New Project : Marshall Amp-Speaker Simulator

[Michael Allen]

I'm planning on boxing this up with a Condor for a double sim box to use for recording. Marshall or Fender?

http://www.freewebs.com/loudnoise/

[stm]

Just try the Condor with the components shown in the next figure.  Now a simple DPDT switch can change from Fenderish to Marshallish instantly!



Notice only two caps need to be switched.  Rest of the circuit is as shown at ROG.

These are the resulting curves (Blue:Fender / Red:Marshall)



Have fun!

STM

[Michael Allen]

In my quick scan it looked like there were more parts that needed to be changed to accomdate the marshall mod. I might just try that. Anyways if you want to build the marshall sim....

[B Tremblay]

The above partial schematic contains some "artifacts" from the circuit simulation - specifically, showing R12 and R23 connected to ground.  Those resistors still need to connect to Vref, as shown in the original Condor schematic.

Also, the "Fender" curve in this 2-in-1 version is different from the original Condor.  During my testing, I found the original Condor sound to be superior.    

(STM, please e-mail me)

[changes]

stm is there any mod for a vox cabinet

[StephenGiles]

STM - I may be mucho loco or maleducado, and suffering from the ill effects of dulce de leche, but what do X5, X6,X7 etc stand for? By the way, my wife is planning a visit to Cordoba, Argentina next year which will be the nearest we get to Chile this time.
Stephen

[B Tremblay]

what do X5, X6,X7 etc stand for?

Those are op-amp buffer stages.  The feedback connection isn't shown, nor are the inputs.  Another artifact of the circuit simulation.

I highly recommend that builders first breadboard the original Condor if they're considering the version posted above by STM.  Using the "Condor - FNDR" values does not sound the same as the Condor posted at the 'Groove.  The difference may not matter to you, but I found it quite noticeable.

[stm]

Sorry if the circuit caused confusion.  As Brian from ROG states, this circuit was taken directly from a SPICE simulation, and is not a circuit to build just as it is.

I said in my message you have to COPY the corresponding component values into the Condor circuit.  Also, the Vref statement is absolutely valid.  Just substitute values into the circuit.

By the way, I am using "unity gain buffers" in the sim, labeled as X1, X2 etc.  The X is the prefix for macros in SPICE, but in the real circuit you have the op-amps connected as unity gain followers.  (I used them for speed and simplicity in the simulation.)

The statement that the adapted Fender values do not sound identical (and not as good) as the original Condor surprises me, but it is a valid possibility.  Let's me explain:

In order to simplify the components that need to be changed from 6 to just 2 capacitors I had to do some trade-offs in respect to the two original curves.  One could say a-ha! then they should sound different.  However, the values I suggest produce frequency responses that differ a maximum of +/- 1 dB from the original Condor and Marshall curves, which in my *belief* shouldn't matter.  However, I have not breadboarded both circuits to do a *hearing* comparison, so perhaps they actually matter.

I need to give it a further revision.  For the moment, here are the "original" and "new" curves obtained with the suggested circuit:



Red and Blue curves are the curves of the proposed circuit above.
The other curves are the original ones.

Regards,

STM

P.D.  Brian, I haven't got mail from you since the Condor was officially launched!  Will check my e-mail account, since I suspect it could be a kind of automatic anti-spam service that's blocking your address.