Ok maybe it's not particularly class D related, but how to add gain adjustment to a class D power amp.
Purifi and (Hypex) Nilai have implemented it in their designs so you can switch between different gain values to properly match pre- and power amp.
And what kind of solutions are possible and with what influence on the audio signal? I mean is there a better and worse way to design?
Thanks in advance
Purifi and (Hypex) Nilai have implemented it in their designs so you can switch between different gain values to properly match pre- and power amp.
And what kind of solutions are possible and with what influence on the audio signal? I mean is there a better and worse way to design?
Thanks in advance
A non-inverting op-amp gain stage would be the easiest method assuming you need a high input impedance (i.e. you want the circuit to interface with standard equipment but perform the same no matter what's connected). Gain of 2 is 6dB gain, G=4 is 12dB. Use a relay to switch it in and out of circuit. I think this is what most of the Hypex et al demo boards use. If you want volume control or multi-level gain matching, there are variations.
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My situation is the opposite (want to have a lower voltage signal), the signal to my power amps is too strong/loud...
To understand fully, do you have any desire to modify the existing amp/input buffer, or would you like a solution fully external to the existing circuit? And, do you want the gain reduction fixed, switchable, or fully variable like a volume control?
Just a 10k volume control is fine.
Or else a fixed series and shunt resistor for a permanent setting.
These resistors should be close to the amplifier input.
Use a series 10k, and a shunt 5k, for -10dB loss.
Adjust only the 5k up or down from there.
My problem is the volume is too loud too quickly (there's little margin between soft and slightly louder) and when turned off I still can hear the music softly playing.
In the preamp there's an Alps RK27 Blue Velvet, 10K (motorized).
If possible a fixed internal solution.
In the preamp there's an Alps RK27 Blue Velvet, 10K (motorized).
If possible a fixed internal solution.
Ok, if you want to try adding just one resistor to each channel inside,
connect a 5k resistor from the volume control wiper to ground in each channel.
Adjust the value of the resistors if necessary, but don't go below 2k.
But probably the 10k/5k input attenuator placed before the volume control would work better.
I think you have a linear (instead of a log type) volume control.
connect a 5k resistor from the volume control wiper to ground in each channel.
Adjust the value of the resistors if necessary, but don't go below 2k.
But probably the 10k/5k input attenuator placed before the volume control would work better.
I think you have a linear (instead of a log type) volume control.
You need to add a Volume control or a fixed attenuator straight at the power amp input, as suggested by Rayma.
Attenuate as much as needed.
From your description, his suggestion of 10k series plus ~5k to ground should be close enough, adjust rising/lowering the 5k shunt as needed (3k3, 2k2, whatever it takes) , then your fine timing comes from the normal volume control included in your preamp.
The fixed attenuator does not need to be "perfect" , just enough to set gain near the "comfort zone"
It takes only 2 resistors per channel so no PCB needed, only 10k from input jack to board input, the second one from input to ground.
Attenuate as much as needed.
From your description, his suggestion of 10k series plus ~5k to ground should be close enough, adjust rising/lowering the 5k shunt as needed (3k3, 2k2, whatever it takes) , then your fine timing comes from the normal volume control included in your preamp.
The fixed attenuator does not need to be "perfect" , just enough to set gain near the "comfort zone"
It takes only 2 resistors per channel so no PCB needed, only 10k from input jack to board input, the second one from input to ground.
Thank you all for your answers.
Last question. One of my devices has to do with the change in volume I guess
I now have more sensitive speakers. Streamer, DAC and pre-amp haven't changed. All in all the signal going from source to speaker is 'too much'.
But when I want to add another source to my chain (with another signal output, read lower output) can I still use the modified power amp?
Last question. One of my devices has to do with the change in volume I guess
I now have more sensitive speakers. Streamer, DAC and pre-amp haven't changed. All in all the signal going from source to speaker is 'too much'.
But when I want to add another source to my chain (with another signal output, read lower output) can I still use the modified power amp?
Try it first.
If you need to lose the attenuation, switch the aforementioned 5k out of circuit.
For more specific help, post a link to your amplifier.
If you need to lose the attenuation, switch the aforementioned 5k out of circuit.
For more specific help, post a link to your amplifier.
Most recent sources will have similar output levels, so it should work well enough.
Worst case would be either a low gain phono stage, or a classic component from the 60s-70s.
I suppose you could add a switch to select the attenuation or not, if necessary.
Yes I am aware of different output voltages when's talking about cartridges (especially low output MC). I didn't know 'vintage' devices had also low gain.
Thanks again.
Thanks again.