Dynaudio C1 and Pass amp

Hi Rr999,
Does Aleph 3 go into A/B mode after it goes out of class A? My understanding is Pass only starts doing that with their XA.5 series. This should help in dynamic swings and maybe able to explain your 100Hz roll-off? I could be wrong.

Regards,

Thank you for the comments. I shall find out next week.

Xti, how big is your room?

Looking back some of old XA30.5 and c1mk1 threads, it seems member vinw and audiofeil had had success using XA30.5 to drive Dyn difficult loads, c1mk1 for vinw and Sapphires in audiofeil case. Not sure about audiofeil's room but vinw's 21x17 room is only slightly smaller than my 18x25 room (my listening position is pretty much in the middle of the room with speakers a good 2 feet from the short wall). I think my room is above average in terms of acoustics as well, based on freq sweeping with 2 different sets of speakers using Anthem ARC.

On top of that, xti, who I think has tried both c1mk1 and c1mk2/sig, thinks c1mk2/sig is easier load. Perhaps I'm just making myself feel better before the arrival of c1sig. :) I shall find out soon enough and will make sure to report back. My budget definitely won't allow me to go up to XA60.5 esp. after buying c1sig and I'm too in love with Pass XA.5 to part with my XA30.5. C1sig also sounds like reference monitors that I've been waiting for (just read a European mini review in which they pair both c1sig and diablo utopia to devialet and favor c1sig slightly but declared no clear cut winner....except diablo stomped c1sig in terms of aesthetics lol, no argument there)

Meantime, crossing my fingers :)

Hi Rr999,
I do have a Paradigm Studio Sub12. But I'm thinking not to run with it at first and see where it takes me. During my brief demo at a dealer, C1Sigs did sound like powerful mini floorstanders and have more than enough bass to satisfy me. We shall see.

BTW what speakers do you have now? Sounded like you don't have the C3s anymore.

Hi Yeast,
Not so fast. :) I am not selling XA30.5 for foreseeable future yet. I just love this amp.

From talking with Desmond from Pass when I bought the amp (I believe he holds a very high position at Pass), XA30.5 output is actually closer to 60 class A watts into 8 ohm (spec says 30 watts class A). That probably also means 100-120 class A watts into 4 ohm. I didn't directly ask this but I just assumed. One can always hope.

Like you mentioned, my understanding also is Pass XA.5 series amps don't just stop at their rated class A spec. They go higher in class A/B to a certain level if needed (for dynamic swing peaks). Based on Stereophile measurement of XA30.5, the clipping (THD 0.1%) happens at ~200 class A/B watts into 4 ohm.

In terms of current, XA30.5 has double the bias current than that of Pass X150.5 (150wpc class A/B rated), which, in its own right, is not a slouch.

But I think it's more than 3-4 db benefit by going up to XA60.5 mono blocks. One being, obvious separate power supply. Secondly if I remember correctly, from Nelson Pass's "leaving class A" article on Pass website, XA60.5 has more bias current than XA30.5, almost 3 times the bias current of X150.5.

Hi Keithr,
I already have the XA30.5 and C1 Sigs are on the way as well. I shall find out soon enough. If X250.5 is indeed more "suitable", there's always Reno Hifi to move "up". :) But looking at the numbers from Nelson's Leaving Class A article, XA30.5 seems to have higher bias current and higher class A peak - 1.3 vs. 0.8 and 57 vs. 20. I'll make sure to report back how XA30.5 drives the C1 Sigs in my big room.

Hi Paul,
Good to hear from you again. To be honest, it is your review of C1s that made me start looking at them. It has been awhile when I first stumbled upon that review, but Xti just reminded me the other day to read it back again, which I did and gave me a whole new perspective.
I used to have Bryston 4BSST2 but XA30.5 is just at another level entirely in terms of refinement and seduction. I didn't get to test them out driving difficult loads however, as my old Electra 1008 Be2s were quite efficient. Both amps drove them with ease.

Best,

Hi Pnmeyer,
Keep it posted how it goes. C2 II and XA30.5? I thought I was optimistic. But I guess it depends heavily on the size of the room. With C2 II though I don't suppose your room is remotely close to small at all.

Phreak12,
How big is your room?

Not yet for me. But I will pretty soon.

C1 Sigs have arrived. XA30.5 has absolutely no problem driving the Sigs in my 18x25 room. My normal listening level is 75-80db average SPL with peak of 85-90db at the sweet spot (I listen with lower level at night). Meter doesn't move from 11:30 position even for bass heavy materials. I tried to push a bit harder and it seems I have a good 8-9 db headroom above my normal listening level before the Pass needle starts to move to the right side (leaving class A). And that is at very loud level and I'd never listen at this level for extended period of time.

I set the speakers on the short wall with 8 feet between them. 2 feet from the back wall and sweet spot is 9 feet away from both speakers. The music has great slam and dynamic swings are handled pretty well.

Hi Acropora,
Interesting. Would you care to elaborate "some of dynamic range go away"? As far as I can tell, at my normal listening level, it is not missing much in big dynamic swings, if any.

I guess the easiest way to find out is getting another Pass amp like X250.5 (as suggested above by Keithr) and do an A/B. But I'm not sure if I need to do it. The amp needle doesn't move.

Best,

Pnmeyer, thanks for sharing. Hope you're enjoying your C2s. I'm sure they sound as good as they look. My room should be great for C2s but I can't swing it right now, plus I prefer audio gears that can be moved by one person.

Xti, you know what I'd wish? A medium size between C1 and C2. Something like C1 + a bass driver from C4. :p