Makes sense, the AR Pre has a maximum input level of 10V, so, setting your dCS for 6V output would match the best. 
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Where does one find those sorts of figures, @Anupc? Iād love to be able to approach this from both the āthis should make senseā side as well as the āIāll give it a go and see what I getā angle.
When I read of other people preferring their dCS kit direct I wonder what settings theyāre using, and what sorts of patterns there are.
The Stereophile reviewer preferring his Rossini direct into his Pass XA200.8s, for example ā Iād assume that the specifications of his mono-blocs would be similar to mine, but Iām not quite sure which specs I should be referring to. Is it the input impedance of the power amp? And at which voltage they put out maximum power?
Ultimately it will come down to what I like the sound of most, but itās good to learn a bit around the potential why, too.
Yours, mired deep in untechnicalness 
Ben, itās usually in the technical specification section of the Pre-Amp on the website or in the Manual under āinput sensitivityā. I took a look at your Passlabs XP 30, strangely, thereās no technical specifications in Manual. You could try emailing Nelson for it. 
Will do. The Pass people are such sweethearts, theyāll help out.
What is the full complement of specs I should ask for, for both the XP-30 pre and the XA60.8 mono-blocks?
This is one helpful forum 
Usually āinput sensitivityā, or āmaximum input levelā that the unit supports.
Itās important to know so that one doesnāt overdrive the Ampās input by setting a voltage thats too high on the dCS (who by the way include that clear warning in the manuals 
).
Different vendors seem to use different terms, generally it means the maximum input voltage level that drives the Preamp/Amp to itās maximum output level (with no attenuation).
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Iām surprised that itās not stated anywhere official (that I can find), but Suncoast Audioās site notes the XA60.8ās input sensitivity as 1.1V at a 26dB gain.
Would that suggest that going direct from the DAC at 0.3V and 0.6V are the only options that are likely ever to make sense without attenuation somewhere else?
Thanks Anup! Nice to know that my ears made the correct choice 
The XA60.8ās specs are on Passlabās site actually, along with the other Amps; https://www.passlabs.com/wp-content/uploads/2019/12/Point8_specs_2.pdf
Couldnāt find the same for the Pre-Amps though, strange.
Yep, 0.6V would be the right 
Youāre a search ninja
Thank you so much.
Great to have that table to refer to. Iāve asked Pass for the figures on the preamp, but in the meantime (and if my brainās at least partly functional) I think youāve managed to educate a total tech numpty.
As a testā¦if I had:
XA30.8 ā Iād use 0.6V out (rated 0.7 for full power)
XA200.8s ā Iād use 2V out (rated 2V for full power)
ā¦provided my speakers meant I was likely ever to want near full power, since otherwise Iād be throwing away oodles of bits to attenuate the DACās signal down to something that wouldnāt make my ears bleed.
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(Hope the OP doesnāt mind me continuing to post here. It feels like itās on topic, at least.)
Reporting back about comparisons between the following configurations (in ā SPOILER ā descending order of preference):
- BartĆ³k at 6V, via a Pass Labs XP-30, with the preamp doing the attenuation.
- BartĆ³k at 0.6V, direct into the Pass Labs XA60.8 monoblocks, using the dCS to control volume.
- BartĆ³k at 2V, via the XP-30, with the pre doing the attenuation (and amplification, I guess!) again.
Until I tried the BartĆ³k at 6V I was convinced I was selling the preamp. Going direct at 0.6V was clearly better for almost everything I listened to.
But ā annoyingly ā thatās no longer the case. Itās a pity, because I loved the simplicity I had with going direct. One (gorgeous) remote control. Less to go wrong. Fewer boxes. Fewer interconnects. The apparent logic of removing bits from the signal path (<- an only partly intentional pun) being better. The extra thousands that I could put toward a better DACā¦
I tried all sorts of music, and the majority of genres were just more enjoyable in configuration #1. Initially, going direct sounded so good that I was convinced that I was home and hosed, and oh-how-nice-it-is-that-I-can-put-the-money-from-selling-the-XP-30-toward-a-Vivaldiā¦
If I were to try and pin the differences down, it would be that going direct in my system sounded lovely in a slightly ethereal way ā extremely impressive, gently otherworldly, but very āhi fiā sounding. (This was a great thing for electronic music, of which Iām a huge fan.)
BUTā¦adding the preamp meant that it was easier to just sit back, soak it all in, and grin. Not getting as much of that gorgeous airiness was ok, because what I got instead was something just a little bit more believable for most of what I listened to. More weight, stronger images of people putting tunes in the air in front of me.
Itās now got me wondering whether a simpler pre-amp wouldnāt be better than the behemoth I have. The XP-30 is a gawjuss thing, but itās rather overkill for a one input guy like me.
@Anupc ā itāll be interesting to hear what the Pass Labs peeps say about the XP-30 when they reply.
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Iām also actual quite curious why the Passlabs folks chose to post online technical details for their Amps but not their Pre-Amps 
I found this:
ā¦but this doesnāt have the figure weāre after, does it?
@Anupc in this context what specs for the preamp are we looking for in specific that could be useful and relevant?
@all2ofme
you are absolutely on pointā¦ and you summed it up perfectly as well.
with dac direct there is definitely a lot of clarity in the upper mids and highs.
with the preamp there is sense of weight and full bodied sound especially in the lows/bass
source , preamp and the interconnects all together determine the tonality and color of the sound .
its how you want to season it and cook your recipe to get a final sonic output which you like
Yeah. Iām not sure why; they happily state it for the Amps, but not for the Pre-Amps?
Passlabs are not the only ones of course, quite a few manufacturers these days tend to omit the input sensitivity specifications - I guess they just expect people to fully utilise their volume knobs 
Got a response back from Pass Labs ā as expected, they were proper honeys.
āThe XP-30 front end would overload at roughly 7 volts rms.ā
Thankfully, then, feeding it from the Bartok at 6V isnāt frying anything.
My thoughts now are:
- I wonder how a Rossini or Vivaldi direct would compare to the Bartok via the XP-30. If it were close (or in the better DACās favour), Iād be back on the just-one-remote train again. And thatās one attractive locomotive.
- I wonder how a (great) passive pre would compare to the XP-30. Like the Townshend one that @PaleRider loves so much. (Another thread entirely. Brace yourself, Greg
) - What makes for ideal/very attractive matches between a dCS DAC and a power amp in terms of specifications. Obvious enough that you want the DAC between -10 and -30dB (though I read the Vivaldi is still pretty good even lower), but itās a shame for that to mean that youāre only using about half of your power ampās output. Having my Bartok at 0.6V when the XA60.8s put out their maximum at 1.1V must mean that Iām barely scratching the surface of my finned beasties, no?
- Is there a portion of their range where volume pots sound especially good as a rule of thumb? Iām around midway on the XP-30. I was a fair bit higher at 2V, and it didnāt sound as good.
(I realise that there are many, many variables in all of this, but since it feels like this discussion is helping me, perhaps itāll help others too. As well as future me, who has a terrible memory 
)
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I think thatās going to depend on the design, its age, amount of use, etc. From a design perspective, Iām not at all sure one could identify a specific sweet spot or range of consistent good SQ. Too many variables. But as Ben notes, Iām sold on the Townshend Allegri Reference; they arenāt the only folks using an AVC, but I have yet to find one better. And I demoed more than a few.
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Well, @PaleRider, you have a lot to answer for 
An Allegri Reference is on the way. I hope to be comparing it to the Pass XP-30 next week, or the one after. December will be fun. Only one will be around come 2021!
Had a great chat with Max*. We talked cars, short shorts at school ā I didnāt realise he was a fellow Antipodean ā and a wee bit of audio too. Highly recommended.
Iām expecting to drive it at 6V as weāve been discussing on this thread, and to hook it up with existing cables to start with (Tellurium Qs of various persuasions). I understand from another thread that youāve swapped out some of your Iconoclast OCC ICs for the Townshend Fractal F1 ICs (between Vivaldi and the Legacy speakersā extra doohickeys). Would love to hear how that went. Iāve been a fan of as little mixing and matching as possible until now, but Max was pretty insistent on going with the Fractals, and I doubt youāll have made that change yourself lightly.
I wonder also whether I should be aiming to go S/E into and out of the Allegri Referenceā¦given that Iāve loved the Bartok and the Pass XA60.8s so much balanced via the XP-30. This may be another cable merry-go-round!
*What a fantastically appropriate name for someone who makes a preamp that passes through maximum voltage when you ask it to get out of the way.
I liked the Fractal ICs [and they are much more forgiving and flexible of cramped spaces], but I swapped the Iconoclasts back in. The specs are just slightly better, and I prefer to have all the same cables in the system.
Obviously, one being passive and the other not, theyāre really two different creatures, but it should be fun for you!
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In fact the Allegri Reference doesnāt actually offer balanced connection. It is all single ended. To make it balanced Max would have needed to incorporate additional transformers for the inputs/outputs to enable the differential connection. I read somewhere that he didnāt want to do this. However I think I remember that there was an earlier top end Allegri that did offer balanced connection ( it was very expensive for the time) . There are indeed XLR connectors but not, however, for balanced connection.
Max is an amazing guy. A real original thinker backed up with proper technical knowledge. I too have always enjoyed my odd talks with him. I also had to wear shorts at junior school in the 1950s but in our sunny, warm English winters 
.
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