Let me introduce you to Dr.Boogey

[electrictabs]

Emulation of Mesa Boogie Dual Rectifier Solo Head
It combines characteristics from orange and red channel
sounds great.ultra high gain although i prefer it with the gain pot at 12 o clock max for a great rock lead.
if you find it too gainy(even though it is as gainy as the amp)
read this topic about lowering the gain of fet emus.it might be a cool mod to have less-gain switch.
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28810

[MartyMart]

That looks great ! are you the next "ROG" perhaps ? :wink:

Thanks for sharing,

Marty.

[ragtime8922]

Nice work electrictabs! My emu build list grows yet again.

[ronnie]

I hope Bucksears draws a layout for this one So I can build it, I've already built the last 2, JCM800 and Boogeyman MKIIC, Great work.

[panasonic_youth]

haha, i was working on doing a straight emulation of that as well. nvm that, get a layout up man! that looks great! could you get some sound samples?


also, the beauty of this is that you could socket the components that distinguish red and orange, and even add in the "raw" and "vintage" switches quite easily.

[GreenEye]

Before I run out and grab a bunch of parts....

1.  Anyone have a ranking of the JCM800 and two Mesa sims?  I'm not trying to start a war, just curious.
2.  These circuits look relatively large to me in schematic form - are they not as suitable for perfboaring?
3.  Anyone have any pics of their JCM800 or 2 Mesa sims?

[Peter Snowberg]

Very cool electrictabs!!!

[petemoore]

Hey Doc !!! I need some boost !!! You got any  ....Yeahhh

[electrictabs]

That looks great ! are you the next "ROG" perhaps ? :wink:

Thanks for sharing,

Marty.

No i never meant to be the next ROG
Those guys (and Doug) are the teachers or masters should i say
i am one of the many students who loved their emu circuits and is trying to make his own...
thanks for all the kind word guys
i owe you some soundclips of Dr.Boogey and JCM-800 emu coming probably at the end of the week

[william]

The PCB layout I have at http://216.250.178.122/circuit/wrecktumflinger/index.html should work for this emulation.  The only change is the resistor marked R1 should be bypassed with a jumper.  I have another version that I am updating with soon that removes some of the switches and simplifies the tone stack, but most of that can be accomplished with this layout also.

[Dragonfly]

looks good...i might have to build that one soon

rawk on !

[vdm]

looks great!

it makes me more determined to finish my proto's of the orange ad30 and slo-100 amps... too many circuits not enough time i say!

william:
i was just looking at your layout and noticed you have P4 connected on both outside lugs, but nothing connected to the wiper. This will just give the total value of the pot no matter where you turn it (im not sure what it does either.. volume?)

trent

[michael_ibrahim]

If I may propose another way of doing a circuit like this,...

Firstly, the cool thing about FETs is that they have a max gain similar to that of a tube (35-40db), as well as the fact they they're both voltage controlled current sources. So sticking the same value components around a FET as the tube should give you the same ball-park behaviour. The only problem is the fact that FET won't be biased correctly.

Varying the source resistor to get the correct operating point affects the gain of the circuit. Another way to do it would be to vary the drain resistor to get the correct operating point. The only problem with this is that you'd also change the frequency response of the stage (since you're have a different RC constant).

So here's a better way to do it:

Let's say that you want to build the first stage of a recto amp, which consists of a 220k plate resistor, a 1M grid resistor, a 1.8k cathode resistor with a 1uf cathode cap to ground. The FET circuit would have a 220k source resistor, a 1M gate resistor. Now here's the good bit. The drain would be connected to a trim pot (250k will do) and a very high value cap, at least 22uF. The other end of the trimpot goes to ground, and it's wired up as a variable resistor. The other end of the high value cap goes to the network from the real tube stage, namely a 1.8k resistor in parallel with the 1uF cap both connected to ground.

To set-up the circuit you'd adjust the trim-pot till the source DC voltage read 4.5V (for a 9V main rail). Now the circuit is biased correctly, and the AC equivalent circuit is exactly like the tube circuit, since the trim-pot will probably be set at about 150k, and the low frequency drain resistance will 1.8k||150k which is about 1.8k. This will go to 0 as the cap starts to pass signal.

Just one word about emulating tube circuits with this type of config,... obviously a tube circuit had much more head-room, so building exactly the same circuit with the same gain will result in way too much distortion (since the FET circuit runs off 9V, while the tube runs off about 400V). Luckily, the ratio of tube to FEt operating voltages (say 400 tp 9) is about 33db, which is the same gain as a tyipcal tube stage. In other words, removing the first FET stage and replacing it with a voltage follower should do the trick.

[panasonic_youth]

well, way too much distortion sounds right up my alley, i have a fender stage 160, and it sucks the distortion right out of my MXR distortion plus. the preamp kills it, i can run the pedal into the cabs and it sounds ok, but the preamp sucks distortion, so this looks like a good build.  electrictabs, do you have any clips up yet??

[petemoore]

If I may propose another way of doing a circuit like this,...

Firstly, the cool thing about FETs is that they have a max gain similar to that of a tube (35-40db), as well as the fact they they're both voltage controlled current sources. So sticking the same value components around a FET as the tube should give you the same ball-park behaviour. The only problem is the fact that FET won't be biased correctly.
 >>>? What is a voltage controlled current source? Does this have no terminological reference to an FET 'source'? Does it mean voltage goes in the gate and larger current is output from the Drain?

Varying the source resistor to get the correct operating point affects the gain of the circuit. Another way to do it would be to vary the drain resistor to get the correct operating point. The only problem with this is that you'd also change the frequency response of the stage (since you're have a different RC constant).

So here's a better way to do it:

Let's say that you want to build the first stage of a recto amp, which consists of a 220k plate resistor, a 1M grid resistor, a 1.8k cathode resistor with a 1uf cathode cap to ground. The FET circuit would have a 220k source resistor, a 1M gate resistor. Now here's the good bit. The drain would be connected to a trim pot (250k will do) and a very high value cap, at least 22uF. The other end of the trimpot goes to ground, and it's wired up as a variable resistor. The other end of the high value cap goes to the network from the real tube stage, namely a 1.8k resistor in parallel with the 1uF cap both connected to ground.
 >>>I can't follow, I see the Drain going through a resistor to ground, or...Hmmm...no possibility of a reference schem snippet?

To set-up the circuit you'd adjust the trim-pot till the source DC voltage read 4.5V (for a 9V main rail). Now the circuit is biased correctly, and the AC equivalent circuit is exactly like the tube circuit, since the trim-pot will probably be set at about 150k, and the low frequency drain resistance will 1.8k||150k which is about 1.8k. This will go to 0 as the cap starts to pass signal.
 

Just one word about emulating tube circuits with this type of config,... obviously a tube circuit had much more head-room, so building exactly the same circuit with the same gain will result in way too much distortion (since the FET circuit runs off 9V, while the tube runs off about 400V). Luckily, the ratio of tube to FEt operating voltages (say 400 tp 9) is about 33db, which is the same gain as a tyipcal tube stage. In other words, removing the first FET stage and replacing it with a voltage follower should do the trick.

I used highlight, copy...puter gets stuck for some reason, wouldn't past, back don't werk...sorry for the long quote /short questions, actually I have more questions, just don't know how to phrase them concisely yet.

[Bucksears]

Man, Electrictabs!!!!

See, this is making it harder and harder to NOT just go out and get a clean amp (Fender Bassman LTD) for my next amp. I've been considering amps with tube distortion: the Traynor YCV50Blue, the Peavey JSX combo and (not yet released) Valve Kings. But all of these emulator pedals and a great clean amp are quite a temptation.

We're expecting a LOT of snow here this weekend in NC, so I will more than likely have time to whip up another PCB.

Great work, Electrictabs!!

[ronnie]

That's great Bucksears, I've been waiting for this, I used your last 2 layouts which worked great, thankyou so much for takeing the time to draw all this up so people like me and others are able to build these great pedals electrictabbs is creating.

[scottosan]

Man, Electrictabs!!!!

See, this is making it harder and harder to NOT just go out and get a clean amp (Fender Bassman LTD) for my next amp. I've been considering amps with tube distortion: the Traynor YCV50Blue, the Peavey JSX combo and (not yet released) Valve Kings. But all of these emulator pedals and a great clean amp are quite a temptation.

We're expecting a LOT of snow here this weekend in NC, so I will more than likely have time to whip up another PCB.

Great work, Electrictabs!!

While I think that tube preamps can be well emulated, I'm still a big fan of tube power sections.

[Bob N]

I've been lurking for quite some time and have been thoroughly impressed with the projects that I've seen here. I undertook this project over the weekend and must say that the build was really not that difficult. I used the original circuit board design that was posted by Electrictabs on his website and wired jumpers in place of the switches as per Bucksears' slimmed down version, but I'm having a bit of an issue, which is what prompted me to register and post now.

I've built many circuit projects in the past, but never anything Audio in nature until this project. I just finally got sick and tired of listening to my crappy Crate practice amp distortion and took on this build before I threw the amp out the window in frustration, figuring if I can get this circuit to run properly, I could simply run the Crate clean and have a pretty nice sound.

I have audio, meaning I hear everything just fine, but I've been playing with the trimpots for the better part of the entire evening and can't seem to get the great overdriven sound that I've heard posted. There's a ton of gain, but right when I get to the threshold of the sweet distortion, I get a squealing, much like a stuck pig. I'm a complete Noob to JFets, so I have no idea how to set the pots on this circuit. I saw the earlier posting about source voltage and tried it that way, but still end up pretty clean for some reason. I've tried searching for similar projects that explain this procedure and have come up dry. That's not to say they don't exist, but rather I can't seem to find them.

Can anyone point me in the right direction? Have pity on a noob.... Please give me a clue on how to dial this thing in...

Thanks a ton and keep up the awesome work!

Bob

[electrictabs]

HI
first of all the circuit board that works for the schem i posted is the one Bucksears created(search forum)
another board that was posted some time ago was not posted from me or Bucksears but from another person reffering to a slightly different schem.
So check out that you have the proper board...

if get it right when you say squealing you mean an awful noise...
check if you biased the fets right (measure half of the supply voltage at fet's drain)
if that's ok then i guess that if you house the circuit in a metal box and with proper grounding then you won't have any issues.