How to split pre out to connect power amp and sub

There is a more significant issue to what you are proposing to do, which is that a tube amp should NEVER be operated without a speaker load, at least while music is being played through it, or it is likely to suffer serious damage (such as a blown output transformer).

By running the Shanling's pre-outs into the Prima Luna power amp, with the speakers connected to the Prima Luna power amp, that is exactly what would happen to the Shanling. If you would like further technical explanation of that, let us know and I'll answer tomorrow if necessary -- I have to sign off shortly for the night.

Apart from that, the answer to your question is that you could split the pre-out's with a y-adapter and send those outputs into both the sub and the power amp, provided that the parallel combination of the input impedances of the sub and the power amp is substantially higher than the output impedance of the preamp outputs. An example of "substantially" would be a 200 ohm preamp output impedance working into a combined sub+power amp input impedance of say 10K (10,000 ohms) or more.

If the impedances don't meet those criteria, no damage will result (as far as that issue is concerned) but sound quality may suffer.

To calculate the combined input impedance of the sub and the power amp, divide the product of the two impedances by their sum. Example: If the sub's input impedance is 25,000 ohms (25K), and the power amp's input impedance is 50,000 ohms (50K), their parallel combination would be (25 x 50)/(25 + 50) = 16.67K.

But again, DON'T DO IT, or you will destroy the power amp section of the Shanling.

Regards,
-- Al

P.S. The comments in my previous post about the y-adapter and impedance matching are based on the assumption that your sub has separate left and right channel inputs, or alternatively that you have a separate sub for each channel. Upon re-reading your post I'm not sure that is the case -- please clarify and I'll answer further tomorrow, if necessary.

Regards,
-- Al

A further thought: Since the Shanling has such a low power output, that would make it readily practicable to substitute a resistor for the speaker load which would no longer be connected to it. Doing so would completely eliminate the possibility of damage that I described!

Radio Shack part number 271-120, which is an 8 ohm 20 watt non-inductive resistor, costing $1.49 each according to an older catalog I have, would do the trick. Get two of these, and connect one between the Shanling's red and black left channel speaker terminals, and connect the other one between the red and black right channel speaker terminals.

Hope that helps,
-- Al

I am going to be purchasing a preamp (CJ Premier 10) with one pair of outputs. If I have two active subwoofers that I can connect mono (one run to each), am I okay splitting the signal at the Premier 10 with y-adapters at each terminal, one in each pair (channel) going to amplifier, and the other going to a [powered] subwoofer? Will this result in a signal quality loss? Can I split again to make it a three way split? Thanks for your help!

Solst1ce -- As I indicated above, whether or not doing that results in sonic degradation would depend on whether the combined input impedances of the sub and the power amp (and the third device, if you choose to split three ways) remains much larger than the output impedance of the preamp.

Also, keep in mind that the cable capacitance which the preamp would have to drive is the sum of the capacitances of the two (or three) cables that would be connected to each channel. That could become a significant factor if preamp output impedance is high and cable capacitance per unit length is high (e.g., 100 picofarads per foot) and cable lengths are long (e.g. 20 feet each). So I would suggest using low capacitance cables (e.g., less than 40 or 50 pf/ft, especially if the run lengths are long). Otherwise, upper treble rolloff may result.

In your case, I suspect that you'll be ok in all of these respects. I found the following statement at the CJ website about the Premier 10:

The audio circuit of the Premier Ten consists of a single triode amplifier direct coupled to a triode cathode follower. The low output impedance of the cathode follower permits the use of the Premier Ten with highly capacitive amplifier interconnect cables without attenuation of the high frequency information.

BTW, to calculate the combined impedance of three loads in parallel, calculate the combined impedance of two of them as I described above (product divided by sum), then calculate the product divided by the sum of that result with the third impedance. Or, alternatively, the impedance of the parallel combination of three loads is the reciprocal of the sum of the reciprocals of the three input impedances.

Regards,
-- Al