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Audio Source Amp-100 catches fire!
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Watthour
Electron Rancher - JS3600
So the whole thing weighs a meager 11 pounds. With the "toroidal power supply" (as indicated in their literature) that's not much of a transformer for the power rating. Even if it had a switching supply, that's pretty light weight. Anyone think that they might just be pushing the thing a little too hard? Smoke would be nearly inevitable.
I have a similar, low-grade power amplifier supposedly rated at "8Ω, 20-20,000 Hz. 2 channels, 250W/channel" and yet the output devices (2SA1941s) are rated for 100W maximum, and the manufacturer specifies them for use in a 70W audio amplifier. I'm afraid that all the misrepresentation, outright lies, and Madison Avenue drivel has permeated the audio market once again.
If the AudioSource sales literature states "50 watts RMS per channel @ 8 ohms" (as it does) for the AMP100, it's probably truly only capable of a continuous 20-25W without going full-incendiary. I'll guess that the actual transformer in this doorstop is probably only 0.200KvA, or maybe 250 on a cold day. You can perform the rest of the math, but if you won't, consider 80V P-P on the main rails, the RMS factor, and then Ohm's Law. That transformer needs to be at least 0.560 KvA not counting ANY overhead or reserve. A bare-minimum 560VA transformer alone (even a toroidal at 20-25% less than an E-core unit) would weigh over 10 pounds: https://www.parts-express.com/avel-lindberg-y236803-500va-35v-35v-toroidal-transformer--122-665
Tell me again how this is a 50WPC (continuous) amplifier. A TRUE 50WPC stereo amplifier like an SA-8500 weighs almost 30 pounds, not eleven.
Failing with smoke? Yes, Mildred, that would be expected.
I have a similar, low-grade power amplifier supposedly rated at "8Ω, 20-20,000 Hz. 2 channels, 250W/channel" and yet the output devices (2SA1941s) are rated for 100W maximum, and the manufacturer specifies them for use in a 70W audio amplifier. I'm afraid that all the misrepresentation, outright lies, and Madison Avenue drivel has permeated the audio market once again.
If the AudioSource sales literature states "50 watts RMS per channel @ 8 ohms" (as it does) for the AMP100, it's probably truly only capable of a continuous 20-25W without going full-incendiary. I'll guess that the actual transformer in this doorstop is probably only 0.200KvA, or maybe 250 on a cold day. You can perform the rest of the math, but if you won't, consider 80V P-P on the main rails, the RMS factor, and then Ohm's Law. That transformer needs to be at least 0.560 KvA not counting ANY overhead or reserve. A bare-minimum 560VA transformer alone (even a toroidal at 20-25% less than an E-core unit) would weigh over 10 pounds: https://www.parts-express.com/avel-lindberg-y236803-500va-35v-35v-toroidal-transformer--122-665
Tell me again how this is a 50WPC (continuous) amplifier. A TRUE 50WPC stereo amplifier like an SA-8500 weighs almost 30 pounds, not eleven.
Failing with smoke? Yes, Mildred, that would be expected.
FWIW output device is a TDA7293 power IC. 560 VA is overkill for a 50 watt per channel amplifier. 200 VA should be barely able to make spec. (having done the math myself) (assuming about 50% efficiency at full power). For audio use (not testing) 200 VA would be fine.
That being said, bridging or running 4 ohms would be highly not recommended. Better heat sinking would help too. My 2 cents.
That being said, bridging or running 4 ohms would be highly not recommended. Better heat sinking would help too. My 2 cents.
runnin'
Super Member
Failing? I don’t get it. If a modern amp gets overdriven and heats up beyond a certain point, shouldn’t its thermal safety kick in and shut it down?
I know that over the top ad copy never left us( even Emotiva measures the 4 ohm rating at a higher THD than the 8 ohm with some of their amps), but either it doesn’t have thermal shut down or it doesn’t work reliably. Is it even UL rated?
No modern amp should start to go up in smoke when overdriven. The little Adcom I’ve got, a current production 6002, has distortion and thermal warning lights and will shut off. Anyone looking for a reliable design, it’s 70 wpc and Adcom has it on sale over the holidays, $320 instead of $499.
there are many examples of resistors in ordinary amps that smoke due to something
else failing and taking the "heat" for it.
thermal shutdowns may be only those parts (like power ICs) but the only other
protections are in the muting circuits incase something goes out of boundaries
and fuses as a last resort.
there's only so much that can be designed in and only if necessary.
else failing and taking the "heat" for it.
thermal shutdowns may be only those parts (like power ICs) but the only other
protections are in the muting circuits incase something goes out of boundaries
and fuses as a last resort.
there's only so much that can be designed in and only if necessary.
Wonder if the Model One A will do that?
I picked up one at a thrift recently and when connected to speakers, even without a sound source, it buzzes so loud you would think it's going explode
Perhaps I should destroy it so no one get hurt, including myself
I picked up one at a thrift recently and when connected to speakers, even without a sound source, it buzzes so loud you would think it's going explode
Perhaps I should destroy it so no one get hurt, including myself
Watthour
Electron Rancher - JS3600
I must've calculated incorrectly.
± 40V main rails (80V P-P), presuming a sine wave, RMS factor of 2.816667 (P-P/RMS), and 50W power, let's see...
...That should be the same as 80V P-P ÷ 2.816667 = 28.4V RMS available to the final transistors.
Factoring for the typical internal voltage drop of a pair of P-N junctions at 0.5V average, and a 1 Ω total emitter resistance per pair (or a total of around 11Ω), the voltage at the speakers would be about 23.5V RMS. But the transformer still has to deliver that current at 80V P-P, or 28.4V RMS.
At a continuous 50W per channel, that would be 50 ÷ 23.5 (at the speakers), or 2.13A per channel. With 2 channels driven, that would be 2.13 x 2, or 4.26A from the transformer secondary. 4.26 x 28.4 V RMS = 121 VA. Presuming a 50% efficiency, your 200VA number would seem close to appropriate.
That means a toroidal transformer in that unity should weigh a minimum of 4.8 pounds, or just under half of the unit's total mass. That still seems somewhat "optomistic" to me, especially considering the 50WPC rated units from the '70s and '80s weighed 25 pounds or more - And that's just an amp, not a full receiver.
± 40V main rails (80V P-P), presuming a sine wave, RMS factor of 2.816667 (P-P/RMS), and 50W power, let's see...
...That should be the same as 80V P-P ÷ 2.816667 = 28.4V RMS available to the final transistors.
Factoring for the typical internal voltage drop of a pair of P-N junctions at 0.5V average, and a 1 Ω total emitter resistance per pair (or a total of around 11Ω), the voltage at the speakers would be about 23.5V RMS. But the transformer still has to deliver that current at 80V P-P, or 28.4V RMS.
At a continuous 50W per channel, that would be 50 ÷ 23.5 (at the speakers), or 2.13A per channel. With 2 channels driven, that would be 2.13 x 2, or 4.26A from the transformer secondary. 4.26 x 28.4 V RMS = 121 VA. Presuming a 50% efficiency, your 200VA number would seem close to appropriate.
That means a toroidal transformer in that unity should weigh a minimum of 4.8 pounds, or just under half of the unit's total mass. That still seems somewhat "optomistic" to me, especially considering the 50WPC rated units from the '70s and '80s weighed 25 pounds or more - And that's just an amp, not a full receiver.
Aiwa sa-p50 9 pounds. SAE mk31b 17 pounds. Aiwa uses toroidal transformer too, and is actually a very good little amp (better IMHO than the SAE or the Audiosource"
Yes, the amp 100 is an "air box". but it pretty much works as advertised.
IMO Video shows what happens when you use your basic tinfoil fuse...
Yes, the amp 100 is an "air box". but it pretty much works as advertised.
IMO Video shows what happens when you use your basic tinfoil fuse...
runnin'
Super Member
Why are we making excuses for crap, folks? Suggesting that it must have a tinfoil fuse is misdirected. Go onto the amazon owner reviews for this model. Click on any of the 1 or 2 star reviews and realize that this model has up to a 20% failure rate. Completely unacceptable, make all the excuses you want.
Bottom line, you get what you pay for.
Bottom line, you get what you pay for.
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Not sticking up for this amp...I have no experience with it. But one cannot draw conclusions as regards its failure rate from user reviews, as they are not a statistically valid data source.
Thanks so much for your kind words. I certainly defer to your obvious expertise.
For anyone else who may be interested, you can find a detailed analysis of this cheap little amp here:
https://www.kenrockwell.com/audio/audiosource/amp-100.htm
For anyone else who may be interested, you can find a detailed analysis of this cheap little amp here:
https://www.kenrockwell.com/audio/audiosource/amp-100.htm
I’ve had quite a few of them.
All used.
All work.
Usually the stuff I get is 50/50 good/bad.
These seem to do better than average in my experience.
Most Audiosource stuff that shows up works.
I can’t remember any that didn’t.
YMMV
All used.
All work.
Usually the stuff I get is 50/50 good/bad.
These seem to do better than average in my experience.
Most Audiosource stuff that shows up works.
I can’t remember any that didn’t.
YMMV
I don't know about the 100 but I have an Amp Three running a 4 ohm subwoofer bridged and it's never so much as broken a sweat. 
Is this amp even in production anymore?
Is this amp even in production anymore?
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