Advice wanted on how best to integrate a DSP (Accuphase DG68) into my system

Audio Systems
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Ok, just to be clear up front, as these types of threads sometimes turn into something other than originally intended… I am not asking for advice on whether I should or should not get a DSP, nor am I asking any advice on buying one as I already have one on order.

That said, I heard the difference the DG58 (prior generation) made on my friends system, and it was mind blowing… as I’m dealing with a very smallish room, and smallish speakers (McIntosh XR50s)… This was a marriage made in heaven for me… until I began dealing with the nightmare of how best to install it in my audio chain, and especially not have it by-pass my Rossini as the digital processing platform of my system…

So… I drew a diagram to explain the path I am proposing, but I feel like I’m missing something …

The recommended installation (even by Accuphase) is to insert the Digital EQ DSP between the Pre-Amp and Amp, and connect via two XLR analogue balance cables.

My proposal in the diagram is only so that I can make use of the better DAC in the DG68 when listening to SACD… as my SACD player is also an Accuphase (DP560) and has an inferior DAC to the DG68… Accuphase uses a connection called “HS-Link” to get around the Sony SACD licensing issues… so that is the cable I propose to use to connect the two Accuphase products, The dotted line for RCA connections is for an analogue playback for SACD directly into my pre-amp… so for SACD, it would appear I’d have to forget about using the DG68 DSP… but I want all of the rest of my digital audio processing to be on the Rossini.… so that would be…

CD and audio DVD’s, DVD-Rs, etc…, as well as streaming from Qobuz, Tidal, etc.

The system is as follows

McIntosh MC462 Amp
McIntosh C1100 PreAmp (all analogue)
Accuphase DP560 SACD player
Accuphase DG68 Digital Voicing EQ (the new item)
dCS Rossini w/Clock
McIntosh XR50 speakers

So… anyone care to dive into this one? or shall I just bite bullet and keep things setup as is, and insert the DG68 between the Pre-Amp and Amp…

And before anyone asks… yes, the DG68 is ULTRA transparent, even if it uses a AD/DA … I heard the predecessor, DG58 and you could not tell it was on or off, when in “flat” or by-pass mode and turned on/off … not even so much as a gain in volume when on vs off…

Like dCS, Accuphase, don’t fool around and they don’t make crap…

Thoughts? ideas? suggestions?

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Sam, I’m sure Accuphase makes excellent products, but, it’d be an awful waste of dCS’ Ring DAC to be putting the Rossini’s output through an A-D/D-A stage (especially one that uses merchant ESS DAC chip) :stuck_out_tongue_closed_eyes:

If you look at the functional block diagram of the DG-68, you’ll see that it can do everything you want it to do, completely in the Digital domain!

DG-68 Block Diagram
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You really don’t need to use the DG-68’s A-D/D-A stages at all. Meaning, you can equalise your system in the digital domain, and send its processed digital outputs to the Rossini and onto your Pre-Amp, in other words; DP-560 --> DG68 --> Rossini --> Pre-Amp --> Amp.

The DP560-to-DG68 HS-Link2 can remain a separate path to your Pre-Amp on a separate line input, and all your other Digital sources would go to the DG-68 instead of the Rossini, which would then be just a pure DAC for the digital output of the DG-68 (which is exactly what dCS’ are renown for :wink:)

You’ll still be able to enjoy the full digital-signal-processed/equalised benefits across the entire chain including with the Rossini inline. So, the steps to equalise your sound would remain exactly as described by Accuphase. :+1:t3:

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I wonder, though, if by using the DG-68 as the final component before amplification whether Sam envisions using the Rossini network board to provide access via Mosaic to Qobuz and Tidal which he specifically cites as a desired source that he wants to EQ ? Your setup suggestion ( which I broadly agree with 100% otherwise) would not allow this and he would have to find another way of accessing these online resources to send them to the DG-68. There is also a question of upsampling ( Rossini again ?) which I am uncertain of in that sequence of processes (a genuine question).

This also leaves him without a renderer for Tidal Master ( MQA) files which cannot, of course, be EQ’d in the digital domain. Can he pass these through intact to Rossini without some kind of switching ?

I hope that I am right on this but frankly I am a bit muzzy headed tonight. I hope I haven’t caught something, especially that which shall be unnamed :grinning:.

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Quite right Pete, with the setup I described, Sam wouldn’t be able to benefit from the DG-68’s equalization for streaming services into the Rossini! (you’re not that “muzzy headed” tonight after all! :wink:).

One (compromised) solution would be to route the Rossini’s RCA outputs to (feedback) into the DG-68’s analog input. So, when listening to just the streaming services, Sam would need to switch to the DG-68’s analog input [as the source]. MQA would be covered as it would be a fully rendered by the Rossini when output on the RCAs.

Upsampling on the Rossini shouldn’t be affected by the DG-68 DSP/Equalization stage that happens before the Rossini I would think.

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And of course there is always the option to insert it between the pre-amp and amp … Which might be my first way to try to set this up and see how everything sounds before trying to fix a problem that doesn’t exist yet.

edit, although I heard back from a dCS rep who says it would sound best to keep the DG68 between the Rossini and the Pre-amp…

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A VERY helpful and capable guy posted this up on another forum … I think this is my solution, even if it’s a bit complex… it’s the best way to make this work based on the consensus that the Rossini needs to be the digital primary …

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Yep, spot on Sam, there’s just maybe one potential problem that I didn’t elaborate on before

That link from the Rossini’s analog RCA output to the DG-68’s analog input (for listening to streaming services) might cause the DG-68’s analog output to your Pre-Amp to oscillate as the DG-68’s DSP engine converges the signal towards your intended equalisation (because it’s effectively a global feedback loop between the Rossini and the DG-68).

You won’t know for sure until you try it out. Just be sure to keep your Pre-Amp volume down when testing :wink:

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@Anupc not gonna lie, that went way, way over my head… but I am going to give it a try nevertheless…

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@Anupc … this is the response I got when I presented the potential issue to my friend on the other forums…

There is no signal loop (see previous answer).

If a ground loop should occur between DG-68 and Rossini (this depends on how the input switch of the Rossini is done), you have two options:
1) Swap XLR analog and RCA analog on the Rossini.
2) Use Toslink instead of 75 Coax between DG-68 and Rossini SPDIF input.
The purpose would be to galvanically separate the grounds of the DG-68 and the Rossini.

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Sam, I don’t mean ground-loops, so nothing to do with the physical interconnects.

The potential oscillation issue has to with the fact that the Rossini’s digital input comes from the DG-68, and the Rossini’s resulting output is then fed-back as the original source for the DG-68.

That’s a classic feedback loop! In other words; “the first system influences the second and second system influences the first”.

Whether or not the system will oscillate and in what way depends on quite a few factors (too many for me to guess at, so just give it a try). Hopefully it’s a convergent oscillation, and you’re good to go. If it’s some how divergent , you’re going to hear it pretty quickly I think - set volume low, and be ready to switch off your DG-68 :laughing:

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Sure, I understand what you mean, and my goal is to minimize the effect of the tone of the DG68 on the Rossini, even if from what I witnessed the DG-58 (the predecessor) is absolutely transparent… that said, if I get some strange behaviors with this setup, I will revert to the Accuphase recommended suggestion of inserting the DG-68 between the pre-amp and the amp… not idea in that we go AD/DA again, but it’s after all of the real digital processing work is done, at least that’s how I understand it.

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On all three units involved you can only select one input at a time. All other inputs will not be active.

The following input selection combination does indeed create a feedback loop:
DG-68 RCA and Rossini SPDIF.

If you make it a habit to always select HS-Link on the DG-68 before switching it off, there will never be an unwanted feedback loop (RCA input then inactive).

The following input selection combinations will not create a feedback loop:
DG-68 HS-Link (RCA input inactive) and Rossini SPDIF or streaming.
Rossini streaming (SPDIF input inactive) and DG-68 HS-Link or RCA.

On the preamp, for silver discs you can select corrected signal from DG-68 or Rossini.
For streaming you can select corrected signal from DG-68 or uncorrected signal from Rossini.

If you would add a Network Bridge, you could use the DG-68 exclusively in the digital domain (up to 192kHz) without AD/DA and the Rossini for all upsampling and DA (but not streaming).

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The AD/DA of the DG-58 works up to 176.4kHz PCM.
The AD/DA of the DG-68 works up to 352.8kHz (DXD).
The corrections are calculated at the corresponding sample rates.

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Welcome to the forums @meltemi …

He’s the smart guy who put together the diagrams I posted above btw… and soon to be a dCS customer again :+1:

Gonna have to be closer to Christmas before I get the DG-68 and we try all of this stuff out to find the best way to go.

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Soon to be a dCS customer ?
I’m a dCS user since 2002 (dCS 904 / dCS 974 / dCS 954) and a proud Vivaldi DAC V2 owner (and user) since 2019.

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@meltemi … that should have read “customer AGAIN” … you are buying something new as I recall?

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Nope.
Just thinking about a Network Bridge to replace streaming via PC.

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Welcome to the community forum Martin :slight_smile:

Good point. If the source is the Rossini’s Streaming services, then Sam has the option of routing it’s output via the DG-68’s AD/DA in the chain in which case the DG-68’s analog output would feed the C1100 directly - a bit of a waste of the Ring DAC though, but I can understand how some might want (need?) a parametric EQ like the DG-68.

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I think the way Martin has it diagramed above (in post #6) still makes use of the Ring DAC though… right?

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Thanks for your hint about the feedback loop, and sorry for overlooking it. I should have known better.
The danger can be avoided by using the correct switching sequence:
Going from silver disc to streaming:
select streaming on the Rossini before selecting the RCA input on the DG-68.
Going from streaming to silver disc:
select HS-Link on the DG-68 before selecting SPDIF on the Rossini.
There is no real “waste of the Ring DAC”, since the analog output of the Rossini (Streamer / Upsampler / DAC) feeds the AD/DA of the DG-68. And one could run the DG-68 completely in the digital domain by adding an additional Network Bridge (“waste of one streamer” then).
IMHO in small rooms (e.g. domestic environment, studio control rooms) electronic room compensation is an absolute necessity. If you ever tried out one, you will not want to live without it afterwards.
BTW the DG-68 is 1/6 octave 67 band graphic EQ for voicing plus a 1/6 octave 80 band EQ.

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