Which Threshold s are best?

Threshold SA/1 mono block (pure class A) power amps are the best sounding poer amps that Nelson Pass had designed, period.

Personally owned just about every Threshold amp that was ever made, and still have about two dozen Threshold pieces.
The SA/1's standout alone on top.

As good as many Threshold amps are, they can all benefit from component upgrades / internal modifications.

One of my friends has a very highly modified Stasis 2. He swapped out many of the caps, diodes, etc... of the existing circuitry, increased the filter capacitance of the power supply and then had Jon Soderberg of Vintage Amp go through and align it. While this was the most heavily modified amp that Jon has ever worked on, he also said that it was probably the best sounding Threshold amp that he had ever heard. Given that Jon used to work for Threshold and has probably repaired / modified hundreds upon hundreds of Threshold based products, even after they went out of business, i think that his comments should say something about how much parts quality equates to what we hear. This is just another reason why i encourage others to upgrade / modify what they already have, if they are basically happy with it.

With that in mind, i don't think that you can go wrong with any of the mid to later series Threshold pieces, even in stock form. Some are better than others, but all of them have the potential to sound very nice. While I can't say that i've even come close to hearing or examining every amplifier or design out there, Nelson Pass is my favourite amplifier designer at this point in time. He has been for several years now. Sean
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For class AB, the S500e and 550e are the best I have heard. For class A, I prefer the T400 driven balanced by the T2 preamp. I think this is the best I have heard period. The T400 is basically dual mono unlike the lower power amps in the T series. John S mentioned that the bridge rectifier can fail on the T200 when driven hard over long periods. He has a simple fix and can update the bridge to the fast recovery type. Please note that most preamps cannot handle the low impedance on the balanced inputs very well.

Why don't you pose the question to hime or others at the DIY.com BB which he posts at .

Not trying to say you will not get an adequate answer here,but it just stands to reason that there you might get some more or different feedback.NP might answer your question himself.

Another point that should be made is that synergy is everything and you should match your speakers with a particular amp that is known to work good.

The opinions I have heard favor the SA series and T series. I would much rather use a ClassA than AB amp ,but watch the electric bill. NP says his amps should be left on 24\7.

Good luck!

The T series of amps were not designed by Nelson Pass. These are amps that were designed after he had sold Threshold. This is NOT to say that they are bad amps, they just aren't of Nelson's "bloodline". The Forte' 4, 5, 6, 7 & 55's were also post-Pass products. Sean
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