Ruby Guitar Amplifier Old intercom speaker retrofit and revamp

Ruby guitar amp circuit from www.runoffgroove.com installed in an old office intercom speaker. The speaker was found in a storage garage, and was in rotten shape with the veneer broken and peeling and the structure coming unglued and warping. Jim liked the design and asked if there was anything I could do with it. Since the veneer was beyond repair, I peeled the remaining veneer off and cleaned, reglued and sanded the entire cabinet. Then I added new beechwood veneer, cutting the grill to match the original and stained and oiled the entire box. The Ruby circuit was installed on a new custom back control panel made from Ambrosia Maple and Spanish Cedar....and a jack was installed.

Category:

Howto & Style

Tags:

• cigar
• box
• guitar
• amp
• intercom
• speaker
• retrofit
• Ruby
• Amplifier
• Eric
• Butler
• Jim
• Macaluso

[IYanoplathizoI]

I am thowing my first one together. I have little electronical knowladge so can I ask a few questions?

1. Will two 8ohm speakers in parallel for 4r? Will that do?

2. Can I use a CA3140EZ as the MPF102 FET?

Cheers,

Yano

[chainduck]

@IYanoplathizoI Two 8 ohm speakers will work fine. I'd test them first though...reason being is that sometimes one speaker will actually sound better on its own than two....not sure about the science. But, I've noticed this before.

I don't know about the transistor. Substitutes are fine. But, check a cross reference table to make sure.

I'm no electronics wiz either. I just solder things together and maybe vary circuits just to see what works. I

[nihilnoise]

@IYanoplathizoI MPF102 aren't hard to find, if i was you id try and stick with whats recommended cause using an unknown transistor could be the one thing that yield an amp that doesnt work, could be for many reasons, different pin out or not even the right type, is this CA transistor a FET?

just google MPF102 for sale and you should find em, very cheap too

i recommended Small Bear Electronics

[chainduck]

@nihilnoise I had trouble finding them, but my local electronics guy gave me an equivalent that works just fine.  I'm using them in all these amps.

2N5485 costs about a dollar, I think....

Eric

[isethaitchison]

really, it must be a really good speaker lol

[chainduck]

Well, it was torn. I fixed the tear with rubber cement and a bit of paper. These old speakers are often low wattage...perfect for the little Ruby circuit. It has a heavy steel voice coil over an Alnico magnet. But, the actual winding is minimal. If you look in many pre 70's cheap stereo speakers, you see similar. Most are rated at around 6-8 watts...and midrange heavy. I keep an eye out for those old speakers for just this use.

[1FenderGuy]

add one with reverb! so i can do AC/DC at low wattage

[H0LL0WBELLY]

stunning amp.absolutely stunning.

[frankoenburen]

so sweet!

[boagley1]

Sounds just like a pignose! Nice work!!!!!