About Guitar Amps Newsletter 25th June 2007
About-Guitar-Amps Newsletter
Welcome to the latest update from About-Guitar-Amps.com. I hope you find
the information here useful.
As always, please contact us if you have suggestions related to Guitar Amps that you would like to see on the
website or in our newsletters, or in fact if you would like to write an article for the newsletter : ) You can email or use the contact form
on the website.
New Schematics Added since the last Newsletter Latest Guitar Amp Schematics
Hope these help : )
Marshall Schematics Updated 6th May 2007
Fender Schematics Updated 6th May 2007
Carlsbro Schematics Added 21st June 2007
Engl Schematics Updated 21th
June 2007
Trace Elliott Schematics Updated 21st June 2007
Roland Schematics Added 25th June 2007
Amcron and Crown Added 25th June 2007
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Pots Confuse! - This article on Potentiometer Marking is one I hope will
help
Potentiometer Markings
This is something that can be confusing sometimes. The codes used were standardised, then changed, but unfortunately there was a period of time between changing when a Linear Pot with the old code and Log Pot were both marked 'A' - Confusing eh!
The codes for Lin (Linear) Log (Logorithmic) and AntiLog (Reverse characteristic of Log) are shown
below.
Taper Old Code New Code Alternate Linear A B LIN Log (Audio) C A LOG Antilog F N/A N/A
As far as resistance value marking goes this isn't standardised but goes something like this:
A 100k pot could be marked as 100K or 104 or 10, followed by 4 zeros, or 100000 (100k)
ohms.
So what happens if the markings are missing, soldered over, or illegible? How do you find the value of a
Pot.
Well this is what I normally do. Measure accross the two outside tags of the pot (assuming the pot has three
tags that is) with an ohm meter - the reading in ohms from your ohm meter will be the value of the pot.
To work out if the pot is LIN or LOG, turn the pot spindle to half it's travel and measure the resistance
between one of the outside tags and the centre tag. If the reading on your ohm meter is about half the resistance between the two
outside tags, then the chances are it is a LIN pot. If the reading is much higher or lower than the value of the pot then it's probably a LOG
pot.
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Useful Websites
I came accross this website the while back and it has a lot to offer
If you scroll down to Guitar effects and amplifiers you'll find 20 odd guitar amp
schematics
but then there are 50 or so effects schematics plus a variety of other interesting circuits like
tube mic pre amps, a simple mixer, 10 band graphic and even a Theremin!
If you've never heard of a Theremin check this out - it's amazing
If you ever want some data on Transistors, IC's etc There are three I use
http://www.datasheetcatalog.com/ (this is the one I prefer)
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Your Feedback Welcome here http://www.about-guitar-amps.com/Contact_Us.html
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See you next time : )
David
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