Gain into my preamp from DAC

Not sure how one 'geberally' uses anything, however understand it to be very difficult :-).

If your preamplifier is not balanced, then you won't get higher gain on the  XLR inputs because it's using them single-ended.

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". 

Ai, thanks again for your reply. I knew after making the comparison that the input stage on the Jolida pre's XLR was not configured to deliver the expected gain, I was not sure as to why, or if it was even possible. I know know the answer to both questions. As always, your reponse was both succinct and articulate.

Cleeds, I have never assumed  XLR connection to be balanced, particularly ones found on single ended gear. However, as I have found out from Al's response, it can be possible for a unbalanced preamp to to capture the additional gain supplied by a balanced source if it's input is configured to do so. This is likely not the norm however. 

Gs5556, I understand the 10dB  ~= 2X volume relationship, However a 6dB gain is substantial.

I should add that I was not troubled by the lack of a differential gain between the RCA and XLR inputs on my pre. If anything the 20dB gain offered by the Jolida is more than required for my system. I am over attenuating the signal. Should I consider having Jolida modify my unit I will ask if the gain can be adjusted. 

I Truly appreciate the education provided by many on this forum.

Thanks for the nice words, Mesch.

As an FYI, a commonly seen example of a preamp (or integrated amp or power amp) having a single-ended internal signal path while providing 6 db of additional gain for an XLR input compared to the gain provided for an RCA input, would be a solid state design which utilizes an "op amp" ("operational amplifier") integrated circuit configured to differentially receive the balanced pair of input signals while providing a single-ended output. That kind of an input circuit can be configured to provide 6 db of gain, zero db of gain, or any other desired gain within a wide range of limits, simply by changing the value of two resistors.

Best regards,
-- Al

Thanks once again Al. I am going to call Jolida and ask how the XLR input is configured. 

After talking to Jolida, Al's second descriptor for what accounts for my gain issue best fits. There is no conversion stage (op amp?) on the Jolida's XLR input. 

I now think I might be better off using the Brystons RCA outputs connected to the RCA inputs on the Jolida. I will need a 0.5M pair of Audioquest Columbia interconnects to make this comparison. Once found I will do this and report back.