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Posts by wakibaki

Don't do it that way.   Either use the volume control on the amplifier or whatever source you are using, or put a resistor divider (not just a single resistor) or a pot (variable resistor) between the source and the amplifier. You'll need a dual-gang (stereo) pot.       Putting a resistor between the output and the phones will almost certainly have a negative effect on the sound.   w
I don't think much of virtual ground circuits, but I drew this:-     As drawn it draws just 1.4mA, has an output offset of 6 nanovolts, and an output impedance of ~0.1 ohms. Build it with the LT1097 shown for the best performance, pretty much any complementary NPN/PNP pair will do, the bigger the beta the more current you will be able to sink/source (within the dissipation of the transistor). You could use the 2N3904/6 for modest currents, they have loads of...
  As shown simulated including worst case LT1097 input offset -   1.4mA total current   6 nanovolts output error   0R1 ballasts   With cheap LM2904 and 1R buffers, 50mV error, 3.4mA   Current flows out of an LM317 adj, btw.       w
  What does it do?
Some people thought up the idea of a ground channel.   They built amplifiers with it. They did measurements they thought showed it was better. They sold the idea to a lot of people, even though some other experts thought their theory was flawed.    Later somebody else came along with professional test equipment and did some measurements that were very hard to argue with, that showed that it was worse.   The people who thought up the idea could not admit that...
If you want a hybrid headphone amp, then the Millett 'Starving Student' is highly regarded. In fact it's so outstanding there isn't really anything else in the same league. The problem is, you can't get the tubes, and if you want to go with a variant, like the 12AU7 version, you can't get PCBs. That's to the best of my knowledge, somebody might know better   Fred_fred2004 made his own PCBs, you could ask his...
What's the 30R1 doing between C2 and the output jack? If you take a look at the Millett design that this is modelled on, it doesn't have this resistor, which AFAICS just increases the output impedance and wastes power. Unless somebody can point out a good reason for having it there, I'd take that out and put a jumper in. It keeps the rolloff down, but at the cost of reducing the damping factor and distorting the frequency response with phones that don't have a constant...
    w
  Absolutely not. It will make the crosstalk worse.   w
You can build a CMoy with an AD8397 as a direct substitute for whichever opamp. You will need to etch a board, however, to take advantage of the high current/power of which it is capable. It needs the pad on the bottom soldered to a large area of copper on the PCB to act as a heatsink. The easiest way to do that is to use SMT components on the top side, leave the bottom surface unetched and drill a fair-sized hole that will allow you to fill it with solder and make a...
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