try a higher value resistor?)

[Joecool85]

One thing to keep in mind is that the lm386 isn't rated to do anything below 8 ohms.  On that same note, if doing an MKII littlegem with bridged lm386s, you'll want 16ohms or more.  Now, keep in mind people (myself included) have run way lower ohmage, but it isn't recommended, and you will normally have poor results.

[343 Salty Beans]

after I installed it to the box and closed the box It got some really beautiful tones. I realized that the speaker's cab takes a really great part in shaping tones...

Tell me about it. When I record with my SWR LA15, I can mic it from the front or the back. From the front it's just a duplicate of what comes out of the speaker. From the back, it's got this great, warm, natural reverb that just resonates for a year. Depending on whether or not I remove the handles (holes in the cab body) or the foam inside, I can get some superversatile tones.

To mess with the kinds of tones you get, try putting some different fabrics in there (mine is like this fiberglass/cotton mix or something, something you'd expect to find in the stuffings of a seat on a bus.)

Just an idea, but why not make a mic hole in the back with a hing or something to swing it open and shut? to expand your live/recording sound possibilities 

[Quackzed]

yeah.. you could even cut a hole big enough for the base of a mic..and twist a mic into the hole and seal the mic inside!  instant isolation box/ guitar cab! close up th box and just plug a mic cable in when you want to record... it will be isolated from all the other sound in the room... although a true iso box/booth keeps your sound from everything else... it would be more like having a very small separate room with just your mic'ed amp in it!

[Mark Hammer]

One thing to keep in mind is that the lm386 isn't rated to do anything below 8 ohms.  On that same note, if doing an MKII littlegem with bridged lm386s, you'll want 16ohms or more.  Now, keep in mind people (myself included) have run way lower ohmage, but it isn't recommended, and you will normally have poor results.

My understanding is that the recommended speaker load will vary with the supply voltage used.  The same 386 that does not like seeing 4 ohms when powered with a 9v supply, may be more at home when powered with 6v or even 4.5v.

[Foxpaw]

One thing to keep in mind is that the lm386 isn't rated to do anything below 8 ohms.  On that same note, if doing an MKII littlegem with bridged lm386s, you'll want 16ohms or more.  Now, keep in mind people (myself included) have run way lower ohmage, but it isn't recommended, and you will normally have poor results.

Huh, it is a must to read the data sheet of the 386... 

[squigglefunk]

WOW!

That looks great!


I love my ruby halfwatt amp! Here's a clip:

http://lumpygravyband.com/sounds/halfwatt.mp3

and a pic:

[Foxpaw]

I love my ruby halfwatt amp! Here's a clip:

http://lumpygravyband.com/sounds/halfwatt.mp3

and a pic:

Wow! Really-really-really awesome... What gear have you used? (guitar, cab, effects, mic, etc...)
The most wonderful ruby clip I have ever heard!
Thank you for posting this...