Hello there...
I have a hacked Behringer umc-202hd with balanced input.
You can look at this thread here if you are curious:
https://www.diyaudio.com/community/...-for-measurements.341309/page-31#post-7364968
I'am very happy with it, it's easy to use with REW to take very good measurement's of audio stuff 👍
Regarding the output protection, the Behringer is protected on it's input with a 1uF, 400Vdc capacitor, ancient-lamp/resistor and clamping diodes... So it can withstand alot i guess... Anyway I will add a resistor, and maybee space for a capacitor (elcap or polyprop) at output. Good idea'
Jesper.
I have a hacked Behringer umc-202hd with balanced input.
You can look at this thread here if you are curious:
https://www.diyaudio.com/community/...-for-measurements.341309/page-31#post-7364968
I'am very happy with it, it's easy to use with REW to take very good measurement's of audio stuff 👍
Regarding the output protection, the Behringer is protected on it's input with a 1uF, 400Vdc capacitor, ancient-lamp/resistor and clamping diodes... So it can withstand alot i guess... Anyway I will add a resistor, and maybee space for a capacitor (elcap or polyprop) at output. Good idea'
Yes, I added a relay for the output GND now.
So you suggest to add a "dual" buffer right after the input attenuatorstring/stairs ?
Jesper.
Buffer would make divider output have exact voltages as calculated ,if you care about exact decibels .I'm unsure if with current schematic load of both dividers is identical - it means you have worse common mode rejection like mains frequency noise, because for any active variant of conversion input voltages must be equal. Also ,why you used two opamps to convert from balanced to se ? In post #2 i gave you link to simple schematic , which does same ,but uses just one opamp, so less noise probably and complexity. And second channel probably can be used as rectifier .I remember exists a circuit with opamp and two diodes ,which uses again one opamp to rectify AC to get DC .Even biased NPN emitter follower can serve as rectifier , loaded with resistor and capacitor in parallel.
I have recommended you to use 100k resistors for conversion earlier ,not to load divider , as you had very low output voltage with 1k resistors. With 1k it would work too ,less noise again , but such load needs to be connected after buffer ,so where a buffer would help and simplifies things .
I have recommended you to use 100k resistors for conversion earlier ,not to load divider , as you had very low output voltage with 1k resistors. With 1k it would work too ,less noise again , but such load needs to be connected after buffer ,so where a buffer would help and simplifies things .
Have just simulated simple rectifier circuit and its output .May be useful. Output waveform with 1 KHz 1V input and 1KHz 10mV input .
Nice sim.
When it's working I can lower the 100k's on the "secondary" opamp's to maybee 1k or 4.7k.
Well I will try to plugin another dual-opamp between the input attenuator and the rest of the circuit. I will try to use lower values resistor's to get some useable output. Maybe 10k or so, let's see.
When it's working I can lower the 100k's on the "secondary" opamp's to maybee 1k or 4.7k.
Well, I will use SMD1206, 0.4W, thinfilm, 1%-0.1% resistor's so the values on inputs (+/-) will be identical. -But I'am not sure if it's this you mean?
I will consider this also, but reason I used the other circuit is, that I belive that the idea with the rail to rail TLV2462 with this circuit TI is good.
Hi here.
Just a short update.
I've been doing some test, finding the right attenuation and gain circuit for my autoranger.
Status right now, is that i have a lot of it working as expected. (on protoboard only)
I have a lot of coding working very fine also, and the ESP32 is fast. - I bought a bigger display (4x20 LCD) to better show thing's.
Right now I'am starting to code the userinput via an encoder, but it's not done at all yet 🙂
There is some issues with my balanced in/out, I will be back one of the day's with quistions regarding this.
Jesper.
Just a short update.
I've been doing some test, finding the right attenuation and gain circuit for my autoranger.
Status right now, is that i have a lot of it working as expected. (on protoboard only)
I have a lot of coding working very fine also, and the ESP32 is fast. - I bought a bigger display (4x20 LCD) to better show thing's.
Right now I'am starting to code the userinput via an encoder, but it's not done at all yet 🙂
There is some issues with my balanced in/out, I will be back one of the day's with quistions regarding this.
Jesper.
Hi all...
I simplified the schematic I use, to only show the "analog" part of it.
The ESP32 is controlling the inputlevel, through the sensecircuit (TLV2462 active rectifier).
This is in ~6dB levels from -0dB to -32dB giving the circuit a working window from 300mVrms to around 45Vrms when output around 1200mVrms is chosen.
The output is controlled via the OPA1656 instrumental amplifier part I.
The output can be set in 100mV levels. E.g. when you choose to have output at 1200mV, an input from around 300mV to 1000mV can be scaled to this.
This is working fairly good, using combinations with relay's K9 to K13, giving gains close to x1,2 ... x2.2 in 100mV steps.
This way, I can reach the best scale on my soundcard.
I hope I can also success in coding this to other windows like e.g. 2500mV to 3500mV, let's see... It should be possible to do soo 🙂
The SingleEnded (SE) is send through the OPA1656 instrumental amplifier part II to the soundcard.
The balanced output are supposed to be used between the instrumental amplifier part I and part II.
But I'm not sure this is the right way of doing it?
I see other autoranger's where they convert the balanced input to SE, and then rebalance it at the output, but I would if possible avoid this.
Also I'm in doubt where I must GND circuit when using it SE ?
Comment's about the circuit is also very welcome.
Jesper.
I simplified the schematic I use, to only show the "analog" part of it.
The ESP32 is controlling the inputlevel, through the sensecircuit (TLV2462 active rectifier).
This is in ~6dB levels from -0dB to -32dB giving the circuit a working window from 300mVrms to around 45Vrms when output around 1200mVrms is chosen.
The output is controlled via the OPA1656 instrumental amplifier part I.
The output can be set in 100mV levels. E.g. when you choose to have output at 1200mV, an input from around 300mV to 1000mV can be scaled to this.
This is working fairly good, using combinations with relay's K9 to K13, giving gains close to x1,2 ... x2.2 in 100mV steps.
This way, I can reach the best scale on my soundcard.
I hope I can also success in coding this to other windows like e.g. 2500mV to 3500mV, let's see... It should be possible to do soo 🙂
The SingleEnded (SE) is send through the OPA1656 instrumental amplifier part II to the soundcard.
The balanced output are supposed to be used between the instrumental amplifier part I and part II.
But I'm not sure this is the right way of doing it?
I see other autoranger's where they convert the balanced input to SE, and then rebalance it at the output, but I would if possible avoid this.
Also I'm in doubt where I must GND circuit when using it SE ?
Comment's about the circuit is also very welcome.
Jesper.