Losing volume when sub is hooked up

Yes, 100K input on the speaker/high level inputs is a very easy load for your integrated. I agree that is the best way to configure the sub in your system.

herman, these are specs on my integrated if you didn't see them already...THE M100SE-PLUS -- REMOTE VOLUME AND SELF -BIASING
EL34 integrate amplifier might be the most successful model in CONSONANCE tube products line. Including M100,M100MKII, M100SE and M100plus, the well improved push-pull set has already satisfied more than ten thousand user around the world. This amplifier may also be ordered in 300B version named M100Splus or 6L6GC version named M99plus with less power output.

Features:

1.Class AB,push-pull design delivering 40 watt output power.
2.A pair of EL34 output tubes running in ULTRA-LINEAR mode per channel.
3.12AT7 and 6SN7 dual triodes for input stage and drive stage (one 6SN7 drive pair of EL34).
4.Little negative feedback with precision RC circuitry for more linear output.
5.IEC Jack
6.REMOTE VOLUME CONTROL
7.SELF - BIASING

SPECIFICATION:

CONTROL FUNCTIONS: Volume, Input, Power On/Off
POWER OUTPUT: 40 watt x 2, RMS 1kHz
TOTAL HARMONIC DISTORTION: less than 1%(40watt, 1kHz)
FREQUENCY RESPONSE: (-3dB points at 10 watt) 6Hz-60kHz
INPUT SENSITIVITY: 180mV
INPUT IMPEDANCE: 100k
OUTPUT IMPEDANCE: 4,8 ohms. (User selectable.)
SIGNAL/NOISE: 90dB
CONSUMPTION: 90watt
INPUT INTERFACES: 3 groups (RCA) - 1,2 and 3
VACUUM TUBE: EL34 x 4, 12AT7 x 2, 6SN7 x 2
DIMENSIONS: 446(L) x 264(W) x 155(H) mm
WEIGHT: 17kg(net);17.5kg(shipping)\

wow herman, great research work. and i think you are 100% correct on this. i guess that is why even rel says to use the high level neutrik speakon cable and connect to speaker jacks on preamp. the manual says the impedance is 100k for high level inputs. did you see that? ok, i really wanted to make sure there is no problem with my preamp. i'm using the high level inputs. thanks again herman. makes me feel much better.

I found this spec sheet for the sub and it says the input impedance for the line input is only 2.5K. That is very low. That might be a misprint but it explains what you are hearing. I see other RELs that state 10K, also a relatively low value.

Your tube integrated probably has a relatively high output impedance from it's pre out. I couldn't find a spec for that. In any case the higher the input impedance is to the sub the easier it is for the pre out to drive it.

When you hook up to the line in on the sub you are putting the input to the sub in parallel with the input to the power amp section of the integrated. This lowers the impedance that the pre sees and therefore the output voltage drops and therefore the volume goes down. You really aren't losing any power as long as you can turn it up a little bit to get the voltage back to where it was.

Your real concern is that as the impedance drops it will tend to roll of the bottom end. However, since your are adding a sub you can probably balance things out by adjusting the sub. I really don't see it as a problem but if it bothers you you could always just use the speaker inputs to the sub. Another choice is to raise the input impedance of the sub. It is probably set by a single resistor at the input to each channel and a competent tech could replace it with a higher value. I did this with an MBL sub I used to have and that worked out just fine.

ok sorry. it is a consonance m100 plus tube integrated, rel q108e sub. someone told me it's because it is tubed and the tubes are doing more work. but it is a powered sub so i don't understand that.

What sub is it? What integrated? You will get better advice if you provide details.

i meant that i have to turn the integrated's volume knob up more, therefore i am losing power

yes, the main speakers lose volume. sub does have seperate line level and speaker level volume controls. it sounds ok but i just have to turn the volume knob up more to get the same volume level i had before hooking up sub to pre-outs. i just don't like losing the power......

Do you mean the main speakers lose volume?
Does the sub have a line/spkr level switch?

Maybe it's in spkr and loading down the pre.

not sure about that. i know the ic is about 10 feet long tho. and when i hook the sub up directly to the speaker connections on preamp, there is no volume loss.

I wonder if your integrated uses a passive pot or attenuator? If it does and is unbuffered,it will tax the output of your source when used with fairly long ICs connecting a subwoofer. You need a buffer or a integrated with an active preamp section.