You might think about using an IRFP240 instead of that IRF540. True they both have a 150w rating but the thermal resistance of a T0220 insulator is a lot higher than one for a T0247 package and the input capacitence is a lot lower too.
The simplist solution to improve the performance without altering the power supply is to sub in an ECC86. You will have to choose a suitable cathode resistor to get your 10mA but you can increase the load resistor as it only requires 12V DC to operate.
This also opens up the possibility of a Mu-follower driver stage with the same B+ which would giove vastly better performance than a plate load resistor.
Shoog
This also opens up the possibility of a Mu-follower driver stage with the same B+ which would giove vastly better performance than a plate load resistor.
Shoog
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How much regulation is required here to smooth the ripples? Can simple rectifier followed by usual capacitor banks work? How big of a capacitor is needed - as obviously, its tougher to find large values at these higher voltages. I have some 50uF 450V motor start caps - would a pair of those suffice if I want to go the route of using 120vac rectified to get the 170vdc?
If you refer to the schematics in post #1, you will find that the B+ is only 50VDC and all the values concerning the operation of the tube are accordingly.
The idea was to make a simple low cost nice sounding amplifier. I belief the circuit in post#1 has achieved that. Everyone that has listened to it agreed.🙂
If you like to keep cost down, stick to the basics. However, if you do not mind spending a bit more and make it a bit more complex, go for a higher B+. You just need to recalculate the resistor values.
If you refer to the schematics in post #1, you will find that the B+ is only 50VDC and all the values concerning the operation of the tube are accordingly.
The idea was to make a simple low cost nice sounding amplifier. I belief the circuit in post#1 has achieved that. Everyone that has listened to it agreed.🙂
If you like to keep cost down, stick to the basics. However, if you do not mind spending a bit more and make it a bit more complex, go for a higher B+. You just need to recalculate the resistor values.
Ok great - I did not know that the 54v was the same as the one from the main PS. I thought there was other ancillary "tube supplies" not shown. If so this is really simple and I am good to go. My PSU has a spare 7vdc output that is perfect for the filament .
How is it coming along xrk971?
I had mine hooked up to the big speakers and my DIY preamp. Oh my! I hardly can belief how nice it sounds.
I am still waiting for tube to come in. I also have a 300va 32v torpid that should make 49v rectified and filtered. If it needs a preamp I have a JLH class A preamp.
XRK971 if you get your bits, just check out my revised schematics.
The value of some of the resisters has changed. I have added a cathode resistor (68 Ohm) and I have changed the plate resistor to 3.3K Ohm. This improved the sine wave and increased the gain.
When I load tested the amp, I found the bias needed a bit of tweaking to center the sine wave. So R4 is now 2.2K Ohm.
The output is now just under 4W on the onset of clipping.
These values are for a 50Vdc supply on the rail.
I did run it with a pre amp just for the sake of it, but it is not really needed. That is what your 6922 is for.
The value of some of the resisters has changed. I have added a cathode resistor (68 Ohm) and I have changed the plate resistor to 3.3K Ohm. This improved the sine wave and increased the gain.
When I load tested the amp, I found the bias needed a bit of tweaking to center the sine wave. So R4 is now 2.2K Ohm.
The output is now just under 4W on the onset of clipping.
These values are for a 50Vdc supply on the rail.
I did run it with a pre amp just for the sake of it, but it is not really needed. That is what your 6922 is for.
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Great - thanks for the update. Still waiting for 6922. I actually have some copper clad boards now and may try to etch my very first PCB for this project 😀
I have had PCB's made in Singapore for $10 (works very well Apex FX8) but takes a month.
I have had PCB's made in Singapore for $10 (works very well Apex FX8) but takes a month.
In preparation for the tube's arrival, I realize I don't have tube sockets. Is there a budget way to connect tube pins? Is it ok to solder flying leads to pins?
I was looking at your photo and tube pin out diagram and just realized that the tube and your protoboard amp has two sides - stereo in one tube. That's convenient. 🙂
I was looking at your photo and tube pin out diagram and just realized that the tube and your protoboard amp has two sides - stereo in one tube. That's convenient. 🙂
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Soldering to the pins is just not going to work reliably (the pins will wick away to much heat to get a good solder), but Glossmaster's idea would get you going.
Valve sockets are cheap though so do yourself a favour and get some.
Shoog
Valve sockets are cheap though so do yourself a favour and get some.
Shoog
No, the inductor would not work. Use 3 x 10w 100R in parallel to experiment. They will get very very hot (130C), dissipateing around 35W. So be careful of where you place the resistors. Mine are on the heatsink. I am waiting on some 50W 27 ohm resistors for the proper build.
Alternatively you could try a suitable incandescent light globe with preferably a carbon filament. (In the US 110v/300w I think)
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