Help wiring up a Ruby mini-amp

[PB Wilson]

I'm really interested in building my own Ruby amplifier. It sounds like a great project. The problem is that I'm having a tough time getting my mind around the wiring.

Should I wire it up like an effect pedal with the output going to a speaker? Is it possible to use headphones with it? If I want to use an LED, do I need true bypass using a 3PDT? It's not bypassing anything, so I'm confused. I was thinking about using a DPDT toggle switch I have laying around instead of a stomp switch.

Any help is appreciated, especially if there is a similar layout someone can direct me towards.

[RDV]

Hey, I just do the ring of the stereo jack on the input to turn the amp on or off, you can hook up the LED where you bring your power & ground to the board. I don't see the point of an on/off switch unless you want to be able to leave it plugged in when you turn it off.

Regards

RDV

[Marcos - Munky]

You need to wire it like a guitar effect, just wire the output to a speaker, or maybe a jack. You can use a headphone. For the LED, you can use the input jack to switch the power on and off or use a DPDT switch.

[BILLYL]

I simply put a switch on the back of the volume pot (Alpha pots will allow you to add a switch) And since I am using 12 volts I wired up a LED to go on when the power is switched on and it works nice.  I use a headphone alos

BILLYL

[blabj]

i have a very inportant question... in my local shop they did not have a MPF102 or a 2n5457, so i bought a 2n5551 and a 2n5401, will theses work? if not i will have to postpone the building of my ruby untill monday, and even then it may not work as the second shop i want to visit may not have the 2n5457
thanks for any replies
callum

[smoguzbenjamin]

Almost any FET will work but get something with specs close to the MPF102, a J201 will do but not as good

[B Tremblay]

The problem is that I'm having a tough time getting my mind around the wiring.

I would suggest using the same approach as BillyL describes: an SPST which breaks the power supply connection, as part of the Volume pot.  An added bonus when using this setup is that you can use a mono input jack.  Use an LED in series with a current limiting resistor for the "power on" indicator.

There is no need for a bypass switch.

The output can connect directly to the speaker terminals or a mono jack to allow using an external cab.  If you want to have a hard-wired speaker and headphone capabilities, use a normally closed headphone jack to break the connection to the speaker when the headphone plug is inserted.  If you aren't using a hard-wired speaker, then the headphones can simply plug into the output jack.

i bought a 2n5551 and a 2n5401, will theses work?

Neither will work since they are not FETs.  Check the FAQ for J201 substitutes that your shop may carry.

[PB Wilson]

Thanks for the help. I think I'll use two mono jacks and not have the speaker hard wired, but I'm not sure how to hook up the SPST switch to the volume pot (Alpha 16mm).

Also, I'm about to order some parts at SmallBear, and he has two 386 ICs. One is an NJM386D and the other is an LM386N-3. Which one is recommended?

[javacody]

I would go with the JRC (NJM) chip if I were you, but you might also order them both and see which one you prefer. You could use the other for one of the lm386 distortion circuits out there (also at runoffgroove).

[B Tremblay]

I haven't seen an add-on SPST for 16mm pots, but of course that doesn't mean they don't exist.

Circuit Specialists has an appropriate pot/switch: http://www.circuitspecialists.com/prod.itml/icOid/1393

I've tried only the JRC386D and the RadioShack LM386.  Of those two, I like the JRC (same as the NJM from Small Bear) better.

[BILLYL]

The addon switch was for the larger pot (24mm?)  I got the add on at the local Radio Shack.  But you could easily wire in a SPST switch.  When I get a chance I'll see if I can post a few photos.

BILLYL

[PB Wilson]

I would appreciate a picture and I had never realized that pots were available with switches on them like the ones Brian mentioned. I envisioned a small toggle switch used to turn the amp on and off. Thanks for all the help. I'd been waiting to build a project like this for a while.

[smoguzbenjamin]

Hey, toggle switches look cool on almost anything!

[PB Wilson]

I do like the look of toggles myself and looking through my parts box, I've decided to wire it up with a SPST switch. I'm going to put it all together in a tall BB-sized box (C-size) to better accommodate the AA battery pack. I think I'll put the knobs, input jack, LED and switches on the side to make it look like a miniature head. Maybe I'll even cover it with tolex and put a handle on top!