Thiel Owners

@dickieboy , Ah, that's a bit different. And with that I agree. Even here on Audiogon it's often over generalized that all Thiels are demanding of amplifiers. The CS 1's 1.2's, 2's, 3's and 3.5's all had impedances over 4 Ohms (though the CS 3's and 3.5's did have the eq demands as well). Look at this rather benign impedance plot:

Thiel CS2 loudspeaker Measurements | Stereophile.com

@lars888888 , I suggest limiting your search for amps that are actually spec'd to 2 Ohm loads. If an amp is truly capable, the manufactures are likey to brag about it. I'd avoid amps from manufactures that rely on ancedotal marketing. If the amp is truly up to the task, let them put it in writting. Some (but not all !) amps from Krell, Levinson, and Threshold amongst a handful of others could qualify. If looking at some older models; I'd look for amplifiers that have been recently recapped by the manufacturer or manufacturer endorsed tech. These amps are typically heavy and costly to ship so having had this done recently could be prudent. Power amps tend to work better than integrateds for speakers such as the CS 2.4's, . As Intergrateds often are less adept at lower impedances and/or are less richly biased than the power amp offerings

Regarding amps: In addditon to my hotrodded learning labs of Classé DR9s and Adcom GFA555s, my reference amp is the Benchmark AHB2. A single stereo amp may not have the oomph you need/want, but in bridged mono a pair might. Power aside, the distortion and noise characteristics of this amp is extraordinary and its unique feed-forward topology pegs the output signal profile as nearly identical whether stereo or mono. The only difference is that the damping factor goes to half in mono, but chopping your speaker cables to half length corrects that. They maintain their operating characteristics to below 1.5 ohms.

It took me awhile to get comfortable with their operation and differences from 'normal' amps. I'm hooked. You can read all about it at

@tomthiel 

That's good to hear because I can't see Adcom amps as being used as a reference when you're designing or refining previous speaker designs. From my own experience with an Adcom amp many years ago, they just aren't that good.

roxy54

Since the mid 90s, I have used a pair of Classe DR9s in mono for my professional studio and consulting needs. They were more than adequate, especially via RCA inputs rather than the OpAmp quasi balanced mode. After I bought Thiel' Audio's ashes in 2018, I migrated to a Benchmark stack (DAC3B, HPA4 headphone/preamp, and a pair of AHB2 power amps.) They meet my present playback and research needs very well.

Along this recent path I wanted ways to power Thiel's difficult loads at prices musicians could afford. To that end I've tested a lot of gear that comes across my radar - much of it via this forum. Adcom was such an exploration. Here's a snatch of what I learned. Some of the Adcom gear was designed by Nelson Pass, whom I adore. Much other of their gear is more ordinary. In particular the GFA555 (straight) was Nelson's shot at simple, clean, innovative design that checked his boxes of voltage/current stability, short signal path, stability into low impedance, etc.

I bought a low serial number GFA555 and later a higher number 555 and then (on recommendation) a 555 MkII. My evaluation was the low# 555 was clean and direct, the higher# 555 was somewhat shouty and jittery and the MkII was smoother, less engaging, more ordinary.

Jim Williams of Audio Upgrades in Carlsbad rebuilds/ upgrades studio recording consuls. He hotrods the GFA555 (not MkII) and informed me that Nelson's 555 depends on high quality parts to shine. The early 555 renditions featured best of form Japanese components assembled in Japan. Later they went to Taiwanese parts and board assembly. The MkII was a French outsourced design that shared only the chassis from the original 555 plus the name.

I sent one of my 555s to Jim. The upgrade was wonderful. Increased bandwidth on both ends, better transient speed and settling time, noise floor, etc. all substantially improved. For a few hundred bucks. That amp went to Bill Thalmann of Music Technology for audiophile tweak recommendations. Then back to Jim for implementation including best of form film resistors, etc. Point of exercise is to create a no-excuses solution with under $1K investment for folks in my world.

The Adcoms don't perform at the Benchmark level. And the Benchmark might be  outclassed by high end gear, usually at prices beyond the reach of most.

I'm thrilled with the Benchmark's performance and price; plus the Adcom GFA555 (modified) and Classé (modified) ground me to my personal history with performance that I judge as really fine, especially considering price.