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previous: Tom Hmm I see. Very interesting. I gues... -- 1/8/2001 1:34 AM View Thread

Re: A bunch of really stupid questions

1/8/2001 4:22 AM
Steve F
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Re: A bunch of really stupid questions
"Hmm I see. Very interesting. I guess whatever source I read about capacitors was crappy."  
 
 
 
Maybe, but maybe you just misinterpreted something that you read - capacitors can be used to store a charge which can be released all at once, as in a photo flash. But it doesn't go through the  
 
dielectric.  
 
 
 
"So from what you're saying, theres already a lot set-in-stone EQing that has happened before the signal has even reached the EQ."  
 
 
 
Well, sort of. This usually takes the form of  
 
smaller caps used as coupling caps to cut out  
 
some low end, bypass caps around volume controls,  
 
etc. As far as being set in stone, not really. These are really among the easier things  
 
to change on most tube amps because you can just  
 
swap parts out. It's easy to reverse if you don't  
 
like it, too.  
 
 
 
About a couple of your other questions - maybe I  
 
can provide some answers without taking up too  
 
much space:  
 
 
 
Regarding the "pitchfork" shaped symbol on some  
 
schematics, that's a schematic representation of  
 
a connection to the circuit ground.  
 
 
 
About resistors - they fulfill so many functions in  
 
amp circuits that it's not practical to discuss here.  
 
 
 
Re: transformer lead identification. Most transformer manufacturers standardize the color coding of the wires coming from their  
 
transformers. These color codes may or may not  
 
match up with those of other makers. There is  
 
"sort of" a standardization of the leads found  
 
on typical power transformers, but I doubt it's universal. The following is typical of many units:  
 
 
 
Black - primary connections (connects to 120V)  
 
Red - secondary connections (high voltage supply)  
 
Red/Yellow - secondary centertap (if present)  
 
Green - 6.3 V filament connections  
 
Green/Yellow - filament centertap (if present)  
 
Yellow - 5 V filament connection (for rectifier tubes, typically)  
 
 
 
Some guitar amp transformers will also have windings  
 
for supplying a lower voltage for the bias supply.  
 
That's typical of the units used in Fender amps,  
 
for example. When checking out an unknown power  
 
transformer, some recommend using a low voltage source such as a 120V/6V transformer to  
 
feed the primary of the unknown unit, and checking  
 
the voltages at the various pairs. The voltages  
 
found will be proportionally lower - just multiply  
 
them all by 20 to get the approximate value you'd  
 
get if the transformer is connected to 120VAC.  
 
Sounds like good advice to me, it's a lot safer,  
 
for sure.  
 
 
 
Best regards,  
 
Steve F.