Autoformer vs Speaker impedance Curve


Autoformers vs speakers with wild impedance curve swings (for instance; MC601 amp paired with B&W 802D3 speakers).

There’s a wealth of information about tube amp audio transformers interaction with speaker impedance, but I can’t find anything regarding Autoformer and speaker impedance/phase curve relationships. 

Can any techies enlighten me? 

Thanks!

(I tacked a similar post onto the end of a 10 year old thread but thought I might get a few more hits with a new thread.  Sorry for the redundancy)



73max
Thanks caphill!

I’m definitely a Classé fanboy.  I absolutely love the sound of my 2300 and can only imagine how good your CA-M600s sound. I haven’t ruled them out, but the fan noise has been an issue for me.

I’m in an extremely quiet and smallish room with fairly extensive acoustic treatment so the slightest noise can be heard. Once I que in on the fan noise I fixate on it and notice it even more. I’ll definitely try cleaning the filter. 

A pair recently sold for $6500 and I almost bid on them, but it was a local pickup (not in my area) and I still have my concerns about fan noise. 

Im a little afraid of the class D stuff. No good reason as I haven’t even listened to one. Maybe I will. They seem to be improving rapidly. Manufacturers  must love them, as they seem considerably less expensive to build. They are passing some of that savings on to the consumer…For now. I’m certain as acceptance becomes greater the prices will increase.  

  There are quite a few McIntosh MC 601s on the market due to the new 611 coming out. I haven’t ruled that out either.  I have listened to a Mac 452  with 802D3s and preferred my 2300. However that Mac was in a horribly set up room. I’m still going to try to listen to a 601 with the 802D3s.  I have to admit, I am a sucker for the big blue meters!  I absolutely love the way the macs look. But, sound first! 

I’m still going through all  the other recommended amplifiers on this post. A lot to consider. 
I personally have never heard Pass XA-160.8 or any Pass amps on the B&W. 
I have heard Pass amps on different speakers such as Focal, Magico etc But not on B&W. 
73max OP14 posts08-27-2018 3:48amAny thoughts on Pass Labs XA-160.8 with 802D3s?


While great amps and very nice sounding, it's bit of 6 of one 1/2 dozen of the other for your speakers though, they are Mosfet and when done in complimentary n and p channel push pull, can't really supply the current like BJT's (bi-polars) can, there are a one or two Mosfet amps that are push pull, but they only use an N channel for both top and bottom which may do the job (much higher current), but I can't remember what is was.    This if you read will give you the gist, of not being able to do your speakers justice "maybe" not worth the chance in my opinion.
https://www.stereophile.com/content/pass-labs-xa160-monoblock-power-amplifier-measurements

Cheers George
Thanks for the link. Doesn’t look like a good match.  There is a Classé Omega for sale for that is tempting, but I just can’t bring myself to part with that kind of coin for a 15 year old amp.  Too close to a recap.  Not sure I could find a local tech willing to hoist these monsters on the bench... never mind sourcing parts.  The hunt continues.