I know enough about electronics to be dangerous. I also know how to be effective. I have built stuff from scratch, but to be completely honest I have never actually designed a complex audio circuit. But I have tweaked the living wee out of them.
I mucked deeply into my tube equipment as parts from 40 or 50 years ago simply were not that good. That was just swapping out for new and better.
I am much more reserved in transistor stuff. My favorite tweak is to the power supply. If you are in the high end cult you may buy plugs to go from the wall to your precious equipment that cost silly money. If you do you are silly. Golden ears will swear they hear an effect, and they actually may, but better or not is not a given.
Power to your machines comes from the wall socket. The wires in the wall are plain single conductor and unshielded unless you built your house to order. The power to your home comes through high voltage cables and line transformers and is not really very clean. Perfectly clean power would be a 60hz pure sine wave. (50hz in many places on the globe)
Even with fancy plugs the power coming into your devices is not perfect. You may buy surge protectors and filters for your computers and TV that is all about noise and poor quality power.
My thing is dealing with this inside the box. All audio equipment resolves alternating current into direct current. It takes the noisy sine wave and makes it clean and steady plus + and minus - volts. The quality of that is how steady. Tiny variations can be heard.
Electrical power has a wonderful analog, water. Imagine you had a device that runs on water pressure (analog to volts) and is available in large volumes (analog to amps). Now think of that water coming from a fast moving stream that surges and jumps (analog to the house current). You want it calm and placid. You dig a pond or build a dam to hold the water and calm it down. The calmer the pond the more steady the supply. If you want it really calm you make as big a pond as you can so the effects of the stream are dissipated.
It is exactly the same in amplifier power supplies. The pond is a thing called a capacitor. It charges up and acts as a reservoir of power. The bigger the capacitors the bigger the pond the calmer the power for the machine.
The first thing you can do is plug the biggest capacitors in that will fit. The downside is you can overwhelm the rectifier device that separates the plus and minus as a big capacitor that is not charged draws huge currents at start up. For small devices that is not much of an issue for big ones it is.
Also there is the fact that big capacitors are like batteries using chemicals. They are very fast high current batteries, but they only respond well to low frequencies. Noise on the line will get through to your precious circuits. Noise being anything that is not exactly 60 hz pure sine wave. The fix to that is to ground the capacitors with a smaller film type that respond to high frequencies.
The final big picture thing is each channel needs it’s own power. If you have stereo you need two power supplies. see below.
A tale of three amplifiers
I have three stereo amplifiers. Each is considered good for its time and is collectable. They are very different.
Carver Magnetic field M -200 T. Roughly mid to late 1980′s vintage. This is a cool device. The magic part is the power supply. A standard power supply converts wall current to DC at 60 hz in North America. That means the capacitors get charged in pulses 60 times per second. You can hear 60 hz it is that background hum that is so annoying. As I understand it Mr Carver did the simple and brilliant thing of artificially increasing the AC frequency so the power supply is charged far more often therefore requiring smaller capacitors to filter the current. They can therefore respond much faster. It sounds very nice and is also one of the beasts tweaked to sound like a cost no object high end amplifier in a blind test.
Harman Kardon Citation 12. This is a classic design from the early 70′s and is half the rated power of the Carver. Its magic is the power supply. Inside the box it is two completely separate amplifiers. This means Two power transformers, two full wave rectifiers, 4 power supply capacitors. It is otherwise dead conventional.
The difference between these two is far more than just the power supply, but the Carver shares the power between two channels so a big sound in one channel will draw power from the other. It is subtle but this hobby is all about subtle. The Citation sounds better even though it has poorer test scores. The way it sounds better is the stereo image drawn between the speakers is clearer and more steady.
Even though both are “old” they both have been repaired and tuned up in the last two years so they are fresh. I credit the superiority of the Citation to the separated power supplies. One channel is free from the other.
Dynaco 410 / 416. The beast. Design dated to the 1970′s. I built this thing from mostly prefabricated circuits while adding extra output transistors. The Amplifier circuit is identical to the Dynaco 416 but in a black box. I built it with two separate full wave rectifiers into two completely separate capacitor banks each the same size as “stock”. That avoids the problem with excessive current at turn on. So it is dual mono just like the Citation, but for sharing the HUGE transformer which is ok cuz its HUGE.
The capacitor banks are bridged with film capacitors to kill the noise from the wall. All by itself this thing sounds amazing. It is clear and clean and has huge bass and solid stereo imaging. I fear no amplifier that may come against it.
Comparing all three the Dynaco is the king. There is no contest on the clarity and the performance. Recall that the Carver is reputed to be indistinguishable from very expensive high end amps of the day.
The final bit is my tweak to the tweak. Just before Dynaco Inc. bit the dust they made an accessory to their top 416 model that was an enormous additional capacitor bank to plug into the 416. It has a pretty complicated circuit to control the charge at turn on. If it did not, it could fry the house wires. I built one with a stupid simple charge circuit. I found a bunch of big capacitors and built a set of 4 banks with 1 Farad of total capacitance. That is 50 times the size of the stock design.
My trick here was that the capacitors charge through big resistors to limit current going in. Those are them back fed through really fat diodes to let the current out very fast. The effect of plugging it in is profound. An already quite amp goes silent. The image of a well recorded orchestra is solid where you can place every instrument and feel the metallic sound of the brass and the woody sound of the woodwinds. In Rock the bass is solid and deep. Vocals are just amazing.
Now the car stereo geeks will go meh. “We use one farad caps all the time.” Not the same kids. The power in a capacitor is proportional to the square of the voltage. A car uses 12 to 14 volts. My beast uses 74 volts. That is about 30 times more power. You could weld with it.
The Carver and the Citation have at best factory tweaks to “normal” circuits. The designers were very good to brilliant. The Dynaco was designed by a team that included people working on state of the art (1970′s) and included great and brilliant names too. It was very good, but they were accused of hobbling it to hit a price point. The 416 was apparently an attempt to un-hobble it.
I have vintage equipment. I respect the Carver and the Citation and do no more than keep them maintained. The Dynaco is another matter.
The lesson here is you can have extraordinary equipment if you buy vintage and twist its arm a bit.
