Deacon Posted February 28, 2006 Share Posted February 28, 2006 Here's a couple of questions for you amp gurus. I'm familiar with concepts about guitar pot values, but what about amp pots? I'd like to know if changing the value of the gain pot would make any difference, or have any benifit. I'm talking about 15w solid state amp with a 100k gain pot. And related to this, are there any good sites or forums that deal with mods and DIY specifically for solid state amps? I've found some great amp sites (amptone, for instatnce), but they all deal almost exclusively with tube amps. Link to comment Share on other sites More sharing options...
Pappy P Posted February 28, 2006 Share Posted February 28, 2006 Did you check out the Ask Myles Thread? He knows a lot about amps. www.birdblues.com My Stuff On Sound Click Link to comment Share on other sites More sharing options...
JipThePeople Posted February 28, 2006 Share Posted February 28, 2006 Deacon - This may be too much information but here goes: SS distortion is typically achieved using an op amp with an input resistor and a feedback resistor (i.e., one end connected at the input, the other end connected at the output). Two diodes are then connected either from the output of the op amp to ground or in the feedback loop of the op amp. The diodes will limit the signal once the level reaches a certain point and this is where clipping is achieved. So, tweaking the pot value to a higher value MAY increase the gain, but it would depend where in the circuit the gain pot is located. If it is in the feedback loop of the op amp, then a higher value pot will give you more gain. If however the pot is located in front of the op amp/gain circuit and it acting as a signal attenuator, then a higher value pot will accomplish nothing. One more thing, if you replace the gain pot with a higher value, make sure you use the same TYPE of pot (there are linear tapered and audio tapered). Check out this book: http://www.amazon.com/gp/product/0825695023/qid=1141147950/sr=2-1/ref=pd_bbs_b_2_1/102-2300395-8446528?s=books&v=glance&n=283155 It is an older book and I don't know if there has been an update lately but is a good book for making your own pedals, etc. Good luck! Link to comment Share on other sites More sharing options...
LPCustom Posted February 28, 2006 Share Posted February 28, 2006 Originally posted by Deacon: Here's a couple of questions for you amp gurus. I'm familiar with concepts about guitar pot values, but what about amp pots? I'd like to know if changing the value of the gain pot would make any difference, or have any benifit. I'm talking about 15w solid state amp with a 100k gain pot. And related to this, are there any good sites or forums that deal with mods and DIY specifically for solid state amps? I've found some great amp sites (amptone, for instatnce), but they all deal almost exclusively with tube amps. In general most people don't fiddle about with SS amps much. They are PCB based amps that have transistors that are not easy to substitute. It's doubtful that you'll get any more gain by changing the pot, though. A pot is just two resistors with variable resistances that always add up to the stated value. The signal is merely routed more in one direction than another based on the resistance of the two legs of the pot. With the gain pot maxed, all of the signal is going for gain because that leg of the resitor is basically set for zero resistance (0 ohms). With the gain pot turned all the way down, all of the potential signal for gain is typically routed to ground rather than to the next stage. Born on the Bayou Link to comment Share on other sites More sharing options...
LPCustom Posted February 28, 2006 Share Posted February 28, 2006 Originally posted by JipThePeople: Deacon - This may be too much information but here goes: SS distortion is typically achieved using an op amp with an input resistor and a feedback resistor (i.e., one end connected at the input, the other end connected at the output). Two diodes are then connected either from the output of the op amp to ground or in the feedback loop of the op amp. The diodes will limit the signal once the level reaches a certain point and this is where clipping is achieved. So, tweaking the pot value to a higher value MAY increase the gain, but it would depend where in the circuit the gain pot is located. If it is in the feedback loop of the op amp, then a higher value pot will give you more gain. If however the pot is located in front of the op amp/gain circuit and it acting as a signal attenuator, then a higher value pot will accomplish nothing. One more thing, if you replace the gain pot with a higher value, make sure you use the same TYPE of pot (there are linear tapered and audio tapered). Check out this book: http://www.amazon.com/gp/product/0825695023/qid=1141147950/sr=2-1/ref=pd_bbs_b_2_1/102-2300395-8446528?s=books&v=glance&n=283155 It is an older book and I don't know if there has been an update lately but is a good book for making your own pedals, etc. Good luck! Exactly. What I was referring to is the second case. I don't have any amps or (schematics for them) that are wired to work in the first manner. Great recommendation on the book, BTW. Born on the Bayou Link to comment Share on other sites More sharing options...
Deacon Posted February 28, 2006 Author Share Posted February 28, 2006 Thanks for the replies. This is exactly the kind of information I'm looking for. And LPCustom, your comment about PCB based amps and transistors makes a lot of sense. I've recently gotten into DIY effects building and I can understand amp owners not wanting to get into this kind of mod. PCB's are an acquired taste. Link to comment Share on other sites More sharing options...
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