Tech Question

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Dr_Wu
Dr_Wu Posts: 320
I would like to keep my streaming circuit direct from the DAC to the amp, using the streamer as a preamp. At the same time, if possible, I would like to use my turntable and CD running through my preamp. Have been advised to consider running the preamp to the amp via the XLR inputs, and the DAC as it is now via RCA inputs (the only output option for the DAC). The amp can be switched between balanced and unbalanced inputs. Unfortunately, my preamp does not have XLR out connectors. My thought is to use XLR/RCA adapters - I realize this will defeat the "balanced" feature, but over a .5 meter IC, should be fine. I understand that there may be a difference in gain between the inputs to the amp (XLR being higher than RCA), but I don't know if (a) that would be true using the adapters, or (b) if that is a problem.
Any thoughts or advice other than "just buy a new preamp"? :D

Comments

  • Dr_Wu
    Dr_Wu Posts: 320
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    If this is the wrong section for the discussion, could a Mod move it? (2-channel, maybe?)
    Thank you!
  • mhardy6647
    mhardy6647 Posts: 33,244
    edited May 6
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    I mean, a line level connected switch would work fine for such an application (if I am understanding your "ask" correctly).
    Sounds like you want to share two "sources" feeding the same power amp(?) -- one is the DAC's analog output (the volume of which presumably can be controlled upstream of it?) and the other is the analog output of a full function preamp.

    If so -- then, yeah, an A-B switch. I'd recommend building one, allowing you to use whatever components (wire, jacks, and switch) you like. Otherwise I'd probably go "bespoke" and contract someone whose work you like to build you one. We're talking the simplest possible passive device for line-level signals. :)
    Balanced vs. unbalanced isn't really an impediment -- just one more connection to switch for the balanced component.
    If you need to convert balanced to unbalanced (or vice versa), a transformer is the best simple way to do it. Hifi baluns won't be inexpensive. I am sure there are active balanced/unbalanced converters for audio -- mostly for the pro (PA/sound reinforcement market).
    PS and my apologies if I have misunderstood your question! :blush:

  • Gardenstater
    Gardenstater Posts: 4,232
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    Can you look up the specs for the output V of the RCA and XLR of the DAC and also for the preamp?
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Dr_Wu
    Dr_Wu Posts: 320
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    @mhardy6647 Yes, that's what I want to do. The DAC volume is controllable from the streamer (Lumin U2 Mini). Since the amp has a switch for balanced v unbalanced inputs, would that not do what your switch would?
    @Gardenstater The Chord Qutest DAC has adjustable volume output: 1V, 2V, or 3V. It is currently set at 2V. The NAD C165BEE preamp has 2 preouts. I can't seem to find the Preout 1 value, but the Preout 2 volume is adjustable from the Preout 1 value to -12dB. Does this help address the gain questions?
    Thanks to you both!
  • invalid
    invalid Posts: 1,302
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    I would think if the amp has a switch from single ended inputs to balanced inputs that is all you would need.
  • Dr_Wu
    Dr_Wu Posts: 320
    edited May 6
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    Thanks for that. Though I will say the switch suggestion would be much handier than getting to the switch on the back of the amp, a Parasound A21.
    Regarding the possible gain discrepancy, is that a real concern given that the preamp does not have balanced outputs, and the IC cables from the preamp to the amp will not actually be XLRs; rather, RCAs plugged into an XLR adapter?
  • Clipdat
    Clipdat Posts: 12,684
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    Why do you want to do this?
  • Gardenstater
    Gardenstater Posts: 4,232
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    Pre out is specified at "> 10V into a 600 Ohm load", so the gain loss from just using the DAC would probably be pretty significant but if you have enough excess watts it might not matter and may or may not sound better w/o the extra component. Just my 2c.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Dr_Wu
    Dr_Wu Posts: 320
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    Clipdat wrote: »
    Why do you want to do this?

    One amp; two source circuits that I'd like to keep separate. Reason being, the digital circuit sounds better to me when I use the streamer as a preamp for volume control and connect the DAC directly to the amp (not through a second preamp).
    I've been streaming exclusively with this setup for awhile. But, once in awhile I'd like to use the turntable or CD. Both of these components (and the NAD preamp) have been sitting "out of the loop".
    Probably only makes "sense" to me. :p
  • mhardy6647
    mhardy6647 Posts: 33,244
    edited May 7
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    Dr_Wu wrote: »
    Clipdat wrote: »
    Why do you want to do this?

    One amp; two source circuits that I'd like to keep separate. Reason being, the digital circuit sounds better to me when I use the streamer as a preamp for volume control and connect the DAC directly to the amp (not through a second preamp).
    I've been streaming exclusively with this setup for awhile. But, once in awhile I'd like to use the turntable or CD. Both of these components (and the NAD preamp) have been sitting "out of the loop".
    Probably only makes "sense" to me. :p

    You should see the circuitous pathway(s) used by various sources to get to my power amplifier. :blush: Just kind of evolved. All unbalanced, though (just like me).