Dynaudio C1 and Pass amp

I just purchased the new PASS INT 30A which is almost identical to the XA30.5 ( a XA30.5 with passive attenuator). This is a 30 WPC class A amp and has all the amp one needs for hard to drive speakers like Dynaudio's. I called Pass labs and they say when really pushed, these amps switch into class AB and can sustain 100 wpc for musical bursts with no clipping. In fact, the INT 150 (150 WPC AB)is essential the same amp with a slightly bigger Transformer to raise the rail voltage about 5 V above the INT30A +/- 42V.

Most music rarely uses sustain demands above about 10 WPC even for difficult speakers. Thats why Pass designed all his amps to play in class A for the first 10 Watts.

I asked them if this is enough power to drive Avalon acoustic speakers (I think they are wonderful and require enormous current/power) and he said that the 30.5 is one of their finest and will drive easily anything with ease in a normal room.

Finally, I think if you double the power you only get about 3-4 dB more sound pressure.

I have sonus FABER Cremora Auditor M's and the INT30A is overkill, but wonderful. I'm going the REL route for sub myself.

Wish I could afford to take the XA30.5 off your hands...Its one of Nelson Pass's favorites.

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.

I had the X250.5 amp on the C1s and they LOVED the power. I would not even attempt a XA30.5.

Wonderful speakers that need high current.

Hi Kzhtoo,

Congratulation for your new speakers! I have seen that you have also posted a
message on "my" Focal Micro Be vs. Dyn C1 review thread. Sorry,
for the late reply, I too have bought new speakers (Avantgarde UNO) and was
busy setting them up :).

IMO there is no reason you should doubt your current amp. Watt ratings can
be very deceiving, e.g. both me and Xti have reported cases where "small"
quality amps (like yours) have put to shame power horses like Bryston when
driving the C1s.

Keep us posted!
Paul

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,