Neil's Secondhand Naim Buyers Guide

POWER AMPS (NAP)

A couple of people have pointed out to me that the power amp numbering system stems from the total power output into a 4 ohm load (and adding both channels where applicable). So for example a 250 would give 125W per channel into 4 ohms. In an ideal world we could then divide by 2 to get W per channel into 8 ohms (ie, from the idea that the amp can give twice the power into 4 ohms than into 8 ohms)... but of course in reality, things aren't ideal and the amps can't quite attain the doubling of power into 4 ohms, and so the factor to divide by is more like 1.8 or so.

Having said all that, I find that W per channel is not a great guide to Naim amps anyway. They invariably sound more meaty and powerful than their power rating implies (when partnered with the well suited speakers at least). I feel a big step forwards is attained with the amps that have the regulator boards ie, the 250 and 135. They are much more controlled and smooth.

250

The original power amp, but which is still going strong (as is the 135). The circuit is a classic from the 1960s using quasi-complementary NPN output. It can supply an average of 10 amps (about 15 amps peak). It runs from a single power supply, and this powers both the left and right channels (ie this amp is stereo!). The amp has Naim's very effective regulation boards. It supplies somewhere in the realms of 70w per channel, though tends to sound more powerful than that. Note it will not power a preamp. Full width box. Second hand price (old style) around 700 pounds.

135

This is the mono version of the 250 (ie you need 2!). The same amp and regulation boards but run at a slightly higher power. But each channel (being mono) has the power supply all to itself. The amp's heatsink has a fan which cuts in when the thing gets hot (which allows you to drive it harder, hence the slightly higher power available compared to the 250). It gives around 75w, but tends to sound significantly more powerful than using a 250. This power amp takes some beating. Note it will not power a preamp. Full width box. Second hand price (old style) around 700 pounds.

110

This was Naims cheapest `grown up' power amp. It basically had the amp boards from the 250 albeit running at slightly lower power but doesn't have any of the power supply regulation. The supply is smaller too (around a 200 VA coil I think) and both left and right channels run from the one rail (like the 250). Rated somewhere around 35w per channel. It can also be used to power a preamp (with a single 24v rail). Second hand price around 200 pounds.

160

This was basically a 250 but without the power supply regulation (and coil voltages adjusted accordingly) so making it a bit more affordable. It ran from a single power rail and gave somewhere around 50w per channel. Similar beast to the modern 180 amp (in that it's essentially an unregulated 250). I think it may have had the facility to run a preamp from it (like the 110). Full width box. Second hand price around 400 pounds. (There were actually monoblock versions of this amp but I can't remember the numbers...)

140

A current amp that's been around for a long time which is a slightly more refined version of the 110. Almost identical in fact, except that the (unregulated) supply is split into 2 channels to supply left and right separately. Gives around 45w per channel. It can also be used to power a preamp (with a single 24v rail). Second hand price (old style) around 300 pounds.

90

The baby power amp Naim never wanted to make, but did in the end due to public demand. It's not a great deal more than the power amp section from the Nait but uprated to give more power. Starter amp really, but still surprisingly capable. No regulation, offering around 30w per channel. It can also be used to power a preamp (with a single 24v rail). Second hand price around 200 pounds.

180

A current amp which is a resurrection of the idea behind the 160 ie, sell the 250 but without the power supply regulator boards. However, the supply has been split into 2 channels so powering left and right separately. Hence this is basically a 140 but with a double size power supply. Gives around 60w per channel (slightly less than a 250). It can also be used to power a preamp (with a single 24v rail). Full width box. I would guess that secondhand price would be about 600 pounds.