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Best Tube Amp For Sonus Faber? Or Pass XA-100.5? $6-7,500 Budget, Purchasing Used.

As the title says, I have a pair of Sonus Faber Olympica III's that I am more than pleased with, for which I am trying to determine the best available amplifier, preferably tube. Of course, there are always budget limitations and my budget for this amp would be $6-7,500, and I would be buying used to maximize purchasing power.

Based on a lot of research, and quite a few auditions at brick and mortar stores, various home systems, Axpona, etc. I'm honestly not sure if there are any truly exceptional tube amplifiers available within that budget that meet my needs. These speakers need 100wpc tubed, or 200 wpc solid state, into 4 ohms to really open up and perform. 

If, in the end, there are no really great tubed options, I've always heard that the Pass Labs XA-100.5's were probably the optimal choice in solid state for former tube lovers. I would also appreciate any thoughts on that option from owners. 
nightfall
georgehifi's avatar
georgehifi
10,312 posts
 
They only dip into the 2ohm territory very briefly
Yeah but this dip spans between 70hz to 150hz, the power region for bass, if the amp can't deliver current into it, you'll get a big dip in power in that region, especially from an 8ohm tap.
https://ibb.co/hoYNyF

Cheers George  
audioman58's avatar
audioman58
4,097 posts
 
I too have the Sonus Faber Olympica-3 Loudspeakers.
I was using a dual mono 50wpc 4ohms pass labs 
And had 100 watt AR  tube amp softens the leading edge these speakers like current dual woofers give excellent bass yo around 30 Hz. 
But only if you give them power .I  tried my friends Ampzillo mono blocks 
Very good vs pass or anyone these to for over $10k
And will go to to toe with amps $$$.
Underwood wally has these on special. Don't take my word for it .
Read the reviews. I just bought the smaller but Very capable son of Ampzilla MK-2
350wpc into 4ohms  .on d of the guys st our sudio group has one and Very close yo the mono in every way  never need more power.
djfst
169 posts
 
The 8ohm taps were clearly better, and had a hard time understanding why based on the impedance graph.   There is another audiogon forum discussing this where someone else mentions the Olympica III runs better on 8ohm taps for them too.   It was interesting, because the Primaluna taps were, 4, 8, 16.    But the VAC 200 iQ (and probably other VACs) have ranges for their ohm taps:  1-2, 2-4, 4-8.   This may explain better why the VAC runs the Sonus Fabers better, since there is a broad range where the ohms are constantly changing.  Maybe the VAC is better at handling this?   Not sure.   All I know if the 4-8 ohm taps (and the 8 on the Primaluna) were clearly better.   Judge by your ears in the final analysis.

Nightfall, the Preamp I have been saving for.  Initially was the Primaluna preamp, but would eventually love to upgrade to one of the following (again a tube guy):  Zesto Leto, EAR Yoshino 868 or 912, Herron Audio, or VAC.   I think VAC is coming out with a more affordable preamp this year.... at least that was the rumor a while ago.  
djfst
169 posts
 
georgehifi,

I noticed the bass improvement the most when going from the primaluna to the VAC.  that would coincide with what you were saying.  The best bass on a tube amp I've heard was with the VAC.
djfst
169 posts
 
Nightfall,

Remember that the Olympica III is moderately efficient at 90+db.  so even if it dips low with the ohms briefly, there is more at play with how well an amp can drive speakers.  The VAC dealer on the audio shark forum commented that the 100 watt specs for the 200 iQ was very conservative, and is likely much more power that is giving out.  I've noticed that in my experience with it as well.
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