c-j technical questions

Actually, I have contacted c-j. Yes they they are pretty good, but, they seem to have a policy of not providing specific power out-put of their solid state amps other than into 8 Ohm loads. Well, I have a pretty demanding steady 4 Ohm load. What's a lad to do?

Hi Chuck, Thiel 3.5's. These speakers are 89db at 1 watt/meter and a use an active equalizer with an in-put impdeance of 91 KOhms and an out-put impdeance of 130 Ohms (RCA's only) that draws up to 12 db of boost below 70Hz. Thiel recommends between 50-250 watts per channel, but, that is based on an amps 8 Ohm rating and ASSUMING that the amp can double down. That boost coupled with the 4 Ohm nomial/minimal rating is what concerns me. If I'm correct, and assuming that the speaker could regularly draw 15 watts that after boost it could be drawing 240 watts. Knowing how amps could actually perform in it's intended use could narrow my choices down to a reasonable number. Thiel recommends c-j amongst others and c-j claims that their amps work with Thiel, but, I think it's fair to suggest that I deserve more concrete answers. The equalizer also adds a bit of complexity with regard to impdeance matching and to the fact that it doesn't offer balanced in and out between pre and amp, but, I think this might be less of a concern, unless of course any one has other ideas. I'm open to suggestions.

Chuck, Thiel rates the 3.5's as having a 4 Ohm nominal, 4 Ohm minimal load. I have seen two independent tests that both show this to be pretty accurate. Both tests show a slight peak at about 33 Hz where the impedance rises to between 8 and 10 Ohms and basicaly flat across 4 Ohms the rest of the way. The testers attributed the peak to the sealed box resonance. I agree with you that Thiel's present a constant steady load with out the peaks and valleys most speakers present. Most amplifiers appreciate this kind (of) load. That the 3.5's don't drop below 4 Ohms is even easier on amps. It's the demands of the equalizer that concerns me. I'm sure you are aware that your 3.6's dip into 2 Ohms will require an amps 8 Ohm rating to double down twice to provide the appropriate power. If I am corect in my assumption(?) the equalizer's 12 db push will require the amp to double out(?) 4 X to provide appropriate power. That might be like a -2 Ohm power requirement (not really, but you get the idea). If my assumptions are correct(?) then perhaps Thiels maximum recommendation, may be their best. I take that to mean 500 watts into 4 Ohms. C-J has quoted different opinons on their 4 Ohm rating to me at different times. Once it was "we don't offer 4 Ohm ratings on our solid state amps". Once it was "close to to doubling down". Once it was "close to 400 watts". Once it was "480 watts". Well what it is it? This inquiring mind would like to know. Mind you I have been using c-j solid state pre and power on Thiels CS 2's for years and have always recieved very good customer service from c-j. I don't have an axe to grind, I'd just like to have needed information to make informed choices.

Mcmiller, I also have a pair of CS 2's which I used a c-j MF 80 on. Worked great! Not to beat a dead horse, but, it's the 3.5's equalizer that concerns me. Though the 3.5's are 2 db more sensitive than the 2's, the 2's unequalized impdeance at 5/6 Ohms is pretty easy compared to the 3.5's equalized 4/4 Ohm load. I think the sound starts to get hard when moderately pushed. I think, I just need more power. I was happy with MF 80, so I naturally thought of a bigger c-j for the 3.5's.

Thanks to all, and especially you Stan!

P.S. went to the Sterophile web site, it's not available for free. It is available via back issue purchase, which is fine. I'll order it Monday. Too bad it may take 3 weeks to arrive. Oh well, at least I can get it. Thanks again to all those that were kind enough to reply.

Stereophile's latest buying guide lists the c-j 2500A as capable of 250 watts per channel into 8 Ohms and 400 watts into 4 Ohms.
In Stereophile's December 1999 issue the 2500 was reported by Martin Colloms as "Tested with the UK's 242V, 50Hz power supply, the MF2500 reached 309W into 8 ohms, one channel driven, and 295Wpc, both channels driven. It wasn't shy at 4 Ohms, and the shared power supply was man enough for 451Wpc into 4 ohms. This, only 1.3dB below the 8 ohm single channel test result, indicates good regulation and load driving ability.
Playing music-related (IHF tone-burst) signals, the MF2500 pushed 24.9dBW inot 8 ohms (315W) and 24.77dBW into 4 ohms (600W), but began to current-limit a little into 2 ohm loads with 23,9dbW (976W) available. This relative indifference to loading provides good verification of the easygoing muscularity identified in the listening trials. The maximum peak current capability was approximately +/-35A--good enough for all but the most severe speaker loads, and certainly those nominally rated at 4 or 8 ohms."

Stan, thanks for the kind words. The volume setting on your pre may have more to do with the amplifiers sensitivity than its ultimate power output.