howdy folks, i decided to build this simple amp as a first step into building amps,,its a dean markley chip amp but the preamp is pretty cool,its capable of driving 10 watts into a 4ohms speaker.
i included the circuit here for anyone who's interested
anyways i have some points wich are not so clear to me in this circuit,
1/wuts the R1 for ?
2/about the caps its written for example c1= 473M,,, wut the hell is M?? microfarads?and some caps like c13 is 22/16 ,,whats that stands for? 22microF/16 volts??
3/i didnt get what the rocker switch connet n disconnect,,can anyone discribe the way it works(what terminals it connects n dont)?
4/about the pots ,, wuts A250K B250K ?? wut ranges should they take?
5/can i get rid of c19? or its better to have it?
6/wuts the point of having R10 and C11
7/any comments about what kind of speaker and op-amps are suitable for this circuit is pretty welcome
.....thanks already for any answers,,hope this amp sounds good

thnx teemuk for this explanation
i would consider a book but its so hard to find such books where i live.
thats why im goin for the net.
if you know some free ebook i can download it would be great.
thanks again

here is the schematic

Howdy folks, i was just surfin the rickenbacker site and i got this cool schematic ,,it looks neat and simple so i decided to included here for anybody interested.
if anybody knows how this amps sounds like let me know.
any explanation about the D1 D2 D5 D6 Q4 Q6 C4 is appreciated
,,have fun

i have seen many schemtaics that build preamps with discrete BJT or mosfet transistor voltage divider bias circuit gain stages..some others use opamps
any idea how does this affect the sound? which one is better?
because using opamps means including many transistors in the circuit,,doesnt mean slower response to the input signal?
and same question about tone controls,,,active or passive? any one knows what diefference in the sound dose it make?
thnks already for any answers

QuoteI can't really recommend you a schematic since I hardly know what type of music you play, what features you need, how much complexity in the circuit you "tolerate"

well i play country music and the blues
about the complexity of the circuit i just need a practical one containing all the circuits it should has,im doin the fifth year of electronics engineering so i can handle it if there is a little explanation,
although as a first build i would recommend a simple shot.

QuoteI suggest you make the preamp versatile and nice sounding, then build the power amp section based on a chip.

what do u exactly mean versatile? what can it has more than a tone control and amplification?
and im really considering desiging with discrete elements in the perpose of educating myself ,,i dont want chips.
its true what u say about that its a hard shot and maybe someone would quite but i think ill just work my ass off for it
thanks for noting about the websites lookslike there are loads of schematics over there,,but are they reliable to build?

QuoteTIP142/147 (output devices). This of course depends a lot on the circuit you are intending to build. Those are pretty good for a 60 W amp but overkill for 10 - 20 watts.

why overkill? what could go wrong if they dont use their full range of amplification?
anyways,, how many amps have ya built? whats the best shot for country music? ,,,maybe i should try to get the sound of tubes..

QuoteAccording to datasheet, 1N4007 should have a forward voltage of about 600 mV at 10 mA (my sim shows 7 mA through diodes at idle).

lookslike my proteus is using another type of 1N4007 ,,!!! possible?
i got really shocked on this. i spent hours to modify the design because of this.

QuoteI wouldn't build a unity gain power amp - or even a discrete power amp for less than 30 W of (RMS) output power.

...whats wrong with that? is it not worth the effort?

QuoteI have been dealing with amplifier circuitry (researching & developing, repairing, building etc.) for few years. I'm for the most part self-educated in electronics

thats Awsome,why dont u consider a career in amps! lookslike u have a big load of info about em.

also seems like the bootstrap circuit is some heaven for amp design.
anyways
im really considering to build a first amp
what schematic u think i should go for?
an opamp or the differential amp configuration for an input stage?
what power transistors u prefer for the output?
and about cutting high frequencies to protect the speaker,,is it a must?
should the -3db freq be at 20000hz?
how much phase shift is allowed for the sound signal to be heard without any distortion?
i also did read some stuff about ground loops,,here in the ssguitar and somewhere in epanorama ,its really somthing to be concernd about,
whats the best wiring u think to get rid of it? i liked the star one,lookslike its pretty neat.
again thank u and im sorry if im asking too much,its just im new to this.

thnks for the info.
lookslike the best deal is to design a preamp with a pot to adjust the gain.

i just have a little question,
whats the peak voltage an electric guitar can output?
isnt that something important to consider
when building a pre-amp ??

well thanks man you did a great job to the amp but i still have some points thats not so clear to me.
the diodes ,,,again,,the BE junction of the BD139 is not the same diode as the 1N4007.
i did some simulation to the circuit u attached,for example if the opamp out is at 0 volts,the amount of current thats gonna pass the first diode is about 10mA and this current introduces a 0.2 v voltage drop across the 1N4007 diode which is clearly pretty far from opening up the BD139 BE junction cuz its totally a different diode so there is clearly no quiescent current at all!
the BE junction of the BD139 introduces a voltage drop of 0.61 volts when running 10mA through it, while the 1N4007 introduces only 0.2 volts thats basically why i put 5 diodes in my design.
again,, werent you against using the 5mega resistors???
and also in the schematic u draw u havnt included a lowpass filter of 20000hz
is it that the zobel configuration is enough?
one thing more ,whats the bootstrap circuit for? i would really welcome a little explanation about it.
again really thanks for the great job uv done to the circuit and yes your modification really helped me understand more about ss amps.thanks alot.
how long have ya been in building amps?
did u build the schematic u included me?
does it work fine?

sorry again there is a mistake in the second resistor value in the bandpass filter
instead of 5k it is 11k to provide a gain of 12

well thanks man for being concerned in the design
first of all im sorry about the drawing,,ill make sure to make better drawing next times
second about the circuit ,,i havnt built the circuit but i simulated it over proteus. it works fine there .
about the diodes .... in the proteus software when using only 2 or 3 diodes the provide only around 0.5 voltage drop between the two bases .....is that enough to open up the 2 transistor base-emitter junctions to create some quiescent current?
by using 5 diodes i can have a voltage drop of 1 volts when the input signal is -0.5 and so i have 0.5 volts on each base emitter junction which is enough to create a quiscent current of 30mA .... thats what i see by proteus ,,,
and yes i mean by the downward arrow -15 and the uppward one +15.
i thought that this is very common.....
what are the vaules of the emitters resistors should be?
,,and about the unity gain stage. it is just to offset the signal by -0.5 volts,and i chose the 5 M cuz i didnt know that it would cause that much noise ,,thnx for the information..
again about the resistors to the collector of the transistor pairs ,ive seen schematics that include them and some they dont,, still not sure what s the main benefit of them.
thanks again for the schematic u included and do u know any source that explains that feedback u told me about? to include the output transistors in the feedback loop of the opamp?

hey folks ,,this is the amp that i told ya about ,,again i wanna say im new to this and i designed this one hoping it works
i would like to know if there is any mistakes and problems in this design.
the output transistors are
Q1 = BD139
Q2 = BD140
Q3 = BD540
Q4 = BD539
the op amp im using is the TL074 because it has a high slew rate about 13v/uS
in the offset circuit im using 2 opamps because one cannot sink the currnet coming from the diodes alone.
i put 5 diodes in series with the 0.8k resistor to provide quisent curent of 30 mA which i think is suitable and to provide enough voltage drop between the first two base emitter transistors junctions.
the offset circuit is nessasry bcz the output voltage is 0 when the input signal down the diodes is -0.5 volts,so i offset the signal by -0.5 volts before driving the power transistors
in the tone control citcuit im using a pot that should take the values between (10k and more) and a variable cap between (10nf and more)
to give the pot the minimum value which is 10k is to boost the bass.
to give the cap the minimum value which is 10nf is to boost the treble.
the bandpass fiter i chose is the first order one because the phase response is the best.
i hope that u guys tell me what do u think about this amp and any advice would be welcome.

alright im gonna post the schematic in the schematics section
and provide some info about the amp ..

Howdy folks, im new to this forum so i gorra say howdy to everyone.
my name is Ben and im an electronics engineering student.
pretty much interested lately in audio .
i have very much information about electronics and pretty good in theory but i havnt built my first amp yet.
it is time to do so,,i have designed the amp (20 watts) using proteus and matlab to design my filter and tone control.
i would like to anybody to see the schematic and give me advice on wether its gonna work or not ,,or if there are some mistakes .
if anyone is willing let me know.
general info about the amp : >>
im using the compound configuration for my power transistors
they are the BD139-BD140  OUTPUTS TO BD539-BD540.
outputs +-12 volts into 8 ohms speaker
i used a first degree band pass filter 20-20000hz
and the general filter configuration for the bass-treble control with the variable cap and a pot.
let me know if anybody is interested so we can talk this amp up

thankya'll already

BeN