He should have used C++ and Qt. It might have worked out better than java.

Back in high school, I played bass in a country music band (*can't believe I'm admitting that, I hate modern country music now*). A friend bought an  old Ampeg SVT head with an 8x10 cab from a school auction, and sold it to me for what he paid for it, $40. It worked great for me for a while and finally died. The output transformer was toast (not my diagnosis). At the time, I knew very damn little about vacuum tubes or even basic electronics, and didn't know the OT could fry if the amp was on without the speaker cab plugged in. I'm guessing that's what I did. I ended up GIVING THE SVT HEAD AWAY :duh . I don't even remember what happened to the cab. Knowing I could fix it if I still had it, and seeing what they go for on ebay today makes me very sad.

I like you JM. You remind me that 35 isn't so old after all. 

This is pretty much a repeat of what I put on http://www.riemer.us/cmos-power-inverter-amplifier-version-2



I decided to refine my CMOS Power Amplifier design (See CMOS Power Amp for the original version). I played with different ideas, and dropped the idea for a while. Then, tonight, I came up with this (See above schematic). While the schematic for the old version has a MOSFET buffer, I left it out of this design. I'm not that concerned with that part of the design. Several buffers can be used, and might not be needed depending on whatever preamp one uses. 

This design has several similarities with the original. The CMOS Inverter is midpoint biased and has variable feedback for gain control. It uses the same MOSFETS.

However, there are some major differences. This looks less like a digital CMOS inverter than the original. While the original has a Class A Bias, this has a Class AB bias using pots R2 and R3 to adjust the bias. The gain pot is between the input and output of the inverter stage, rather than in front. I also decided to see how this works with a 24V supply. Because the biasing pots have some effect on the feedback ratio of this amp, I added R1 to make adjustments to where one has unity gain with R6 set to 50%. The two 1uF capacitors, C1 and C3 help the signal to bypass the biasing pots to reach the gates of U1 and U2. I'll explain pots R5 and R8 in a bit.

Here is a screenshot of this design in a running simulation (paused actually) in MultiSim:



Even with double the voltage, this amp is MUCH more efficient than the original. (That being said, I did not mind that the original was inefficient. I liked having a quiet overdriven amp, and it was still kinda too loud.) This behaves like one would expect a unity gain amplifier to behave. The simulated function generator fed a 24 Vpp (12 Vp see Function Generator window) sine wave at 1 kHz. The output voltage was about 22.7Vpp and was clipping hard. With a slightly smaller input voltage, or with more feedback, the inverter put out a nice sine wave that matched the voltage of the input. The frequency response was fairly flat.

At one point, before adding R5 and R8, I noticed that I was not getting the nice sine wave I had expected, but rather a heavily rounded, clipped output like you might see from a midpoint biased CMOS inverter. This didn't make sense until I noticed that I forgot to connect C3 and C1 to the junction between R1 and R6. After connecting them, I got a slightly but abruptly clipped sine wave like in the above screen shot. It occurred to me that I could use switches to disable C3 and C1 to allow for control of the clipping characteristics of the inverter. Disabling only one could allow for some asymmetrical clipping. Then, I thought, why not use pots to fine tune the clipping characteristics.

The following screen shot shows the results:



Notice how the oscilloscope window shows an output wave form like one might expect from a CMOS inverter. Adjusting R5 and R8 allows one to get something in between this and a hard-clipped sine wave.

R7 simulates an 8 ohm speaker load (not very well of course.) It looks like this can produce a bit more than 8 watts of clean output with an 8 ohm load. If I tweak the bias and try different speaker impedances, I might get more.

This screen shot shows a quiescent current of about 250 mA. After taking this screen shot, I got it to a bit less than 70 mA, which isn't horrible.



Of course, this is all simulation. I haven't bread-boarded any of this yet. When I try to, I might find out that this design doesn't work the way I expect, or maybe doesn't even work at all. I can't wait to find out. 

A Distortius Maximus clone might be pretty good for metal, too.

A computer case will rattle like a mofo.

Without pulling them, you should be able to see if you can measure a voltage across them with the power on. If you do, you've got an open, since there should be no voltage drop  across a good fuse (actually, there will be a super small drop across a good fuse).

How does the tone stack differ from the Doctor Boogie tone stack? Can't find the schematic anymore, but it seems you had a buffer after the tone stack. Also, have you considered selling any PCBs?

It would be best to have a separate clean channel all together. High gain circuits, like the Dr. Boogie, are going to cut lower frequencies to keep the distortion from getting too muddy. If you simply bypassed a stage or too or attenuated the signal before the DB circuit, you won't get as good a clean sound as you would get with a different preamp optimized for a clean sound.

I've seen mensur's schematic, but can't find it any more, so I can't really tell you the difference. If I remember correctly, he had a buffer after the tone stack, and the tone stack had different value pots and caps. The DB uses j201's with a 9v supply while Mensur used 2n5754's with a 24v supply if I remember correctly. I don't remember the differences with the PCB layouts. Perhaps Mensur's isn't as compact, since he's not worried about fitting it in a stomp box. I know some Dr. Boogie layouts can have problems with oscillations. Perhaps his layout is less prone to such problems. Maybe Mensur will enlighten us.

I think his version of the Dr. Boogie is just a little bit different.

Hehehe, I'm glad I'm not the only one. Makes me not feel so silly.

I think he might just be looking to buy a pcb from someone. Maybe someone made a reply regarding this and I'm not reading all the replies. His choice of words are perhaps ambigious. At first read, it seems like he is saying "A mesa style solid state project would be perfect for me. (can you point me in the right direction)" where he might have meant to say "A mesa style solid state project would be perfect for me. (I'm sure glad I found this thread)".

Holy *s!!t*, I didn't pay close attention did I. :loco

Check this out: http://gaussmarkov.net/wordpress/circuits/dr-boogey/. I've built this one, and like it. There is also a variation of this build by Mensur, one of the users on this site. Do a search on Mensur's post, and you'll run across it.

The gain of these inverters can be tweeked via the ratio of the feedback resistor to the input resistor. Obviously not as good has having the differential input of an op amp, but definately doable.

I wouldn't use the Fetzer valve topology for a buffer. A simple op-amp buffer would work great. A MPF102 source follower would be fine two.