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Old 12th August 2008, 05:05 PM   #11
lineup is offline lineup  Sweden
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Default Re: Re: Re: Re: 100 watt audio amplifier

Quote:
Originally posted by Andy L. Francis
OMG! I need a coffee.
Awfully sorry!!! [/B]
if you look at my sgnature below this post
this is supposed to make all think before posting!!!

but i do not mind too much .. i have said some worse things
than is put into my own mouth at times .. at this board

no problems mate
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Old 12th August 2008, 05:11 PM   #12
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Default some times we read posts too fast

i have nothing against the circuit as a kit though is the cra***piest you can buy ......

the bdv 66-67 inside make might be one Philips and one SGS that is a guarantee that the amp will not work .....

also the rest of the material inside the kit is the cheapest available

also the statment 100w is not real so yes thats a bad amp

andy ...something else

from the way the starter of the thread writes i think he is a rookie ( no effence hopefully )

so if he buys a kit and then start to change this and that may be he ends up in the wrong situation

the conclusion is that may be the schematic is good or very good but this has nothing to do with what the kit provides .....

this is what i always scream about ...... stick to the subject ....otherwise posts are getting too long without a reason ....hell this poor guy kibet85 probably cannot understand all this we talk about .....

excuse my tone but often somebody asks a simple thing in the forum and he might get directions on how to built a space ship to go to mars except a simple answer or opinion of someone with a bit more expirience ....

since this greek made you dont want to know how many i had to mod or repair since i was 14 and this kit was allready in the market and until today no update at all ....... now days i am 42 ...thats a long time
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Old 12th August 2008, 05:35 PM   #13
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Default what you say is true

Quote:
Originally posted by Andy L. Francis
Some more comments...

P3A hasn't got public PCB design.
P3A hasn't got shortcircuit/overcurrent protection.
DX-amp hasn't got shortcircuit/overcurrent protection.
Symasym hasn't got shortcircuit/overcurrent protection.

Anyway I'm not sure that Kibet85 could find the driver/OP devices in Kenya for DX-amp/Symasym - however this project uses only cheap and easily available parts.
trruth and verry correct
but at least all of these amps sound very fine and also choosing to built one of them he will get loads of forum support
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Old 12th August 2008, 07:43 PM   #14
kibet85 is offline kibet85  Kenya
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Thanks guys..first,m a rookie....i just love loud sound..now,this amp has already been made..its intended use is a subwoofer amplifier(actually,m using it right now)..the thing is,its not responding to those low bas notes...e.g..i hope you guys know this song'get ur walk on'by xzibit..it has some deep bass..this amp is not responding to those kind of beats..could u guys tel me wats the problem is...
M using a +-38 transformer with 4700 microfarad caps rated 100 watts..for the outputs,1 pair of darlingtons...mj2500 and 2n6388...thught of adding another pair and increasing the caps to like 15000.... my sub is a pioneer 800 wats rated 4ohms...
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Old 13th August 2008, 07:04 AM   #15
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Default questions

are you using 38+38 ac ????? so your rails are something like 50+50 volts ????

then in this case what is your idle ????

did you managed to set the idle as was or you made any mods???

also mj 2500 and 2n6388 are they complementary ????? can they be complementery ????? do they share the same specs ????

have you checked the device with a scope ????is it symmetrical ???is clipping symetrical ????
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Old 13th August 2008, 10:19 AM   #16
kibet85 is offline kibet85  Kenya
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Hi sakis..what u have just asked is too technical..but anyway,lemmie give it a try...when u ask about complementary,i guess ur asking if they pair up wel?i can say they do..i adjusted the current to 50milliamps as stated..one thing i'v discorved is that its gain is low..i was testing it today at my friends place..we were using a boschman eq and had to put tha sub gain to half...with his amp,u can feel the dedication to respond to deep beats... His amp is the cheap 150 wat amp!!i knw,crap amp..anyway,if u have any suggestions,holla back..it would be much appreciated...then,i was thinking of my next project as the lynx amp..v2.1...cuz it uses darlington outputs which are available here..is it ok?
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Old 13th August 2008, 10:24 AM   #17
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Default sorry i cannot be a part of this

i think the information i will give you are not usefull since you can use it properly ......

i am sorry
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Old 13th August 2008, 07:05 PM   #18
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Default listen mike

facts
- this amp is designed to operate in 40+40 volts
- increase the rails of the amp is almost 53 volts thats out of specs
- will effect the gain
-will effect the bias
-will effect the protection circuit
-will effect safety
then .....

one amplifier to operate properly in this class has to be symmetric IE the transitors used have to be complementary IE same make brand and cahracteristics ....

for example 2n6388 is 80 volt .....too litle for operating at 53+53 volts then 10 ampere and can dissipate 65w totaly ..... you are asking to more than 100w...thats not right ......b1000 is the grade of amplification you get from this transistor and finally this transistor is not designed to use for audio is for small switching application or power supply

now mj 2500 is even worst only 60 volt .....cannot operate at 53+53 volts 10 ampere and then 150w ( thats the only good but very diferent from 2n6388 ) and atleast can go up to 3mhz that makes it a transistor that can work for audio .....

more facts
they way this amp is built it will fail any minute now and its disuster waiting to happen .... unless all these is a mistake and you have 38+ 38 volts DC ...in this case transistors are barely enough but will not work as long as their not complemetary ......first it will fail the 2n6388 then will also destroy the mj2500 and then your speaker .....even if you have fuses on this will not be fast enough to save your speaker ...

in case you have 53+53 volts rails the protection circuit needs to be redesigned to be able to operate at this voltage .....

also the idle you state of 50ma is totally wrong and the only way to calculate bias properly for this configuration is to measure the voltage drop acroos every emiter resistor 0.47R 5W for every transistor respectively .and then calculate with ohms law

..... i bet you that if you do you will see that the one has like 10 mv and the other has 50 mv since this is coming from the diference of the transistors .....

the only possible solution is to get the brother of mj 2500 that is the mj 3000 or any other set of complementary transistors .... for example mj 11015-16 that are 160 volts devices and then either remove totaly the protection circuit or recalculate it for the specific application ....

in this case you will almost make at least 120w of solid power and also very stable

ALso somewhere you state something like 100w power if this your transformer is not enough for this application if you have an amplifier that you expect to produce 100 w you need a minimoum of 200w to make operate properly .....



amplifier lesson one finished ( there is probably more but i just told you the basics )

good luckprobably your amp is working but out of balance and since you have to much rail voltage probably there is a lot of power but protection circuit will allow enough drive cause of too high rails voltage ...... if you remove the protection for a minute you will have about 120 w of power for about 1/4 of a second ,...... then it will blow
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Old 13th August 2008, 09:44 PM   #19
kibet85 is offline kibet85  Kenya
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Default Thank's you

Thank's sakis for that informative piece of advice..i now understand what your asking through wat u have just told me...as for tha amp,i'l go look for the outputs u have jus said..if you dont mind,what tips can u come up with,to mod the amp..
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Old 14th August 2008, 06:33 AM   #20
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Default i have never mod

this amp considering higher rail voltage yet

state your rail voltage first and then we will see ....i need to know if you have 38 +38 DC or AC ????
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