I understand they can not be bridged to mono, however, a quick call to CJ would answer that question for sure. I would recommeng the 2500 for it's higher output capability. Also I would not even consider a non "A" model. Having had my MF2500 upgraded with the "A" modification I can assure you it is a substantial improvement in practially all areas of performance.
I own both a MF2250 ("non-A"), & a MF2500A. They are both excellent amps. The MF2250 is surprising in it's power given it's compact size, & sounds very clean & smooth with excellent dynamics. Of course, the 2500 sounds just that much better with hard to drive speakers. I can't really see any point to buying two 2250's instead of one 2500, altho I did consider that myself at one point. I think it's worth holding out for a 2500A since they only sell for $200-$300 more (used) than a "non A", & it costs $500 for CJ to do the upgrade. (But I'm sure the "non A" is excellent also given my experience with my 2250). Good luck!
I'm curious how these amps do with 4 Ohm loads or less. Conrad-Johnson has an odd policy of stating their tube amps out put into 4 Ohms, but, refuses to do so for their solid state amps. I've got to believe that many people are dismissing their products out of hand due to this weird policy. I've asked this before, but , I'll try again; has anyone compared the older all mosfet high powered 2300 amps to the newer 2250 mosfet/bipolar amps? They are about the same price on the used market. Sorry if I'm stealing this thread.
1.CJ MF 2500A cannot be bridged.It is impossible by design.
2.I bought 2 MF 2500A to biamp my Snell type B which is 4 ohm/86 db sensitive and is hugely dissapointed.These amps are bipolar design and they sound absolutely unConrad Johnson like.They also failed to bring my speakers to life.
Before i used a number of older CJ mosfet SS amps (like mf 2200, mf 200 which i still have) and was always amazed at how good they sounded and their ability to grab the woofers.MF 2500A in comparison sounds very thin and lean and there is a huge gap in lower midrange/upper midbass region.They have a good high freq extension though so if your speakers have no more than 3 drivers you might be satisfied with them.Mine has 2 midrange drivers,2 tweeters,1 10" woofer and 1 10" subwoofer per side so the hole in the freq spectrum is very apparent.
Also MF 2500A sounds terrible at low volumes as opposed to older amps so you need to really crank up the volume which might be a problem if you live in the apt bldg.Older CJ mosfet amps handle all kind of loads with ease.ML as i know is one tough load so i can see a potential problem.The speaker can sound lifeless like in my situation.
If you like 50s-60s jazz or classical,i say go for it,but all your rock cds will become unlistenable.If you have any questions feel free to e-mail me.Take care.steve.
Msilin, please accept my appologies for stealing your thread.
Overhang, in my case I find my present speakers have slight tendency to be a litlle soft in the lower midrange-upper bass, perhaps a little leaness might be beneficial? How ever if by "huge gap" your talking about a "suckout" I would imagine that would only make things worse. BTW, I'm currently using the original Conrad-Johnson all mosfet amp and a ss c-j preamp. Since my move, my listening room has doubled in volume and think I need more power. On the other hand bipolars have the reputation for tightening bass response. I can achieve the volume levels I want, how ever the sound starts to become a bit harder as a raise the volume. This was something that didn't occur in my old room. The softness previously described has always been there in some measure, it's just more notice now. I just may have to move up to a bigger speaker as well. I really do like the the speakers quite a bit, so I may just move up to the next size from the same manufacturer. My present speakers have a 6 Ohm load that drops to 5 Ohms. The ones I'm considering are a steady 4 Ohm load. Am I correct in thinking that you suggest an MF2300 over an 2250 which sell for about the same price used. I weclome your experienced thoughts.
Yes,i like the old mosfet sound better.It is not as transparent on top as 2500 but it has that tubelike magic with solid state power.2500 sounds like SS.As for bass control i now have a very unpleasant rubbery bass,individual notes are not defined (no midbass,remember),all i hear is congested bass ramblings.This is strictly my experience and you may find these amps very pleasant.I will still keep both amps for my second system (there is no way i will make close to what i paid by selling them).I will be very selective when buying speakers for them.I heard them in a store paired with AP Virgo III and the results were really good,just don't match it with a full range/tough load speakers.You will lose.
I think I may be able to help you with the MF 2300. I have been using CJ's prior line of amplifiers for a long time, and I think they are an excellent combination of power and warmth.
I first purchased an MF 2100 for my nominal 6 ohm speakers. I was very impressed with the sound of the amplifier, for it easily powered my moderately inefficient speakers quite well throughout the entire spectrum. The bass was tight and controlled, the midrange was warm yet detailed, and the highs were very detailed but not etched. I credit my CJ preamp for some of this as well, but I tried this amplifier with four other distinctly different preamps, and I always found the amplifier to have similar characteristics. There is no question that the CJ preamp and MF 2100 yielded the best results.
I then bought an MF 2300A. When I connected it to my system (cold) after an extensive listening session with the MF 2100, I was stunned by the improvement. The soundstage was deeper and wider, and the bass response was even deeper and more articulated. Whether at low volume or high, the MF 2300A produced incredible musicality. When it had warmed up for an hour, the sound of the amplifier was even warmer.
I later upgraded my speakers to a pair of ribbon hybrids that fluctuate between 3 and 6 ohms. The MF 2300A was still able to control the deepest bass easily, and the highs were even more impressive and natural (the ribbons really make a difference). I can't say enough about the MF 2300A's performance.
I have no experience with the current CJ solid state amplifiers except for a brief period at a dealer. From everything I have read about the new amps, it sounds like they do not have CJ's typical sonic characteristics (i.e. warmth and tube-like performance).
I hope that this is helpful to you. If you can purchase a used MF 2300 or 2300A in good condition, I think that you will be very happy.
Msilin, thanks for your indulgence.
Overhand and Vortex, thanks for your input.
What is the difference between a MF2300 and MF2300A?
MF 2300A is upgraded version of the amp,better sounding one.
Overhang: Thanks for that info. Does this mean that both CJ 2300 and 2300A are both MOSFET-based amps?
Has anyone else noticed the "hole" in the MF2500A's lower mid/ upper bass that was described by Overhang?
Yeah,they are both mosfet amps,2300 and 2300A i mean.The hole is described in one of the reviews posted on CJ website.
Overhang, I just read the reviews you refered to. It seems to me they were describing a leaness in the upper bass region not a suckout or "hole". In a perfect world I wouldn't recommend faults to band aid problems, but, budgets do exist and sometimes we must resort to "band aids" for the best affordable sound. I wonder if this leaness would tighten up and compensate for the softness in this region in my system?
I have gone back from a Premier 11 to MF2500, fed by a CJ Premier14, driving my good old Dunlavy SC-IVs as I value more the dynamics and the low noise level of SS.
Question: there is a MF2300A on a local Craiglist listing, should I consider to acquire that to replace the MF2500 or maybe to use it to bi-amp my Dunlavys?
I suggest you keep the MF 2500, and don't mix amps with Dunlavys.
The only thing I would do with a MF2500 is either send it in for an "A" upgrade to CJ, or send it to Bob and Gary Backert and let them do their own upgrade. The latter certainly did a good job on my aging MF2250.
Updating this thread-
anyone still using, new or older, CJ SS power amps?
I have a Sonograph SA-250 (I see there is one for sale on this site right now) and although I have not used it in awhile due to equipment swapping, in my opinion it is a very fine sounding amp. I believe this is a Mosfet amp.
I think the Sonographe amps unlike the c-j MF ss amps used bipolar devices. Though sounding slightly different, both were very good. Either one might be preferable depending on the rest of the system.
^Perhaps I should have said earlier c-j MF ss amps. I believe the latter ones use both mosfets and bipolars.
Very nice- j_stereo & unsound.
I still want a 350SS Premier.
^While the current delivery might not be ideal, it could be adequate for your Thiel 2.4 SEs.
Yes, this would be a consideration, unsound.
I know that it drives Eggleston loudspeakers, specifically, the WEGG 3 model.
^Even for one with an extraordinary amount of experience, the more variables, and some variables garner more weight than others, the less pertinent such auditions are.