leigh
Well-known member
[quote author="PRR"]But note that dividers in general ARE "limiter gain cells". Here you have a 2-part $6.13 divider (opto and resistor), and you are working your way around to a 30+-part measurement plan. You will have more solder, and probably more money, in the metering than the audio itself. Is that wrong? No! More meters! But when you go way overboard on one side, it is worth thinking about the Total Box and if money/effort may be getting thin someplace it matters.
...
Close and cheap often trumps precise and fussy.[/quote]
Great answer, PRR, thank you. I was coming around to the simple/cheap side of things after a couple frustrating days at the bench, trying for something precise and fussy...
I did go and look around at some voltage dividers (the multiplier w/feedback loop approach), and quickly said, hell no, not for this.
I will need to order some new parts to try the split LDR approach you describe. It definitely sounds like the most elegant way to incorporate a VU meter. I currently have the VTL5C2 parts, but those just have a single LDR cell.
For now, I'm planning to finish this circuit with a really simple LED indicator, to increase brightness as compression increases. It'll get fed from a point post-sidechain filter. I may drive the LED directly off the LM386, or buffer it so I can include a little RC circuit to simulate the 500ms release time of the VTL5C2 cell.
Another change in the works: moving the threshold pot to the output of the LM386. This will allow using the 386 for an audio output, as previously discussed here. Also, the 386 has 50K input impedance, and I've currently got a 100K pot across that, and I think it's doing something weird to the level near the top of the pot's throw (it's either that, or some kind of opamp/vactrol saturation, but there's some weird level change there). So the threshold pot will get moved to after the 386, and will likely need to be changed to a smaller resistance value.
There are a few other things to play with, and I'll post a revised schematic of the comp when it's all working right.
Oh, and I agree, the insight gained from all this mucking about on the bench has been valuable. I've been building stuff for years, but this is my first time getting this down and dirty with the design portion.
cheers,
Leigh
...
Close and cheap often trumps precise and fussy.[/quote]
Great answer, PRR, thank you. I was coming around to the simple/cheap side of things after a couple frustrating days at the bench, trying for something precise and fussy...
I did go and look around at some voltage dividers (the multiplier w/feedback loop approach), and quickly said, hell no, not for this.
I will need to order some new parts to try the split LDR approach you describe. It definitely sounds like the most elegant way to incorporate a VU meter. I currently have the VTL5C2 parts, but those just have a single LDR cell.
For now, I'm planning to finish this circuit with a really simple LED indicator, to increase brightness as compression increases. It'll get fed from a point post-sidechain filter. I may drive the LED directly off the LM386, or buffer it so I can include a little RC circuit to simulate the 500ms release time of the VTL5C2 cell.
Another change in the works: moving the threshold pot to the output of the LM386. This will allow using the 386 for an audio output, as previously discussed here. Also, the 386 has 50K input impedance, and I've currently got a 100K pot across that, and I think it's doing something weird to the level near the top of the pot's throw (it's either that, or some kind of opamp/vactrol saturation, but there's some weird level change there). So the threshold pot will get moved to after the 386, and will likely need to be changed to a smaller resistance value.
There are a few other things to play with, and I'll post a revised schematic of the comp when it's all working right.
Oh, and I agree, the insight gained from all this mucking about on the bench has been valuable. I've been building stuff for years, but this is my first time getting this down and dirty with the design portion.
cheers,
Leigh