I am after some help with a new project; this will probably be my last as I am finding it harder to retain the knowledge.
My existing amp which took me a few years to do is a triamp with active line filters, a microprocessor controlled attenuator with a pic 18f4525 and three pga digipots. There is a single lcd readout for attenuation of each channel. A single optical encoder controls the attenuation of each channel.
The system works great and I want to stay with a triamp but use digital inputs with a digital filter and a three channel attenuator.
I think a digital filter would improve the cut off's between each frequency band compared to what I have in analogue.
I have never done any work with digital filters but my idea is to have a digital input spdif ? or optical ? , then a three stage filter for high, mid and low frequencies followed by attenuation for each channel (so six channels in all allowing for the balance in each pair). I would then need a dac for each pair of channels. Finally the analogue outputs would go to separate stereo amplifiers.
Can anyone point me in the right direction.
I built a high spec amp in March this year which didn't work but with the help from two engineers on this site I got it working great after about 3 weeks so I am really hopeful of some advice here.
My existing amp which took me a few years to do is a triamp with active line filters, a microprocessor controlled attenuator with a pic 18f4525 and three pga digipots. There is a single lcd readout for attenuation of each channel. A single optical encoder controls the attenuation of each channel.
The system works great and I want to stay with a triamp but use digital inputs with a digital filter and a three channel attenuator.
I think a digital filter would improve the cut off's between each frequency band compared to what I have in analogue.
I have never done any work with digital filters but my idea is to have a digital input spdif ? or optical ? , then a three stage filter for high, mid and low frequencies followed by attenuation for each channel (so six channels in all allowing for the balance in each pair). I would then need a dac for each pair of channels. Finally the analogue outputs would go to separate stereo amplifiers.
Can anyone point me in the right direction.
I built a high spec amp in March this year which didn't work but with the help from two engineers on this site I got it working great after about 3 weeks so I am really hopeful of some advice here.
Faster filter roll-offs do not always translate to better sound quality. Problem is that linear distortion of phase tends to get worse as roll-off rate increases. The phase shifting can cause the crest factor of transients to become flattened (some might say 'smeared out'). At low frequencies things like bass instruments, drums, etc., may sound less real. You might have to try it and see if you notice anything that bothers you about it.
Of course, if using digital filters it is possible to go linear phase which tends to sound more like a volume control for frequencies, rather than like analog crossover filters which have natural phase shift. A possible issue with linear phase filters is pre-echo (not the same thing as pre-ringing, the latter should not be audible). That said, pre-echo can be suppressed using high quality filters.
Probably the best way to do digital filtering of audio is in a computer. Some of the guys next door in the 'PC Based' section of the forum can provide a lot of info on that. Some speaker builders also do a lot of work with digital filtering, so that section of the forum can be useful to take a look at too.
In this particular section of the forum, 'Digital Source,' we tend to focus more on the DAC part of the system that follows the DSP filtering. However, some people do work with DSP chips in this section. Since it is not PC based filtering those threads tend to get classified as 'Digital Source.'
Of course, if using digital filters it is possible to go linear phase which tends to sound more like a volume control for frequencies, rather than like analog crossover filters which have natural phase shift. A possible issue with linear phase filters is pre-echo (not the same thing as pre-ringing, the latter should not be audible). That said, pre-echo can be suppressed using high quality filters.
Probably the best way to do digital filtering of audio is in a computer. Some of the guys next door in the 'PC Based' section of the forum can provide a lot of info on that. Some speaker builders also do a lot of work with digital filtering, so that section of the forum can be useful to take a look at too.
In this particular section of the forum, 'Digital Source,' we tend to focus more on the DAC part of the system that follows the DSP filtering. However, some people do work with DSP chips in this section. Since it is not PC based filtering those threads tend to get classified as 'Digital Source.'
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Thanks for the info; I will also be looking at the DAC's after the digital part and because all this equipment will be in a case I will have to look carefully at size and location. The three amps take up quite a lot of room and my earth collection board alone had over 30 separate earth wires coming from the amps, filter, attenuator and control power source.