ruby amp

[javacody]

Aren't two of the legs on an MPF102 interchangable? I doubt its the orientation of the JFET, but did you use a socket there? Rule number one, always socket transistors, JFET's, MOSFet's, and opamps. Maybe even input and output capacitors.

I've built the bassman modded version of the ruby, and it is a killer amp. I don't even need effects with it, it has such a smoove clean sound.

[Image_sounder]

Hi Mr Tremblay, I have been finished my Ruby and the sound is great for my effect. But, the volume control didn`t act like a master volume but act like a boost volume. cause if I down the volume the distortion will down too. It is true or there problem in my ruby ?    

[Brian Marshall]

looking at the schematic it seems that both pots are both gain and volume pots depending on how much over all signal you are trying to push through.

it also appears that if you look at it from a traditional amplifier stand point they should be labeled the other way arround... but then again there is only one gain stage.  Seems like it would make more sense to just have one control... is there something about the 386 input that im not understanding?

[Peter Snowberg]

To get a master volume control that doesn't vary the boost level, try inserting a 500 ohm pot in series with the 220uF output capacitor.

Welcome to the forum Ubertar & Image_sounder.

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Hey EVERYONE! Check out Ubertar's web page!
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[siaoguitar]

ok, as of now, my ruby's volume lug is not to ground, is that why it is not working? maybe? I 'm using a 2N3819 trans in place of the mpf102.

i 've switched pin 2 & 3 of 2n3819 around as the spec sheet of 2n3819 shows it to be 1)Drain 2)Gate 3) Source .whereas a mpf102 is DSG when you insert into the trans socket.Am i rite in doing that ? Or must i use another tranny with the same pinout as a MPF102?

[B Tremblay]

Maybe something else is wrong with mine, then, because if I connect lug 1 of the volume pot to ground, it shorts out the circuit and I get nothing.

If "correcting" that connection silences the circuit, then yes, there is definitely something else wrong.

...the volume control didn`t act like a master volume but act like a boost volume. cause if I down the volume the distortion will down too.

That is normal for the circuit.  If you want more distortion at lower volumes, turn up the Gain.  To implement a Master Volume, check out the Little Gem or use Peter Snowberg's recommendation.

it also appears that if you look at it from a traditional amplifier stand point they should be labeled the other way arround... but then again there is only one gain stage. Seems like it would make more sense to just have one control...

The controls are very interactive and may seem redundant on paper, but each has a range that the other does not.  We can't really switch the names of the controls, since the Gain doesn't silence the amp when turned down all the way (like a Volume should).

We justified the inclusion of both controls based on the fact that when the Volume is at maximum, then you can adjust the Gain for the amount of overdrive.

ok, as of now, my ruby's volume lug is not to ground, is that why it is not working? maybe? I 'm using a 2N3819 trans in place of the mpf102.

Yes, not grounding Lug 1 will result in the Volume pot having nearly no effect .

You can use another FET, but make sure the pins are correctly oriented.  It sounds like you did that.

[David]

B. Tremblay:

I'm not trying to hijack the thread!  This just prompted a question.  Could ROG do a "bridged" version of the Ruby (like the Little Gem II) for increased gain?  Also, what about incorporating Java's 3-band EQ?

[B Tremblay]

Could ROG do a "bridged" version of the Ruby (like the Little Gem II) for increased gain?  Also, what about incorporating Java's 3-band EQ?

A bridged version will increase output volume, but not gain.  We probably won't be creating such a project, but you're welcome to try!

[troubledtom]

So replacing the FET might do the trick?

i like your site :twisted:
   peace,
       - tt

[javacody]

I don't think a bridged Ruby would be that hard to do. You have all the pieces you need on the Runoff Groove, you just need to connect them on  a schematic.

[siaoguitar]

ok, i 've grounded my volume lug 1 last nite, still there;s no sound coming out of my 1w,8 ohms speaker. :evil:

very agitated man!

[B Tremblay]

Check the orientation of the FET and IC.  Double-check all the grounds are connected.

[javacody]

siaoguitar, definitely check all of your grounds. When I have problems like this, it is almost always because I missed one or two connections. Try printing out the schem and tracing your circuit. Use a marker on the printed version to trace out all of your connections.

[ubertar]

I didn't have time to try a new FET today, but I connected volume lug 1 to ground again, and this time it didn't short out. Something else must have been going on the last time. But while it didn't short out, it didn't seem to change anything either. Also hooked up a bigger, better quality speaker, and it sounds great.

[B Tremblay]

ubertar,

I'm glad to hear that you've made some progress!  It's very frustrating when seemingly invisible errors conspire to render a circuit non-functional.  However, determined de-bugging will often pay off.

[Jim Jones]

Hope you get it debugged!

I just built a Ruby awhile ago and am really enjoying it.  Here's a clip I did for giggles driving the Ruby with a Rangemaster and running it into a Marshall 4x10 bottom.  I thought it sounded pretty cool for a little beast.


http://members.shaw.ca/house-of-jim/Audio/Ruby_Rangemaster.mp3

Jim

[siaoguitar]

HI JAVACODY & TREMBLEY, i 've wired everything together, and the ground is connected, is there a possibility that the resistor or capacitor could be faulty that causes the signal to not flow through?
I will try to post some pictures

[javacody]

You may have fried the JFET, but I would triple check your circuit. Do you get sound after the buffer? (hint read about the audio probe at GEOFEX, use the link at the top of this forum)

[ubertar]

Turned out a connection wasn't being made as well as it could've been. Nothing wrong with the FET. I still like the 200k audio pot for volume. I have a 5k audio for gain (couldn't find a 1k at rat shack) and it's fine.
I installed it in an old briefcase with a good sized oval (Jensen?) speaker that came from an old portable PA called a "roving rostrum".

This amp kicks ass. Great 70s hard rock (zep, who) kinds of sounds. Plenty of balls. Should be a nice recording amp. Thanks to the folks here who designed it!

[ubertar]

I've got pictures up now:

//www.geocities.com/ubertar/amp