Will do. The Pass people are such sweethearts, they’ll 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 “input sensitivity”, or “maximum input level” that the unit supports.
It’s important to know so that one doesn’t overdrive the Amp’s 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 it’s maximum output level (with no attenuation).
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I’m surprised that it’s not stated anywhere official (that I can find), but Suncoast Audio’s site notes the XA60.8’s 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 XA60.8’s specs are on Passlab’s site actually, along with the other Amps; https://www.passlabs.com/wp-content/uploads/2019/12/Point8_specs_2.pdf
Couldn’t find the same for the Pre-Amps though, strange.
Yep, 0.6V would be the right 
You’re a search ninja 
Thank you so much.
Great to have that table to refer to. I’ve asked Pass for the figures on the preamp, but in the meantime (and if my brain’s at least partly functional) I think you’ve managed to educate a total tech numpty.
As a test…if I had:
XA30.8 — I’d use 0.6V out (rated 0.7 for full power)
XA200.8s — I’d use 2V out (rated 2V for full power)
…provided my speakers meant I was likely ever to want near full power, since otherwise I’d be throwing away oodles of bits to attenuate the DAC’s signal down to something that wouldn’t make my ears bleed.
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(Hope the OP doesn’t mind me continuing to post here. It feels like it’s on topic, at least.)
Reporting back about comparisons between the following configurations (in — SPOILER — descending order of preference):
- Bartók at 6V, via a Pass Labs XP-30, with the preamp doing the attenuation.
- Bartók at 0.6V, direct into the Pass Labs XA60.8 monoblocks, using the dCS to control volume.
- Bartók at 2V, via the XP-30, with the pre doing the attenuation (and amplification, I guess!) again.
Until I tried the Bartók 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 — annoyingly — that’s no longer the case. It’s 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 DAC…
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-Vivaldi…
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 — extremely impressive, gently otherworldly, but very “hi fi” sounding. (This was a great thing for electronic music, of which I’m a huge fan.)
BUT…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.
It’s now got me wondering whether a simpler pre-amp wouldn’t be better than the behemoth I have. The XP-30 is a gawjuss thing, but it’s rather overkill for a one input guy like me.
@Anupc — it’ll be interesting to hear what the Pass Labs peeps say about the XP-30 when they reply.
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I’m 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:
…but this doesn’t have the figure we’re 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 point… 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. I’m 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 — as expected, they were proper honeys.
“The XP-30 front end would overload at roughly 7 volts rms.”
Thankfully, then, feeding it from the Bartok at 6V isn’t 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 DAC’s favour), I’d be back on the just-one-remote train again. And that’s 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 it’s a shame for that to mean that you’re only using about half of your power amp’s output. Having my Bartok at 0.6V when the XA60.8s put out their maximum at 1.1V must mean that I’m 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? I’m around midway on the XP-30. I was a fair bit higher at 2V, and it didn’t 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 it’ll help others too. As well as future me, who has a terrible memory 
)
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I think that’s going to depend on the design, its age, amount of use, etc. From a design perspective, I’m not at all sure one could identify a specific sweet spot or range of consistent good SQ. Too many variables. But as Ben notes, I’m sold on the Townshend Allegri Reference; they aren’t 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 — I didn’t realise he was a fellow Antipodean — and a wee bit of audio too. Highly recommended.
I’m expecting to drive it at 6V as we’ve 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 you’ve swapped out some of your Iconoclast OCC ICs for the Townshend Fractal F1 ICs (between Vivaldi and the Legacy speakers’ extra doohickeys). Would love to hear how that went. I’ve 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 you’ll have made that change yourself lightly.
I wonder also whether I should be aiming to go S/E into and out of the Allegri Reference…given that I’ve 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, they’re really two different creatures, but it should be fun for you!
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In fact the Allegri Reference doesn’t 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 didn’t 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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Quite right Pete. I knew full well that the Allegri Reference is single ended through and through, but conflated the two things as I typed. Sloppy of me. What I meant was whether it’s likely to make a jot of difference by having the cables be terminated as RCA or XLR, i.e.
A: Bartok–(XLRs)–Allegri Reference–(XLRs)–XA60.8s
or…
B: Bartok–(RCAs)–Allegri Reference–(RCAs)–XA60.8s
I’d need new interconnects for scenario B, which would be a pain. I quite like my current cables…
I’ve got a hunch that B) is what dCS advise, however (use single-ended cables when you’re not connecting properly balanced equipment etc.).
Am I right in thinking that you went for option A on your Iconoclasts, @PaleRider, leaving them as XLRs rather than having them re-terminated?
(The winters in Dunedin weren’t so warm either, Pete. My wife would say that even the summers don’t really merit the name…)
Yes, single-ended all the way through. I run XLR cables into mine, because they solved a slight hum I had with RCA.
Hi all, apologies, I realise I’m rehashing some points already covered in this thread, but I want to make sure I’m not misunderstanding and I’d appreciate your thoughts/views.
I currently connect, fully balanced, from my Bartok to an MFA Baby Reference V2 pre-amp and then into my Karan KAS600 power amp. The preamp is passive and the Karan has an input sensitivity of 2v. My speakers are Magico A3s.
I set my Bartok output to 6v, my preamp to approx 2/3 volume and end up listening with volume on Bartok set to between -15 and -5db. It’s reasonably loud, not as loud as I’d like but I usually listen after others have gone to bed so I have to be reasonable! Everything sounds very nice indeed…
However, I’m trying to determine if my preamp is really adding any value, or whether I can sell it to raise some funds for use elsewhere (ideally an upgrade to a Rossini). The preamp doesn’t have a remote control so it doesn’t really give me the ability to set the Bartok to 0db and control volume via the preamp, hence the reason for me controlling the volume from the Bartok. So therefore it has to deliver sonic benefits to justify keeping it.
In order for me to compare against a direct output from Bartok to Karan, I need to decide what output voltage to set on the Bartok. My first test was at 2v to match the amp but the volume is much too high - I have to set the Bartok to around -25db for normal listening levels. 0.6v turns out to be the right setting, enabling me to get the Bartok back to approx -10db (+/- 5).
I’ll be doing more listening tonight but initial impression was I couldn’t really hear a difference - sounded great both ways. I’ll do doing more listening tonight.
Does anyone have any thoughts on whether I’m (at least in theory) losing anything by removing the preamp and setting the Bartok to 0.6v? Am I right to be setting the preamp at 2/3 volume to get the best from it?
I realise it’s my ears that ultimately need to decide but I’d like a view as to what you would EXPECT to be the best arrangement and settings.
All views welcome!
Thanks, Mike.