Piękna sprawa. Oglądałem inne ich układy i tego jakoś przeoczyłem. Najwyżej się ograniczy volume przy większej dostępnej mocy ;) Sprawdziłem i tak jak pisałem źródło dźwięku ma Lout+/Lout- oraz Rout+/Rout-. Jakieś pomysły na opcjonalne przejście na mono? To o czym pisałem wyglądało tak: http://obrazki.elektroda.pl/2119472700_1462557415_thumb.jpg Może tak być? Czy to lipa? ;) Dodano po 49 : Hmm, znalazłem cały artykuł o tym, więc wrzucam dla potomnych ;) Chyba będzie działać - trzeba sprawdzić na żywym organiźmie ;)
RaneNote
WHY NOT WYE?
Why Not Wye?
(or, “Successful Monoing Of Your Low End”)
• Splitting Signals
• Subwoofing in Mono
• Unbalanced Summing
• Balanced Summing
• Output Impedances
Introduction
Wye-connectors (or “Y”-connectors, if you prefer)
should never have been created.
Anything that can be hooked-up wrong, will be.
You-know-who said that, and she was right. A wyeconnector used to split a signal into two lines is being used properly; a wye-connector used to mix two
signals into one is being abused and may even damage
the equipment involved.
Here is the rule: Outputs are low impedance and
must only be connected to high impedance inputs—
never, never tie two outputs directly together—never.
If you do, then each output tries to drive the very low
impedance of the other, forcing both outputs into current-limit and possible damage. As a minimum, severe
signal loss results.
Dennis Bohn
Rane Corporation
RaneNote 109
© 1991 Rane Corporation
Why Not Wye?-
Monoing Your Low End
Summing Boxes
One of the most common examples of tying two outputs together is in “monoing” the low end of multiway
active crossover systems. This combined signal is then
used to drive a sub-woofer system.
Since low frequencies below about 100 Hz have such
long wavelengths (several feet), it is very difficult to tell
where they are coming from (like some of your friends).
They are just there—everywhere. Due to this phenomenon, a single sub-woofer system is a popular cost-effective way to add low frequency energy to small systems.
So the question arises as how best to do the monoing, or summing, of the two signals? It is done very
easily by tying the two low frequency outputs of your
crossovers together using the resistive networks described below. You do not do it with a wye-cord.
INPUT 1
SUMMED OUTPUT
Unbalanced Summing Box
Figure 1 shows the required network for sources with
unbalanced outputs. Two resistors tie each input
together to the junction of a third resistor, which connects to signal common. This is routed to the single
output jack. The resistor values can vary about those
shown over a wide range and not change things much.
As designed, the input impedance is about 1 kΩ and
the line driving output impedance is around 250 Ω.
The output impedance is small enough that long lines
may still be driven, even though this is a passive box.
The input impedance is really quite low and requires
600 Ω line-driving capability from the crossover, but
this should not create problems for modern active
crossover units.
The rings are tied to each other, as are the sleeves;
however, the rings and sleeves are not tied together.
Floating the output in this manner makes the box compatible with either balanced or unbalanced systems. It
also makes the box ambidextrous: It is now compatible with either unbalanced (mono, 1-wire) or balanced
(stereo, 2-wire) ¼ " cables. Using mono cables shorts
the ring to the sleeve and the box acts as a normal
unbalanced system; while using stereo cables takes full
advantage of the floating benefits.
Stereo-to-Mono Summing Box
Figure 2 shows a network for combining a stereo input
to a mono output. The connectors are either ¼ " or
3.5mm jacks. The comments regarding values for Figure 1 apply equally here.
470 Ω, 5%
10k
5%
INPUT 2
STEREO
INPUT
MONO
OUTPUT
470 Ω, 1%
470 Ω, 5%
470 Ω, 1%
Figure 1. Unbalanced Summing Box
Why Not Wye?-
20 kΩ, 1%
Figure 2. Stereo-to-Mono Box
Balanced Summing Boxes
Figures 3 and 4 show wiring and parts for creating a
balanced summing box. The design is a natural extension of that appearing in Figure 1. Here both the
tip (pin 2, positive) and the ring (pin 3, negative) tie
together through the resistive networks shown. Use
at least 1% matched resistors. Any mismatch between
like-valued resistors degrades the common-mode rejection capability of the system.
INPUT 1
2
1
3
INPUT 2
2
1
3
(+)
SUMMED OUTPUT
(+)
2
1
(–)
3
470 Ω, 1%
(–)
470 Ω
(+)
470 Ω
20k
1%
(–)
470 Ω
Figure 3. Balanced summing box using XLR connectors
INPUT 1
470 Ω, 1%
470 Ω
INPUT 2
470 Ω
SUMMED OUTPUT
20K
1%
470 Ω
Termites in the Woodpile
Life is wonderful and then you stub your toe. The
corner of the dresser lurking in the night of this Note
has to do with applications where you want to sum two
outputs together and you want to continue to use each
of these outputs separately. If all you want to do is sum
two outputs together and use only the summed results
(the usual application), skip this section.
The problem arising from using all three outputs
(the two original and the new summed output) is one
of channel separation, or crosstalk. If the driving unit
truly has zero output impedance, than channel separation is not degraded by using this summing box. However, when dealing with real-world units you deal with
finite output impedances (ranging from a low of 47 Ω
to a high of 600 Ω). Even a low output impedance of 47
Ω produces a startling channel separation spec of only
27 dB, i.e., the unwanted channel is only 27 dB below
the desired signal. (Technical details: the unwanted
channel, driving through the summing network, looks
like 1011.3 Ω driving the 47 Ω output impedance of the
desired channel, producing 27 dB of crosstalk.)
Now 27 dB isn’t as bad as first imagined. To put this
into perspective, remember that even the best phono
cartridges have channel separation specs of about this
same magnitude. So, stereo separation is maintained at
about the same level as a home system.
For professional systems this may not be enough.
If a trade-off is acceptable, things can be improved.
If you scale all the resistors up by a factor of 10, then
channel separation improves from 27 dB to 46 dB. As
always though, this improvement is not free. The price
is paid in reduced line driving capability. The box now
has high output impedance, which prevents driving
long lines. Driving a maximum of 3000 pF capacitance
is the realistic limit. This amounts to only 60 feet of
50 pF/foot cable, a reasonable figure. So, if your system
can stand a limitation of driving less than 60 feet (18
meters), scaling the resistors is an option for increased
channel separation.
Figure 4. Balanced summing box using ¼ " TRS connectors
Why Not Wye?-
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 USA TEL 425-355-6000 FAX 425-347-7757 WEB www.rane.com
Why Not Wye?-
04-04