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Buffalo II

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#49
It seems to me that questions concerning various tube amps are outside the scope of this particular thread and forum. Such questions are more suitable to "Tubes / Valves" forum.

Generally speaking, concerning any DAC's output in current mode feeding a tube amp:

The simplest solution is to add a very low value resistor at the input(s) of the tube stage, before the decoupling capacitor. About the exact value of the resistor I believe Brian would now better.

The second solution is to have an input trafo, whose primary is connected to the DAC's balanced output and the secondary is connected to the stage's input. This solution is suitable especially for SE tubes stages, the input trafo converts the DAC's balanced output to the tube stage SE input.
 
#56
glt said:
I'll say that for short runs, any cable will work. Cat 5 is actually very good copper and they come in twisted pairs that provides shielding (if you want more shielding, you can get cat-6). You can connect all the "white" wires to gnd.

If you look at the RJ45 connectors, it is basically two wires touching each other, except that if you use the Ethernet-ready sockets, they have a little pcb with some funny looking trace patterns which I think is for high speed issues (reflection and so forth) which I'm not sure matters or not in audio.
Click to expand...

I was out of town for a bit, sorry I didn't respond more quickly. Thank you for the tip on the cat-6, I think I'll try that instead of the cat-5. I'll look at some RJ45 connectors and see how they might be utilized.

The reason why I asked is because the digital cabling is data transmission, so the little bit that I already know and understand about analog audio cables might not apply to digital transmission. I have been looking at how manufacturers have implemented I2S connections, and a lot of them are using RJ45's, so perhaps that is a good way to make the digital connection (and the bonus is that the cables are already made up and inexpensive).

Bunpei-
Thank you for sharing your experience. The DIN connector sounds like it would work as well. I don't understand the reasoning behind not using differential cabling for non differential connections. A differential cable is defined by the number of connectors it uses, not by the way in which the cable is built, right?

Thanks again to both of you.

Best,
Aaron.
 
#57
orpheus said:
Bunpei-
Thank you for sharing your experience. The DIN connector sounds like it would work as well. I don't understand the reasoning behind not using differential cabling for non differential connections. A differential cable is defined by the number of connectors it uses, not by the way in which the cable is built, right?
Click to expand...

Differential has two conductors, but instead of one being ground and the other signal. they both carry signal, with one line out of phase with the other so the receiver can cancel common-mode noise. Twisting the pairs ensures noise is coupled equally to both wires.

Typical I2S connections between CD and DAC are on the order of a matre, with a minimum clock rate of 1.4 MHz, so correct impedance along the line is useful for preventing jitter caused by reflections. The RJ-45 is better suited to the task than the DIN connector because it keeps the conductor spacing the same as in the cable, whereas the DIN spreads them out.
 
#58
DSP_Geek said:
Differential has two conductors, but instead of one being ground and the other signal. they both carry signal, with one line out of phase with the other so the receiver can cancel common-mode noise. Twisting the pairs ensures noise is coupled equally to both wires.

Typical I2S connections between CD and DAC are on the order of a matre, with a minimum clock rate of 1.4 MHz, so correct impedance along the line is useful for preventing jitter caused by reflections. The RJ-45 is better suited to the task than the DIN connector because it keeps the conductor spacing the same as in the cable, whereas the DIN spreads them out.
Click to expand...


Thank you for helping me with selecting a cable and connector. Sounds like RJ45 would work the best, which makes sense since it is designed to transmit digital signals. I need to look at the options and decide which ones to buy and which wires to connect to which signals.

From what you wrote, ideally I should also run the CAT5 or 6 cable from the RJ45 connector to the inputs on the Buffalo, to keep the spacing the same until the input.

Thanks again for your help.

Aaron
 
#59
orpheus said:
Thank you for helping me with selecting a cable and connector. Sounds like RJ45 would work the best, which makes sense since it is designed to transmit digital signals. I need to look at the options and decide which ones to buy and which wires to connect to which signals.

From what you wrote, ideally I should also run the CAT5 or 6 cable from the RJ45 connector to the inputs on the Buffalo, to keep the spacing the same until the input.
Click to expand...

I'd use pins 1&2, 4&5, or 7&8 for the bit clock because they're close together on the connector, whereas pins 3&6 are further apart. See here:

Ethernet Cables RJ45/Colors & Crossover - Illustration

And you might consider terminating with 100 or 110 ohms at the Buffalo, depending on whether the I2S driver at the transmit end can handle that.
 
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