Need advice about splitting a signal

What you sound like you need is a bypass looper. There are many kinds. Saturnworks and Loop Master come to mind right away. Check them out,
True Bypass Multi Looper Pedal | Saturnworks Pedals
Loop-Master Pedals - True Bypass Looper & Pedal Switchers

 

I use a bypass looper strip style myself. It helps keep your tone and signal strong and it makes operating multiple pedals easy as heck.

You can avoid that tone suck from the filter by plugging it into one of the loops on a bypass strip. That way its completely out of your chain unless you engage that specific loop.

 

The tone suck might be related to lack of proper buffering. Is it an active or passive bass you're playing? Also what type of envelope is this?

 

Often when you use long cables from bass to a bunch of effects connected by smaller cables followed by another long cable to the amp you end up getting some loss in the high end of your bass tone because the way the electronics of the guitar and cable works creates a low-pass filter, and when the capacitance of the signal builds up as the cable length gets longer the more high-end you lose.
Check out this video for a better explanation than I could ever provide:

How would you describe the "difference in tone" that you're experiencing? Is it a loss of high end? Or could it be something else? Bad cabling maybe?
How many effects are you running? Are they all true bypass? Are they vintage pedals and have crappy bypass circuits?

 

I know it is rather expensive, but I use the Lehle RMI Basswitch for this purpose.
The other Lehle splitters are top quality, too. They've put a lof of effort into not letting pedals degrade the quality of your signal. Even "true bypass" pedals. They are not "witches": if a pedal is really degrading your signal, no matter what, and your signal goes through this pedal, Lehle can't prevent this from happening...
The basswitch is a top-notch DI. And has a serial and a parallel-effects loop. The serial-effects loop can be set to off. You can decide if the DI-signal carries both effect loops and the EQ or just the boost or just the pure signal of your instrument.

Here is a picture of the basswitch on Marcus Millers' board:


What follows is an exerpt of the manual for the Basswitch. For sure it is marketing, but nonetheless I think it explains very well the problems with pedals etc. even if you are not interested in the Lehle pedal:


"True Bypass and True Sound
Today more and more effect pedals fea-
ture true bypass switching to completely
bypass the pedal in the signal routing
when the pedal is switched off. The target
of this design is to ensure that the pedal
does not affect the electrical signal when
it is switched off. This way the sound is
left unaltered ‑ in theory.
In practice, however, connecting several
pedals featuring a true‑bypass design in
series does not improve the sound or keep
it unaltered at all. Long runs of cable and
multiple connections lead to a weak and
lifeless sound. On large pedalboards the
overall length of the cable is enough for the
capacitance of the cable have a negative
effect on the sound. The capacitance of the
cable acts as a low‑pass filter (= the low
frequencies pass through the filter while
the high frequencies are filtered out). The
price and quality of the cable you are using
will not change this physical phenomenon.
A solution would be to use only devices
with buffered bypass design instead of
true bypass. This, however, is only a good
solution if the buffer is of very high qual
‑
ity. If several units with buffered bypass
are connected in series it only needs one
buffer to be noisy, cut the dynamics of
the sound signal or negatively affect the
sound in any other way for the sound of
the whole effect chain to be spoilt. As the
saying goes „a chain is only as strong as
its weakest link”. In addition, the noise of
the individual buffers adds up to produce
audible noise; it is a fact that every buffer
produces some noise, even if it cannot be
heard when only a single buffer is used.
The ideal solution is to have a very
high‑quality buffer at the beginning of
the chain that brings the signal down to
a very low impedance. This makes the sig
‑
nal insensitive to the length of the cable.
It is important, however, that this buffer
is of the highest quality with the dynamic
range and headroom necessary to ensure
that all the details of the bass signal stay
are retained unaltered.
The effect pedals in the downstream loops
should then ideally have true bypass so
that they will not have a negatively effect
on the now buffered signal, as the true
bypass design does not reduce dynamics
and headroom or produce any noise.
Conclusion:
Having a True Sound Lehle buffer at the beginning of your effect chain combined with good true‑bypass‑equipped effects in the loop guarantees the best sound."

Source:
http://www.rmi.lu/assets/brochures_manuals/Basswitch_Manual_EN_(web).pdf

 

T1M Mini Buffer MB | Reverb

Not mine, some reputation issues with the builder, but I have one and it works great!!!!! Fixes that wet blanket issue and its $30