thermionic
Well-known member
- Joined
- Jun 3, 2004
- Messages
- 1,671
Hi,
I've built a two-channel (for stereo use) version of the IN13 40dB VU meter here: http://m.bareille.free.fr/vu-in13/vuin13_v21_schem.pdf
The issue I'm having is that the channel linearity doesn't match.
Let's say ch1 is @ -10, ch2 might be @ -8. But then, as you boost level, ch1 will out-accelerate ch2, so it now reads 2dB more than ch1 when @ +10...
Can anyone see an aspect to the schematic that might affect linearity in such a manner? It's easy to calibrate both IN13s to match at, say, 0dB - but they will not align together at lower or higher levels.
My initial thought was that the IN13 tubes needed 'matching' - but I now know the linearity was is due to the driver circuitry as I've swapped tubes between PCBs.
Which components do you think could explain the linearity issue?
Thanks in advance.
I've built a two-channel (for stereo use) version of the IN13 40dB VU meter here: http://m.bareille.free.fr/vu-in13/vuin13_v21_schem.pdf
The issue I'm having is that the channel linearity doesn't match.
Let's say ch1 is @ -10, ch2 might be @ -8. But then, as you boost level, ch1 will out-accelerate ch2, so it now reads 2dB more than ch1 when @ +10...
Can anyone see an aspect to the schematic that might affect linearity in such a manner? It's easy to calibrate both IN13s to match at, say, 0dB - but they will not align together at lower or higher levels.
My initial thought was that the IN13 tubes needed 'matching' - but I now know the linearity was is due to the driver circuitry as I've swapped tubes between PCBs.
Which components do you think could explain the linearity issue?
Thanks in advance.