Hi, No. And its a totally inept suggestion, rgds, sreten.
What is your problem with the LM386 ?
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it's meant to emulate the age ol' back to back zener diode clipper/limiter circuits.
it's used in many newer fender and marshall amps (nasty sounding if you ask me)
matter of fact if you read the notes on the supplied schematic it mentions how to achieve different distortion levels...
it's used in many newer fender and marshall amps (nasty sounding if you ask me)
matter of fact if you read the notes on the supplied schematic it mentions how to achieve different distortion levels...
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I like the way Fets sound when pushed a bit, mild overdrive. They are generally quiet and don't get all fizzy sounding. You can always switch in some diodes if you want that type of dirt, though.
Dear yeto, you posted it all over the Internet 😛
Already answered in full in your Music Electronics Forum post, where also distinguished Merlin B and Teemuk answered ... a dream team if you ask me 😀
As a side note, it is not
unless Rock Guitar distortion is considered an error and not part of the sound, that is.
As I mentioned in the answer elsewhere, a similar design was part of early SS VOX amplifiers (think what The Beatles used), and conceptually similar (although using FETs, go figure 😱 ) by Gallien & Krueger and H&H .
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guitarpoppa... please restrict all commercial sales to a single thread in VENDORS BAZAAR.
Thank you.
guitarpoppa... please restrict all commercial sales to a single thread in VENDORS BAZAAR.
Thanks you.
OK man, I apologize 🙁
Guitar Poppa
A smart micro amp that works great with guitar
Hello,
I have a solution for you...
>>> First, you'll have to connect a little power amp between your stompbox and any speaker. It should be about 1W, 9 or 12V supplied...
>>> Second, this amp should give a beefy sound even if the supply voltage his only 9V. It means its architecture has to be designed especialy for that use, not any common schematic that would be downsized, and would have very poor response on attacks and other peaks. The best circuits you could get as reference were designed in late 60s and mid seventies... They were devoted to car radios, and were able to give a maximum of power, with no losses, and with a good stability. They often have no bootsrap circuit, that always brings unsymetrical distorsion when overloaded, but a special negative feedback that uncompassed the whole circuit, and even the speaker. These schematics are a little forgotten now, but they are very better than the integrated circuits that came later, whose only interest was they were cheaper.
I have some of these schematics, that i have tested and optimized on computer simulation. I join one I often use...
>>> The best results according guitar sound is to use silicon transistors in the first stage (higher impedance, and low noise), and germanium in the power amp. The germanium gives a better overdrive and even very musical distorsion when cranked, and often an awesome compression on clear sound. The types on the schematic are common european germanium transistors. Russians MP38A (NPN) and MP42b, MP21 (PNP) will work very well in place off AC127 and AC125, respectively. AC180K/181K were the best push-pull at that time. AC128K/AC176K are good, a little less robust. AC188/187 were common, but the quality was not so good, they could be very leaky, and so difficult to bias. A good deal is AC141K(NPN)/AC142K(PNP), less known but very good and rather easy to find. Don't forget a little piece of metal as heathsink.
>>> On my schematic, the only setting concerns the symmetry of the push-pull. Adjust it with the 250k trimer, speaker connected. Adjust to have half supply voltage between ground and the common node of the two 1 ohm resistors. Then you can adjust with more sonic precision when playing near the maximum level. This way, you'll get a symmetric overdriven output signal, which is more consonant. As with every germanium circuit, those settings should be done after a least 5 to 10 minutes power on, letting all germanium cristal have their inner currents and temperature stabilized.
There is no zero signal current setting. The first reason is the germanium transistors have an "automatic" polarization through their own leakage currents. Young people and XXIe century techs usually can'y believe it, but its true, I'm 63 years old, I have always experimented that "good defect" in vintage electronics. There is a second reason : the 39 ohms resistor give just what need the power transistors to be a little biased when power is set on. Warming and leakage do the rest of the job... The germanium diode avoid thermal runaway.
If you prefer using silicon transistors, use the ones indicated on my sheet, or equivalents. The 39 ohm resistor should be upsized to about 100 to 200 ohms. You should use a trimpot and prudently increase the value of the resistance between the two bases.
Just 2 warnings :
-- Dont change the 39 ohm value with germanium transistors : with 47 ohms, the amp will not stand 12V supply...
-- Don't use less than 1 ohm resistors on the emitters of push-pull transistors : they assure a negative feedback that prevents the transistors from thermal instability an runaway.
I think you should try to realize that amp. I made numbers of them for me or some ather people playing guitar or harp. You'll be surprised by this tiny-beefy amp !
If you want more informations on such amps, just google "GeAmp1W"
Happy to give a hand !
Reggie, aka Guitar Poppa
Hello,
I have a solution for you...
>>> First, you'll have to connect a little power amp between your stompbox and any speaker. It should be about 1W, 9 or 12V supplied...
>>> Second, this amp should give a beefy sound even if the supply voltage his only 9V. It means its architecture has to be designed especialy for that use, not any common schematic that would be downsized, and would have very poor response on attacks and other peaks. The best circuits you could get as reference were designed in late 60s and mid seventies... They were devoted to car radios, and were able to give a maximum of power, with no losses, and with a good stability. They often have no bootsrap circuit, that always brings unsymetrical distorsion when overloaded, but a special negative feedback that uncompassed the whole circuit, and even the speaker. These schematics are a little forgotten now, but they are very better than the integrated circuits that came later, whose only interest was they were cheaper.
I have some of these schematics, that i have tested and optimized on computer simulation. I join one I often use...
>>> The best results according guitar sound is to use silicon transistors in the first stage (higher impedance, and low noise), and germanium in the power amp. The germanium gives a better overdrive and even very musical distorsion when cranked, and often an awesome compression on clear sound. The types on the schematic are common european germanium transistors. Russians MP38A (NPN) and MP42b, MP21 (PNP) will work very well in place off AC127 and AC125, respectively. AC180K/181K were the best push-pull at that time. AC128K/AC176K are good, a little less robust. AC188/187 were common, but the quality was not so good, they could be very leaky, and so difficult to bias. A good deal is AC141K(NPN)/AC142K(PNP), less known but very good and rather easy to find. Don't forget a little piece of metal as heathsink.
An externally hosted image should be here but it was not working when we last tested it.
>>> On my schematic, the only setting concerns the symmetry of the push-pull. Adjust it with the 250k trimer, speaker connected. Adjust to have half supply voltage between ground and the common node of the two 1 ohm resistors. Then you can adjust with more sonic precision when playing near the maximum level. This way, you'll get a symmetric overdriven output signal, which is more consonant. As with every germanium circuit, those settings should be done after a least 5 to 10 minutes power on, letting all germanium cristal have their inner currents and temperature stabilized.
There is no zero signal current setting. The first reason is the germanium transistors have an "automatic" polarization through their own leakage currents. Young people and XXIe century techs usually can'y believe it, but its true, I'm 63 years old, I have always experimented that "good defect" in vintage electronics. There is a second reason : the 39 ohms resistor give just what need the power transistors to be a little biased when power is set on. Warming and leakage do the rest of the job... The germanium diode avoid thermal runaway.
If you prefer using silicon transistors, use the ones indicated on my sheet, or equivalents. The 39 ohm resistor should be upsized to about 100 to 200 ohms. You should use a trimpot and prudently increase the value of the resistance between the two bases.
Just 2 warnings :
-- Dont change the 39 ohm value with germanium transistors : with 47 ohms, the amp will not stand 12V supply...
-- Don't use less than 1 ohm resistors on the emitters of push-pull transistors : they assure a negative feedback that prevents the transistors from thermal instability an runaway.
I think you should try to realize that amp. I made numbers of them for me or some ather people playing guitar or harp. You'll be surprised by this tiny-beefy amp !
If you want more informations on such amps, just google "GeAmp1W"
Happy to give a hand !
Reggie, aka Guitar Poppa
Hi Reggie, thanks for sharing your experiences and good explanation of operation. It would be a good start for someone wanting to build discreet low wattage amp, learn from it and apply to larger scaled amps. Learning the principles is important, and this is a good way to do it.
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