I am waiting on a soundstream reference 500 to arrive after i bought it second hand and apparently it is stable from 1/4 of an ohm up

im planning to get an IDMAX ver3 to run off it in a sealed box and im wondering which voice coil combination people would reccomend as best to buy either dual 4 ohm to run at 2ohm or dual 2 ohm to run at 4 or 1 ohm

I want it to sound the best it can and while spl is desired sq is more important. Being class A i can imagine it getting very hot at 1 ohm and losing some wattage and increasing its distortion levels when it get hot? am i best to run it as a 2ohm amp or at 4 ohms for sound quality? it apparently outputs the same power at all impedances (much like the higher end JL's)

any discussion is welcome...

It's not a Class A amp. It only has a Class A input stage. Just like the rest of the Class AB amps.

To find out if it's a Class A amp, just measure the idle current. It should read more than 5 amps of current draw.

The SS manual never mentions what the idle current of the amp. All Class A amps draw quite a bit of current because the PS does not switch.

ok well none the less any thoughts on what version of the IDMAX I should get?

Actually class A's draw a lot of power not because of the power supply but because of the output stage - a pure class A amp will have it's DC bias point half way between Vcc and gnd - and hence draws (Vcc/2)/R current at idle (ie bloody heaps ) - which of course leads to their poor efficiency ratings

Class A amps will still use a SMPS (switch mode power supply - transformers don't work too well with DC ) but are generally single ended (ie only a + rail and ground) rather than a typical SMPS which is double ended (+/- and ground) which is required for B/AB operation (and hated by SQ purists due to the PNP/NPN on/off switching)

ANYWAY BACK ON TOPIC
if you're just running a sub of the amp look for the lowest coil impedances possible and then parallel the mofos... I think the ref500 was one of the old "cheater amps" that made diddle all power at 4 ohms but once loaded down to <1ohm started to take off!

so dual 2 ohm voice coils? should be good anyone else know anymore about the ref 500?

HAHAHAHHAHAHAHAH Stik79 how did i know you were gonna go into the nitty gritty

TRUTech perhaps you found your new design engineer for your latest line up of amps in Stik79.


HAHAHAHHAHAHAHAH

From memory the REF range was only stable down to one ohm, whereas the Class A range was stable down to 1/4 ohm. In this case, the D2 would be the natural choice, but, if it were me, I would go with the D4 which will give improved damping and control and only lower output level by 3db. As SQ is your main concern this should give a better overall result.

Guys, the Soundstream Reference Series which the Ref500 model belonged to were marketed as 'Pure Class-A' amplifiers, which of course - they weren't. I pressed Soundstream's then international training manager Devon about this on one of his Aussie training visits in 1996 to which he privately replied .. "It's like McDonald's 100% Pure Beef claim - it's just a registered trademark - nothing else".

While all Reference series amplifiers were capable of providing current sufficient to drive low impedance loads (other than the main four channels of the Ref405) it was only the 3.0 and 6.0 models that were specified to run impedances below 1ohm with any performance advantage - which made them suitable to the lower classes in competition at the time.

The Ref500 is best left running 2ohm bridged loads or 1ohm stereo loads and no lower. However, the switch to 'High Current' mode simply reconfigures the internal voltage rails to better suit low imedance (as low as 0.5ohm) but won't make any more power - just the same power at lower impedance loads. In fact, if left in high current mode but run above 2ohms bridged the amp will make LESS power.

Also note the 'mono' input markings on the left RCA inputs are a misleading marking. You still need both left AND right audio inputs to achieve a summed mno output.

Im assuming that the sub output of my head unit is already a summed mono

so you reccomend that i run a 2 ohm voil coil off each channel? or bridge it and run 2 ohm mono?

A dual 4ohm voice coil woofer wired in parallel and bridged from the outputs, with two summed mono RCA inputs plugged into the inputs, would be the ideal solution if you want just one woofer.

so anyway... the ref500s does 2x250 at .5 ohm and 1x500 at 1 ohm so go duel 2 altho their voltage regulators are spontaniously combustable.... well mine was

It does what Mr Niel says in High Current mode, but in High Voltage mode it makes the same power at higher impedences.