Has anyone tried this "350 watt" amp

[srinath]

2Pcs L20 350W+350W Audio power amplifier Kit - eBay (item 190487777635 end time Jan-13-11 20:27:19 PST)

That is a 350 watt into 4 ohm amp ? OK has anyone tried it ? did it sound good, did it work long term or die in a week.
Anyway, Just doing some checking before plonking the $.
That seller actually is ok, I bought a few chip amps and they work fine.
Thanks.
Cool.
Srinath.

[AndrewT]

I don't know the amplifier nor what components have been used.

The 4pr output stage should be robust enough to do 200W into 8r0 and into 8ohm
If 1943/5200 are used I would not use a +-70Vdc PSU.

I think the 4pair output stage could survive driving a 4r0 load but I cannot have confidence that it can drive 4ohm reliably. If MJL4301/4281 are used I would have much more confidence in ONsemi reliability and this assembly.

[Tekko]

Most of these cheap kits on ebay are way overrated. I'd say this is a 100 watt into 8 ohms and 200 watts into 4 ohms amplifier on 50V rails.

I doubt their even tested into claimed loads and that claimed wattages are just based on number of outputs and the supply voltage.

If an amp cannot double the wattage into 4 ohms, its not really 4 ohm stable.

[AndrewT]

Originally Posted by Tekko

If an amp cannot double the wattage into 4 ohms, its not really 4 ohm stable.

A really good audio amplifier, even a ClassA version cannot double it's power output when the load resistance is halved.
Cordell's "rule" is 180% power into halved load resistance.
I used to aim lower than this, but have revised my modeling methods to achieve Cordell's rule.

driving a 4r0 load is no guarantee of stability.
doubling power in halved load resistance is no guarantee of stability.

If this amp actually tested at 200W into 8r0 and 350W into 4r0 then that gets very close at 175%, but that does not mean it can drive a 4ohm speaker.
Resistive test loads prove very little, other than current delivery.

[jeannotvh]

Because even the best non-regulated power supply and output transistors do not have a 0 ohms resistance at clipping, and also because of the emitter resistances, you will never see exactly double the power in 4 ohms as in 8.

Also, despite that variation most of the difference between the 4-ohms and double-the-8-ohms measurements are due to a sagging power supply.

[indianajo]

Originally Posted by AndrewT

If MJL4301/4281 are used I would have much more confidence in ONsemi reliability and this assembly.

Wow, MJL4302 PNP are over $6 each today, where as MJL4281 are only $4.50. What makes these better than MJL21193/4G which are $4.13 and appear to have more SafeOperating Area at 80V. I realize 4302/4281 are TO264 and 21193 are TO247, is the TO247 to hard to fit in the kit under discussion?
(datasheet from datasheetcatalog says MJL4302 is complement to MJL4281).

[ostripper]

Originally Posted by Tekko

Most of these cheap kits on ebay are way overrated. I'd say this is a 100 watt into 8 ohms and 200 watts into 4 ohms amplifier on 50V rails.

I doubt their even tested into claimed loads and that claimed wattages are just based on number of outputs and the supply voltage.

If an amp cannot double the wattage into 4 ohms, its not really 4 ohm stable.

4 pairs = 100w ?? Maybe if fake semi's are used. I do agree the components may be cheap , but the boards are worth it. BTW, 2 pair njw0281/0302's can do 120w ALL DAY 8R- 200W/4R. I saw the design for this one , basic fully complimentary front end- standard EF2 ... should sound "accurate" (good bass). I won't go beyond 2 pair now without a triple , 4 pair on a EF2 sucks for 4R.

ALL ebay chinese class AB amps = VERY basic designs , no "frills" (cap multipliers , TMC , accurate CCS's) many lack base-stoppers , rail decoupling, some even oscillate !! .... most are quick ripoffs of OEM's or DIY designs ... really.

OS

OS

[ostripper]

Originally Posted by indianajo

Wow, MJL4302 PNP are over $6 each today, where as MJL4281 are only $4.50. What makes these better than MJL21193/4G which are $4.13 and appear to have more SafeOperating Area at 80V. I realize 4302/4281 are TO264 and 21193 are TO247, is the TO247 to hard to fit in the kit under discussion?
(datasheet from datasheetcatalog says MJL4302 is complement to MJL4281).

Get NJW0281/0302 $2.10 each ($1.90/25 mouser) ... 90% of the MJL SOA. I have not blown one yet in real world use. 200+ repairs with this pair from ON semi - 0% failure. These are so cheap , I use them as the drivers in triple OP's (cheaper than MJE15032/33(to-220).

4 pairs of these excellent devices run paralleled 8R woofers in my local church (over 1 year now) 250-300W easily.

OS

[Ian Finch]

I have some experience assembling and using local kits available here for several years now, based on five pairs of MJL21193/4. Intended for DJ work, they have good basic reliability but can still manage a genuine 350W/8 ohms, 500W/4ohms with great fidelity.
There is no apparent reason that an amp using four pairs may not produce an assumed rating of 350W/4ohms. provided similarly rated components are used, plenty of copper on the PCB and a substantial 0.4 deg.C/watt heatsink is used for optimal bias in class AB.

Rail voltages typically must be reduced to suit the lower impedance for safety and obviously, this will reduce the 8 ohm capabilities unless you can tolerate poor audio from current limiting action at 4 ohm loads. This will be just one of the compromises likely with $38/pr amplifiers. Compared to the likely total amp cost, it's peanuts so why skimp on the heart of the investment?

[jaycee]

it's 4 pairs, they just mount some top side and some bottom side. doesnt seem mechanically sound to me.