Gain into my preamp from DAC

Hi Mesch,

That kind of result is not unheard of, and two possible explanations occur to me:

1)The balanced input of the preamp is processed through a stage which receives the balanced pair of signals differentially, converts them to a single-ended signal, and in the process intentionally introduces a 6 db gain reduction, perhaps for the purpose of matching the gains provided for the single-ended inputs.

2)The circuit in the preamp which receives the balanced pair of signals just processes one of those two signals, in single-ended fashion, and ignores the other signal.

A means of distinguishing between those two possibilities would be to connect the RCA output of the DAC to the XLR input of the preamp using an RCA-to-XLR adapter. The adapter would route the signal on the center pin of the RCA connector to pin 2 of the XLR connector, while grounding the other signal pin of the XLR connector (pin 3).

If doing that results in the same volume as when an XLR cable is used, for a given setting of the volume control, it would point to explanation 2. If you hear essentially nothing when you do that, it would also point to explanation 2. (That result would occur if the preamp utilizes the signal on XLR pin 3 and ignores the signal on pin 2). If the volume is 6 db less than when an XLR cable is used, it would point to explanation 1.

Best regards,
-- Al

Cleeds, I am not sure that the input portion of a single ended device can't be configured to accept both signals from a balanced device when connected via XLR such that the 6 dB gain is enforced. This was one aspect inherent to my question, and as mentioned, I remain unsure of this. 

Al, I was hoping you would chime in on this, and as always you did not disappoint. Regarding explanation 1), is it possible that the 6 dB gain can be maintained while the conversion from balanced to single ended is accomplished, as opposed to a designer wanting to maintain equal gain across inputs? Regarding the two possibilities, I do not have the required RCA to XLR adaptors, however I am planning on asking Jolida as to their XLR input and with the information provided I am better positioned to formulate my questions to them. Thanks!

mesch

Cleeds, I am not sure that the input portion of a single ended device can't be configured to accept both signals from a balanced device when connected via XLR such that the 6 dB gain is enforced.

I think you're assuming that an XLR connection is inherently balanced and, if so, you're mistaken. If your preamplifier is not a true balanced differential preamplifier, it doesn't benefit from the gain of a balanced connection. Depending on the circuit, you may get some of the benefit of a balanced connection's  noise rejection, but you won't get the gain.

... I am not sure that the input portion of a single ended device can’t be configured to accept both signals from a balanced device when connected via XLR such that the 6 dB gain is enforced. This was one aspect inherent to my question, and as mentioned, I remain unsure of this....

... is it possible that the 6 dB gain can be maintained while the conversion from balanced to single ended is accomplished, as opposed to a designer wanting to maintain equal gain across inputs?

Yes, a design can certainly be implemented in that manner. Based on your findings, though, the preamp has not been designed in that manner in this particular case.

Best regards,
-- Al

That's because our ears do not equate doubling sound pressure level (6db voltage) to perceived loudness. We need to experience about a 10db increase to perceive "twice as loud".