XLR to RCA to XLR

The Rane piece looks good. I like that it's totally passive. I wonder if it would work well just for balanced to unbalanced when -10 to +4 conversion is not a concern.
What's confusing is, it seems balanced doesn't always mean "pro" or +4 and unbalanced doesn't always mean "consumer" or -10. What does most high-end balanced home audio (not pro) gear operate at, +4 or -10?

01-23-13: Rdeckard
What's confusing is, it seems balanced doesn't always mean "pro" or +4 and unbalanced doesn't always mean "consumer" or -10. What does most high-end balanced home audio (not pro) gear operate at, +4 or -10?

The reference to unbalanced signal levels on consumer equipment being around -10 dbV lost whatever meaningfulness it may have once had when the CD medium was introduced, which was standardized with a full scale (maximum) level of 2 volts, for unbalanced outputs. 2 volts is +6 dbV, or +8.2 dbu. Some digitally based equipment will exceed even those numbers significantly, while phono stage outputs will usually be considerably less.

Each situation needs to be analyzed individually, although it is more common these days to have too much signal and too much gain, rather than too little, regardless of whether the connections are balanced or unbalanced.

Grant (Tvad), thanks for your always knowledgeable inputs.

Regards,
-- Al

Thanks everyone for all the helpful info!

Here is more info on my setup and my latest experiment...

My preamp has both RCA and XLR outputs, which can be used simultaneously.

I only want the KUBE on the LF in a biamp'd config. I have read that even if you do not adjust the HF contour on the KUBE, it can still muddy up the wonderful midrange on these speakers just by being in the signal path, which is probably another debate altogether...

Anyway, I am feeding the XLR outputs of the preamp straight into the the XLR inputs of my amp for the HF.

I then figured I'd use the RCA outputs of the preamp to feed the KUBE, and then the KUBE output would go to a second set of amp inputs (it's a 7 channel amp).

Last night, I tried this with just RCA to XLR cables on the output of the KUBE to my amp using cable #17 on this page: http://www.rane.com/note110.html

It "worked", but the output from the LF side was significantly lower, even when using the variable output of the KUBE and cranking the pot on the back.

I sent a 60Hz tone through the system at low volume and with a volt meter, measured .40v on the HF speaker terminals and .30v on the LF speaker terminals. I'm sure this is not very scientific, but I wanted to somehow confirm what my ears were hearing.

I guess I have voltage mismatches by using the unbalanced outputs from my pre to the KUBE compared to the straight balanced connections for the HF.

Now I am thinking I should NOT use the unbalanced preamp output, but rather split the balanced preamp outputs with XLR Y-adapters (this is sounding less and less high-end as I write), feed one directly to the amp for the HF, then send the other to a Jensen PI-2XR to feed the KUBE.

The unbalanced output of the KUBE would then go through another PI-2XR to the second pair of balanced amp inputs.

I figure in this setup I should (hopefully) have similar gain/voltage at both pairs of amp inputs when the KUBE is inline (and bypassed).

Here are some quick specs on the gear:

KUBE 200:

Input Impedance 51 k ohms.
Maximum Input Voltage >1.9 V rms above 20 Hz.
>8 V rms above 50 Hz.
Maximum Output Voltage >5 V rms.
Output Impedance 100 ohms.
Output Noise Level <6 uV A-weighted.
Signal-to-Noise Ratio >104 dBA ref 1 V rms.
Distortion <0.005 % for 1 V rms input @ 1 kHz.

Preamp:

Unbalanced line-level outputs:
Maximum Output Level: 4 Vrms
Output Impedance: 100 ohms

Balanced line-level outputs:
Maximum Output Level: 8 Vrms
Output Impedance: 200 ohms

Amp:

Balanced line-level audio inputs:
Input Impedance: 24k Ohms balanced
Maximum Input Level: 4 Vrms balanced

Also, since it just says balanced and unbalanced "line-level" I don't think I need to worry about +4 to -10 conversion, etc.

Apologies for the long post. Any advice or suggestions at this point (or a slap in the face if I'm doing something stupid) would be most appreciated!

Rdeckard, I took a look at the manual for the Kube 200, and I see that its level control provides a maximum boost of 5 db for its variable output, relative to the level of the fixed output. Your findings seem consistent with that.

The approach you are considering would work, except that it may be that a PI-2RX should be used between the Kube and the power amp, rather a PI-2XR connected "backwards".

HOWEVER, in the light of Grant's (Tvad's) comment above that ...

Jensen makes 1:1, 1:2, 1:4, 2:1, 4:1 transformers, and I suspect any of these could be built into their XLR>RCA or RCA>XLR converter boxes at a customer's request.

... a call to Jensen would seem to be in order, to explore additional possibilities.

Those possibilities would include stepping up the signal level by 1:2 (6 db) between the Kube and the power amp; or stepping down the mid/hi frequencies by inserting into the XLR connection between preamp and power amp a PI-2XX (XLR ins and outs) specially configured with a 2:1 stepdown transformer (with no transformers being used in the low frequency part of the signal path, unless one is needed to eliminate groundloop hum).

Looking at all of the numbers that are involved I don't see anything that would necessarily rule out any of those alternatives. But my instinct, assuming that you are not presently using your volume control near the upper end of its range, would be that it is generally better to step down than to step up, given the cautions I expressed yesterday in my post about the Rane unit. And also given the very high degree of transparency Tvad and others have reported the Jensen transformers as providing.

Hope that helps. Regards,
-- Al

Rdeckard wrote, "I only want the KUBE on the LF in a biamp'd config. I have read that even if you do not adjust the HF contour on the KUBE, it can still muddy up the wonderful midrange on these speakers just by being in the signal path, which is probably another debate altogether..."

According to the KEF museum, the KUBE is just an option for the 105/3, not integral to the design as it is for the 107/2. Why not just try it between the preamp and amp, and judge for yourself whether it muddies the midrange?

The 107/2 KUBE doesn't muddy the sound of my spectacular 107/2s that are bi-amped between the amps and the speakers.

db