Well there are two reasons that made me do this.
First of all i really miss that happy feeling everytime the R.O.G. guys release a new emu-circuit.
The second reason is that i read in an article that Slash used a JCM-800 master volume preamp (not the jubilee) for the recording of sweet child o' mine (one of my favourite licks).Grab your Les Paul switch to neck pup and you can nail that tone.
What i really did was modding my thunderchief clone so nothing really difficult here...
Samples as soon as i get my Cubase to work again...
Haaaappy New Year!!!
(http://www.geocities.com/electrictabs/jcm800.png)
Hey, that's the exact same thing I'm doing. I'm working on a 2203 JFET Emulation also. I have the schematic laid out, almost identical to yours. My tonestack is in a different place though.
Once I get it on breadboard and tested out I'll post results.
Quote from: vanhansenMy tonestack is in a different place though
well i followed the amp schem for placing the tone stack.looks and sounds good to me.
I'm working on one as well.
*cough*orange 1974-era MKII graphic 120watt*cough*
(you can imagine my excitement)
I'm waiting on my caps and FETs and enclosure bits and peices from smallbear to finish it up, but my layout is done and i have the majority of it hooked up already.
I can't freakin wait.
Quote from: electrictabsQuote from: vanhansenMy tonestack is in a different place though
well i followed the amp schem for placing the tone stack.looks and sounds good to me.
I just looked at mine again. It actually is in the same spot. I some errors in mine though after comparing the amp schematic with it. It's my first shot at an emulation and it's been a few weeks since I've looked at it. Gotta study it some more (learning experience for sure)
Can't wait to hear some sound clips.
I see the difference between your schematic and mine. I was using only half of each preamp tube, like the Thunderchief, but yours has a J201 for each half. Off the first J201 I put a 10K to ground rather than the resistor/cap combo. Same with the second J201, only a 1K resistor to ground. That and I had the second 470p/470k junction between the preamp volume pot and the second J201, then on to the tonestack and on to the end like the Thunderchief.
Once I acquire all the parts to do this, which I hope I can do soon, I'll have to see how my schematic sounds versus yours.
Is the voltage bias for the J201's 4.5v in your circuit?
I love what you guys are doing. I would love to make an emu of the Mesa-Boogie Mark IIC+ but the schematic I have isn't clear and I can't read the values. Anyway, in order to do this do you guys use the exact same values for every component and just simply replace each half of the preamp tubes with an FET? If so are the FETs chosen by ear or another method?
PLEASE, post the results of that 1974 Orange :!:
Quote from: ragtime8922@aol.comAnyway, in order to do this do you guys use the exact same values for every component and just simply replace each half of the preamp tubes with an FET? If so are the FETs chosen by ear or another method?
Pretty much, yes, the same values are used. Some tweaking with values may be necessary here and there but in my comparisons with the emulations out there from ROG and the original amp schematics, the values are almost all the same. The fun part is in the phase inverter stage and the power amp stage. If you search the forum, you'll find a post I put up earlier this month or late last month about this as well. Bryan from ROG answered a lot of questions for me and explained the different stages.
The J201, MPF102 and 2N5457 are the ones I've seen most commonly used. Their pinouts match that of the Anode (Drain), Grid (Source) and Cathode (Gate) of a preamp tube.
Runoffgroove has some good info on this and diagrams in the FAQ. http://www.runoffgroove.com/faq.html
Thanks Vanhansen. What do I search for? ROG Emulations? Also, I didn't realize that the emus went further then the preamp. Are you saying that the power section is included in the emus? I was going to ask what was done after the master volume section of the jcm800.
Anyway, thanks!
-Chris
Quote from: ragtime8922@aol.comThanks Vanhansen. What do I search for? ROG Emulations? Also, I didn't realize that the emus went further then the preamp. Are you saying that the power section is included in the emus? I was going to ask what was done after the master volume section of the jcm800.
Anyway, thanks!
-Chris
Chris, here's the post.
http://diystompboxes.com/sboxforum/viewtopic.php?t=27611&highlight=
If you look at the Thunderchief schematic, the second to last JFET is the phase inverter, the last JFET emulates the power amp section, plus there's a dual low pass filter in there. So yes, the power section is included.
In the JCM800 that electriclabs did, and mine is similar, after the Master Volume comes the phase inverter, or the 3rd preamp tube. Then, after that, from the 22n to the last J201 is the power amp stage. The 2n2 off the volume at the end that eventually leads to ground through the 100k resistor looks like the low pass filter.
Now, you can rip out the tonestack for that "always on 10" sound. Again, referencing electriclabs' schematic, that would mean removing the components starting at the 4th JFET right before the tonestack through to the Master Volume. The 3rd JFET would then go right to the Master Volume or remove that as well and go right to the 22n cap at the start the phase inverter.
I hope all this makes sense to you. This is a new road for me. Actually, all of it is but the emulations have caught my attention big time since listening to the Thunderchief, Eighteen, Professor Tweed and the others from Runoffgroove.
Anybody, please correct me where I'm wrong, if I'm wrong (probably am somewhere a little bit).
Somebody build this thing already. I would now but I don't have time.
RDV
Quote from: RDVSomebody build this thing already. I would now but I don't have time.
RDV
And I don't have the parts yet. :cry:
Parts I got, time I don't. It really looks promising.
RDV
If anybody has parts, I knew you would, Ricky. :D Being relatively new to this I have yet to build up my parts bins. My mother-in-law may help me there with old VCR's and stuff she has in closets. Being that I have a breadboard now, I'm looking forward to building it.
Hey electriclabs, got your Cubase working yet?
Ricky, was my explanation a few posts up on the stages correct?
how does one go about making a JFET simulation of an amp? i would like to make a mesa boogie rectifier sim....
crp
alright, but what JFET to use?
crp
Thanks for helping out, Torchy. Happy New Year from across the great big pond.
panasonic_youth, not sure if you read the whole post but most of what Torchy mentioned I posted for another member earlier on.
Once you read the stuff posted here, study the ROG stuff, study the original amp schematics, it will all start to make sense.
alright, i still need a good referance for biasing, but aside from that, all i need is the money now. i have this lined up after a punch-in-the-face build, so who knows when i'll have the cash. haha. oh, also, which preamp version should i use: http://www.tubefreak.com/mesa.htm#recto . version 1 or two? the main differances seem to be for noise reduction, if im reading them right.
... all those trim pots.. for biasing the drain on each fet? to what value(s)?
Start with channel one. See how it sounds. Then try channel two. With something like this, experiment to find which channel sounds better to you.
As for biasing each fet, it can be different depending on the circuit. The Thunderchief biases at 4.5 volts as do a few other of the ROG emulators. You can start there and tweak to find the "sweet: spot.
Good luck and Happy New Year!
thanks van hensen. i just drew up #1, if anyone cares about it, i have it. looks like i'll have to break in and buy a multimeter after all. the question i have is this: do you have to change any of the component values to suit the differant voltages? and the rectifier doesnt use 12AX7s in the preamp, that wont mean anything as far as the JFETs go will it?
On the JCM800 emulator, I see that there's three volume controls: pre-volume (gain), master volume and volume.
Since I really don't need two volume controls, can I ditch the one of the two and still have a usable circuit?
Thanks for giving me yet another circuit for my 'to do' list that will never finish! :wink:
- Buck
www.bucksears.com
Quote from: BucksearsOn the JCM800 emulator, I see that there's three volume controls: pre-volume (gain), master volume and volume.
Since I really don't need two volume controls, can I ditch the one of the two and still have a usable circuit?
Thanks for giving me yet another circuit for my 'to do' list that will never finish! :wink:
- Buck
www.bucksears.com
if you ever got the chanse to play a jcm800 on full, you probably know that the trick to get them to sound GREAT is to balance the preampgain and the poweramp ( mastervolume ) against eachother. ofcourse that would be VERY loud and you probably need a powersoak of some kind..think of the gain and master as two different gains, giving different carracter, and the last volumepot as tha powersoak...
...I probably wount build this one since I allready have the amp :D , but the concept has been proven to work with all the R.O.G emulators, so..great work..
Johan
Quote from: JohanQuote from: BucksearsOn the JCM800 emulator, I see that there's three volume controls: pre-volume (gain), master volume and volume.
Since I really don't need two volume controls, can I ditch the one of the two and still have a usable circuit?
Thanks for giving me yet another circuit for my 'to do' list that will never finish! :wink:
- Buck
www.bucksears.com
if you ever got the chanse to play a jcm800 on full, you probably know that the trick to get them to sound GREAT is to balance the preampgain and the poweramp ( mastervolume ) against eachother. ofcourse that would be VERY loud and you probably need a powersoak of some kind..think of the gain and master as two different gains, giving different carracter, and the last volumepot as tha powersoak...
you couldn't answer better
thanks
Quote from: ragtime8922@aol.com
I love what you guys are doing. I would love to make an emu of the Mesa-Boogie Mark IIC+ but the schematic I have isn't clear and I can't read the values. Anyway, in order to do this do you guys use the exact same values for every component and just simply replace each half of the preamp tubes with an FET? If so are the FETs chosen by ear or another method?
this is what you ask for
http://diystompboxes.com/sboxforum/viewtopic.php?t=25327&highlight=mesa+boogie
edit:i also have to note that i omitted the dual lpf on the output of the jcm800 emu cause i prefer it that way.feel free to try for yourself which one is better.
...sooooo.. how does the sound compare to the real-meal-deal?
and how do these fet emulators work driving a power amp into a guitar cab?
or are they to be used guitar->fet emu->soundcard for recording?
i never managed to get that cleared up heh :lol:
i mean sure they can be used as preamps but what is the original idea, and for what purpose do you guys use them?
Quotefrom TubeFreak.com
By no means use it to try to built a replica, it won't work. These schematics are only here for information & repair. Trying to replicate it is useless
Does this mean that something critical has been left out on purpose to prevent replication?
Branimir -->
Quotefrom the ROG FAQ
Are the FET-based amp emulators used differently than other pedals?
No, they're regular stompbox circuits. Use them in the same manner as any pedal.
Quote from: ethrbunnyBranimir -->
Quotefrom the ROG FAQ
Are the FET-based amp emulators used differently than other pedals?
No, they're regular stompbox circuits. Use them in the same manner as any pedal.
oh. i always get confused with these devices since i know the same thing won't sound the same on a fender, marshall or a ss randall :wink:
dunno, i don't like tonestack when a tonestack is already present in a chain aftewards.. although these designs have simple tone controls.. hm...
well..
:shock:
back to the drawing board.
happy new year.
QuoteQuote:
from TubeFreak.com
By no means use it to try to built a replica, it won't work. These schematics are only here for information & repair. Trying to replicate it is useless
Does this mean that something critical has been left out on purpose to prevent replication?
On some of the schematics yea. Mostly, its useless to replicate because mesa amps use double sided PCB boards, and lots of parts. Also, it can potentially be very noisey if not layed out well. When decideding to do a jfet emulation of a mesa amp, you need to decided what fuctions you wish to settle on. For instance, do you want the red or orange channel? How will you handle the Negative Feedback loop, which is where the mesa's control the Vintage, Modern switch. Also worth mentioning is that the fets will sound diffrent than the tubes. You may need to alter some parts before everything sounds good.
How close (ly?) can FETs match tubes? Isn't this the basis of the whole SS v tube debate?
That's a whole 'nother subject. :D We're not trying to recreate the wheel, just putting a good sounding amp circuit in a stompbox form. Emulation circuits may sound somewhat tonally similar, but not exact 100%. They'll get in the ballpark though.
I was inspired to make an attempt at the JCM800 2203 after hearing the Thunderchief and studying the schematic with the original Marshall Super Lead schematic (1959 model).
I have a big Marshall amp already, but something like this would be great to use for practicing and noodling around without the neighbors hearing it.
Just waiting for Smallbear to reopen so I can get some parts.
smallbear is great for some stuff...
but i tried mouser out the other day and all i have to say is wow.
as soon as you get over the intimidating catalog, the prices and shipping are very nice. the packaging even gave me a warm fuzzy feeling in my heart...the appropriate static-guard baggies, an invoice indexing all the parts and so on. TWO THUMBS UP FOR MOUSER. if smallbear was a small army and he could get his stuff shipped faster I'd love him just as much. I'm waiting on a shipment i ordered like 3 weeks ago :roll:
PS - to you guys thinking there's no application for FET emu's with larger amps... I've got a 1974(or so, i havent dated it yet) silverface bassman that is cleaner than clean...so a nice FET in front of it gets it the dirt and dynamics it needs in those gainy situations. still EAGERLY awaiting my parts from smallbear to finish the '74 orange graphic 120watt FET. WOO
hello
if you're gonna breadboard this circuit try these out
they are not exactly mods but maybe sound better to your ears
since everyone is using different gear
1.the all knobs to 10 mod bypassing the eq
(just like in thunderchief)
resulting in just a little more gain
2.the dual lowpass filters on the output emulating some speaker response (refer to thunderchief schem if you don't know to do)
Thanks for sharing. My first schem eliminated the tonestack then I decided to add it in. Once I did that I also decided to put on the dual LP filters. Gonna be breadboarding it soon.
Has there been any progress with this? I'm starting to feel the burn to build this sucker.
Not on my end unfortunately. We're saving for a new house some a majority of my DIY has gone to the backburner. Pretty much have to use what I have and salvage parts. I'm sure someone has built this. I'd love to hear some some clips (dry, no reverb or delay) to get a general idea of how it sounds.
anyone have any clue how will this thing sound into a SS 100 poweramp and into the 2x12" celestion vintage 30s box?
:)
I built it and when audioprobing it sounded pretty great up to the "phase-splitter stage", which I couldn't get to bias properly with any of the MPF-102s that I have. It inherited the same hard-to-bias problem as the thunderchief which it was somewhat based on. Tried the ROG fix with little success. Hopefully the J201's from small bear that are waiting for me at home will work, but I won't know til May :(
Oh, and if you haven't seen it, there's a nice pcb layout that Bucksears made here: http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28551
(Scroll down a couple posts for the PCB)
Seems that Bucksears finished his and says he'll have sound clips up soon... so watch this thread if you haven't seen it yet!!!
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=31723
Can it get as close as this?
:lol:
http://home.comcast.net/~scottosan2004/GNR.mp3
Both links to sound samples are dead...
I wonder if the PAL 800 JCM emulator is based on this circuit? It looks similar, but it adds a presence control (good idea) and omits the pre gain control (bad idea...).