Electric fence

I don’t normally make the effort for tech reviews as simply don’t have the time. However should one be considering the purchase of an amp and looking for information on this amp, this will be worth a read as the reviews available on this amp seem to be fairly far and few between.

From a power and structural build point of view, this is not a bad amp (compared to some of the other rubbish) Everything is solidly mounted, heat sinks and cooling is reasonable. Personally, however, I would not put my faith in this amp on important gigs though – read on… find out why!

Where I have real issues with this amplifier is in the circuit design and it’s “repairability”. If you are purchasing one of these amps based on the cost savings, come the day it needs to be repaired, you may very well pay the price.

The first thing that I really cannot tolerate in a professional amp is circuit mods that are done at factory. Surely they could make the effort to at least get the PCB correct?

This pic of the input boards show wire link mods and cut tracks – both boards have mods!

A major issue is with the FETs that provide the “extra” power or voltage when the amp is driving over 55v. These FETS are rated at 60v and situated in such a way that they are across the 110v and 55v meaning that they are 55v across them – only a 5v margin. Not great! If the 55v fuses blow, even one of them (there are 12 pico fuses PCB mounted on the power board), then it means that there is suddenly 110v across the FET that is rated at 60v. Instantly the FET is taken out and most likely both of them.

Another issue in the amp is the wiring coding is not tech friendly! The use of same colours for both boards is not ideal. However in an amp that requires the correct bridge to correct channel, this becomes a real pain – add to that that the circuit diagram has a few errors making it a real challenge to correct it if you mix them up. Incidentally there are approximately 7 errors in the diagrams for the amp.

A further challenge with the Alto Macro 2400 amplifier is that there are quite a few surface mount components on the boards making them difficult to repair also. Sure this is becoming more and more frequent, but the use of surface mounts is leading to more and more of a technology that involves replacing entire channels, not just repairing them. In an environment where amps are designed as slaves and are generally under extreme pressure from misuse, being able to repair an amp without surface mount seems to make more sense. Failing that, at least get an amp where they are willing to give you a guarantee of some form like crowns 3 year. At least then if a module needs to be replaced, its not likely to set you back a couple of thousand Rand.

The coupling resistors in the amp are 0.2 ohm 5 watt! These little guys help to distribute the power evenly through the transistors. 5 watt resistors are fairly standard in home hifi or smaller amps, not an amp capable of 800w per channel stereo. At peak voltages, there could be as much as 30w at these resistors. At the very least they should be in the order of 11w, what you normally find in an amp this size. (30 watt is not necessary as it very short periods that it operates there) It also makes a lot of sense in one forum I read that the amp protects very easily at high power – it simply cannot afford to run continuously at 800w for long periods.

Doing trouble shooting in the Alto Macro 2400 requires the use of lots of fly leads and extensions to work on the boards externally from the amp as when the modules are in the frame, they are very difficult to trace (the surface mounts on the bottom add to this challenge) What’s more frustrating is channel B relies on a fair amount of preamp circuitry from channel A meaning even if you are only working on B, you might have to also remove A!

Bottom line is there is not a lot of margin of safety used in the Alto Macro 2400 amplifier to keep it alive and repairs will be inevitable and most likely required a lot sooner than some of the brands like Crown, Crest etc. Personally I would consider the extra outlay and think of it as a saving in the future. Bottom line it is cheap for a reason and the cost saving on the components is where it shows.

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