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cctsim
Silver Member
United Kingdom
418 Posts |
 Posted - 06/22/2009 : 02:49:57
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Hi Guys,
I was wondering if members of the forum would be interested in a circuit simulation tutorial based on something simple like the tone stack of a boss pedal but with scope to extend to more advanced stuff like clipping, etc.?
I could prepare something if there is interest.
I am currently using LTspice but the principles should be the same for other programs. LTspice is free and good enough for me anyway. Also, I am not an LT employee.
Best Regards
Harris
Circuit Simulation Tutorial (in 20 steps, or so)
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The aim is to simulate the frequency response of the 1st stage tone stack of BD-2 and optimize individual components. Here is the schematic of the circuit:
Step 0: Download and install LTspice from
http://ltspice.linear.com/software/LTspiceIV.exe
Step 1: Start LTspice and create a new schematic and save it. The name is arbitrary, I've used "boss_BD2_1"
Step 2: To place a component, such a resistor, capacitor etc we can use the available toolbar:
Step 3: Click on the resistor icon and press Ctrl+R to rotate the component (if necessary):
Step 4: To change the name of the resistor, right click above R1 and type R36 to conform with the BD-2 schematic:
Step 5: To change the value of the resistor, right click above R and type the required value. You can use k for kilo, and Meg for Mega.
Step 6: To move the component we can use the corresponding icon:
Step 7-9: Repeat a similar procedure for the capacitor C26. For capacitor values, u stands for micro, n for nano and p for pico.
Step 10: Repeat similar procedure for the rest of the circuit. Finally, we add two ground symbols too.
Step 11-12: Now we need to add a voltage source by clicking on the component icon and selecting voltage from the dialog window:
Step 13: Right click on the voltage symbol to enter the required parameters and click "Advanced":
Step 14: For the frequency analysis, we enter DC 0V, AC 1V and phase 0 (degrees) on the corresponding entries.
Step 15: Once finished, we can use the "Wire" icon to connect the components:
Step 16: The complete circuit should look as below. To run the simulation we press the corresponding icon:
Step 17: From the simulation dialog we select the AC analysis TAB and enter the following parameters and press OK:
Step 18: Once the simulation is complete we can click on a specific node to see either the voltage of current response. Since we have used the 1V as input the output voltage (at right side of C34) represents the voltage transfer function of this circuit.
Step 19: To add grid on the plot, you can right click on the plot and select grid.
Step 20: To get rid of the phase plot, left click on the right axis of the plot and select "Don't plot phase"
This plot maybe explains the sound characteristics of BD-2 in a pic:
Now if we want to change the values of a specific component, lets say R36, and see how the frequency response is affected. In this example, we change R36 to take the following values: 10k, 22k, 47k, 100k and 220k. To do that, we need to use a parametric value for R36. From the edit menu we select "Spice Directive" or press S on the keyboard and enter the following:
We need also to modify the value of R36:
If we run the simulation again we obtain the parametric frequency plot with respect to varying R36.
Similarly, we can use the same principle to vary other components in the circuit.
I hope it was helpful for all of you technically minded modders.
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Edited by - cctsim on 06/24/2009 01:29:35 |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 06/22/2009 : 03:24:12
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| A simple tone stack of a vintage amp would be killer. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/22/2009 : 03:51:38
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The idea is to demonstrate the principle of simulation. After that, you could simulate anything provided you have the schematic.
I have already the first tone stage of BD-2, which is based on the fender bassman tone stack (I think).
Which vintage amp do you have in mind ? Could you provide a schematic ? |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 06/22/2009 : 04:44:30
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| Nothing specific I suppose.. probably just an old Fender Deluxe Reverb or something. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 06/22/2009 : 09:45:40
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Hi cctsim
Sounds like a great idea to me. 
Regards Dr. Bob  |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/22/2009 : 10:50:18
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Hi Dr. Bob,
I am in the process of preparing the screenshots for the tutorial. What is the best way to copyright the images so that they are associated with bossarea.com ?
I remember you did something similar but I can't find the images. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 06/22/2009 : 11:58:22
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quote:
Originally posted by cctsim
Hi Dr. Bob,
I am in the process of preparing the screenshots for the tutorial. What is the best way to copyright the images so that they are associated with bossarea.com ?
I remember you did something similar but I can't find the images.
Hi cctsim
Here is a link to some of my pics in the Pedal Internals thread:
http://www.bossarea.com/forum/topic.asp?TOPIC_ID=4147&whichpage=15
I have been adding the following (yellow) text to the pictures:
� Dr. Bob posted to www.bossarea.com
Or something similar in your case.
It's a bit of free advertising for the site, in case someone finds them posted in another forum-site-CD, or where ever.
Plus a lot of us, go to great effort to take these pics, & then upload them tot he forum.
Basically it's credit where credit is due.
Although not everyone is of the same opinion.
Hope this helps you out.
Regards Dr. Bob
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 06/22/2009 : 23:08:50
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| cctsim - this is killer! Thanks! |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/23/2009 : 00:03:22
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| Cheers Laurie ! |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 06/23/2009 : 00:11:01
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| nice man |
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moonmarkcus
Silver Member
Nicaragua
224 Posts |
Posted - 06/23/2009 : 03:21:24
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Hey ... my friend....Thank you, you�re awesome!!! 
Thank for share your wisdom...
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 06/23/2009 : 09:17:33
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Hi cctsim
Excellent Work & Tutorial...
Nice job on the DIY Chip adapter in the other thread as well.
Regards Dr. Bob |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/24/2009 : 01:31:04
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Update: I added how to automatically vary specific components to get the parametric frequency response.
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bassinyourface
Bronze Member
France
76 Posts |
Posted - 06/25/2009 : 21:05:58
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Hey man this is an awesome topic !
Thanks ! |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/30/2009 : 13:37:58
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Update: Added simulation file under:
uploaded/cctsim/boss_BD2_1.jpg
Download this file, rename it to
boss_BD2_1.asc
and open it with LTSpice to run the simulation. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/05/2009 : 06:39:23
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| Just downloaded and tried LTSpice. This tutorial made getting up and running a breeze - without it, I would have been slogging through the manaul and help files. |
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Topic |
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Circuit Simulation Tutorial (Frequency Response)
