EFFECTS CONSTRUCTION Q&A
Q: What do I do with the ground connections?
A: This is by far the most frequently asked question. On my pc boards, all grounds are usually tied together to a common point that is labeled "GND" or maybe just "GR". This is the ground for the board and it should be connected to the power supply ground.
Usually the metal box for an effect is used as a universal ground. The input and output jacks' ground lugs will automatically connect to the metal chassis (unless they are the plastic body Re'an brand). The wire from the pcb ground connection can then be connected to one of the in/out jacks' ground lug; it doesn't matter which. The power supply ground ground also will connect to one of the in/out ground lugs - exception: see next question.
Q: You show a stereo jack on the input of the effect; is that right?
A: Sometimes a stereo jack will be used to switch a battery on and off. The tip connection of the stereo jack carries the signal and the middle (or ring) connection is wired to the battery ground (usually the black or negative wire). The body of the stereo jack is grounded to the case, as with a mono jack.
When a mono cable plug is inserted into the stereo jack, the middle connection is connected to ground by the body of the plug, since there is no ring connection as with a stereo jack. Therefore, this allows the battery to make connection to ground thus completing the circuit and allowing power to flow. Once you are through using the effect, the plug is pulled from the jack, the battery connection is then broken and no current flows. Typically I put this battery switching circuit on the input jack.
Q: What is the point that is labeled as "Vr" on the schematics?
A: That merely stands for "Voltage reference". All points labeled as Vr should be connected together.
Q: What software do you use to do your schematics and PCB layouts?
A: This is probably the second most frequently asked question. I use "Fontasy" which is an old DOS drawing program in which I created special fonts with pcb pads. It works quite well for me but I have been using it for probably 10 years. I tried to buy the rights to this program to sell this as a pcb layout program to go with my special fonts, but was unable to get the owner to do this. I cannot find this software anywhere on the web.
Q: Can you put up a wav file for "xxx" project or effects unit?
A: Probably not. The reason is that I only have a limited amount of online storage space and much of it is already taken up with articles, schematics, etc. I have been thinking about putting up a different wav file each week so that everyone can have a chance to hear each effect.
Q: What should I use to draw schematics and PCB layouts?
A: I suggest that you look at Paint Shop Pro (PSP). It is available from Jasc Software and is easy to use and powerful. I have used it on a couple of the schematics. You can easily cut and paste symbols from other schematics.
Also EasyTrax is available from Protel as freeware. Many people swear by it but I have found PSP to be more to my liking.
Q: Can I substitute a component with a close value to the one shown on your schematic (ex: 47k potentiometer for a 50k unit, or a 270 pF cap for a 250)?
A: Yes, components within 10% of the listed value should be no problem. There may be special cases where this isn't a good idea, and that will be addressed in the article for that project.
Q: Where are the power supply connections for the ICs?
A: The most common pinout dual op-amps like the TL074 and similar use pin 8 for V+ and pin for V- (which is sometimes grounded). A single 741 type op- amp uses pin 7 for V+ and pin 4 for V-. Special IC chips like the SSM2165 have custom pin designations which should be detailed on the schematic. You can always follow the traces on the pc board to see where the power supply connects to the chip.
Q: I have built one of the effects and it doesn't work. Can you help troubleshoot it?
A: Maybe. Since I can't see or hear the unit and cannot measure voltages on the board, this is very difficult.
Start to find the problem by measuring the dc voltage supply and see if it appears to be correct. Follow the power supply trace to the chip and see if the proper voltage is present. Is the chip oriented in the socket correctly? Are the transistors wired properly (are you sure; this is a common problem)? Is the ground commonly connected to in/out jacks and pcb? Are the diodes oriented properly? The band on the diode corresponds to the end of the diode on the schematic that the arrow is pointing to... that is, the bar on the diode schematic and the band on the physical device are on the same end.
Most importantly, check and recheck your work, especially the orientation of transistors, diodes, IC chips, and electrolytic capacitors.
If you get diodes or transistors too hot while soldering, they can be destroyed. Radio Shack sells small copper clips that I use as heat sinks when soldering.
Q: I cannot download your schematics, can you e-mail all of them to me?
A: Yes, I really get this question and the answer is: No, absolutely not. My web site gets 10,000 to 15,000 hits per month and I get hundreds of e-mails. I like to use my leisure time to design and build effects instead of collecting together files to send; that's why they're online for you to retrieve for free. My best advice is that if you are getting what appears to be a blank GIF, save that file to disk and open it offline with a graphics program such as Paint Shop Pro. I have found that usually works. I check every single file after uploading so I know that the links will work. AOL can get very busy during the evening hours and it can be slow in sending the images.
Q: Where can I find 1N34a diodes? 1N914 diodes? 2N3904 transistors?
A: Radio Shack, Mouser, Digi-key, etc. These are common components.
Q: Can you build me a custom effects unit?
A: Yes, starting price is $200. Extra charges for expensive chips, special chassis or other custom components.
Q: Do you know that there is already a band named "xxxx" that you have listed on your band names page?
A: Yes, no matter what the name, someone has e-mailed me before on it you can be sure.
AMZ-FX Home Page
Lab Notebook Main Page
Guitar Effects Blog
©2016 Jack Orman
All Rights Reserved
AMZ-FX Home Page Lab Notebook Main Page Guitar Effects Blog
©2016 Jack Orman