Many Denon AVRs have speaker level outputs for passive speaker connections (mostly around 90W for Dolby Atmos surround systems) and I think I can step down the speaker level to line level to run RCA/XLR cables to speakers with each having their monoblock amplifiers. But the problem is, these Denon AVRs have 4/8ohm output impedances from their speaker outputs and if I use an audio transformer to step down with 1:10 ratio, speaker level impedance being already being either 4/8 ohm, impedance gets even lower to 1/100 ratio of 0.08/0.04ohm. ChatGPT suggests that feeding too low impedance line level signal to power amplifiers can damage the amplifiers. Is that correct?
As far as I understand if I step down speaker level signal voltage with a 1/10 audio transformer, input being 8ohm, I get 0.08ohm (1/100 ratio) impedance. Would this harm a mono power amplifier if I feed this line level 0.8 ohm signal to it?
Not: My aim was to have more gain than Denon provides with separate amps and since power amps I see on internet have line level inputs, I thought of stepping down the speaker level to line level as a solution but not sure if this is a good idea.
As far as I understand if I step down speaker level signal voltage with a 1/10 audio transformer, input being 8ohm, I get 0.08ohm (1/100 ratio) impedance. Would this harm a mono power amplifier if I feed this line level 0.8 ohm signal to it?
Not: My aim was to have more gain than Denon provides with separate amps and since power amps I see on internet have line level inputs, I thought of stepping down the speaker level to line level as a solution but not sure if this is a good idea.
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[ Pedantically a step-down transformer is 10:1, not 1:10 ] Yes this will present a 0.08ohm source impedance to the monoblocks (not an issue to have low source impedance), and reflect the monoblocks impedance (probably 10k or 50k) back as very high impedance to the AVR which again is not a problem.
But a transformer will introduce distortion, and probably frequency response issues (especially if not loaded at its designed load impedance), whereas a resistor divider is linear and much cheaper. 9k1:1k divider for instance, with 1/2W rating for the 9k1, would handle the power levels and only introduce 4nV/√Hz noise
Chat GPT doesn't understand, it parrots, and here it got it wrong.
But a transformer will introduce distortion, and probably frequency response issues (especially if not loaded at its designed load impedance), whereas a resistor divider is linear and much cheaper. 9k1:1k divider for instance, with 1/2W rating for the 9k1, would handle the power levels and only introduce 4nV/√Hz noise
Chat GPT doesn't understand, it parrots, and here it got it wrong.
As much as I love transformer coupled circuits, Mark hits it on the nose. This is a job for a resistive divider. Use it.
@umutzd For the record, your Denon AVR does not have a 4/8 ohm output impedance. The actual output impedance is much lower than that. The "4/8 ohm" specifies a recommended load impedance. (Very important distinction there.)
Don't get confused with calculations based on that misunderstanding.
That said, unless you have a need to use a transformer, a simple voltage divider (as recommended by Pano) is perfect for this job.
Dave.
Don't get confused with calculations based on that misunderstanding.
That said, unless you have a need to use a transformer, a simple voltage divider (as recommended by Pano) is perfect for this job.
Dave.
Interesting, there are 6$ resistor level adjusters on Amazon and it says impedance converter on it but I see only resistors - and capacitors:
Would it make an audible difference if we buy some expensive special resistors and use them instead? There are some capacitors on this device too and not sure what they do.
Or a direct series resistor connection to the inner pin of RCAs is what we mean by voltage divider?
Would it make an audible difference if we buy some expensive special resistors and use them instead? There are some capacitors on this device too and not sure what they do.
Or a direct series resistor connection to the inner pin of RCAs is what we mean by voltage divider?
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Note that 90W into 8 Ohms is potentially 26.8 Volts, through a 1:10 transformer and you have 268Volts, which could be dangerous for you and your equipment. There are certain situations when you do want to step up an output, for e.g. 70V and 100V line distribution, but in this case, you want to step down the speaker output ~10:1, which means you do not connect the amplifier to the 8/4 Ohm tap of a transformer. The impedance of a transformer tap is just a convenient pre-calculated use assuming you are using it as expected. A transformer actual specs are voltage ratio (turns ratio) and inductance. The rated impedance is where the inductance creates a rational low frequency "cut-off" compromise.
You do not want 90W of power into the input of another amplifier, so you do not load the output to 8/4 Ohms. The output of an amplifier is typically a voltage and you do not usually need to load it. Assuming the amp you are driving has an input impedance of at least 10K, a 10:1 isolation transformer would present a load to the first amp of 10K*100= 1meg, and that should be just fine, except that winding a transformer for 1Meg is not realistic. However, if the inductance is only enough for 1K, an 8 Ohms output is still not going to be loaded.
Coupling transformer should be loaded because transformers have a self-resonance at the top of their range that needs to be damped. As others have suggested, a good idea is to use a 600:600 Ohm transformer and pad it with resistors. Also note that 26.8Volts may saturate a small transformer, so you want to pad the amp out before the transformer, not after.
But unless connecting the amplifier grounds together cause a ground loop (hum), a pair of resistors is probably the best solution, to avoid distortion and transformer low frequency loss and self-resonance. You could start with 10K in series and 1K Ohms shunt.
You do not want 90W of power into the input of another amplifier, so you do not load the output to 8/4 Ohms. The output of an amplifier is typically a voltage and you do not usually need to load it. Assuming the amp you are driving has an input impedance of at least 10K, a 10:1 isolation transformer would present a load to the first amp of 10K*100= 1meg, and that should be just fine, except that winding a transformer for 1Meg is not realistic. However, if the inductance is only enough for 1K, an 8 Ohms output is still not going to be loaded.
Coupling transformer should be loaded because transformers have a self-resonance at the top of their range that needs to be damped. As others have suggested, a good idea is to use a 600:600 Ohm transformer and pad it with resistors. Also note that 26.8Volts may saturate a small transformer, so you want to pad the amp out before the transformer, not after.
But unless connecting the amplifier grounds together cause a ground loop (hum), a pair of resistors is probably the best solution, to avoid distortion and transformer low frequency loss and self-resonance. You could start with 10K in series and 1K Ohms shunt.