What to use as a subwoofer amp

I use an old Acoustat Transnova amp on my subs and it works great. Hafler makes more current versions of this amp that can be found fairly cheap. A 350W/Ch version went unsold on Ebay this week for $750.

Good luck.

Because of their wide pro use and good reputations, I did consider the Crown and Hafler 9505 Transnova amps as well.

My experience with Bryston's are that they don't work that well with low impedances. Other comments by reviewers in Stereophile also support my findings. Take these comment for what they are worth i.e. simply my point of view. Obviously, others have contrasting points of view / experience, so i may be in the minority here.

I would suggest looking for a a Phase Linear 400. This should set you back about $200 give or take. Upgrade the capacitors in the power supply ( 60 - 80,000 uF's is a good starting point ), replace the internal speaker wires and power cord with something heavier and change the binding posts if you feel the need. You will end up with an amp that is better than the Bryston for less money ( easily under $400 if you are handy ) AND you can watch the large back-lit meters swing to the beat of the bass : )

Not that i think that it means a lot, but many people equate a high damping factor with increased bass control. The Phase was rated at a damping factor of 1000 at 8 ohms. Since you are running a nominal 4 ohm load per channel, the damping factor would still be a very high 500 ( give or take due to production tolerances ). I will say that a lower damping factor simply means that the reflected emf ( voltage ) from a large woofer or sub-woofer motor can more easily influence or "modulate" the amplifier. As such, a higher damping factor is never a bad thing.

As to having 1000 watts for bass and thinking that it is "too much" power, you might be surprised. With bass heavy music and high volumes, it's not that hard for you to suck a big amplifier dry during long duration low frequency passages. In order to handle this, you need both high rail voltages, steady state current and a good amount of reserve power supply available on a dynamic basis. Bryston's use low rail voltages, have a good amount of current available but are not that hefty on power supply reserve. While you can increase the power supply reserve by adding capacitors, you can't get around the low rail voltages without re-designing the whole amp. The Phase has high rail voltages, a good amount of current available and a small amount of power supply reserve. As such, it is two-thirds of the way there with the last part of the equation easily corrected.

As a side note, both designs use bi-polar outputs and iron-core ( non "toroidal" ) transformers. Quite honestly, i find that a good sized iron core is far superior to a toroidal of equivalent power rating when it comes to bass impact and definition. As such, weight DOES matter when it comes to amplifiers as "old school" transformers have to have a lot of metal in them to really do what you want them to do. Sean
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Since 1981 I have been using stereo subs. First of course with passive subs and then subs with internal power. Phase Linear 400 and 700 at that time where both ill defined and proved to be unstable. Dynaco 400 and SAE 3cm where much the better amps designed by John Bongorno, later of Great American Sound. The relativley small Apt Holman amp designed by Mr.THX himself proved to be a huge improvement over the much larger and more supposedly powerfull Phase Linear stuff. Apt was able to play louder and was more stable and tunefull at the same time. Last external power amp I used was a Krell Ksa150. Each of the two channels driving three 10in woofers. This was a 1.8 ohm load and was no problem at all for the Krell. This impedance load allowed the Krell to produce over 600 watts of true class A power. The Krell was the most tunefull of many amps I had used to power passive subs. First and foremost look for an amp that is stable with both low impedance and reactive loads, as well as having no current limiting. Remember rated power is not always what is claimed. If you cannot go the Krell go Bryston. The Bryston will exert much more control over a large and unruly moving object such as a subwoofer than will a noisy and unstable Phuzz Linear. Tom

The Kenwood L-07M monoblocks are some of the best bass amps out there, if you are lucky enough to find a pair. 150 watts.