Good upgrade amp for my Thiel 3.6s

You're right about risking damage at 500 watts. Damage can occur at lower wattage, too. For example, the tweeter will fry if you put 400 watts into it. Also, if your amp power is relatively low and you turn up the volume until it clips, the clipped signal can damage your speakers fairly easily. I generally regard the manufacturer's upside wattage specification as a guideline not to turn the volume beyond a certain level. The 400 watt specification suggests to me that the speaker is relatively robust and can play fairly loud. I believe the speaker can withstand substantially higher power peaks for very brief periods using musical material.

The low end specification of 100 watts suggests that the speaker is relatively inefficient, which the 86 db sensitivity rating implies also. Of course, you can get decent volume out of the speaker using only a few watts, but you need more to reproduce peaks at realistic concert hall levels. I don't know if the 86 db rating is on target or too high. I would rely on Thiel's honesty in ratings and engineering capability for properly identifying the speaker's sensitivity. Naturally, the loudness we perceive will be dependant on our room acoustics, which could easily cause as much as several db of difference.

I never had any trouble driving my 3.6's with the 7B st's. I never damaged any of my drivers. (I did once overtighten the speaker's cable binding posts, to my huge embarrassment.) However, I rarely turned the volume way up. Mostly, I listened to small acoustic jazz groups at live volume levels. I think the 7B st's are a good match for the 3.6's for their high current and high power capabilities, as well as good sound and reasonable cost.

Justin, what is it about the sound you're getting that you don't like? I can't imagine a KSA-150 not being able to drive the Thiel's adequately, IMO; so I'm not convinced more power is what you need. The particular sound you're getting is another matter. In what areas is the sound lacking? Is it too bright? too sterile? not warm enough? not fast enough? too fast? do you want a bigger soundstage? would you maybe like more dimensionality of images (200+ VTL watts). It's not always clear what "better" is. I look forward to your response.

Frogman makes a good point but in general, a bit more power might give you better defined bass and that over all effortless feeling like the amp isn't constrained at all. This was very noticeable for me when I went from my Classe CA-100 to the CA-200 amp driving the smaller Thiel CS 1.5's. For the Thiel 3.6's I would lean toward an amp that can produce at least 200w/channel but preferably 300w/ch or so into 8-ohms. Used Classe CA-200's can be had for around $1400 and CA-300's for around $2000. I just sold a pristine near-mint condition CA-300 a month ago. Good luck!

Justin,
My Thiel CS 3.6's have been driven by the KSA-150 which was not bad at all! Then I bought a KSA-250 and it got even better. After talking to the guys at Krell they recommended finding a second KSA-250 and sending them up for conversion to the MDA-500 mono blocks. I'm done! I could not want any better sound from the 3.6's being driven by the MDA-500's. These are incredibly hard to find but you can get the same performance from the MDA-300's for the price you are looking at. The MDA-300's are KSA-150's converted over to Mono Differential Amps. If you already have the 150 then a second 150 would cost you less than 2000.00 *There is also a pair of MDA-300's for sale here from a gentleman in NY which would mean instant gratification without waiting for your amps to come back from Krell. My cables of choice for this system are the MIT balanced inter-connects and MH-750+ series II speaker cables.

The 3.6's can handle large amounts of power and the more clean power you have the less likely you are to damage them. The KSA-250 will sound better than the KSA-150 does. Not by a lot but it does!

Hi Frogman,

I was following some posts that I'd seen here and elsewhere from other 3.6s owners that said that 3.6s like as much power as they can get. The general concensus was that the soundstage opens up more. The imaging improves. The overall sonic capabilities of 3.6s improve with increased power. One poster I recalled saying that "you need at least a 250wpc amp to really make them shine." Though it's not really clear what that means.

I wouldn't say I'm unhappy with the sound of the Krell. I like the soundstage and bass response I get from it. I'd hate to give that up. But I don't have a lot of experience with the sonic characteristics of other amps out there. I'm new to the high-end market, having bought a good system within the last couple of years. Prior to this I was listening to CDs through a Toshiba DVD player into Technics speakers.

Since then, I've upgraded to:

Linn Ikemi CD player
Adcom GFP-750 preamp
Krell KSA-150 amp
Thiel 3.6 speakers

interconnects are another story. Haven't done much with those.

I was just starting to do some research on it. I wanted to get opinions from others who have owned the 3.6s longer and tried them with different amps. I didn't audition that many amps before going with the Krell. I bought it used about 2 years ago. I like its sonic characteristics, it fit my budget, and I went with the dealer's recommendation on it (over new choices like a McIntosh and Bryston 4B). At the time, I listened to a pair of Pass Labs Aleph 100 watt monoblocks, which I liked a lot. I liked the detail they produced but they were more than I could afford.

The Krell literature I have says that the KSA-150s are conservatively rated at 150wpc, and are more likely 250wpc. I listened to a newer Krell series in a store the other night, the KAV2550 I think. I didn't like it. Sounded thin and I thought the presentation was too bright.

I was getting the impression from just a quick look in local shops that to increase performance/power over my amp would be a huge cost. One store tried to "entice" me into buying a Krell FPB300 for $7500!

But maybe there's a used amp out there that might make a difference.