I'd like to use a Sanwu TDA7498 board with a pair of 4-ohm bookshelf speakers.
A few comments I've found on the subject range from "it's completely out of the question", through "might work, might not", to "I'm doing it right now, no problem!". The TDA7498 data sheet only shows it with 6 or 8 ohms. Sanwu's product description says "Recommended Speaker Impedance: 8 ohms best (4 ohms 6 ohms can also work)".
The amp is cheap enough that if it blows, I won't be too upset - but if it takes my speakers with it, I might be.
My amateur theory is that if it can do max. 100 watts into 6 ohms, if I keep it to around 65 watts into 4 ohms, it should be ok, since that will be about the same amount of current.
One way of doing that could be to limit the supply voltage, to maybe 24 volts. That way I can use the old "if you hear it clipping, turn it down" method. Another way might be to keep a higher voltage for more headroom, and just not turn it up so loud that the over-current protection kicks in.
I understand that the speaker impedance will change the output filter frequency, but on the other hand I can't hear anything above 14kHz, so maybe it doesn't matter so much?
Am I missing something? Anyone with practical experience of success/fail?
Thanks...
A few comments I've found on the subject range from "it's completely out of the question", through "might work, might not", to "I'm doing it right now, no problem!". The TDA7498 data sheet only shows it with 6 or 8 ohms. Sanwu's product description says "Recommended Speaker Impedance: 8 ohms best (4 ohms 6 ohms can also work)".
The amp is cheap enough that if it blows, I won't be too upset - but if it takes my speakers with it, I might be.
My amateur theory is that if it can do max. 100 watts into 6 ohms, if I keep it to around 65 watts into 4 ohms, it should be ok, since that will be about the same amount of current.
One way of doing that could be to limit the supply voltage, to maybe 24 volts. That way I can use the old "if you hear it clipping, turn it down" method. Another way might be to keep a higher voltage for more headroom, and just not turn it up so loud that the over-current protection kicks in.
I understand that the speaker impedance will change the output filter frequency, but on the other hand I can't hear anything above 14kHz, so maybe it doesn't matter so much?
Am I missing something? Anyone with practical experience of success/fail?
Thanks...
I run 4 ohm and have no problem. Indeed, the amp runs a bit cooler with no signal that way (don't know how). Make sure it has 22 not 33 inductors.
Thanks for the info. What kind of power supply do you use?
The board I'm looking at does have 22 uH inductors, Sanwu SW-HF05
https://world.taobao.com/item/43892376365.htm?fromSite=main
The board I'm looking at does have 22 uH inductors, Sanwu SW-HF05
https://world.taobao.com/item/43892376365.htm?fromSite=main
The 100W power comes with 10% THD, I do not think you want that. At 0.2 % THD, output is at ~ 50 W for a 6 to 8 ohm load.
If a 4 ohm speaker put on too much current demand on the amp, it will just shut down. I do not believe it will blow up. There are a number of protection mechanisms built-in.
Regards,
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