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Proprius with a subwoofer.

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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2015 at 6:04pm
I see your point Bruce about proper stereo 2.0 rather than 2.1. I must confess that my subs aren't connected at the moment as I unplugged them before fine tuning the GX300 (floor standing) speaker positioning at the weekend. Although I miss the lowest bass, it is less of an issue than when I had the stand mounted GX100's at the front.

On the cabling types for sub connections, it may help to clarify my language:

High level = speaker connection so something resembling speaker cable should be fine to connect the amp to the subwoofer. I wouldn't use a screened cable for the loading reasons you pointed out, even coax.

Low level = line level connection from AV amp and a good quality screened cable should be used that includes a low resistance ground path IMO.

And you are right about the sublime Proprius amps!
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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BAK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2015 at 9:04pm
Originally posted by Fatmangolf Fatmangolf wrote:


On the cabling types for sub connections, it may help to clarify my language:

High level = speaker connection so something resembling speaker cable should be fine to connect the amp to the subwoofer. I wouldn't use a screened cable for the loading reasons you pointed out, even coax.

Low level = line level connection from AV amp and a good quality screened cable should be used that includes a low resistance ground path IMO.


Jon, given your clarification, I believe the connection "discrete badger" and Gary are talking about is high level (directly from the Proprius speaker terminals).
 It may be fine after all to use very low capacitance coaxial cable to connect directly from the Proprius speaker terminals to a high level input on a sub-woofer "plate amplifier".
 Note: Most power amplifiers have an internal 0.1 uF
capacitor directly across the speaker terminals in a filter network to compensate for the inductive characteristic of voice coil dynamic speakers.
[My 60 watt RMS power amplifier has a
0.1 uF capacitor in series with a 10 ohm resistor in this filter network... others have a 0.1 uF capacitor in series with a 4 ohm resistor in this filter network, and others a 8 ohm resistor.]
A very low capacitance coaxial cable of moderate length should not add too much capacitance.
Here the added external
capacitance to the speaker terminals from using coax must be kept very low to not upset the output filter network.
 At low value impedances of 4 to 16 ohms, it would take some added
external capacitance without any problem, as long as there is a 4 to 16 ohm load...IOW, as long as the speakers are connected.
Again;
RULE OF THUMB: always double check speaker-to-amplifier connections.Wink
Before the AC power is applied.
Bruce
AT-14SA, Pickering XV-15/625, Technics SL-1600MK2, Reflex M, Lautus, Technics SH-8066, Dynaco ST120a, Eminence Beta 8A in custom cabs;; Using Majestic DAC
Enjoy Life Your Way!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2015 at 11:21pm
The phase and gain margin on the Proprius is generous so cable capacitance isn't a big deal for it.

The series RC filter inside power amps is called a Zobel network which is designed to compensate for load capacitance within a small bandwidth and preserve stability.

Of greater importance is the use of an output inductor. Most amp designs I've seen use a few turns of wire around a "damping" resistor, and most of these simply aren't effective. It is quite difficult to guesstimate what value is going to do the most good because there are so many parasitics that the "sliderule" answers of old tend not to work. By modelling in parasitic parameters into a schematic, SPICE modelling reveals quite a lot, and the inductor and damping resistor values can be found - often a lot larger than one would think.

The output inductor on the Proprius is a network of components designed to offset parasitics over different frequency ranges and to not compromise the sound.

From the model's point of view capacitance up to 50,000pf with a load of 10k has no effect on stability.

Open-loop gain also has a bearing on stability - large amounts of negative feedback can often lead to oscillation because the negative feedback becomes positive under certain loading conditions. The Proprius can run without its negative feedback loop and only 18dB of negative feedback is applied by the loop - very much like tube amps.

So please feel free to try what you like (within reason).

However, low capacitance close spaced conductors have low magnetic and electrical fields which are good for low EMC emissions and immunity, and that guards against RF interference, and any amplifier so assisted is going to perform better, so low capacitance slow/tight twist or coax cable is best.

High capacitance cables and wide spaced conductors invite RF because of their large magnetic and electrical fields and make a big difference to how an amp can sound - basically by driving it into its unstable operating area. You can get a huge soundstage - completely unnatural but very impressive - and this is often considered an improvement (by the easily led). Many a well-known amplifier has fried using such cabling. Such amplifiers don't use output inductors...

Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2015 at 4:56pm
I am about to connect my MJ Acoustics Pro 50 sub to my system, as my little Frugel horns could do with a bit of help low down (when the wife is out).

The RCA output is taken by the AV amp, so I am looking at taking a feed from one of the Proprius using speaker cable, to a Speakon high level connector on the plate amp of the sub.
Does this sound sensible?

It is for occasional use only, and if I like it, I may get a bigger/better sub later.

I just want to check before I do anything daft to my system.
Kevin

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CageyH View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2015 at 5:19pm
Manufacturers instructions:

You connect the 3 bare end wires of the Neutrik Speakon cable alongside your existing speaker cables on the back of your amp as follows:
RED to left + (positive)
YELLOW to right + (positive)
BLACK to ONE of the - (negatives) NOT BOTH
.
This is the most common connection for stereo amplifier users who do not have a dedicated sub output and wish to extend the bandwidth and add a new depth dimension to their existing speakers.

So I guess I am going to have to make up a cable to take the feeds from both speakers, to the sub. What a pain...
Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2015 at 7:23pm
I did manage to connect my old BK XLS300 up to my pair of Proprius, as suggested earlier by Graham, by connecting red to right +, yellow to left + and black to both left and right -. Everything worked fine but it highlighted the deficiencies of the sub so now I'm using a B&W PV1D and all is well. It's not the deepest sub but it's definitely musical.
Solo ULDE, CuSat50, Spatia Links
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