Pass Aleph 0s vs XA 30.5

[Masterlu]

McKen... Welcome to AA!

[Glisse]

Originally Posted by McKen

I own a J2 also and love it driving Zu Soul Supremes. With those speakers it rocks the house but also sounds amazing at low volume. I run it direct with a tubed DAC by Wavelength but always wonder if it would sound even better with a good preamp...

Pass often seems to design with quite low input impedances on his amps. This can be an issue if the source has a relatively high output impedance, which can be the case with a tubed source (rarely with SS). Typically, the output impedance should be 10 to 20 times lower than the input impedance, otherwise the source amplifier may have trouble driving current through the connecting cable (voltage isn't a problem, but current is).

But it also depends on the quality of the output stage - a lot of DACs are just using an IC op-amp, and these really need a very friendly impedance to work okay. But some output stages can be discrete, with robust power supplies.

I'd ask Gordon Rankin, after letting him know the input impedance of the J2, whether he feels there would be any benefit in using preamp vs whatever output he is using for the DAC.

Then again, from your description, you don't have any issues anyway. If there was an impedance mismatch, you would have limited bass extension and softened dynamics.

[McKen]

Originally Posted by Aercool

I love the look of those Soul Supremes/Superflys, but the 16 ohm impedance kinda freaked me out initially, so I opted for the cheaper 12 ohm Omens. Good to hear that the J2 handles them with ease. I do see myself upgrading at some point - but the thought of repacking these monsters gives me a headache... Fwiw, Nelson Pass also uses a pair of Soul Superflys.

I emailed with Nelson and he recommended the J2 for these Zu's. Also said they were rated more like 12ohm vs 16. I also run them of my MC275's 8 ohm taps and they sound better there than 16ohm

[McKen]

Originally Posted by Glisse

Pass often seems to design with quite low input impedances on his amps. This can be an issue if the source has a relatively high output impedance, which can be the case with a tubed source (rarely with SS). Typically, the output impedance should be 10 to 20 times lower than the input impedance, otherwise the source amplifier may have trouble driving current through the connecting cable (voltage isn't a problem, but current is). But it also depends on the quality of the output stage - a lot of DACs are just using an IC op-amp, and these really need a very friendly impedance to work okay. But some output stages can be discrete, with robust power supplies. I'd ask Gordon Rankin, after letting him know the input impedance of the J2, whether he feels there would be any benefit in using preamp vs whatever output he is using for the DAC. Then again, from your description, you don't have any issues anyway. If there was an impedance mismatch, you would have limited bass extension and softened dynamics.

thanks very much for your advice. I will check with Gordon but I think I'm okay.

[McKen]

Originally Posted by Masterlu

McKen... Welcome to AA!

Thanks very much! This is a great forum. I learn a lot from reading it.

[Aercool]

Originally Posted by McKen

I emailed with Nelson and he recommended the J2 for these Zu's. Also said they were rated more like 12ohm vs 16. I also run them of my MC275's 8 ohm taps and they sound better there than 16ohm

Before finding the J2 I was using a singled ended amp and was having issues with bass extension and tightness. Really fuzzed out bass, the higher the output voltage of the CD player, the worse it was.

I tried different output taps on this amp too, and agree that the 8 ohm taps sounded better than the 16 ohm. A lot of that midrange magic was gone on the 16 ohm tap, just seemed to sound 'flat'.

If I could find someone local that wanted cash + my Omens for their Soul Supremes, I'd do it. And then I'd go buy a bunch of lottery tickets because it was clearly "my day".

[McKen]

Originally Posted by Aercool

Before finding the J2 I was using a singled ended amp and was having issues with bass extension and tightness. Really fuzzed out bass, the higher the output voltage of the CD player, the worse it was. I tried different output taps on this amp too, and agree that the 8 ohm taps sounded better than the 16 ohm. A lot of that midrange magic was gone on the 16 ohm tap, just seemed to sound 'flat'. If I could find someone local that wanted cash + my Omens for their Soul Supremes, I'd do it. And then I'd go buy a bunch of lottery tickets because it was clearly "my day".

Isn't the Zu/First Watt a great combination? It's really cool when components seem to "lock in" like that. When I mix and match different components in they don't have the same synergy. Really interesting.

[Aercool]

Originally Posted by McKen

Isn't the Zu/First Watt a great combination?

It's been that way for me.

[Aercool]

Welp. I finally took the plunge. I love the upgrade path that Zu makes available if you've bought your speakers directly from them. My Omens are now on their way back to Utah, and a new pair of Soul Supremes will be heading my way next week. Woo hoo!

[McKen]

You're going to love that combination. Plan on 4 months to break those in but it's worth the wait! Congrats!