Classe CA-100 stereo vs bridged

I suppose a little more info would be helpful here. I am running a Rega Apollo into a passive pre amp (goldpoint 25k stepped attenuator). So my pre amp has no gain capability. The Rega drives my CA-100 to near its rated output on most material. So, therefore, I cant afford for bridged mode to yield less wattage per the input signal.

Al is right in that a CA-100 in bridged mode isnt something I need to drive to its 350 watt maximum. Rather, whats most important in my situation is that the Rega can drive the bridged amp at least to the same wattage levels as before.

It sounds like, which ever way one chooses to look at it, that given the same input, I will have more output in bridged mode in terms of watts yielded.

Hi Peter (Csontos),

First, let me repeat what I said:

I wouldn't be surprised if the sensitivity increases by 6 db (i.e., you would have to reduce your volume control setting by 6 db, to achieve the SAME VOLUME [emphasis added] as in stereo configuration)

You then asked, in part:

Won't an amp making three times as much power produce at least 4-5 db more spl at the same volume setting ....

Our two statements seem to me to be perfectly consistent with each other.

The rest of your sentence was:

... with the 'same' sensitivity?

If sensitivity is considered to be the input voltage required to drive the amp to its maximum power rating, whatever that rating may be for the specific mode that is being used (stereo or bridged mono), then the amp's sensitivity would probably be the same.

But my interpretation of the intent of the OP's question about whether input sensitivity would change is that he wanted to determine if there would be a significant change in output power for a GIVEN input voltage.

You have found that to be the case with your Acoustat amps, and I was saying that I wouldn't be surprised if it were the case with his Classe amp.

Whether or not that increase in output power and volume for the same setting of the volume control is considered to be a change in "sensitivity" is a matter of semantics and definition. I chose not to get into semantics and definition, but to respond to what I perceived to be the intent of the question.

Best regards,
-- Al

Okay, I'm confused(nothing unusual). What does having to reduce my volume control have anything to do with sensitivity when the amp is now producing, real world, probably three times as much power at the same setting? Won't an amp making three times as much power produce at least 4-5 db more spl at the same volume setting with the 'same' sensitivity? I ask because I'm running my Acoustats in mono and am curious as to why exactly I have to turn up my self powered sub woofers substantially to eq the system as opposed to using them in stereo.

Thank you, Al

BTW, No degradation. Rather, an improvement. 2nd order harmonics are eliminated, way more dynamic, faster.

My guess is that the 350W/600W 8 ohm/4 ohm mono ratings, which are shown in the manual and in the fancily printed part of the brochure, are accurate.

The white spec sheet showing 200W/400W, that is part of the brochure pdf, I suspect is a document that is earlier and preliminary. I say that based in part on its look, compared to the other documents. But note also that it specifies S/N ratio as "more than 100 db," as if someone made up the spec before they had more precise knowledge of it, while the other documents specifically indicate 128 db (although the reference level isn't specified).

Also, peak vs. RMS would not account numerically for the disparity between the two sets of numbers. Unless perhaps "peak power" is interpreted to mean "dynamic (short term) RMS power," or more precisely "dynamic (short term) average power." But that would make the numbers that are presented for stereo and mono modes completely inconsistent with each other, and be very misleading. I very much doubt that Classe would specify things in that manner.

Keep in mind, also, that potentially/ideally a bridged amp can output four times as much power as when the same amp is operated in stereo mode, since the output voltage swing capability is doubled. Although in practice the 4x factor usually comes out to be significantly less, due to current and/or thermal limitations.

In any event, given the impedance characteristics of your speakers you should be fine either way.

Regarding question 2, I wouldn't be surprised if the sensitivity increases by 6 db (i.e., you would have to reduce your volume control setting by 6 db, to achieve the same volume as in stereo configuration). But without being familiar with the details of the design, I don't think we can be certain of that.

Regarding question 1, I wouldn't want to venture a guess as to how the sonic differences would net out, without having tried it on the same or similar models, and with a speaker having similar impedance characteristics.

Regards,
-- Al

That 600W 4 ohm mono rating has to be peak power. What sane person needs 600W continuous in a home environment anyway? I've known of a few people who have run bridged pairs of various Classé amps, and had no complaints about performance. The company has not been known for inflating power ratings. In reviews their products have always met or surpassed published output specifications on the test bench. If they say their amp does 4 ohms bridged, I trust them.

Yes, the 600w 4 ohm mono rating is a bit suspect, but irrelevant in my case since my impedance low is about 6 ohms.

Thanks for the replies.

Id still like to hear from others as well if anyone has some input.

I definitely think you would benefit from the extra power, and don't see a problem running the amp mono with your speakers. You can download an owners manual and spec sheet here,

http://bwgroupsupport.com/manuals/classe-archive

A power rating is listed for 4 ohms in mono, so that implies it is acceptable, and a 4 ohm speaker would drop below that. Some of the power ratings in the manual and color spec sheet seem a little confusing, may be peak power. The white spec sheet seems to be the most logical for RMS power.

edit: 3) Will driving a 8 ohm speaker that has a 6 ohm minimum impedance be a problem?

Speaker = http://www.troelsgravesen.dk/Jenzen-NEXT.htm with woofer http://www.troelsgravesen.dk/Jenzen-CA_files/CA26RFX.pdf which is a option for the design.

Lets save question 4 for later :)

During my loudest listening sessions, I am measuring 95-97db with 106-109db peaks. Its taking about all of the 100 watts I have to get to this level. Its doesnt sound clipped at this level, but there is a hint of strain.

I dont want the xtra power to go louder than this, rather be able to accommodate this level with more headroom and ease for the amp.

I'm thinking the answer to questions 1, 2, and 3 would be "no", however, I have no idea for question 4.

What speakers are you using? Do they need the extra power?

I cant find my own thread :(