I have a 3116 amp as part of a consumer grade bluetooth amp (bru3p) so it's a digital output. I want to take this output, and feed it into an analogue preamp. I have a car audio high level to low level convertor that uses small audio transformers (from the looks of things). It just dawned upon me the amp is digital, so I guess I have two problems. Transformer efficiency due to higher frequency, then my analogue amp will be trying to run just on/off (or zeros and ones) at a frequency beyond it's ability.
Did I just land on my face?
I'm not sure what to make of the bru3p anyway. It's 2.1 with bass treble volume. Only L&R are amplified. The 'point one' is a 3.5 mono and responds to the bass treble controls, but not the volume. I think in the software this is dac0 and dac1 but I can't clear any of the check boxes, such as trying to make it a stereo output.
Total newbie to this, but the MA12070 boards seem to be £18 not £8 now, and this bru3p is £22. In a box, with bass/treble. Perhaps I can get that L&R straight from the chip to 3116 connection, I need to look or hope for a reply. Then perhaps I need some software that's a bit more powerful, to get these check boxes working. I just don't know. I have not seen stuff like this, though I like the basic filter opportunities I have toyed with.
https://www.ebay.co.uk/itm/175987017014
BRU3P ^^^
Did I just land on my face?
I'm not sure what to make of the bru3p anyway. It's 2.1 with bass treble volume. Only L&R are amplified. The 'point one' is a 3.5 mono and responds to the bass treble controls, but not the volume. I think in the software this is dac0 and dac1 but I can't clear any of the check boxes, such as trying to make it a stereo output.
Total newbie to this, but the MA12070 boards seem to be £18 not £8 now, and this bru3p is £22. In a box, with bass/treble. Perhaps I can get that L&R straight from the chip to 3116 connection, I need to look or hope for a reply. Then perhaps I need some software that's a bit more powerful, to get these check boxes working. I just don't know. I have not seen stuff like this, though I like the basic filter opportunities I have toyed with.
https://www.ebay.co.uk/itm/175987017014
BRU3P ^^^
Well it's 3am, so I shouldn't really be on this project. However, these tone controls. They are not related to the dsp are they? The dsp has 4 analogue outs, but if these tone controls work on both the 3116 amp, and the line-out, then I only have the dsp using two analogue outs. L&R, with tone in the analogue world, before the signal splits for either the line out, or the volume control towards the 3116
The dsp software has three lots of filtering on different outputs. I have music, rec, and mic. I need to look at routing. I have jumped right in as it was cheap. However a mono line-out or stereo digital out, are both little use to me in my current projects.
The dsp software has three lots of filtering on different outputs. I have music, rec, and mic. I need to look at routing. I have jumped right in as it was cheap. However a mono line-out or stereo digital out, are both little use to me in my current projects.
This took a while.
Most class D amp chips won't have a speaker ground, but instead run two amps out of phase, to hook our speaker between. So if I take my class D amps negative speaker output, it's not really a negative at all. It's no more a negative than the positive output terminal. Now, generally the high level inputs of my next amp, will be something like a comparative input, so this won't matter. However, it's possible my next amp has it's high level input ground, actually ground. That would let the smoke out. It really needs checking. If this is the case, some sort of DC blocking cap should suffice. We place that in the positive connection. The negative can have one, or don't have a negative connection at all. That should be fine if both amps share a common ground along the way anyhow. Such as vehicle ground.
I'm actually surprised, seeing at the class D could be a 2mhz signal. I had imagined the second amps input filtering, might of just sent anything like that to ground. I'm not entirely convinced now, but people are doing this.
However, as often happens after weeks of searching, I have had distractions. Just now, I remember my original project was class D into a transformer based high/low convertor, as this is home audio not car. How can that audio transformer not see 2mhz. It's not even got any real audio, and TX efficiency climbs with frequency. I'm not really any closer, but have answered another projects issue, and bumped my thread 🙂
Most class D amp chips won't have a speaker ground, but instead run two amps out of phase, to hook our speaker between. So if I take my class D amps negative speaker output, it's not really a negative at all. It's no more a negative than the positive output terminal. Now, generally the high level inputs of my next amp, will be something like a comparative input, so this won't matter. However, it's possible my next amp has it's high level input ground, actually ground. That would let the smoke out. It really needs checking. If this is the case, some sort of DC blocking cap should suffice. We place that in the positive connection. The negative can have one, or don't have a negative connection at all. That should be fine if both amps share a common ground along the way anyhow. Such as vehicle ground.
I'm actually surprised, seeing at the class D could be a 2mhz signal. I had imagined the second amps input filtering, might of just sent anything like that to ground. I'm not entirely convinced now, but people are doing this.
However, as often happens after weeks of searching, I have had distractions. Just now, I remember my original project was class D into a transformer based high/low convertor, as this is home audio not car. How can that audio transformer not see 2mhz. It's not even got any real audio, and TX efficiency climbs with frequency. I'm not really any closer, but have answered another projects issue, and bumped my thread 🙂
Cracked it open for a look. I can't see much alignment between the app notes I have seen, and the software labeling. It does seem from the app notes, there are just 3 outputs, which are dac outputs. It's suggested L&R are two, and the firmware installed likely links the filtering for each. Then the third is channel X, which gets use for subs. The volume only effects the amp when I checked with a bluetooth input. Though Bass and treble effected the speakers and the 3.5mm jack. I don't imagine they can be wired in the analogue domain. Just 6 pin vr's acting on 3 channels. I'm still head scratching, as the software names more outputs than I have, but not names the chip uses.
Preliminary findings.
1, I have been mixing up my datasheet.
2, The vr's do indeed go to the chip.
3, The sub out, or dac-x pin, seems to be called 'record out' in the software. Explaining why it's not volume controlled. I'm not sure who would want a mono record output, it's a 2.1 in anybodies book. Perhaps I can't see how to make it volume controlled, because it can't be. So can't be called sub-out by the chip people. It's useless as a 2.1 implementation anyway, if you can only change the volume of L&R. In some BT only config, you could perhaps set the volume control to match the sub-out level, then use your BT device to alter the bru3 BT input level.
I should of bought and boxed the nvarcher board
1, I have been mixing up my datasheet.
2, The vr's do indeed go to the chip.
3, The sub out, or dac-x pin, seems to be called 'record out' in the software. Explaining why it's not volume controlled. I'm not sure who would want a mono record output, it's a 2.1 in anybodies book. Perhaps I can't see how to make it volume controlled, because it can't be. So can't be called sub-out by the chip people. It's useless as a 2.1 implementation anyway, if you can only change the volume of L&R. In some BT only config, you could perhaps set the volume control to match the sub-out level, then use your BT device to alter the bru3 BT input level.
I should of bought and boxed the nvarcher board
The item you linked to is 2.0
Why do you think it's 2.1?
Line in and line out are likely TRRS or TRS sockets therefore stereo.
I do not know if line out is volume controlled or not.
Record out would be fixed level.
My best read of the datasheet suggests the device may be operated without speaker load (minimum speaker impedance stated but no maximum & no prohibition) but it's up to you.
Speaker out will be BTL not ground referenced so don't blow anything up!
Class D is not digital.
High frequency switching is filtered on the output so shouldn't be an issue.
If your preamp has volume, just use the line level signal.
Why do you think it's 2.1?
Line in and line out are likely TRRS or TRS sockets therefore stereo.
I do not know if line out is volume controlled or not.
Record out would be fixed level.
My best read of the datasheet suggests the device may be operated without speaker load (minimum speaker impedance stated but no maximum & no prohibition) but it's up to you.
Speaker out will be BTL not ground referenced so don't blow anything up!
Class D is not digital.
High frequency switching is filtered on the output so shouldn't be an issue.
If your preamp has volume, just use the line level signal.
Hello Russ
Yes the amp is 2.0 but that's not really what I bought it for. Like some peeps on another board, I really just wanted the dsp chip, in a reasonable package. For evaluation, but some sort of use after that.
The amp box says line out, but the software says record out. I have used the jack output wired for stereo, pluging in a 3.5 to 2 phono's. Each channel is just mono though. The chip does seem to have 3 dac outputs, with the chip itself calling them L R and X. I'm pretty sure I can apply filters that alter both L&R together. Then I have different filters for the dac-x output, which is just mono. Hence the 2.1 capability is there. I have checked and the line out/record out is indeed mono, so not really line out/record out. I need to wire it all up though, and start playing with the filters, to really see what is what. The naming convention doesn't tie things together well.
I think the software is calling it record out, because it's not specific to this chip. It's software for quite a few different chips, which can carry different firmware. I have different versions of this software, with slightly different functionality for my chip. Thus, bigger chips probably do have a stereo output for record, but I just get a single (mono) dac that's not really record or line-out, but actually of use for 2.1
I'm just using it for it's bluetooth input at the moment. I did have ideas about taking sound from a hifi pre-amp, and using this as an active x-over and bluetooth input point. It can be set to output bluetooth when present, or feed through from the preamp when there is no bluetooth. That stereo system uses an active x-over now, so seemed to be just waiting for this to arrive. Perhaps it will actually work, but I'm not happy about taking sound from the 3116 output. I don't know the switching frequency, but it's presence is needless. I have a car project I might use it in instead. Where a slight loss in fidelity is less of a concern. Still a 2.1 project though.
Yes the amp is 2.0 but that's not really what I bought it for. Like some peeps on another board, I really just wanted the dsp chip, in a reasonable package. For evaluation, but some sort of use after that.
The amp box says line out, but the software says record out. I have used the jack output wired for stereo, pluging in a 3.5 to 2 phono's. Each channel is just mono though. The chip does seem to have 3 dac outputs, with the chip itself calling them L R and X. I'm pretty sure I can apply filters that alter both L&R together. Then I have different filters for the dac-x output, which is just mono. Hence the 2.1 capability is there. I have checked and the line out/record out is indeed mono, so not really line out/record out. I need to wire it all up though, and start playing with the filters, to really see what is what. The naming convention doesn't tie things together well.
I think the software is calling it record out, because it's not specific to this chip. It's software for quite a few different chips, which can carry different firmware. I have different versions of this software, with slightly different functionality for my chip. Thus, bigger chips probably do have a stereo output for record, but I just get a single (mono) dac that's not really record or line-out, but actually of use for 2.1
I'm just using it for it's bluetooth input at the moment. I did have ideas about taking sound from a hifi pre-amp, and using this as an active x-over and bluetooth input point. It can be set to output bluetooth when present, or feed through from the preamp when there is no bluetooth. That stereo system uses an active x-over now, so seemed to be just waiting for this to arrive. Perhaps it will actually work, but I'm not happy about taking sound from the 3116 output. I don't know the switching frequency, but it's presence is needless. I have a car project I might use it in instead. Where a slight loss in fidelity is less of a concern. Still a 2.1 project though.