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Onkyo Super Servo Cable - Tech minded people THIS IS FOR YOU!

DrDarkFish

DrDarkFish

Active Member
Ok....

(THIS THREAD APPEALS TO THE TECH MINDED-NOT JUST THOSE FAMILIAR WITH ONKYO PRODUCTS)

There is one or two threads out there where people have tried to get to the bottom of this mystery. It doesn't appear to be resolved. It isn't rocket science...

I'm determined to work this out..:yes:

How the hell do we make an 'Onkyo Super Servo Cable'???

I just bought myself an Onkyo Integra M-509 Power and P-309 pre.. which have the capacity to use one of these mystery cables.. It simply allows you to connect your preamp to your power amp in a "better way"- at least by early 80s standards.

For those of you who dont know what these cables are, I have attached two photos (among other attachments) of what they look like. They simply look like an RCA cable that has 4 plugs on one end and two plus a grounding wire on the other..

According to Onkyo propaganda:

"In a normal RCA the grounding for both L and R channels is common. Therefore due to cable impendance and pin terminal contact resistance, the right channel signal will tend to flow back through the left channel ground lead and visa versa. The Super servo cable completely eliminates the left/right mutual interference"

I found a diagram in an manual for a Onkyo M-506 amp which explains what's going on. I have attached this to my post. The diagram appears to show how ONE channel operates.

From what I can tell: out of the preamp there are two outputs per channel, one labled 'Signal' and the other called 'Servo Sensor' this comes together as ONE input to the poweramp.

The signal terminal is the positive terminal.. The centre pin carries the signal and conncects to the centre pin on the input of the poweramp. There is a grounding wire that is attached to the outercasing of the (+) plug on the preamp end that also attaches to the outercasing of the input on the power amp but also follows on to the a grounding horsehoe.

The superservo cable is the negative cable, it is connected to the centre pin on the preamp BUT connects to the outercasing of the input to the power amp.

I assume that both grounding wires for the left and right channels come together after being attached to their respective channel plug outercasings and form one grounding wire..​
I don't know how esle to interpret this diagram, it seems right to me.

What are your thoughts? Any help would be greatly appreciated :music:

Cheers,

Fish
 

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It almost seems like they used a balanced type of output from the preamp but used RCA cables instead of XLR.

As if they lifted the ground from the outer shield and then used that for the negative portion of the waveform while keeping the positive portion of the waveform on the center pin.

I stayed at a Holiday Inn Express........
 
Onkyo is trying to claim that the impedance of the shell connection to ground is such that it is not a good enough ground to avoid interaction between the the left and right channels.

BS, if you ask me. I've seen that happen with stereo mini plugs causing a higher than expected crosstalk number, but never with RCA connectors.

That being said, they (Onkyo) is putting the signal ground into a feedback loop to correct for any signal appearing on the signal ground at the far end of the cable.
 
I"ve seen one of those before and didn't realize what it was, this was way before I got my onkyo super servo system. I just wonder if it sounds any better than really good interconnects like I bought from morrow audio
 
I emailed Onkyo a few months ago to see if they still had any of these (figured it was worth a shot) and this is what they sent me.

Does this help?
 

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Okay I'm not a electronics person at all but if this is such a concern, then why not fix it at the amp? Instead of making the ground side common between left and right, why not isolate them if possible? And if that common on the cables side is grounded to the cabinet or chassis, then wouldn't using a ground wire to the cabinet do the same thing and not isolate anything at all? Or is it really creating a separate ground between the amp and the pre like you do with a TT to minimize potential hum and interference? I guess I'm just not getting the reasoning or not understanding enough about electronics.

Or maybe the RCA's in use at the time just weren't that good?
 
Hello,

I just bought myself an Onkyo Integra M-509 Power without the P-309 pre... and was very concerned with not having the super cable. After reading I can rest because no effect should be noticed as long as I use a decent rca cable....

Regards

Pedro, from Santiago Chile.
 
Just think about for a second or two, does Onkyo still use this system? No, why not? Kenwood had their servo cables that went between the amp and speaker, how long did that last? Not very long because it dropped in the next edition of the Basic M2A I think. For whatever reason most if not all of the Japanese companies come up with solutions to non problems or fancy circuits/names that only add more confusion to the non-techies/buyers. It's all marketing gimmicks me thinks.

Craig
 
Hi bros, I just got myself an onkyo P306RS to partner with my M508 and am curious about the super servo connection too. It's interesting to note I plug a normal rca cable in the super servo loop and it sound just fine . I thought the super servo connection need to be connected using special cable? . And where to get the cables?
I have been looking for the P306RS manual to no avail. Anyone has it?
Many thanks
Jeff
 
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Coach Klein said:
I emailed Onkyo a few months ago to see if they still had any of these (figured it was worth a shot) and this is what they sent me.

Does this help?
Click to expand...

Only thing I can say: "if you have an Onkyo pre amp with this servo sensor and not the cable, put a RCA short plug in the left and right servo sensor plug"

I think it's an early attempt to what later became the symmetrical cable with RCA plugs.
 
Thanks for the info bro, you mean to say just plug 2 rca plugs in the super servo loop and normal rca cable in the signal output loop to power amp ?
 
Just now I see it is different people, an old thread, and different equipment, so I could be reacting on wrong information.
So I have no idea but I do understand your confusion...
 
The super servo INPUT on the pre amp is nothing more than a system to supply all sorts of strange cable behaviour in the outer shield of the signal cable, to the feedback of the pre amp output.
It is connected to the inverting input (feedback) of the output amp of the pre amp.
If you don't have the original cable, you can build the cable in the schematic Onkyo provided, or just put the input to ground, which is more less the same thing as what the Servo cable does.
It, simply said, put's the ground, with some theoretical parasitic signal and other HF stuff, in the feedback loop, therefor it should eliminate the strange cable behaviour. I don't think it'll make that much difference, otherwise the cable would be standard on every pre- to power amp.
If you use a normal interlink, the servo input is left open, thus the inverting input is open. That can make all sort of things happen..... So, use a short plug on the left and right Super Servo INPUT, to let it work normal.
My opinion.
I sold this stuff in the 80's and 90's and we've tried all sorts of options, without much improvement

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