Significant loss of volume when using Y-cable (Sub37)

[m10k]

Alright, so I'm trying to sort a volume issue out. I recently bought a new bass amp head (Carvin BX500) with one input so I don't have lug around my vintage Fender Bassman. I'm running the Sub37 and a Waldorf Blofeld into a mono Y-cable and then into the Carvin. Unfortunately, the Sub37 volume gets reduced by at least half while the Blofeld volume stays the same. Things I've tried:

-switching the keyboard cables on the inputs of the Y-cable
-trying a different Y-cable (a mono one and stereo one)
-plugging into an ABY box
-tried the same things with the Bassman with the same results

What am I missing here? Why is this only affecting the Sub37? Thanks!

[robbd]

y-cables are splitters, not mixers.
Beg, borrow or steal a small mixer, (ie: Mackie 1202 or equivalent) and use that for summing your signals.
I'll leave it up to the more well informed to chime in about why.

[m10k]

Thanks for the reply. Yeah, I'm actually buying a crappy little 4 channel mixer today. I just thought it was especially odd that it only reduced the volume of the Sub37 and not the Blofeld. Normally the volume on the Sub37 is incredibly loud at around the 3 notch (9 o' clock) whereas the Blofeld has a pretty low output.

[robbd]

Wish I could give you a definitive answer, but I'm not really geeky on the subject.
I'm "pretty sure" (famous last words ) what you've got happening there is an "impedance mismatch" type of thing.
Google it if you dare, but be warned there's math involved

[tomoog]

m10k,
You could try using the (low impedance) Sub37 headphone out to duke it out with the Blofeld.
Highly NOT recommended because you're still basically short-circuiting 2 outputs to each other.

All you really need is a simple passive resistor mixer, gaff-taped into your Y-cable. See the below pic
Get your electronic friend to solder it up.

[_DemonDan_]

I'm actually buying a crappy little 4 channel mixer today.

If it's not too late... this is a very inexpensive mixer that's not crappy:

http://www.sweetwater.com/store/detail/SplitMix4

It will mix 4 stereo or mono channels (and several other cool tricks) and is completely passive (no power needed). Because there are no amplifiers, you won't get any additional hiss or distortion.

I use this in my live keyboard rig every gig.

[m10k]

Awesome, thanks for the replies! DemonDan, I actually ended up buying a small mixer from a friend for $10 (made by 'Performance Plus' so we'll see how long that lasts). I used it last weekend and it worked out perfectly. I like your option better though because it's passive.