wiring 3 way diode switch for rat mod?

[dano12]

Sorry for the delay....I do all my diagrams, schematics, front panel layout, stickers, etc. in Microsoft Visio.

[dano12]

That'd be awesome, man. Thanks. Here is the component side of the board, and here is the solder side. Pictures are a little blurry, but the end of the diode array facing away from the LED is the one that goes to ground.

Ok, I think this is correct. Desolder the two diodes next to the LED. Then attach wires as shown.  The pins on the opamp should be 2 and 6.

Not sure about the other set of silicon diodes on the board though...

Then hook in your clippers and switches:

[WGTP]

http://aronnelson.com/gallery/WGTP/Mosfet_Switching?full=1

Using Dano12's lovely diagrahm, I redrew a way to use the Mosfet, Mosfet Body diode and GE diode. 

I'll take it down if you don't want me using it.   

[grolschie]

I think I mentioned this in another thread, but using just a GE/Mosfet allows for multiple options.  GE/Mosfet, GE/Mosfet Body Diode, GE, Body Diode, Mosfet/Body Diode, etc.   

Is it better to remove the stock clipping diodes, or to run them with the GE/Mosfet or LED option as shown in the original Dano pic? I am not sure of an easy way to wire up a 3 way switch i.e. stock diodes (rat2) / LED (turbo rat) /  MOSFET.

[dano12]

http://aronnelson.com/gallery/WGTP/Mosfet_Switching?full=1

Using Dano12's lovely diagrahm, I redrew a way to use the Mosfet, Mosfet Body diode and GE diode. 

I'll take it down if you don't want me using it.   

Give me a minute, I just realized I made a mistake.

That is neat idea. Please feel free to pilfer anything from my posted diagrams--they are there for the community.

[jimbob]

I think Dano12 deserves some sort of "diagram of the year award!"  serious! Those are nice. I have them saved and plan to try them out on my tonepad rat tonight- thanks a zillion! I cant wait. I even went to the ratshack to get the mosfet 510's or 20' s ( i dont recall at the moment) And I HATE Radio(wanna buy a cell phone)shack.

[grolschie]

We kinda need a one-stop RAT resource. Maybe people might like to make some additions to the Wikipedia's Proco Rat page. It already lists variants and some mods.

[WGTP]

That's kind of you.  I always get those things confused, but I think it is correct know.  You could also do it for asymmetrical clipping with the body diode/mosfet, but I THINK I have it set up for symmetrical.   You could also use a SPDT swith for each pair and have 9 options.  

[WGTP]

One more thing to keep in mind.  A lot of distortion comes from the op amp and that will occur regardless of the type of clipping you use.  IMHO diode changes are more "observable" in a TS type circuit, where the clippers are in the feedback loop and the op amp is creating a smaller, if any, part of the distortion.   

[dano12]

One more thing to keep in mind.  A lot of distortion comes from the op amp and that will occur regardless of the type of clipping you use.  IMHO diode changes are more "observable" in a TS type circuit, where the clippers are in the feedback loop and the op amp is creating a smaller, if any, part of the distortion.   

That's true, especially in the rat. I use an On/Off/On SPDT for the main clippers--Off takes them out of circuit. It is rather fun to have MOSFETs in the feedback loop and no clippers to ground.

[grolschie]

Nice pic! Any ideas how to incorporate all 3 types (Rat, Turbo, Mosfet) individually? I guess from your diagram, it allows (Rat, Mosfet, none). I take it, this requires one to remove the clipping diodes from the RAT?

grol

[zarathustra]

Ok, I think this is correct. Desolder the two diodes next to the LED. Then attach wires as shown.  The pins on the opamp should be 2 and 6.

Not sure about the other set of silicon diodes on the board though...

Then hook in your clippers and switches

Ahhh, I get it now. I totally missed the part about the "Overdrive" mod being in the feedback loop. Man, that's going to be a lot of fun to play around with. This is some good stuff, dano. Thanks again for the help.

Btw, I'm not sure what's up with those other two Si diodes, either... they appear to be connected in series with the LED resistor? And I can't find 'em in the Rat schem. Weird.

edit: and just out of curiosity, is it worth trying out asymmetrical clipping in the feedback loop?

[zarathustra]

Any ideas how to incorporate all 3 types (Rat, Turbo, Mosfet) individually? I guess from your diagram, it allows (Rat, Mosfet, none). I take it, this requires one to remove the clipping diodes from the RAT?

grol

I'm trying to do this, as well. If the previous posts in this thread are correct, then replacing the body diodes with LEDs "should" allow you to use a 3-position switch to toggle between the LEDs and two other diode arrays of lower clipping thresholds. I'm experimenting with this right now, so I'll let you know how it turns out!

[WGTP]

http://aronnelson.com/gallery/WGTP/Diode_Warp?full=1

Here is another method using the AMZ Warp control to "pan" between a GE and an LED, that are in anti-parallel with an SI.  I couldn't decide which to use on my Rat, so I used all 3.  As the pot is turned, the resistance is added to the GE diode until towards the end of rotation, the LED begins clipping and the the GE plus resistance is phased out.

Other clippers should work, but the value of the Pot may need to change.   

[grolschie]

Any ideas how to incorporate all 3 types (Rat, Turbo, Mosfet) individually? I guess from your diagram, it allows (Rat, Mosfet, none). I take it, this requires one to remove the clipping diodes from the RAT?

grol

I'm trying to do this, as well. If the previous posts in this thread are correct, then replacing the body diodes with LEDs "should" allow you to use a 3-position switch to toggle between the LEDs and two other diode arrays of lower clipping thresholds. I'm experimenting with this right now, so I'll let you know how it turns out!

Is that because the body diodes and the GE/MOSFETs are lower threshold than LEDs. So basically, you turn your RAT into a Turbo RAT and make the mods. I am confused because some of these mods are in the feedback loop, rather than parallel to the newly swapped body LEDs.

[zarathustra]

Is that because the body diodes and the GE/MOSFETs are lower threshold than LEDs. So basically, you turn your RAT into a Turbo RAT and make the mods. I am confused because some of these mods are in the feedback loop, rather than parallel to the newly swapped body LEDs.

Yeah, that's how I understand it. I finally got around to trying this out with the grounded diodes (haven't got to the feedback loop part yet), and it works great, exactly as petemoore described. Basically, I took an SPDT on-off-on switch and wired the signal from the circuit to the middle lug. Then I wired a pair of LEDs to that same lug. Then I wired a Ge/MOSFET pair to one of the outer lugs and a Ge+Si pair to the other outer lug. (The other end of each diode pair is wired to ground.)

When you switch to either the MOSFETs or the Ge+Si pair, the LEDs won't light up even though they're still in the signal path, so you can tell that they're not doing any clipping. All three options sound great, imo, and it's really handy being able to choose between them with just one switch.

Now I just have to figure out how to drill through the steel enclosure to install the switch... 

[grolschie]

Is that because the body diodes and the GE/MOSFETs are lower threshold than LEDs. So basically, you turn your RAT into a Turbo RAT and make the mods. I am confused because some of these mods are in the feedback loop, rather than parallel to the newly swapped body LEDs.

Yeah, that's how I understand it. I finally got around to trying this out with the grounded diodes (haven't got to the feedback loop part yet), and it works great, exactly as petemoore described. Basically, I took an SPDT on-off-on switch and wired the signal from the circuit to the middle lug. Then I wired a pair of LEDs to that same lug. Then I wired a Ge/MOSFET pair to one of the outer lugs and a Ge+Si pair to the other outer lug. (The other end of each diode pair is wired to ground.)

When you switch to either the MOSFETs or the Ge+Si pair, the LEDs won't light up even though they're still in the signal path, so you can tell that they're not doing any clipping. All three options sound great, imo, and it's really handy being able to choose between them with just one switch.

Now I just have to figure out how to drill through the steel enclosure to install the switch... 

Awesome! Thanks for that info! Where on the circuit did you wire the switch to?

Drilling it difficult. I drilled my Rat2 case and found that I had also dented the metal because I was leaning on my drill too hard. Took ages to drill through the steel!

[WGTP]

http://www.elixant.com/~stompbox/smfforum/index.php?topic=38581.0

The low down on Mosfet clipping.   

[grolschie]

Gee, I went to my local electronics store to buy LEDs for to make the Turbo Rat mod, and sheesh there are so many different colours and brightness. As far as tone goes, is a red LED just a red LED, or does brightness factor in here? Which does the stock Turbo Rat use? Cheers.

[neoflox]

Yeah, hi. Sorry for bumping an old thread but my question points directly to this. Maybe Mr.Dano himself can clear this up for me.

I have build a RAT on another PCB than the BYOC-one and want to add the Mosfet Overdrive Mod to the circuit. I can't seem to find the right spot to add the switch in the general schematics. Maybe you can point it out generally?

Thanks in advance for any help!
- Flo