I'll start here with the manual. And I'll start with the psu.
First of all as some of you might know. Everyone has their own preferences in audioworld
So some will swear by choke input psu's and others will prefer a cap input. Some like a lot of uF's others like minimal uF's. Some like tube rectum fryers others prefer sand solutions. Let's not start the discussion about that here, since that is not the point.
AFAIC ( http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=afaic&Find=Find ) the point is getting a rough idea about building a simple psu for a tube amp. (But some of my preferences will ofcourse be used to demonstrate how you might arrive at a hum free psu for your Aikido)
The first thing you need to do is start playing with PSUD2
http://www.duncanamps.com/psud2/
Try to get something that resembles this picture. It is a full wave tube rectified CRCRC supply. With a CCS load (resembling the current drawn by the Aikido circuit)
First of all as some of you might know. Everyone has their own preferences in audioworld
So some will swear by choke input psu's and others will prefer a cap input. Some like a lot of uF's others like minimal uF's. Some like tube rectum fryers others prefer sand solutions. Let's not start the discussion about that here, since that is not the point.
AFAIC ( http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=afaic&Find=Find ) the point is getting a rough idea about building a simple psu for a tube amp. (But some of my preferences will ofcourse be used to demonstrate how you might arrive at a hum free psu for your Aikido)
The first thing you need to do is start playing with PSUD2
http://www.duncanamps.com/psud2/
Try to get something that resembles this picture. It is a full wave tube rectified CRCRC supply. With a CCS load (resembling the current drawn by the Aikido circuit)
An externally hosted image should be here but it was not working when we last tested it.
Ok..have you done that?
You got an error right?
One of the main reasons is the first cap. a Rule of thumb is that the bigger the first cap after the rectifier the bigger the currents that will flow there. See what happens if you lower the value to 2uF? But it's not just the first cap it's also the second cap. The rectifier can "see" a little of the second capacitor. (If the value of R1 had been bigger...the rectifier would not complain, because it can't "see" the big cap. Test this for yourself by making R1 something like 5K. Or changing the RC to an LC.
PS. A solid state rectifier is not bothered by a big capacitor it can handle much higher currents. (But the big currents make the PSU a noise generator)
Now..in the left pane, mark the checkbox V(I1) i.e. you want to see the voltage across I1. I1 is your circuit...in our case the Aikido.
Check what happens if you change the value of c1..by typing in for example 0.1uF and 2uF. Did you spot what happened with the voltage.
Hasta Luego.
Next installment...calculating the wattage of the resistors.
You got an error right?
An externally hosted image should be here but it was not working when we last tested it.
One of the main reasons is the first cap. a Rule of thumb is that the bigger the first cap after the rectifier the bigger the currents that will flow there. See what happens if you lower the value to 2uF? But it's not just the first cap it's also the second cap. The rectifier can "see" a little of the second capacitor. (If the value of R1 had been bigger...the rectifier would not complain, because it can't "see" the big cap. Test this for yourself by making R1 something like 5K. Or changing the RC to an LC.
PS. A solid state rectifier is not bothered by a big capacitor it can handle much higher currents. (But the big currents make the PSU a noise generator)
Now..in the left pane, mark the checkbox V(I1) i.e. you want to see the voltage across I1. I1 is your circuit...in our case the Aikido.
Check what happens if you change the value of c1..by typing in for example 0.1uF and 2uF. Did you spot what happened with the voltage.
Hasta Luego.
Next installment...calculating the wattage of the resistors.
Banned
Joined 2002
I hope it works for you as well
Have you decided what tubes you are going to use?I do now
But until sept 1 you can still change ofcourse...Remember...the Aikido is not really hard to make. After your first 2 on PCB you might have enough courage to build it P2P. The next frontier ...nie noo nie noo nie noo.....
Banned
Joined 2002
Bas Horneman said:
I hope it works for you as well
I do now
Remember...the Aikido is not really hard to make. After your first 2 on PCB you might have enough courage to build it P2P. The next frontier ...nie noo nie noo nie noo.....
I need help on the choice of tubes : O ( I'll get planet 10 to help me..
PSU pcb's anyone?
An externally hosted image should be here but it was not working when we last tested it.
Calculating the wattage of a resistor
In our case the first 1k resistor will have current running through there for both channels.
Let's assume our Aikido is pulling 40mA. Our resistor is 1k.
So we have I = 40mA = 0,04A
and we have R = 1000 ohm
R=V/I
if we want to know the voltage drop we have to change the formula to V=R*I or V=1000*0,04
40V thus the 1000R resistor drops 40V across it.
Now we want to know how many watts the resistor will consume.
W=V*I
V=40
I=0,04A or 40mA
W=1,6 WATT
Therefore a 2 Watt resistor will do (theoretically), but we don't ever want our psu to fail...and since we don't know what the ambient temperature is going to be..we want to be safe rather than sorry.
Doubling or tripling the wattage is a good idea, therefore a good ballpark wattage would be 5 watt resistor.
Ok..your homework is to calculate the value for r2 an r3 or to double check my post...to find out where I made mistakes
In our case the first 1k resistor will have current running through there for both channels.
Let's assume our Aikido is pulling 40mA. Our resistor is 1k.
So we have I = 40mA = 0,04A
and we have R = 1000 ohm
R=V/I
if we want to know the voltage drop we have to change the formula to V=R*I or V=1000*0,04
40V thus the 1000R resistor drops 40V across it.
Now we want to know how many watts the resistor will consume.
W=V*I
V=40
I=0,04A or 40mA
W=1,6 WATT
Therefore a 2 Watt resistor will do (theoretically), but we don't ever want our psu to fail...and since we don't know what the ambient temperature is going to be..we want to be safe rather than sorry.
Doubling or tripling the wattage is a good idea, therefore a good ballpark wattage would be 5 watt resistor.
Ok..your homework is to calculate the value for r2 an r3 or to double check my post...to find out where I made mistakes
A real world example of a good resistor for our R1 would be the
http://www.mouser.com/index.cfm?han...uctid=305018&e_categoryid=356&e_pcodeid=71010
it is a Dale RS 5 Watt wirewound resistor. Wirewound resistors are some of the best and best sounding resistors to use in a tube amp. No need to get resistors with zero inductance in the psu..the inductance is welcome. This particular resistor is safe to use with high voltages as well..but since there is only 40volts across it..I don't think it matters.
http://www.mouser.com/index.cfm?han...uctid=305018&e_categoryid=356&e_pcodeid=71010
it is a Dale RS 5 Watt wirewound resistor. Wirewound resistors are some of the best and best sounding resistors to use in a tube amp. No need to get resistors with zero inductance in the psu..the inductance is welcome. This particular resistor is safe to use with high voltages as well..but since there is only 40volts across it..I don't think it matters.
The dual function voltage divider.
Our voltage divider has two functions:
1.) To provide an elevated voltage for referencing the heater supplies.
2.) To act as a bleeder for the high voltage caps.
On the bleeder. The bleeder drains the high voltage caps, in our case probably not as fast as is required in safety codes. I think it the USA there is a code that says the HV supply should be below 60V within 30 seconds. To comply with that code you might have to solder extra resistors across the high voltage caps..
Remember that a bleeder also draws some current. (pretty low current)
If R1 is substituted by a choke a bleeder might also be necessary to maintain the critical inductance of the choke.
http://www.audioxpress.com/resource/audioclass/ga499ac.pdf
for more info.
Our voltage divider has two functions:
1.) To provide an elevated voltage for referencing the heater supplies.
2.) To act as a bleeder for the high voltage caps.
On the bleeder. The bleeder drains the high voltage caps, in our case probably not as fast as is required in safety codes. I think it the USA there is a code that says the HV supply should be below 60V within 30 seconds. To comply with that code you might have to solder extra resistors across the high voltage caps..
Remember that a bleeder also draws some current. (pretty low current)
If R1 is substituted by a choke a bleeder might also be necessary to maintain the critical inductance of the choke.
http://www.audioxpress.com/resource/audioclass/ga499ac.pdf
for more info.
Banned
Joined 2002
9US$, You need only one per channel.
If you want dual mono you can use 2 pcb's. In this case you would just omit one RC network on each pcb.
The PSU is real easy and no pcb is needed really. But some folks find neatness of their project important. This board is also usefull if this is your first tube amp project. It will make it a easier to succesfully build a preamp.
Banned
Joined 2002
Bass; I have always thought that power supplies although seemingly straightforward are the least understood function in many units. As such there is nothing boring about your posts, they are easy to understand and much appreciated.
By the way, if you go with the PS PCB's, put me down for two.
Regards;
Pete
By the way, if you go with the PS PCB's, put me down for two.
Regards;
Pete
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