consider also the freq response of the speaker
some speakers cuts off lower than 70hz
some others let you hear 40 hz sound

a 4.7 ohms? that should be some kind of output stage resistor
, maybe when you hit the chord hard n load too much current passed by this little resistor and burnt it,,, change the resistor,,you should if you are sure its burnt, and yea it can be only it ,, as long as its an output stage resistor it would have a big effect
although im not quite sure i think if you can provide a schematic we can help more

thanks man for the drawing,, its not low quality at all, great work
yea its kind of the star configuration which i guess i told you before that i prefer,,
thank u

so i understand that th preamp stage ground should go for the node between c17 n c18
the power amp (high current) ground should be connected to the node between c15 and c16 directly
so it can go to the center tap directly without annoying the little sigal current
and the guitar ground should also go for the node between c17 c18.
is thaT it?

about the grounding , idid read the stuff u wrote (teemuk) and you mentioned about the 2 rails transformer (this amp) that the common point should be taken right after the capacitor to avoid hum

do u mean the point between the c17 c18 ?
and what about the guitar ground terminal, also connect it directly to this point?

i would try to take away the high current loops from the input signal loops , i mean make 2 wires come to the final common point
that should fix the noise stuff ,right?

then afterall when i would want to make a pcb i would also consider the same style of grounding, but with shortest circuit possible ,making the high current track a little wider could be more helpfull

yea good link too
it has intensive info about building cabs, i guess ill leave this as a last stage of making the amp

ill just use my testboard as a first stage and make the amp on it and hack a speaker ,, hope it speakes

i went today to a music shop to ask for some cabs with speakers
they said they can provide Marshall,Ibanez and Laney
the cabs were all large ,,somthin like 4x12"
and the price was just about a thousand bucks for a marshall cab, ,

i kind of decided to build my own cab as long as the amp is little
i passed by this article and found it very useful

http://www.duncanamps.com/technical/speaker_cab.html

i would go for an MDF wood open back cab for a 1x10" speaker
just wanna keep it simple
i would go for a carpenter to do the cab, hope it doesnt cost much.
the speaker should be anythin that provides good sound

yea true there are lots of points to give attention to
so i was thinking maybe using a testboard is the best shot at first
isnt it a heaven for such case?

1/its small enough to avoid ground loops
2/very easy to change stuff

although im not quite sure it can handle large currents,,
maybe after changing values and modding i can go to PCB the last design,,
have you ever used a test-board for such a thing?

QuoteI'm planning on making my K-20X a head and building a 4 x 8 box to go along with the 1 x 10 I already have.  It won't be super loud pushing all 5 speakers, but the tone should be excellent.

nice idea, using a 10 inches speaker ill consider to buy one.
im not sure yet about the cab
ill just go to some shop n see if its not very expensive to buy one with a speaker
or build one to fit with a 10 inch speaker

about the amp ill consider making the circuit a PCB ,,isnt it better?
i thought of that just to avoid ground loops
guess the smaller the circuit the better it is

hey folks , i just came by a tutorial about digital filtering using DSP implementation
its really a cure for killing the phase shifts with analog filters,but the circuit and programing would be much harder
its a case of not using a microcontroller but you have to go for a DSP processor for real-time application

thought i'd share it with anybody interested in the digital domain,
it also has a lot of examples and it explains how you can implement these filters using Matlab.

http://ccrma.stanford.edu/~jos/filters/

could be somthin with the supply circuit
check transformer/opamps/wires

well thank u for the information i dont think i wanna get that deep i think its enough to know that there is a roll off @ 3 khz
now i understand maybe why the preamp enhance the treble area.
anyways they should provide some kind of catalog that has the freq response of the speaker when ya buy one

again, what cabs / speakers are good for this?

well yea thats right the lowpass filter cuts up the high gain provided for high freqs but i actually did model a speaker when i did my simulation using spice, or is it the lowpass filter of the speaker should be modeled too?

QuoteAlso keep in mind that everyone has a different idea of what "perfect" tone is.

True but i just noticed that the bass area needs a little more gain,,
isnt it just hot when u play bass notes to amply em up?
anyways thats just a taste.

and yea about the speaker stuff, do u guys have in mind a speaker that i can buy and would be good for this amp?
i actually dont have much info about guitar speakers and cabs
should i get a speaker in a cab?
or can i just have em seperatley?

and yeah adding that reverb stack can be very usefull to play country music solos,,

thanks man, realy awesome shots
i just wonder how an amp would sound GREAT with such freq response.,,
ill try to build this one as it is , and then change with some values n see how does this affect the sound
thanks again for openin the amp ,,owe ya

Quote- I removed and inspected the circuit board and found NO burn marks, exploded capacitors, or anything that would be considered obviously broken or damaged.

if the lightning hit the input cable it should burn up anythin it sees,,
thats pretty weird , anyways maybe some IC's or caps are burnt in the input stage and its not obvious,should check on that.

second, are you sure the speaker is still fine (magnet) after the lightning struck???

reason for not having high volume could be :
1/pots damaged
2/transistor or op amps damaged
3/make sure if the supply still works fine

i would suggest you change the circuit input stage ,,just buy same caps pots ,,so cheap.