This is a project that is evolving out of a need for a gain stage after a popular DSP crossover.
Summary:
4-ch 20dB gain stage "kit". I develop and MFG the PCB, but will be happy to post circuit as this is nothing new.
This will use a quad op amp (LME49740) for the gain stages, plus a line driver IC (THAT1646 or DRV134). Input is unbalanced with RF and DC blocking/filtering. Use of balanced line drivers optional and can be fully unbalanced end-to-end if desired or for lower cost.
Power will be supplied via a DC 18-24V wall switching supply. Internally this will be regulated to 15VDC and then inverted to -15VDC for the analog circuitry. It may be possible for this to be used in an automobile application with a couple of tweaks...
Is anyone interested in something like this?
-Charlie
Summary:
4-ch 20dB gain stage "kit". I develop and MFG the PCB, but will be happy to post circuit as this is nothing new.
This will use a quad op amp (LME49740) for the gain stages, plus a line driver IC (THAT1646 or DRV134). Input is unbalanced with RF and DC blocking/filtering. Use of balanced line drivers optional and can be fully unbalanced end-to-end if desired or for lower cost.
Power will be supplied via a DC 18-24V wall switching supply. Internally this will be regulated to 15VDC and then inverted to -15VDC for the analog circuitry. It may be possible for this to be used in an automobile application with a couple of tweaks...
Is anyone interested in something like this?
-Charlie
OK, it seems that a pure gain stage PCB is not garnering all that much interest...
So, what if it could be a preamp? Would that be of interest?
The builder can populate the PCB and choose the gain. A dual audio taper pot or stepped attenuator could be used to implement volume control using the first set of gain stages, and then the second could implement the actual "gain" stage...
So, rephrasing, is a pre-amp kit of interest?
The board would not include input switching, but that is easily added on with a relay board that could be controlled by an Arduino, which could also control a digital pot like the PGA2311... so, remote preamp!
Interest?
-Charlie
So, what if it could be a preamp? Would that be of interest?
The builder can populate the PCB and choose the gain. A dual audio taper pot or stepped attenuator could be used to implement volume control using the first set of gain stages, and then the second could implement the actual "gain" stage...
So, rephrasing, is a pre-amp kit of interest?
The board would not include input switching, but that is easily added on with a relay board that could be controlled by an Arduino, which could also control a digital pot like the PGA2311... so, remote preamp!
Interest?
-Charlie
A recent post on this forum pointed out this very nice, inexpensive 2-channel volume control unit:
Digital Stereo Audio Volume Control Combo Kit | eBay
This would be a perfect match to the gain boards. Two of the channels are used as the "input" buffers, to set input impedance and do some filtering tasks. The output of these is connected to the volume control unit, and then the output of that is connected to the final gain stages. All that is needed is input switching or a high quality 2-gang rotary selector switch, and you have a nice preamp...
Digital Stereo Audio Volume Control Combo Kit | eBay
This would be a perfect match to the gain boards. Two of the channels are used as the "input" buffers, to set input impedance and do some filtering tasks. The output of these is connected to the volume control unit, and then the output of that is connected to the final gain stages. All that is needed is input switching or a high quality 2-gang rotary selector switch, and you have a nice preamp...
Due to the underwhelming response I'm not going to build a dedicated PCB for this project. But I did test out the concept using a PCB that I already developed that has a general layout that can be built up as various filters, etc.
I built up a 10x (20dB) gain stage using an LME49720 dual op amp and did some testing. THD level is about 0.002% and I was able to get the noise floor below -100dB. More info here:
http://www.diyaudio.com/forums/mini...ain-stage-dc-servo-minidsp-8.html#post3569490
Despite what the like title says, there is no DC servo.
That about wraps it up for me.
-Charlie
I built up a 10x (20dB) gain stage using an LME49720 dual op amp and did some testing. THD level is about 0.002% and I was able to get the noise floor below -100dB. More info here:
http://www.diyaudio.com/forums/mini...ain-stage-dc-servo-minidsp-8.html#post3569490
Despite what the like title says, there is no DC servo.
That about wraps it up for me.
-Charlie
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