In my past six years DIY back ground,ı have done many amplifiers (in my records there are 33 amplifiers vholly complated or tested) and all they are solid state,ı have never done before tube amp.
About two years ago ı said myself "ı need a tube amp" and ı started to research about tube operation theory,tube amplifiers,and output transformers.Now ı give you amplifier thats complated at two years.I make a contact many amplifier master,sent many email,meeting,getting imformation and advice,at the end ı make a desicion to built a simple single ended class a amplifier.
So firstly ı picked up one or two amplifier schema,and ı tested them.After many tests ı draw a new schema with the other schemas parts.
As you see fig.1 this is very simple SE amplifier,just one and half tubes per one channel,the output ,tube can be choosen as EL84,6P43P,6P1P,6P14 .The input tube can be choosen as 12AX7,ECC83,6N2P.The tubes are connected as a cascode.The overall gain is about 20.In my opinion The Out Put Transformer (OPT) is the heart of the amplifiers,so OPT must be so good wounded with minimum air gap,the position of the all 3 transformes is such a important point.You can use the 5k-8 transformer till the 10w.
For the high gain you can improve the bay-pass capacitors but the noise improves too.You can choose the C1 coupling capacitor 0.1uf or 0.47 uf,but dont forget this is change the lower and upper cut off frequency.
For the best sound you have to rearrange the anode current,for each time you change the tubes.
In the amplifiers one of the important points is power supply.Especially on tube amp. If there are any ripple on the supply voltage,you can hear out of the speaker as a noise.So ı chose a CLC filter configuration and DC filament supply to take out some of the voltage ripple and get the noise down.
As you see in fig. 2 my supply is very efficient,especially filament supply is very good for the tube amp to the 2A flaman current.The stability of the filament voltage is very important for noise and filament safety,ıf the filament voltage is rise rapidly for instance from 6.3v to 7,filament can break away.Thats way ı regulated my filament supply to 6.3v with LM317 .I used power supply capacitor at about 1000uf in total but feel free to use more.As ussual the anodevoltage is 300v ,the current is 45mA.That makes 13w anode power dissipation (P=IxV).
Enough heat sink (finned aluminium is good) is provided for filament supply.The filaments need 1.7A current in totall,we apply to the regulator 10v so (P=IxV) 17w power appeard on the transistors.Fig. 3 showsthe PCboard layout for the one channel.Note that the tube's sockets are mounted to the copper side (I did unusual artwork,the photos can be deluded,you must mount the sockets to the copper side,the other to the component side).
Keep in mind that this is a simple enough circuit to be wired up point-to-point.I just want
my amplifier to be enough tidy.Many people think building a chassis is the hardest part.In this matter ı was inspired from old fashion valve amps.Always ı use the aluminium to bulding chassis because to bend,drill or rasp is so easy,You can get aluminium bloc to attache or you can bend a alimunium block as ı did.The other simple way but ı dont recomended is buying a prefab chassis.The chassis of amp is very important in many aspect.So you do a good job and try not to be too cheap about it.You can use copper as well aluminium.I think copper will be good for the chassis.
About two years ago ı said myself "ı need a tube amp" and ı started to research about tube operation theory,tube amplifiers,and output transformers.Now ı give you amplifier thats complated at two years.I make a contact many amplifier master,sent many email,meeting,getting imformation and advice,at the end ı make a desicion to built a simple single ended class a amplifier.
So firstly ı picked up one or two amplifier schema,and ı tested them.After many tests ı draw a new schema with the other schemas parts.
As you see fig.1 this is very simple SE amplifier,just one and half tubes per one channel,the output ,tube can be choosen as EL84,6P43P,6P1P,6P14 .The input tube can be choosen as 12AX7,ECC83,6N2P.The tubes are connected as a cascode.The overall gain is about 20.In my opinion The Out Put Transformer (OPT) is the heart of the amplifiers,so OPT must be so good wounded with minimum air gap,the position of the all 3 transformes is such a important point.You can use the 5k-8 transformer till the 10w.
For the high gain you can improve the bay-pass capacitors but the noise improves too.You can choose the C1 coupling capacitor 0.1uf or 0.47 uf,but dont forget this is change the lower and upper cut off frequency.
For the best sound you have to rearrange the anode current,for each time you change the tubes.
In the amplifiers one of the important points is power supply.Especially on tube amp. If there are any ripple on the supply voltage,you can hear out of the speaker as a noise.So ı chose a CLC filter configuration and DC filament supply to take out some of the voltage ripple and get the noise down.
As you see in fig. 2 my supply is very efficient,especially filament supply is very good for the tube amp to the 2A flaman current.The stability of the filament voltage is very important for noise and filament safety,ıf the filament voltage is rise rapidly for instance from 6.3v to 7,filament can break away.Thats way ı regulated my filament supply to 6.3v with LM317 .I used power supply capacitor at about 1000uf in total but feel free to use more.As ussual the anodevoltage is 300v ,the current is 45mA.That makes 13w anode power dissipation (P=IxV).
Enough heat sink (finned aluminium is good) is provided for filament supply.The filaments need 1.7A current in totall,we apply to the regulator 10v so (P=IxV) 17w power appeard on the transistors.Fig. 3 showsthe PCboard layout for the one channel.Note that the tube's sockets are mounted to the copper side (I did unusual artwork,the photos can be deluded,you must mount the sockets to the copper side,the other to the component side).
Keep in mind that this is a simple enough circuit to be wired up point-to-point.I just want
my amplifier to be enough tidy.Many people think building a chassis is the hardest part.In this matter ı was inspired from old fashion valve amps.Always ı use the aluminium to bulding chassis because to bend,drill or rasp is so easy,You can get aluminium bloc to attache or you can bend a alimunium block as ı did.The other simple way but ı dont recomended is buying a prefab chassis.The chassis of amp is very important in many aspect.So you do a good job and try not to be too cheap about it.You can use copper as well aluminium.I think copper will be good for the chassis.
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Just go ahead, build the prototype and let us know the result.
Take into account that 6P43P has quite different characteristics than EL84.
I would consider to use some NFB since your amplifier seems to be pentode connected SE. Without NFB it is quite a THD-generator. Also the output impedance is quite high.
With AC filaments it is possible to build completely quiet (hum-free=-80 dBc) amplifier, so DC-heaters are a bit overkill. Supply voltage filtering is very essential in SE amplifiers, which you seem to know.
Take into account that 6P43P has quite different characteristics than EL84.
I would consider to use some NFB since your amplifier seems to be pentode connected SE. Without NFB it is quite a THD-generator. Also the output impedance is quite high.
With AC filaments it is possible to build completely quiet (hum-free=-80 dBc) amplifier, so DC-heaters are a bit overkill. Supply voltage filtering is very essential in SE amplifiers, which you seem to know.
The drawing incorrectly links the screen grid to the cathode on the OP tube, TR2 is incorrectly drawn, the 12AX7 is incorrectly drawn. This amplifier will not work at all as drawn.
I would regulate the screen grid way before I regulated the heaters of indirectly heated tubes. It will make a much greater sonic improvement.
You need to implement feedback.
I would regulate the screen grid way before I regulated the heaters of indirectly heated tubes. It will make a much greater sonic improvement.
You need to implement feedback.
thanx for comment.
Sometimes use the el84,but usually ı use the 6p43p because ı have a lots of that valves.The TR2 can be wrong drawing,ı tried to show existance of 300v and 12v.Actually ı dont want to use NFB thats limiting the gaing.In the future ı will try to reduce preamp stage voltage to 180v.
I already have finished my amp building,and ı have done some measurment.The sounds impressed me especially trebles are perfect
here is that
the first scope fig. is 1khz the second 10khz
Sometimes use the el84,but usually ı use the 6p43p because ı have a lots of that valves.The TR2 can be wrong drawing,ı tried to show existance of 300v and 12v.Actually ı dont want to use NFB thats limiting the gaing.In the future ı will try to reduce preamp stage voltage to 180v.
I already have finished my amp building,and ı have done some measurment.The sounds impressed me especially trebles are perfect
here is that
the first scope fig. is 1khz the second 10khz
Attachments
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