Hi, I recently bought a Bartok, started with unbalanced output in to my preamp’s (McIntosh C2500 tube preamp) unbalanced input via a pair of Audioquest Yukon RCA cables, and it sounded great. I received a pair of balanced cable, Audioquest Yukon XLR, a week later; plugged it in and expected it would deliver higher current and therefore sound louder and more power. However, it behaved the opposite, sounding lower power and audible volume. I double-checked the connections but could not find anything wrong. When i increased the preamp volume for balanced input from 38% (comfort volume level for unbalanced connection) to 46% (% is what my preamp displays, not sure how to translate this 8% difference into dB), balanced connection sounded pretty much on par with the unbalanced connection. I looked at the preamp’s input impedance, unbalanced is 22k ohms while balanced is 44k ohms. This probably explains why balanced input sounded at lower volume, based on V = IR. However, I do not have the technical knowledge to say for sure and understand why.
Has anyone experienced what i experienced with Bartok? Does it matter or not? Is balanced input still a preferred connection for you and why? Thanks!
Hi Ryan and welcome. The reason that you need to set the volume control on your preamp higher for balanced input than unbalanced is because the input sensitivity ( not impedance) of your McIntosh C2500 unbalanced input is double that of the balanced input. The specifications are input sensitivity for unbalanced is 450mv and balanced is 900mv. That means that it requires double the input voltage for the balanced input to drive the preamp to the same level as the unbalanced input. However the voltage level of the dCS balanced and unbalanced outputs is the same. So to equalise the resulting sound level you therefore need to increase the volume control on the preamp by 6dB when using the balanced input ( I have no idea what that means expressed in % according to your preamp’s display).
The above in itself has no impact at all on sound quality. It just means raising the volume control which is what it is there for. However the output circuitry on dCS DACs is of a different design type for unbalanced RCA or balanced XLR. You may prefer the sound of one over the other but there will be no difference in regard to output power.
In theory balanced connection will provide increased immunity to electromagnetic interference. It has nothing to do with power, frequency response etc. So on this basis only it may be considered as superior but the significance of this aspect will depend in practice upon the environment it is being used in.
Thank you so much Pete! Your explanations are detailed and really help. Much appreciated!
Hi Pete, I have read some other threads where people discussed different line output levels, mostly 2V versus 6V. Given my preamp’s input sensitivity for balanced, would you recommend me to set the line output at 6V instead? 6V sounds louder and more dynamic as the first impression, but doesn’t sound as smooth after a longer listening. I could not really pin point what made me less comfortable, or it could be just completely psychological. I saw someone said 6V has better signal to noise ratio, but dCS user manual said 6V could cause some distortion to some amps. So a lot of conflicting info out there and I have no enough knowledge to judge.
On the other hand, someone said the line out level should be set lower than 2V (volume level at 0dB), so that the analog volume attenuation can be minimized on the preamp. This argument also seems to make sense.
My current settings on Bartok are 2V balanced out, 0dB on volume (full volume), and preamp running around 46% of 0dB (I have not asked McIntosh how to interpret % into dB why they set the display as % but not dB). If I set line out level at 6V, keep Bartok volume at 0dB, the volume level on the preamp would go down to 38% (more attenuation) for the similar audible volume level. Maybe I should consider 0.2V, if attenuation on the preamp is harmful to SQ?
I think that is a good place to begin as your description actually suggests that the 6V line output from Bartok may just be overloading the preamp’s input causing slight distortion which you may be hearing/interpreting as more dynamic and louder ( the human ear uses distortion as an indicator of loudness). Smoother is more like it should sound.
When you listen at an average level where about is the volume control on the preamp set ( with Bartok set at 0.0dBfs)? The idea is to choose a line level voltage output from Bartok which, listening at a comfortable average level for you, places the use of the preamp’s volume control within an area where it is easy for you to set the volume and is within the volume control’s optimum area of operation. This normally means a setting approximately between 9:00 o’clock and 3:00 o’clock. If you find that to control volume the setting needs to be set significantly below 9:00 o’clock then the Bartok line output voltage is probably set too high. This may also place the volume control in an area where it is likely to be least linear particularly in the tracking of the two channels vis a vis each other.
If you need to set the volume control higher than 3:00 o’clock for an average level then control will be difficult to manage and very difficult for musical passages with particularly loud dynamics where you may just run out of the range of control.
Yes 6V output does provide the best signal to noise ratio. However this has little practical impact as all of the line output voltages on dCS equipment settings in normal usage will provide a noise level way below the human ear’s ability to distinguish it from the signal. It is really only of interest when using measuring equipment.
You really need to find the best compromise that suits you , your tastes, your equipment and your room.
Thanks Pete! Yes, volume at Bartok is set at full volume level (0dB), so the volume control is fully at the analog domain by the preamp. With 2V or 6V line out from Bartok, the comfortable volume level in the preamp is well within the 9am - 3pm range. I agree with you that my ears are probably incorrectly taking the slight distortion from 6V as loudness and dynamics. I will stay with 2V after knowing all these.
By the way, McIntosh told me that some of their preamps give % and dB options for volume level display, but my C2500 only has %. The reason is that there are more customers who are confused by dB, but happy with %. The C2500 will be unity gain at 75% volume level. This is 2V in -> 2 V out. However, I still do not know how to translate 45% volume level into dB after knowing the unity gain at 75%
Thank you Pete. I had the same question as Ryan. Thanks for clarifying.