Possible impedance matching issue with subwoofer?

Ok, one last question so I can make my final decision. I am not sure I want to go the high level hook up route as I simply don't know how the plate amps are wired. Can't see anything as all the sub binding posts are hooked together on a circuit board with the traces hidden from view. I would have to take boards off etc and I don't want to do all that. My amp is fully balanced and I fear causing an issue due to the way the sub high level inputs may well be wired -Keiga KG 5150.

Bottom line. Is the line level hook up going to cause an issue in terms of impedance mismatch or not? Al comments as well as Nsgarch suggest I will not have an issue in terms of sound degregation. Here are the facts on my gear.

Preamps output impedance is 5k ohms
Plate amps input impedance is 22k ohms
My stereo Atlas amp has an input impedance of 470k ohms
My sub cable is very, very low capacitance -Al referred to it above and they 10 feet long. I run two subs.
My ic's between the pre and amp are 3 feet long

While the music sounds good I do wonder if I am rolling off in the bass area and possibly compromising the sound of my main speakers. Again, both Al and Nsgarch seem to suggest no issue. But some other comments suggest otherwise? I would buy a Buson buffer to place between my pre and subs if that is deemed as best. I understand that such a buffer would reduce what the subs see as output impedance down to under 600 ohms and perhaps as low as 100 ohms.

I would rather not spend the money if there is nothing here to be concerned with. I set my subs to play 40 hertz and below only. Since I have 2 I set the volume very low - near the minimum really.

What do you expert say.

I would add to the key facts that you listed for your gear that the output coupling capacitor in your preamp is 3.3 uf. Many tube preamps use somewhat smaller coupling capacitors, which would increase the likelihood of deep bass rolloff. Many tube preamps also have much lower output impedance at mid and high frequencies, which would further increase deep bass rolloff when used with a smaller coupling capacitor, because it would result in more of a DIFFERENCE between the low frequency and mid/hi frequency output impedances.

Per my earlier analysis, my feeling is that you are certainly not experiencing any major deep bass rolloff, and at most any deep bass rolloff would be extremely slight and would only occur on material containing spectral components approaching 20 Hz.

As I indicated earlier, if it were practicable to go to the high-level sub connections probably the most significant difference would be due to putting the sonic effects of the amplifier in the path to the sub. And that difference, while standing a good chance of being significant, is probably unpredictable in terms of being better or worse.

Best regards,
-- Al

That is what I thought and thanks Al.

If you hook the sub up in parallel to the preamp you will go from an output to input impedance ratio of 94 to only 4. I feel that will certainly result in high frequency sparkle loss. You should look into a buffer between the preamp and sub for the line level inputs. The Musical Fidelity X10 v3 has a high input impedance around 400K that will mate well with your amp. I think the ratio would then be about 44:1 and certainly acceptable compared to 4. I am speaking from experience here, not just textbook. I noticed a definate drop in the highs when I hooked up my sub the same way without the buffer. These buffers don't cost that much. Just get one and try it both ways... you will hear a difference.

Koestner, I'm curious as to what preamp you were using. Perhaps it has an output impedance that rises in the upper treble region.

Also, what were the lengths of the cables to both the sub and the power amp, and what was their capacitance per unit length (or alternatively, what was their make and model)? As I mentioned earlier in the thread, the capacitance of the cable from preamp to sub, as well as the capacitance of the cable from preamp to power amp, can roll off the upper treble (as seen by the power amp) if it is high in relation to the preamp's output impedance.

Best regards,
-- Al