Hello people!
As you can see I am new here. I'm brazilian, 19, in College, Bass player and trying this little adventure in the world of "Made by Myself". I'm gonna pre-apologize for any english mistakes that I will make or already made...
This AMP will be like a prototype for any furthers. I gonna use it just for study and playing at home.
I choosed this one: http://www.redcircuits.com/Page66.htm
Amp:
Pre-amp:
The power supply (that I didn't buy yet) gonna be a 24+24V by 3A that will be more than enough.
The darlingtons I changed for TIP142 and TIP147.
The PCB layout isn't ready yet but I will use a software to do it, like Ultiboard or something like that. To start it up I'm just waiting for the transformer and then I'm gonna have an idea about the space inside the chassis.
Talking about chassis... This is one of my questions:
I wanna know what type of material to use, Aluminium, Stell... and the thickness I can use. I think I gonna use a plate in a shape of "+" and fold it into a little box with 200x200x100mm.
I'm thinking about to screw the PCBs in the chassis with a circundal hard-paper between the Chassi and PCB. The transformer directly in the chassis and the cover with 4 screws with a "L" Support in the chassis.
I drawed this... It s***s I know but just to illustrate what I'm thinking about.
So, what do you think about it? It's good enough? Any ideas to improve it? Any sugestions?
Thank you for reading this and... don't be ashamed in replying.
See ya!
As you can see I am new here. I'm brazilian, 19, in College, Bass player and trying this little adventure in the world of "Made by Myself". I'm gonna pre-apologize for any english mistakes that I will make or already made...
This AMP will be like a prototype for any furthers. I gonna use it just for study and playing at home.
I choosed this one: http://www.redcircuits.com/Page66.htm
Amp:
Pre-amp:
The power supply (that I didn't buy yet) gonna be a 24+24V by 3A that will be more than enough.
The darlingtons I changed for TIP142 and TIP147.
The PCB layout isn't ready yet but I will use a software to do it, like Ultiboard or something like that. To start it up I'm just waiting for the transformer and then I'm gonna have an idea about the space inside the chassis.
Talking about chassis... This is one of my questions:
I wanna know what type of material to use, Aluminium, Stell... and the thickness I can use. I think I gonna use a plate in a shape of "+" and fold it into a little box with 200x200x100mm.
I'm thinking about to screw the PCBs in the chassis with a circundal hard-paper between the Chassi and PCB. The transformer directly in the chassis and the cover with 4 screws with a "L" Support in the chassis.
I drawed this... It s***s I know but just to illustrate what I'm thinking about.
An externally hosted image should be here but it was not working when we last tested it.
So, what do you think about it? It's good enough? Any ideas to improve it? Any sugestions?
Thank you for reading this and... don't be ashamed in replying.
See ya!
Hello my dear friend....hummm, nice idea.
Have you watched your brazilian brother thread, the Dx amplifier thread!
Qualé amigo, prestigia nossa gente..... ei!.... eu tou aqui!!!!
Hello my friend...your people is here.... can you see me?
You need power to bass amplifier.... several times more power than your mid range amplifier.
65 percent for bass
25 percent for mids
10 percent for treble.
So...having 1 watt amplifier, a full range unit... a portable player using a small computer speaker as amplifier, for instance, you will need a 6.5 watts amplifier to bass...unless you will have unballanced sound.
In the real world, we use 4 times the mid plus treble power...as you see the subwoofer systems doing this way...the good ones, unless those ones have that proportion.
I will invite you to visit Dx amplifier thread.... green and yellow thread man...people there talks portuguese...qualé amizade?
"Eu morei em Cambé e em Londrina, trabalhei como Chefe de Operações na TV Coroados, hoje pertence à TV Parana eu imagino."
I have lived in your place, your state, Cambé and Londrina were the place i have lived when had the charge of technical manager responsible for the televisions operation.... Enginnering department manager may be the name.... the television name was Coroados (crowded) and now belong the Paraná Network of Broadcasting.
Pisei na terra vermelha amigo...e não prestigias?
regards,
Carlos
Have you watched your brazilian brother thread, the Dx amplifier thread!
Qualé amigo, prestigia nossa gente..... ei!.... eu tou aqui!!!!
Hello my friend...your people is here.... can you see me?
You need power to bass amplifier.... several times more power than your mid range amplifier.
65 percent for bass
25 percent for mids
10 percent for treble.
So...having 1 watt amplifier, a full range unit... a portable player using a small computer speaker as amplifier, for instance, you will need a 6.5 watts amplifier to bass...unless you will have unballanced sound.
In the real world, we use 4 times the mid plus treble power...as you see the subwoofer systems doing this way...the good ones, unless those ones have that proportion.
I will invite you to visit Dx amplifier thread.... green and yellow thread man...people there talks portuguese...qualé amizade?
"Eu morei em Cambé e em Londrina, trabalhei como Chefe de Operações na TV Coroados, hoje pertence à TV Parana eu imagino."
I have lived in your place, your state, Cambé and Londrina were the place i have lived when had the charge of technical manager responsible for the televisions operation.... Enginnering department manager may be the name.... the television name was Coroados (crowded) and now belong the Paraná Network of Broadcasting.
Pisei na terra vermelha amigo...e não prestigias?
regards,
Carlos
Attachments
hehehe foi mal camarada! Agora que fui ver, quanta gente postou lá hein! Pode deixar que vou participar na thread verde e amarela!"
"Sorry dude! I just saw that, so many people replied huh? I gonna participate in the green and yellow thread!"
Thanks for the answers guys!
geminni, I know a little bit about these transformers... Please correct me if I am wrong:
In a normal transformer, I have the 2 wires... The +48 and the Ground... Actually, i think it doesn't matter, because it's AC.
In a central tapped transformer I have +24V, Ground, and -24V. Taking the tap to be the reference, I will have 2 times 24Vrms. But if I leave the tap unconnected I shall take one of the wires(+24V or -24V) to be the "reference" or ground. Then I'll have 48V rms in total, or a 67.9V peak. Retify it will give me 66.5V peak (losing 2x0.7 because of the diodes resistence). Then after filtering it by the Capacitor, assuming the frequency of the main supply 60Hz, the Current of 3A and the capacitance of 4400uF (2x 2200uf)... I will have 5.7V between the Vmax and Vmin. In the end... "5.7V / 2 = 2.85" and "66.5V - 2.85 = 63.65V" that is my Average Voltage, that if I'm right, is the 60V that the guy of schematics says.
Is that right, or I am totally nonsense?
destroyer X,
"So...having 1 watt amplifier, a full range unit... a portable player using a small computer speaker as amplifier, for instance, you will need a 6.5 watts amplifier to bass...unless you will have unballanced sound."
I think you mean 10 watt, right? But what I am trying to do is a Bass Amplifier, the instrument... I won't use any mid or treble.
The transformer is 48V and 3A, its 144Watt. Assuming a 20% of losses I will still have 115Watt. Twice of what I need to a 4ohm speaker.
Well... I think that's it! If I said something (or everything) wrong, PLEASE CORRECT ME!'
See ya!!
Obs: é estranho falar em "inglês" com um brazuka aUhaUhaU
"Sorry dude! I just saw that, so many people replied huh? I gonna participate in the green and yellow thread!"
Thanks for the answers guys!
geminni, I know a little bit about these transformers... Please correct me if I am wrong:
In a normal transformer, I have the 2 wires... The +48 and the Ground... Actually, i think it doesn't matter, because it's AC.
In a central tapped transformer I have +24V, Ground, and -24V. Taking the tap to be the reference, I will have 2 times 24Vrms. But if I leave the tap unconnected I shall take one of the wires(+24V or -24V) to be the "reference" or ground. Then I'll have 48V rms in total, or a 67.9V peak. Retify it will give me 66.5V peak (losing 2x0.7 because of the diodes resistence). Then after filtering it by the Capacitor, assuming the frequency of the main supply 60Hz, the Current of 3A and the capacitance of 4400uF (2x 2200uf)... I will have 5.7V between the Vmax and Vmin. In the end... "5.7V / 2 = 2.85" and "66.5V - 2.85 = 63.65V" that is my Average Voltage, that if I'm right, is the 60V that the guy of schematics says.
Is that right, or I am totally nonsense?
destroyer X,
"So...having 1 watt amplifier, a full range unit... a portable player using a small computer speaker as amplifier, for instance, you will need a 6.5 watts amplifier to bass...unless you will have unballanced sound."
I think you mean 10 watt, right? But what I am trying to do is a Bass Amplifier, the instrument... I won't use any mid or treble.
The transformer is 48V and 3A, its 144Watt. Assuming a 20% of losses I will still have 115Watt. Twice of what I need to a 4ohm speaker.
Well... I think that's it! If I said something (or everything) wrong, PLEASE CORRECT ME!'
See ya!! Obs: é estranho falar em "inglês" com um brazuka aUhaUhaU
It is strange to talk in English with a Brazuka....ahahhahah.
Estranho é .... demais!................ very strange..and a lot!
O teu caso é especial..esquece do meu amplificador...não é bem indicado para você...na bôa!
Not your need..forget my amplifier... it is not good for your purposes...you can believe me...not good for instruments.
regards,
Carlos
Estranho é .... demais!................ very strange..and a lot!
O teu caso é especial..esquece do meu amplificador...não é bem indicado para você...na bôa!
Not your need..forget my amplifier... it is not good for your purposes...you can believe me...not good for instruments.
regards,
Carlos
The amplifier will produce not more than specified...in my mind
Not more than 35 watts over 4 ohms and not more than 20 watts over 8 ohms.
It is not good to guitar amplifier too, as has not enought transistors in parallell to hold the enormous distortion guitar can produce.
Enormous overdrive too into the input.
Those darlingtons are not so strong as we use to think, and they normally oscilate till the destruction if you not solder a 560 picofarads condenser or even more from the colector to the base...in both darlingtons you have in the output.
To guitar, you have to find amplifier that have "overcurrent protection".... they are 2 small transistors that senses the voltage developed over the output emitter resistances, and reduces the signal into the earlier stage, reducing by this method, the output level and current.... this will protect the output devices.
This amplifier may be good for your first "do it yourself" amplifier....mine one need some previous knowledge...some basic experience.
Take a look in the schematic i am providing you....your supply will fit...not problems..... the strange transistors numbers you can replace by BD139 when NPN and BD140 when PNP..
I am talking about the protection...that Q9 and Q10...this will be needed for your bass work.
Good to start...but to be really happy you must use the Krell Klone made by Jan Dupont...and biased class AB....because you can increase supply voltage and produce a good power that is needed to a bass amplifier....you need more than 200 watts to use it as a professional...of course, to home use, a TDA2003 producing 10 watts RMS will be enougth.
Dx amplifier will not fit your need.
regards,
Carlos
Not more than 35 watts over 4 ohms and not more than 20 watts over 8 ohms.
It is not good to guitar amplifier too, as has not enought transistors in parallell to hold the enormous distortion guitar can produce.
Enormous overdrive too into the input.
Those darlingtons are not so strong as we use to think, and they normally oscilate till the destruction if you not solder a 560 picofarads condenser or even more from the colector to the base...in both darlingtons you have in the output.
To guitar, you have to find amplifier that have "overcurrent protection".... they are 2 small transistors that senses the voltage developed over the output emitter resistances, and reduces the signal into the earlier stage, reducing by this method, the output level and current.... this will protect the output devices.
This amplifier may be good for your first "do it yourself" amplifier....mine one need some previous knowledge...some basic experience.
Take a look in the schematic i am providing you....your supply will fit...not problems..... the strange transistors numbers you can replace by BD139 when NPN and BD140 when PNP..
I am talking about the protection...that Q9 and Q10...this will be needed for your bass work.
Good to start...but to be really happy you must use the Krell Klone made by Jan Dupont...and biased class AB....because you can increase supply voltage and produce a good power that is needed to a bass amplifier....you need more than 200 watts to use it as a professional...of course, to home use, a TDA2003 producing 10 watts RMS will be enougth.
Dx amplifier will not fit your need.
regards,
Carlos
Attachments
I built this amp once. Frankly put, it's horrible: The bias circuit doesn't work right since the Hfe of BD139 is too low for those component values - you will have plenty of nasty crossover distortion unless you redesign it. This circuit can also blow the amplifier if the wiper of the trimmer lifts during bias adjustment. There is no mains fuse (easy fix but still), there should be a buffer between volume control and the power amp, there is no output Zobel, there is no short circuit protection, the gain stages of the preamplifier had some mystical problems that kept them in constant saturation, etc. (I built the guitar version of this circuit where the tone controls and "harmonic modifier" were copied from Heathkit TA-17). I don't know whether it was due to an impedance mismatch or what but the tone control circuit was afwully "voiced". It's totally useless. 60 watts for bass doesn't sound like much.
I usually don't like to hammer down a design like this but this is just... bad. There are better designs and I dearly suggest you try one of them instead. Rod Elliott's guitar amplifier looks a lot more promising than this one.
I usually don't like to hammer down a design like this but this is just... bad. There are better designs and I dearly suggest you try one of them instead. Rod Elliott's guitar amplifier looks a lot more promising than this one.
destroyer X, this amp that u mentioned is for music isn't it? I'll try some adventure in that area later.
gaetan8888, Minion and teemuk,
Are u talking about my amp? Are u saying the amp sucks?
Well... I made my choice. This one is gona be the one! Now I need some sugestions about it... But thanks anyway for mention another amp... It's always nice to see another project and compare.
Obs: Next week I gonna buy the transformer, and maybe the final components... And then the chassis. But I need some advices about it...
Aluminium will be good? What about the thickness?
SEE YA!
gaetan8888, Minion and teemuk,
Are u talking about my amp? Are u saying the amp sucks?
Well... I made my choice. This one is gona be the one! Now I need some sugestions about it... But thanks anyway for mention another amp... It's always nice to see another project and compare.
Obs: Next week I gonna buy the transformer, and maybe the final components... And then the chassis. But I need some advices about it...
Aluminium will be good? What about the thickness?
SEE YA!
Shakal,
Yes, I'm talking about the "red circuits" amp. I respect that you have made your choice - likely on the same principle that I did few years ago when I tried to build the damn thing: It's simple, it looks like it's easy to built etc. Well, my project proved to be nice education on how simple things are not always any simpler or easier. The working circuit proved to be a total redesign, which wasn't that simple anymore either.
I never got the preamp to work satisfiably since it had that mysterious saturation problem. The Vce of the transistors is 80V but still they went to saturation in the concerned 60V supply. This will burn down some resistors (since the transistors were essentially in short). The PCB I used had no errors (I rechecked it about 100 times) and the transistors tested good - but only at voltages lower than 40V. I tried several transistors with higher voltage rating but all in vain. I never figured out what caused this thing, neither did anyone I consulted about the problem. I have simulated the gain stages of the preamp with SPICE and theoretically they should work.
Are you familiar with the the concepts of ground return current routing, separating audio and power grounds et cetera? If not, you need to be.
A PCB layout will be crucial component and it doesn't get much harder to design that even if you would build something a bit more complex. Complex designs usually work better when it comes to thermal matters and stability in general. Simple designs are not always best and there are reasons why people don't build amplifiers using this topology any more.
I already mentioned the inadequate bias circuit, the lack of short circuit protection, output Zobel, mains fuse (also safety earth) and buffer between power amplifier and the volume control. You will likely need all these fixes to get the amplifier to work decently. I also encourage using parallel output devices - and driver transistors for the output devices. These are also pretty "easy" mods but you have to do some designing by yourself. My experiences with the concerning circuit were nothing but good.
Maybe I should say something "constructive" then: Unless you have a very heavy amplifier I would use aluminun chassis - mainly because it's easier to drill holes into aluminum. Good transistor amplifiers for electric instruments weight a lot due to heavy transformers and excessive use of heatsinks so don't use too "flimsy" metal for the chassis. Mine was in "U" shaped, about 2 - 3 mm thick aluminum chassis that had some extra bends for bracing.
Use big heatsink - the bigger the better. Unless you use a fan cooling there is practically no way that you could use a too big heatsink. Also realize that the shape usually matters more than the physical volume. If you don't know about heatsinking and how the interface (insulator, lubing etc.) between heatsink and transistor can affect things then it's about time to learn. It makes a huge difference. Also, make sure that you don't restrict the airflow.
You might want to study these designs:
Origin of tone control circuit and harmonic modifier for both bass and guitar "red circuits" amps:
http://demont.net/harmony/documents/schematics/amps/heathkit_TA_17.gif
The origin of the power amplifier in "red circuits" amp:
http://www.swtpc.com/mholley/PopularElectronics/Apr1968/PE_Apr1968.htm
Study the above design carefully and think what changes to this circuit should never have happened and what changes were (or at least tried to be) for the better....
Part 2 of the aforementioned article (preamp):
http://www.swtpc.com/mholley/PopularElectronics/May1968/PE_May1968.htm
Another similar power amplifier design:
http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec_1967_pg30.jpg
Some alternative - yet "vintage" designs:
http://www.swtpc.com/mholley/PopularElectronics/Feb1967/PE_Feb1967.htm
...and...
http://www.swtpc.com/mholley/PopularElectronics/Jul1969/PE_Jul_1969_pg52.jpg
I hope I was a bit more helpful this time....
Yes, I'm talking about the "red circuits" amp. I respect that you have made your choice - likely on the same principle that I did few years ago when I tried to build the damn thing: It's simple, it looks like it's easy to built etc. Well, my project proved to be nice education on how simple things are not always any simpler or easier. The working circuit proved to be a total redesign, which wasn't that simple anymore either.
I never got the preamp to work satisfiably since it had that mysterious saturation problem. The Vce of the transistors is 80V but still they went to saturation in the concerned 60V supply. This will burn down some resistors (since the transistors were essentially in short). The PCB I used had no errors (I rechecked it about 100 times) and the transistors tested good - but only at voltages lower than 40V. I tried several transistors with higher voltage rating but all in vain. I never figured out what caused this thing, neither did anyone I consulted about the problem. I have simulated the gain stages of the preamp with SPICE and theoretically they should work.
Are you familiar with the the concepts of ground return current routing, separating audio and power grounds et cetera? If not, you need to be.
A PCB layout will be crucial component and it doesn't get much harder to design that even if you would build something a bit more complex. Complex designs usually work better when it comes to thermal matters and stability in general. Simple designs are not always best and there are reasons why people don't build amplifiers using this topology any more.
I already mentioned the inadequate bias circuit, the lack of short circuit protection, output Zobel, mains fuse (also safety earth) and buffer between power amplifier and the volume control. You will likely need all these fixes to get the amplifier to work decently. I also encourage using parallel output devices - and driver transistors for the output devices. These are also pretty "easy" mods but you have to do some designing by yourself. My experiences with the concerning circuit were nothing but good.
Maybe I should say something "constructive" then: Unless you have a very heavy amplifier I would use aluminun chassis - mainly because it's easier to drill holes into aluminum. Good transistor amplifiers for electric instruments weight a lot due to heavy transformers and excessive use of heatsinks so don't use too "flimsy" metal for the chassis. Mine was in "U" shaped, about 2 - 3 mm thick aluminum chassis that had some extra bends for bracing.
Use big heatsink - the bigger the better. Unless you use a fan cooling there is practically no way that you could use a too big heatsink. Also realize that the shape usually matters more than the physical volume. If you don't know about heatsinking and how the interface (insulator, lubing etc.) between heatsink and transistor can affect things then it's about time to learn. It makes a huge difference. Also, make sure that you don't restrict the airflow.
You might want to study these designs:
Origin of tone control circuit and harmonic modifier for both bass and guitar "red circuits" amps:
http://demont.net/harmony/documents/schematics/amps/heathkit_TA_17.gif
The origin of the power amplifier in "red circuits" amp:
http://www.swtpc.com/mholley/PopularElectronics/Apr1968/PE_Apr1968.htm
Study the above design carefully and think what changes to this circuit should never have happened and what changes were (or at least tried to be) for the better....
Part 2 of the aforementioned article (preamp):
http://www.swtpc.com/mholley/PopularElectronics/May1968/PE_May1968.htm
Another similar power amplifier design:
http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec_1967_pg30.jpg
Some alternative - yet "vintage" designs:
http://www.swtpc.com/mholley/PopularElectronics/Feb1967/PE_Feb1967.htm
...and...
http://www.swtpc.com/mholley/PopularElectronics/Jul1969/PE_Jul_1969_pg52.jpg
I hope I was a bit more helpful this time....
Gaetan,
Did you type that correctly? C8? No. It's not strange at all - but its value is... That's just an increased feedback for higher frequencies . It's similar to those capacitors you see used in most opamp circuits and it should make the amplifier more stable. ...But the value seems a bit high, though: Most power amplifiers cannot tolerate a capacitance higher than 22 pF - 47 pF at this location. Anything above that tends to make them unstable.
Did you type that correctly? C8? No. It's not strange at all - but its value is... That's just an increased feedback for higher frequencies . It's similar to those capacitors you see used in most opamp circuits and it should make the amplifier more stable. ...But the value seems a bit high, though: Most power amplifiers cannot tolerate a capacitance higher than 22 pF - 47 pF at this location. Anything above that tends to make them unstable.
I never got the preamp to work satisfiably since it had that mysterious saturation problem. The Vce of the transistors is 80V but still they went to saturation in the concerned 60V supply. This will burn down some resistors (since the transistors were essentially in short). The PCB I used had no errors (I rechecked it about 100 times) and the transistors tested good - but only at voltages lower than 40V. I tried several transistors with higher voltage rating but all in vain. I never figured out what caused this thing, neither did anyone I consulted about the problem. I have simulated the gain stages of the preamp with SPICE and theoretically they should work.
This is weird!!
Are you familiar with the the concepts of ground return current routing, separating audio and power grounds et cetera? If not, you need to be.
Not really... Shall I separate it with a resistor?
A PCB layout will be crucial component and it doesn't get much harder to design that even if you would build something a bit more complex. Complex designs usually work better when it comes to thermal matters and stability in general. Simple designs are not always best and there are reasons why people don't build amplifiers using this topology any more.
What is a simple design for you? Componets close to each other?
I already mentioned the inadequate bias circuit, the lack of short circuit protection, output Zobel, mains fuse (also safety earth) and buffer between power amplifier and the volume control. You will likely need all these fixes to get the amplifier to work decently. I also encourage using parallel output devices - and driver transistors for the output devices. These are also pretty "easy" mods but you have to do some designing by yourself. My experiences with the concerning circuit were nothing but good.
What makes the BIAS circuit inadequate?
What would be a short circuit protection? Some transistors?
This buffer that um mentioned... Can I make it with a amp op?
The output devices are the transistors? TIP142 and 147? How is this paralell?
The BD139 isn't a driver?
Maybe I should say something "constructive" then: Unless you have a very heavy amplifier I would use aluminun chassis - mainly because it's easier to drill holes into aluminum. Good transistor amplifiers for electric instruments weight a lot due to heavy transformers and excessive use of heatsinks so don't use too "flimsy" metal for the chassis. Mine was in "U" shaped, about 2 - 3 mm thick aluminum chassis that had some extra bends for bracing.
Hmmm... Aluminium 2-3mm then...
Use big heatsink - the bigger the better. Unless you use a fan cooling there is practically no way that you could use a too big heatsink. Also realize that the shape usually matters more than the physical volume. If you don't know about heatsinking and how the interface (insulator, lubing etc.) between heatsink and transistor can affect things then it's about time to learn. It makes a huge difference. Also, make sure that you don't restrict the airflow.
I think I know what u mean. More air contact area is better than more volume.
Thanks for the sugestions! I'll think about it. I didn't had much time this weekend but I'll take a loot in these websites that u told me.
Thank you again!
See ya!
This is weird!!
Are you familiar with the the concepts of ground return current routing, separating audio and power grounds et cetera? If not, you need to be.
Not really... Shall I separate it with a resistor?
A PCB layout will be crucial component and it doesn't get much harder to design that even if you would build something a bit more complex. Complex designs usually work better when it comes to thermal matters and stability in general. Simple designs are not always best and there are reasons why people don't build amplifiers using this topology any more.
What is a simple design for you? Componets close to each other?
I already mentioned the inadequate bias circuit, the lack of short circuit protection, output Zobel, mains fuse (also safety earth) and buffer between power amplifier and the volume control. You will likely need all these fixes to get the amplifier to work decently. I also encourage using parallel output devices - and driver transistors for the output devices. These are also pretty "easy" mods but you have to do some designing by yourself. My experiences with the concerning circuit were nothing but good.
What makes the BIAS circuit inadequate?
What would be a short circuit protection? Some transistors?
This buffer that um mentioned... Can I make it with a amp op?
The output devices are the transistors? TIP142 and 147? How is this paralell?
The BD139 isn't a driver?
Maybe I should say something "constructive" then: Unless you have a very heavy amplifier I would use aluminun chassis - mainly because it's easier to drill holes into aluminum. Good transistor amplifiers for electric instruments weight a lot due to heavy transformers and excessive use of heatsinks so don't use too "flimsy" metal for the chassis. Mine was in "U" shaped, about 2 - 3 mm thick aluminum chassis that had some extra bends for bracing.
Hmmm... Aluminium 2-3mm then...
Use big heatsink - the bigger the better. Unless you use a fan cooling there is practically no way that you could use a too big heatsink. Also realize that the shape usually matters more than the physical volume. If you don't know about heatsinking and how the interface (insulator, lubing etc.) between heatsink and transistor can affect things then it's about time to learn. It makes a huge difference. Also, make sure that you don't restrict the airflow.
I think I know what u mean. More air contact area is better than more volume.
Thanks for the sugestions! I'll think about it. I didn't had much time this weekend but I'll take a loot in these websites that u told me.
Thank you again!
See ya!
Shakal said:
Indeed
The important thing is to have currents from different stages returning to ground the right route. You don't want high currents to return through low current stages, you don't want power supply currents to return with signal currents etc. I wrote a small tutorial about this thing to another forum (http://www.ssguitar.com/index.php?topic=288.0) and plenty of stuff about this has been written here as well. Go ahead, do a search.
Like I said: BD139 has too low gain to work correctly with those component values. Also, if the wiper of the trimmer lifts the bias current will grow extremely high, which will likely destroy the output stage. It is really easy to see why this happens when you know how the concerned circuit works: Search for vbe multiplier.
Google/search for VI limiter.
You mean opamp? Not easily with that high rail voltages. The last preamplifier stage is a buffer. You could use something similar.
It is not. For parallel configuration you would need (at least) two more.
I call it the voltage amplifying transistor. Some people do call it a driver but I like to use that term of transistors that "drive" the output devices in darlington and Sziklai configurations.
DAMMIT! If u wanted to scare( 
) me, frustrate( 
) me and smash ( 
) my dream... U DID IT!
Sorta...
hehehehehe
Well, I think that project wasn't so complete and right as I thoght... Maybe it will take me a little extra time to re-re-re-re-project it.
I'll read the text about different grounds... Thank you!
Anyway, I think I need some help to remake it... And maybe when I finish it all I can make a complete document of the project with pictures and step-by-steps, etc...
Thanks again!
Bye bye
) me, frustrate( ) me and smash ( ) my dream... U DID IT! Sorta...
hehehehehe Well, I think that project wasn't so complete and right as I thoght... Maybe it will take me a little extra time to re-re-re-re-project it.
I'll read the text about different grounds... Thank you!
Anyway, I think I need some help to remake it... And maybe when I finish it all I can make a complete document of the project with pictures and step-by-steps, etc...
Thanks again!
Bye bye
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