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ALLisNOISE wrote:you can dial in some wonderfully smeared 12bit cascades of cicadas leveling a hail of rockets against an army of rusty box fans!
ALLisNOISE wrote:you can dial in some wonderfully smeared 12bit cascades of cicadas leveling a hail of rockets against an army of rusty box fans!
ALLisNOISE wrote:you can dial in some wonderfully smeared 12bit cascades of cicadas leveling a hail of rockets against an army of rusty box fans!
goroth wrote:If my shitty understanding of electronics is correct unity should have R3 and R4 roughly at similar values.
Zork wrote:I've got some GT308 with a hfe of roughly 60-70 and a few AC126 and AC125 with hfe of about 110. Which one would you choose? To my understanding, the GT308 are much more stable and less sound shaping than the AC125/126 but the hfe value is crucial to the amount of amplification in the LPB-1. The 2n5088s or 2n5133s commonly used in the LPB1 seem to have a hfe higher than 300 typically.
crochambeau wrote:goroth wrote:If my shitty understanding of electronics is correct unity should have R3 and R4 roughly at similar values.
Close, but not quite.. making R3 & R4 identical will simply limit the available output swing the transistor can produce to about one half of the rail voltage (internal equivalent resistance of the transistor in saturation/full on will slightly change the absolute value of the "voltage divider" comprised of R3 & R4). The Beta, or gain, of the transistor can still take a lower level signal and push it up to that point.
ALLisNOISE wrote:you can dial in some wonderfully smeared 12bit cascades of cicadas leveling a hail of rockets against an army of rusty box fans!
goroth wrote:Yeah, if you've already got one just turn the volume down to unity and see if it does the trick, for sure.
crochambeau wrote:goroth wrote:If my shitty understanding of electronics is correct unity should have R3 and R4 roughly at similar values.
Close, but not quite.. making R3 & R4 identical will simply limit the available output swing the transistor can produce to about one half of the rail voltage (internal equivalent resistance of the transistor in saturation/full on will slightly change the absolute value of the "voltage divider" comprised of R3 & R4). The Beta, or gain, of the transistor can still take a lower level signal and push it up to that point.
I like to settle on a value for R4 (which affects bias (which affects input impedance)) and reduce R3 (within reason) to reduce gain. You can also set up a voltage divider/set and forget volume control/trim pot after C2 to normalize levels, as sometimes toying with R3/etc. too much enters the realm of sounding like shit. A lot of classic designs also put the level management at R3 by turning that into two resistors and tapping a divided output signal from there
My advice would be to get your stage sounding the way you want, and then reduce level as needed with some R5 equivalent (it does not have to have a knob) or the R3 divider trick.
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