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Looking for Kube200 for my KEF 105/3
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Tue Feb 19, 2013 11:40 pm    Post subject: Reply with quote

speakerguru wrote:
My memory is far from perfect but, no, as far as I can recall. I would need access to all the old drawings in order to refresh my memory, and that ain't gonna happen, I'm afraid.

No worries - was just curious.

Also, regarding
speakerguru wrote:
I don't follow the "drop in gain" bit. With that cable you are using all the signal available from the unbalanced output. Drop in gain w.r.t. what?

I misspoke - The drop in gain was not because of using RCA to XLR cables from the KUBE , rather, I meant to say I am experiencing an overall drop in gain by not going balanced all the way to the amp. If I remember the specs of my preamp correctly, the max gain using the balanced outputs was up around 4v whereas the unbalanced is 2v. In other words, from what I have read, by going single ended into my balanced amp inputs, I'm probably losing around 6dB of gain.
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speakerguru
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Joined: 18 Nov 2005
Posts: 959
Location: Green Hut, Tovil

PostPosted: Wed Feb 20, 2013 3:23 pm    Post subject: Reply with quote

deckard wrote:
... the max gain using the balanced outputs was up around 4v whereas the unbalanced is 2v. In other words, from what I have read, by going single ended into my balanced amp inputs, I'm probably losing around 6dB of gain.

You still seem to be confusing "gain" and "maximum output". You've got more than enough gain to drive your power amp into clipping, right?

With a transformerless design, a balanced output implies two anti-phase outputs being generated and used; one for send and the other for return. As a consequence the available output voltage swing is doubled. That said, you you don't necessarily get to use that extra capability if you don't have enough gain in the system in order to get up to a higher voltage at that point in the circuit (between pre and power amp). In a domestic set up with short cables and little interference there is little benefit in having balanced interconnections between different boxes. Studios, theatres and mobile locations have to deal with long cable runs (possibly running parallel or in close proximity to mains and lighting cables). They need all the interference immunity and cancellation they can get. Hence balanced audio interconnections. At home they are a bit of a high end fashion accesory. Same as having a four wheel drive vehicle to do the school run. Wink Rolling Eyes Laughing
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Wed Feb 20, 2013 5:32 pm    Post subject: Reply with quote

I agree that balanced is not really necessary for short runs. I've had this argument with people often and have used a very similar analogy myself...

In this case, I am stuck with a balanced-input-only amp.

Re: enough gain to drive the amp into clipping - certainly! (Actually, based on the specs, the KUBE will clip before the amp does). I have a stepped dB volume display on my preamp and have noted that the volume has to be turned up significantly higher than when I was going balanced all the way through to achieve an equivalent level.
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speakerguru
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Location: Green Hut, Tovil

PostPosted: Thu Feb 21, 2013 9:49 am    Post subject: Reply with quote

deckard wrote:
...In this case, I am stuck with a balanced-input-only amp.
..

That's a blessing not a problem. You can join the chassis/cases via the screen, leaving the hot and cold inputs to reference the preamp output.

In order to realize the best common mode rejection that balanced inputs are capable of, you could consider making the preamp output quasi-balanced (equalizing the source impedances of both legs; described in the Rane document). This depends if the construction and type of phono socket used will allow lifting the outer connection from the case.
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deckard
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Joined: 10 Sep 2012
Posts: 32

PostPosted: Mon Feb 25, 2013 5:59 pm    Post subject: Reply with quote

For anyone still looking, a KUBE 200 just popped up on the 'bay:
http://www.ebay.com/itm/Super-Rare-KEF-KUBE-200-Vintage-Speaker-Reference-EQUALIZER-PROCESSOR-/130853359950?pt=US_Home_Audio_Equalizers&hash=item1e7777d14e
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Mon Feb 25, 2013 6:35 pm    Post subject: Question about the KUBE 200 power supply Reply with quote

So the KUBE 200 I bought came from Canada.
The power supply that came with it has the following markings:

KEF KUBE
AC ADAPTER
ADAPTATEUR CA
TYPE SP2159
23V~
300mA
120V~
50/60Hz
9VA

The one I just posted shows a power supply with the following markings:

KEF KUBE
AC ADAPTER
TYPE SP2104
120V~
50/60Hz
6VA

Can anyone explain the differences and let me know if there is any concern with using the SP2159 in the US?
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Mon Feb 25, 2013 11:24 pm    Post subject: Reply with quote

KEF bought in off-the-shelf "wall warts" from different sources at different times for use with later Kubes. Standard units that had the appropriate safety approvals and current rating were selected then re-badged KEF and used. Both SP2159 and SP2104 are fine for use in the North America.
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Headrush
Junior Contributor 10+


Joined: 10 Nov 2012
Posts: 18
Location: Nottingham

PostPosted: Tue Mar 05, 2013 12:16 pm    Post subject: KEF KUBE 200 Reply with quote

I found something interesting... The Meridian 601 stereo digital preamp has some hardwired presets built in. Two of these processes are KUBE 107 and KUBE 200. Apparently they were built in specifically for KEF users and operate in the digital domain whereas the KEF unit is an analog device.

One just sold on eBay for 376. I've only ever seen one before and that sold for 350, although I had no idea at the time what it did. So if your in the market for a high end digital preamp tailored for KEF users, you wouldn't have to sell the house. Only problem is they seem to be as rare as hens teeth Cool
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speakerguru
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Joined: 18 Nov 2005
Posts: 959
Location: Green Hut, Tovil

PostPosted: Tue Mar 05, 2013 7:26 pm    Post subject: Re: KEF KUBE 200 Reply with quote

Headrush wrote:
I found something interesting... The Meridian 601 stereo digital preamp has some hardwired presets built in. Two of these processes are KUBE 107 and KUBE 200. Apparently they were built in specifically for KEF users and operate in the digital domain whereas the KEF unit is an analog device.


I think all the KEF Kubes ended up being built at Meridian. I don't recall giving them the transfer functions, but I guess it wouldn't have taken Bob Stuart long to work them out from the analogue circuits.
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