XLR to RCA to XLR

Hi Jedinite,

Regarding the Rane BB44X, which I see sells at B&H for $279, based on a quick Google search I didn't find much that would shed light on the sound quality it would provide in a high-end home audio system.

Looking at the datasheet, though, a concern would be that while a statement is made that the unit provides "wide bandwidth," the only spec that is provided is that frequency response is 20 Hz to 20 kHz +/- 2 db. The 2 db tolerance is very uncomfortable, IMO, and the fact that no margin is indicated relative to the audible frequency range is as well. Without a margin of 5 times or more (i.e. 4 Hz to 100 kHz), and preferably even approaching a factor of 10, I would not feel comfortable that audibly significant phase shifts wouldn't occur within the 20 Hz to 20 kHz range.

In contrast, Steve McCormack's unit is specified as having a 3 db bandwidth of 0.5 Hz to 150 kHz, and the frequency response graph shown in the datasheet for the Jensen PC2XR shows it as being in a similar ballpark.

Also, some cautions that would apply if any of these level converters were used to step UP "consumer level" to "pro level":

First, using one of these devices in that direction will increase the impedance seen "looking back" from the destination device toward the signal source by a factor of about 16 (corresponding to the square of the nominally 4:1 turns ratio), and will decrease the load impedance seen by the signal source by that same factor of 16. That will result in impedance incompatibilities in many cases.

Second, at 20 Hz the unbalanced input of the Rane device will reach its overload point at only 1.68 volts, with the Jensen PC2XR being only slightly better in that respect. So, as might be expected, one would not want to use one of these transformers to step UP the outputs of unbalanced signal sources which provide the 2 volt kinds of levels that are typical these days, especially with digital sources. And chances are that other components in the signal path would overload as well, if that were done.

These two cautions do NOT apply to 1:1 transformers, such as the Jensen PI models, and do NOT apply to the 4:1 level converter devices when used as step-DOWN transformers, i.e., going FROM "pro levels" TO "consumer levels."

Regards,
-- Al

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!