Thank you so much for this helpful video, Dave. I'm restoring / modding a 1963 Ampeg Jet J-12A my brother gave me in the 80s before he passed away. The face is so pitted it could never be restored, so I have added bass, mid, and treble controls plus a high gain on V1b. Tremolo has been removed. The template for pots, etc is something I intend to do. Fantastic idea! I may get one of your kits in the future. Thanks again ...
04:53 What is not talked about, but may (or may not) be common knowledge is the direction of the twist in the twisted pair. In my experience, it's ALWAYS a good idea to twist the wires in the same direction as the twist in the strands of wire. If they go CCW, then the twisted pair goes in the same direction. If it's CW, then the twisted pair will go in the other direction (CCW = anti-clockwise for Europe?). The result is the ability to achieve a tighter twist in the pair, without it wanting to naturally unwind itself.
Very good video, Dave. The only recommendation I would make is making sure that the power tube wiring is consistent, (ie V3 Pin 2 terminates at V4 Pin 2, V3 Pin 7 terminates at V4 pin 7). This will hum cancel the power tubes. Great job as always!
@@fakundofrontera From what I know, consistent wiring for hum cancellation is only necessary on the power tubes and not from power tubes to the PI and preamp.
You want the lengths of the two wires to be EXACTLY the same. They must cancel each other perfectly. Any wiring should cross them at a perfect 90 degree angle.
after you twist the wires does it matter which end is soldered or do you do a continuity test?, if so, wouldn't it be good to use different colored wires to be sure?
In my kits, I provide the PTFE (teflon) coated wire because it is non burning, clean looking and easy to work and solder. Seven strand 22 ga strand wire is preferred over single strand which can suffer nicks which may lead to breakage. Your mileage may vary.
I use stranded 20 ga. 18 ga is heavier than needed for this application and more difficult to work with. Solid wire is fine, however one must take care not to nick it when stripping it. It is prone to break where it gets nicked.
The old radios typically operate without a power transformer. If you add up the numbers on the tubes they will be close to 110 volts. Tubes were selected so that in total they would use approximately 110 v of heater current which was supplied directly from the household wall outlet. I am going to say that due to this methodology, one cannot put that current to ground through a pair of resistors. Maybe someone else knows something about this. If you have a lot of hum in an old radio, and you haven't replaced the filter capacitors, this would be the likely problem. The blocking caps and bypass caps should also be replaced.
Artificial Center Tap - use two 100 ohm or two 82 ohm 1/2 watt resistors. Connect one leg of each resistor to each of the two heater pins on the 6Bq5 power tube. Let them stick up. Bend the upper legs down and solder them together on the cathode pin. The AC heater current will ride above ground (ground = zero volts) on the 18 V DC cathode current. This is quieter than ground.
Sir! I am sorry to barge in, First of all I must tell you that I am not an Electronics Expert but I do understand little thing or two. My Little Dot MK2 Amplifier has been giving a buzz /Hum which I cannot fix no matter what I do. Somewhere in headfi I have seen someone adding an artificial center tap to his LD MK1 which got rid of the noise. I am thinking of doing this to my LD MK II which is a full tube headphone amplifier. According to what I understood....! I have to solder a 100ohm resistor to each Filament wire of the tube connectors and ground the other end of the resistor. Please correct me if I am wrong. By searching artificial center tap i have found your video (Above)
Thank you so much for this helpful video, Dave. I'm restoring / modding a 1963 Ampeg Jet J-12A my brother gave me in the 80s before he passed away. The face is so pitted it could never be restored, so I have added bass, mid, and treble controls plus a high gain on V1b. Tremolo has been removed. The template for pots, etc is something I intend to do. Fantastic idea! I may get one of your kits in the future. Thanks again ...
04:53 What is not talked about, but may (or may not) be common knowledge is the direction of the twist in the twisted pair.
In my experience, it's ALWAYS a good idea to twist the wires in the same direction as the twist in the strands of wire.
If they go CCW, then the twisted pair goes in the same direction. If it's CW, then the twisted pair will go in the other direction (CCW = anti-clockwise for Europe?).
The result is the ability to achieve a tighter twist in the pair, without it wanting to naturally unwind itself.
Very good video, Dave. The only recommendation I would make is making sure that the power tube wiring is consistent, (ie V3 Pin 2 terminates at V4 Pin 2, V3 Pin 7 terminates at V4 pin 7). This will hum cancel the power tubes. Great job as always!
and from the power tubes to the phase inverter and preamp tubes what order showld i continue with? from the power tubes to what pins in the 12ax7?
@@fakundofrontera From what I know, consistent wiring for hum cancellation is only necessary on the power tubes and not from power tubes to the PI and preamp.
Whoa, it seems to make sense to me. Just like balanced audio works.
You want the lengths of the two wires to be EXACTLY the same.
They must cancel each other perfectly. Any wiring should cross them at a perfect 90 degree angle.
Looks great. Provides a thorough, detailed explanation in video format. Great camera work and editing.
Good video. I hadn't realized that filament heating was provided by AC current. I'm just learning about amp construction. I guess it shows.
This is the video I have been looking for.
Thank you
after you twist the wires does it matter which end is soldered or do you do a continuity test?, if so, wouldn't it be good to use different colored wires to be sure?
3:01 the resistors on the right are your artificial center tap, what are the resistors on the left?
The heaters wiring has an phase and out of phase? you got to follow some order or its the same any wiring to the pins??
if i am going to build an amp kit what kind of wire should i use? solidor stranded? ptfe covered? copper or aluminum? etc etc
In my kits, I provide the PTFE (teflon) coated wire because it is non burning, clean looking and easy to work and solder. Seven strand 22 ga strand wire is preferred over single strand which can suffer nicks which may lead to breakage. Your mileage may vary.
@@davidwhalen5658 Thank you for the info.
Hello!
What kind of potentiometers are these?
They are old stock 2 meg CTS pots. They're a bit too resistive for these amps. (You can't turn the volume all the way down.)
1. What gauge wires do you use?
2. Do you use stranded or solid wire?
Thank you. Looking forward to being a new customer!
I use stranded 20 ga. 18 ga is heavier than needed for this application and more difficult to work with. Solid wire is fine, however one must take care not to nick it when stripping it. It is prone to break where it gets nicked.
20 or 22 ga is big enough for a 5E3 or other 15 watt amplifier.
I am curious about your thoughts on reversing of the 2 heater wires , I have a fender that has them reversed.
Not sure what you mean.
Thanks so much Dave
Great presentation, can you insert the artificial centre tap on a tube radio power tubeEL41 to prevent hum? Many thanks.
The old radios typically operate without a power transformer. If you add up the numbers on the tubes they will be close to 110 volts. Tubes were selected so that in total they would use approximately 110 v of heater current which was supplied directly from the household wall outlet. I am going to say that due to this methodology, one cannot put that current to ground through a pair of resistors. Maybe someone else knows something about this. If you have a lot of hum in an old radio, and you haven't replaced the filter capacitors, this would be the likely problem. The blocking caps and bypass caps should also be replaced.
Interested in the artificial center tap. Where would you add this on a circuit (Kalamazoo Model 1) that has a 12ax7 pre-amp, and a 6BQ5 power tube?
Artificial Center Tap - use two 100 ohm or two 82 ohm 1/2 watt resistors. Connect one leg of each resistor to each of the two heater pins on the 6Bq5 power tube. Let them stick up. Bend the upper legs down and solder them together on the cathode pin. The AC heater current will ride above ground (ground = zero volts) on the 18 V DC cathode current. This is quieter than ground.
Sir! I am sorry to barge in, First of all I must tell you that I am not an Electronics Expert but I do understand little thing or two. My Little Dot MK2 Amplifier has been giving a buzz /Hum which I cannot fix no matter what I do. Somewhere in headfi I have seen someone adding an artificial center tap to his LD MK1 which got rid of the noise. I am thinking of doing this to my LD MK II which is a full tube headphone amplifier. According to what I understood....! I have to solder a 100ohm resistor to each Filament wire of the tube connectors and ground the other end of the resistor. Please correct me if I am wrong. By searching artificial center tap i have found your video (Above)
Your heater wiring is wrong