This is an EXQUISITE demonstration of a balanced circuit. Bravo! The same applies when we use a "balanced" antenna, like a dipole fed with balanced ladder line. There is high differential current, but the common mode current is theoreticaly ZERO when the antenna is truly balanced. Tony, I hope someday you'll tie this video in to what I've commented on. While initially it pertains to ham radio, it will also be part of a good FM receive antenna that is fed with 300 ohm balanced line. In any case, it's GREAT electronic theory that is often overlooked. Thanks for this video. 73 & Happy Holidays.
Nice video! Talking about dual voltage +- power supplys, I just recently had a funny WT* experience when I opened a 1989 Alesis MicroEQ (parametric eq) to deoxit switches and pots and to measure if the elyts are OK. It has 9VAC power input voltage connection (no center tap) and it makes it's +-12VDC dual voltage internal power supply from that 9VAC using (four diodes and 330uF caps ) voltage doubling, feeding around +- 20 VDC to 7812 and 7912 regulators to smooth the ripple voltages. The funny thing was that the polarities (+ markings) of both 4.7uF/50V output electrolytic caps after regulators were printed wrongly to the PCB and both of them were installed in reverse polarised. Those caps were original. Those caps had not blown or leaked only because that device had been used only maybe for 50-100 hours during last 30 years and the reverse voltage was only 12VDC and those caps were rated 50V. I measured those caps, and surprisingly, they were quite OK, 3-5 ohm ESR, no significant leak whatsoever @ 20V, capacitances about 4.8 uF. If they had been for example 16V caps they probably would have blown immediately. 🤔 The PCB of that EQ was populated with many kinds of QC stickers, but seemingly they put those stickers just for fun without any real quality check ever done. 🤣
I spent my life flying for a living. We had lecturers whose knowledge was encyclopedic, however if they can’t transfer that knowledge to their students. Then there are lecturers that have the ability to transfer that knowledge into to their students. Tony is one of those. Amazing video I learnt so much. Thank you.
Hi Tony, this is used in all the high energy distribution that I worked on, at the time I had no idea why there was a current sensor in the neutral and why it was important. as you are trying to convey in a balanced system with more than one power source the neutral current will be low. What an ingenious idea, I never dreamed it would be used in an audio amp! Rich
This reminded me of college when we were learning "Loop and Nodal analysis" of circuits. 😊 In the end, we were expected to design and build an analog power-supply. Infact, I PREDICTED each of your outcomes before you made the changes. (including RMS conversions by multiplying by 1.414)
Excellent explanation Tony, good stuff. Important to understand this as this is common for a lot of amplifiers. BTW not all "Protect circuits" are the same, I recently had a Rotel RB-990 on my bench, a 2 x 200Watts unit. And on it, the protect didn't diconnect the speakers, it only shorted the input audio signal to ground. I would call that "Mute", not "Protect", but anyways...😊
Back in days when I was more into fixing amps I was wondering why they don't put 2 full bridge rectifiers after center tap transformer? In my head it will make much smoother voltage for both positive end negative voltage rails, and maybe then they can use smaller caps...
I tried to work out the values in your schematic but I was off by a factor of 10. In looking at the breadboard and decypering the resistor color codes, I see that you are using 470 ohm resistors, not 4K7 (4,700 ohm) resistors.
I have a question for you?, I have a realistic ST a 64 stereo receiver and on the power supply board they use in SCR transistor, plus there’s also two fuses for protection as well so what is the SCR transistor for?
I’m not speaking for Tony, but I know he doesn’t have enough time to respond to everyone. So, the protection relay does not contribute to the quality of the signal. The signal passes through closed contacts which are basically just a switch.
@@BobWilson84 exactly ! think of the increased resistance and how the signal passing through different material(carbon contacts) could possibly degrade the sound.
I had similar thoughts.I recently added active speaker protection to a dc coupled exposure amp .I can not discern any sonic degradation.(and my precious speakers are protected from a second failure of output transistors)
@@garygranato9164 It's no different than input switches, rca jacks, speaker terminals. These are all just contacts which, in practice, don't affect the quality of the signal if they are clean. And, relay contacts lead pretty nice lives inside of a plastic housing safe from dust and contaminates
Hi Tony, thanks for the great videos and projects you do.ive been thinking about doing some modifications and upgrades on some of my hifi equipment, thanks to your videos and experience I feel I have the knowledge to undertake some projects, wishing you and your family a merry Christmas and great New year.
Great and clear explanation of one of those concepts that we take for granted, but rarely give it more thought. Thanks Tony.
This is an EXQUISITE demonstration of a balanced circuit. Bravo! The same applies when we use a "balanced" antenna, like a dipole fed with balanced ladder line. There is high differential current, but the common mode current is theoreticaly ZERO when the antenna is truly balanced.
Tony, I hope someday you'll tie this video in to what I've commented on. While initially it pertains to ham radio, it will also be part of a good FM receive antenna that is fed with 300 ohm balanced line. In any case, it's GREAT electronic theory that is often overlooked.
Thanks for this video. 73 & Happy Holidays.
Very cool thanks for the explanation!
Nice video!
Talking about dual voltage +- power supplys, I just recently had a funny WT* experience when I opened a 1989 Alesis MicroEQ (parametric eq) to deoxit switches and pots and to measure if the elyts are OK. It has 9VAC power input voltage connection (no center tap) and it makes it's +-12VDC dual voltage internal power supply from that 9VAC using (four diodes and 330uF caps ) voltage doubling, feeding around +- 20 VDC to 7812 and 7912 regulators to smooth the ripple voltages. The funny thing was that the polarities (+ markings) of both 4.7uF/50V output electrolytic caps after regulators were printed wrongly to the PCB and both of them were installed in reverse polarised. Those caps were original. Those caps had not blown or leaked only because that device had been used only maybe for 50-100 hours during last 30 years and the reverse voltage was only 12VDC and those caps were rated 50V. I measured those caps, and surprisingly, they were quite OK, 3-5 ohm ESR, no significant leak whatsoever @ 20V, capacitances about 4.8 uF. If they had been for example 16V caps they probably would have blown immediately. 🤔
The PCB of that EQ was populated with many kinds of QC stickers, but seemingly they put those stickers just for fun without any real quality check ever done. 🤣
I spent my life flying for a living. We had lecturers whose knowledge was encyclopedic, however if they can’t transfer that knowledge to their students. Then there are lecturers that have the ability to transfer that knowledge into to their students. Tony is one of those. Amazing video I learnt so much. Thank you.
Hi Tony, this is used in all the high energy distribution that I worked on, at the time I had no idea why there was a current sensor in the neutral and why it was important. as you are trying to convey in a balanced system with more than one power source the neutral current will be low.
What an ingenious idea, I never dreamed it would be used in an audio amp!
Rich
Excellent demo
Great "nuts and bolts" demo! Enjoyed watching, thanks for your time.
This reminded me of college when we were learning "Loop and Nodal analysis" of circuits. 😊 In the end, we were expected to design and build an analog power-supply. Infact, I PREDICTED each of your outcomes before you made the changes. (including RMS conversions by multiplying by 1.414)
Good stuff Tony, thanks
Yet another very nicely explained circuit with an experiment marked by Tony. Thanks!
Excellent explanation Tony, good stuff.
Important to understand this as this is common for a lot of amplifiers.
BTW not all "Protect circuits" are the same,
I recently had a Rotel RB-990 on my bench, a 2 x 200Watts unit.
And on it, the protect didn't diconnect the speakers, it only shorted the input
audio signal to ground.
I would call that "Mute", not "Protect", but anyways...😊
Nice. I liked the demonstration. I see fused on the ct in some tube amps protecting the other circuits in the push or pull side when a tube shorts.
Thanks Tony, this helps me to understand the circuit.
Thanks, great explanation.
Great video, awesome explanation! Thank you for taking the time to create this video! 👍👍
Never thought this way..
Another perspective, essential push pull amplifier.🙏👍
Good demonstration.
Great video Tony; thanks! 😀
Thanks! Great informative video. Love all your videos. always pro work from a "amateur" :)
Wonder... what goes thru genius minds building, thinking up circuits as these, what if... . Superheterodyne, tv interlacing, stereo multiplex in fm.
Back in days when I was more into fixing amps I was wondering why they don't put 2 full bridge rectifiers after center tap transformer? In my head it will make much smoother voltage for both positive end negative voltage rails, and maybe then they can use smaller caps...
"You can never have too many meters!" Absolutely true! They need to make a multi-multi-meter that has 5 in one :P
Super-excellent
thanks Tony for teaching us this stuff .one knows school only made me dumber lol God bless
Oh just one other thing it kind of looks like maybe they might be using that for a speaker protection of some kind but I’m not sure.
It behaves just like a neutral imbalance in your home 120/240V single phase power system. Kind of a brilliantly simple design.
I tried to work out the values in your schematic but I was off by a factor of 10. In looking at the breadboard and decypering the resistor color codes, I see that you are using 470 ohm resistors, not 4K7 (4,700 ohm) resistors.
I have a question for you?, I have a realistic ST a 64 stereo receiver and on the power supply board they use in SCR transistor, plus there’s also two fuses for protection as well so what is the SCR transistor for?
It probably acts as a DC switch. Check out Tony's video on it at ruclips.net/video/bnfELgSfVHg/видео.html
@@hestheMaster OK thank you, I’ll go ahead and do that thank you very much for the link.
would this "protect circuit" give better sound quality being as the signal isnt passing through a relay ??
I’m not speaking for Tony, but I know he doesn’t have enough time to respond to everyone. So, the protection relay does not contribute to the quality of the signal. The signal passes through closed contacts which are basically just a switch.
@@BobWilson84 exactly ! think of the increased resistance and how the signal passing through different material(carbon contacts) could possibly degrade the sound.
I had similar thoughts.I recently added active speaker protection to a dc coupled exposure amp .I can not discern any sonic degradation.(and my precious speakers are protected from a second failure of output transistors)
@@garygranato9164 It's no different than input switches, rca jacks, speaker terminals. These are all just contacts which, in practice, don't affect the quality of the signal if they are clean. And, relay contacts lead pretty nice lives inside of a plastic housing safe from dust and contaminates
👍👍👍😃😃😃
Hi Tony, thanks for the great videos and projects you do.ive been thinking about doing some modifications and upgrades on some of my hifi equipment, thanks to your videos and experience I feel I have the knowledge to undertake some projects, wishing you and your family a merry Christmas and great New year.