A cellphone is not intended for decent output. Please try a quality source to see if the amplifier performs as it should before changing anything.
To increase the sensitivity, you can eliminate the feedback resistor 6.8 kΩ and reduce the resistor 150 ohms in the emitter 2n5401 to 51 or 27 ohms.
BD139 / BD140 fit as drivers
BD139 / BD140 fit as drivers
Clarification: increase the 6.8 kΩ feedback resistor to 12 kΩ and reduce the 150 Ω resistor in the 2n5401 emitter to 51 or 27 Ω.
Hallo all,
I have tested the amp with an active preamp between a Cellphone output and the amp. It sounds good. Any recommendations of an easy preamp that I can build with discrete trannies or NE/ TL chips that will do a decent job ?😀 The mains tranformet that I am using has 9Vac and 15Vac aux windings. Perhaps Project 88 (espn)from Rod Elliot ?
Regards
Jan
I have tested the amp with an active preamp between a Cellphone output and the amp. It sounds good. Any recommendations of an easy preamp that I can build with discrete trannies or NE/ TL chips that will do a decent job ?😀 The mains tranformet that I am using has 9Vac and 15Vac aux windings. Perhaps Project 88 (espn)from Rod Elliot ?
Regards
Jan
Thanks Terry, do you perhaps know If there is a pcb layout in pdf format ? I will go search, much appreciated !🙂
Mile posted two Linear Pre's. The original was inverting. It sounds really good but inverts the signal. He then posted a non-inverting schematic. I did a layout for both but the use some SMD parts. I will post both of them and you can decide if you want to build them.
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Thanks Terry, I have finished with the build, will test tomorrow, your help is much appreciated, good to see you active again, keep well !🙂
I have had a chance to finish these nippers, build an Apex preamp to drive them. Have biased the modules at 8mv with .33R source resitors. Rail voltage is 59Vdc. It will be used as a barbeque ( Braai in South African) bar amp. It sounds very good, very sweet sound. Thanks Miles !! and Terry😀
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Good day all, guy's need some help plse. As with single rail amps, its makes a dreadful sound on switch off. Is putting a relay on the output the easiest way to just disconnect the speakers ?🙂
Regards
Jan
Regards
Jan
would a 2k2 -1W across speaker terminals help here? just surmising here based jlh1969 type implementation..
Morning Prasi, I have not tried it yet, toooo busy with other stuff that needs my attention, will hopefully get a chance later in the week.🙂
Good day all,
Plse help with a little advise, With this preamp, what will be the bad if one uses a 20K pot i.s.o a 5K pot. The pot seems to be in the feedback loop, will it be detrimental to the sound when using the 20K? I have the 20k in now and it does not sound bad, I am just wondering 🙂
Regards
Jan
Plse help with a little advise, With this preamp, what will be the bad if one uses a 20K pot i.s.o a 5K pot. The pot seems to be in the feedback loop, will it be detrimental to the sound when using the 20K? I have the 20k in now and it does not sound bad, I am just wondering 🙂
Regards
Jan
