Does this amp use a switch mode power supply? - diyAudio
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Old 24th October 2011, 06:25 PM   #1
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Default Does this amp use a switch mode power supply?

Hi

Blackstar Artisan 412 A/B Extension Cabinet

...does this Artisan 412 amplifier use a switch mode power supply to supply it from the mains?
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Old 24th October 2011, 06:34 PM   #2
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Hm...They have a "contact us" on their site. Why not ask them? E
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Old 24th October 2011, 11:49 PM   #3
Enzo is offline Enzo  United States
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Unless I am not reading correctly, what you have linked us to is a 4x12 speaker cabinet. No power supply in it at all. The data sheet refers to its 240 watts, but that means power handling ability. It doesn;t produce any power.


Just a question: if it were a power amp, why would the type of power supply matter?
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Old 25th October 2011, 11:33 AM   #4
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Oh Sorry...i meant this product instead........

Blackstar HT Stage 100 Head Guitar Amp Head

....Its juat that i feel that the SMPS powered ones will be more expensive.....so if its got an SMPS in it, then i will go elsewhere and look for the equivalent product with a simple 50/60Hz mains transformer and rectifier/capacitor bank.
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Old 25th October 2011, 11:39 AM   #5
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You're right to avoid SMPS. They all blow up eventually and when it does it won't be fixable
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Old 25th October 2011, 07:45 PM   #6
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Quote:
Originally Posted by eem2am View Post
Oh Sorry...i meant this product instead........

Blackstar HT Stage 100 Head Guitar Amp Head

....Its juat that i feel that the SMPS powered ones will be more expensive.....so if its got an SMPS in it, then i will go elsewhere and look for the equivalent product with a simple 50/60Hz mains transformer and rectifier/capacitor bank.
Quite the opposite, SMPS's are cheaper, which is why they are becoming more popular, as well as smaller, lighter, much more efficient, and able to work over a wide voltage range.

toprepairman: - More complicated to repair, but by no means 'unfixable', engineers have been fixing SMPS's for over 40 years now.
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Old 25th October 2011, 10:04 PM   #7
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yes but......an smps generally has to be rated for its peak power as if it was continuous...........wheras a 50Hz transformer based PSU, for audio use, can be significantly underrated, and handle the peak power with its overload capability.

So the mains transformer is cheaper, but granted you need the mains to be constant 230V or 115V, whatever.
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Old 26th October 2011, 12:59 AM   #8
Enzo is offline Enzo  United States
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You are taking one parameter out of the context of all the rest. An SMPS can be dsigned for any power needs you specify. I service 3000 watt professional amps with SMPS in them. Little tube guitar amos are starting to sport SMPS. The mains transformer is the single most expensive part in a guitar amp, getting rid of it is a large step in improving profitability of an amp. Even your under rated iron transformer will be more expensive than the SMPS alternative.

At 50Hz, the main filter cap has to hold up the power rail for 100ms. At 50kHz, the filter in that SMPS has to hold up the current demand for 0.1ms. Not only have we removed the big transformer, but we also can shrink the filter caps. And large filters are not cheap either.

And I agree with Nigel, SMPS are no less servicable than anything else. I have been repairing SMPS for at least 30 years now. They are however getting so inexpensive it is often cheaper to replace them than to spend the labor time fixing one. A shorted rectifier on the secondary side is fixed quickly with a 2 cent part.
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Old 26th October 2011, 07:56 AM   #9
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i'm sure you realise its 10ms , instead of 100ms......im sure that was a typo.....but granted, 10ms is a long time to hold up the rail.

...but electrolytics are cheaper and cheaper to assemble than all the paraphinalia associated with smps...........granted the 50Hz solution is likely bigger...but miniturization doesnt seem to have hit the guitar amp world.......it seems, the bigger the better is the attitiude

Last edited by eem2am; 26th October 2011 at 08:09 AM.
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Old 26th October 2011, 09:33 AM   #10
Enzo is offline Enzo  United States
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You're right, I wasn't thinking. 100Hz ripple means 10ms charging cycle. SO 50kHz switcher, 100kHz ripple, charging cycle 0.01ms? It requires a lot less cap to do that.

And no, they are not cheaper. Price a 20,000uf 80v cap and compare it to a 200uf 80v cap. You are saving with smaller caps. Price a large 200 watt power transformer, compare to a whole 200 watt SMPS. But keeping in the spirit of the discussion, compare it to the small SMPS transformer. Rectifier diodes will be about the same. The SMPS will have a couple switching transistors and a small cheap control IC. Plus the mains rectifiers and filters. All of those together do not cost as much as that linear transformer alone, let alone with the large filter caps.

Ther are arguments against SMPS, but cost is not one of them.
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