Santa brought an ART (Applied Research and Technolgy) Pro VLA 2-channel vactrol/tube leveling amplifier.
It seems to be directed toward the recording industry. As most of my music files have been things I digitize myself from analog
sources, I figured this might be enough to smooth things out for my part 15 AM 1620.
Before the compressor it sounded OK, but I could hear crunching in sibilants and "clumping" in the midrange when modulating hot.
When kept below this, dyamic range was indeed better, but avg modulation too low to carry well.
The compressor has two channels which may be linked or unlinked for compressor operation.
I have set up a two-pass channel, unlinked, where the fist pass sets threshold at 0db, ratio maxed, zero makeup gain.
Attack set to fast, release set to Auto.
I see occaisional compression of 20db on peaks for this pass.
Second pass is -12db threshold, 3:1 compression, zero makeup gain. Attack and release both on Auto.
I see average compression of 4 to 10 db , much less peaky than the 1st pass bargraph
My levels seem to be much lower than this device expects, as a -7db output is about my modulator can take before input
overload. I didn't think I'd put THAT much gain into that 6SN7 first audio stage!
I've always been able to run my line-out from processing equipment at 0db (master eq levels).
Running them up to a level where the meters on this compressor read normal is way too hot for my modulator,
so I mostly ignore the meters and use my ears. The vactrol seems to be a light-coupled variable resistance device used
to create a control voltage for variable gain in a 12AX7 triode amp stage.
Very musical, NO pumping action on difficult tracks, and some of the harshest songs have been tamed to sound much better.
Listening at low levels on multiple radios in the house and car revealed silky smooth highs and high density, and a natural sounding compression at any listening level.
Made the sound way better on even my Sangean 803A.
Bass is not swamping out the control signal, and I am sounding close enough to Big MusicRadio sound for $300 that
I'm very happy. Now if only there were a magic way to get decent radiation for a pt 15 on a tiny city lot.
Oh, yes. Out in the car, and driving around the block, it's a real radio station finally.
The higher density sounds like it costs a lot more.
Maybe I should do a recording somehow off the line-out from the car radio detector of the 1972 Motorola.
Designed in USA, no longer built here, which cost another couple hundred dollars, I guess, when they were.
Now built in China, I am still satisfied with the value, but think maybe it should still cost more and pay the Chinese better,
because it seems worth far more than 300 dollars.
Maybe today I will post another AM 1620 aircheck on Pod-O-Matic today. I have some issues with switching-mode pwr supply
noise within the server leaking into the audio. Actually the pwr supply is radiating and intermodulating at RF, not really in the audio.
Big toroid lossers on many leads have so far not killed the little warblies.
The server computer has built-in UPS, gel-cell pack w/charger. It's the dang charger control circuit, I've figured out. Grrrr.
It seems to be directed toward the recording industry. As most of my music files have been things I digitize myself from analog
sources, I figured this might be enough to smooth things out for my part 15 AM 1620.
Before the compressor it sounded OK, but I could hear crunching in sibilants and "clumping" in the midrange when modulating hot.
When kept below this, dyamic range was indeed better, but avg modulation too low to carry well.
The compressor has two channels which may be linked or unlinked for compressor operation.
I have set up a two-pass channel, unlinked, where the fist pass sets threshold at 0db, ratio maxed, zero makeup gain.
Attack set to fast, release set to Auto.
I see occaisional compression of 20db on peaks for this pass.
Second pass is -12db threshold, 3:1 compression, zero makeup gain. Attack and release both on Auto.
I see average compression of 4 to 10 db , much less peaky than the 1st pass bargraph
My levels seem to be much lower than this device expects, as a -7db output is about my modulator can take before input
overload. I didn't think I'd put THAT much gain into that 6SN7 first audio stage!
I've always been able to run my line-out from processing equipment at 0db (master eq levels).
Running them up to a level where the meters on this compressor read normal is way too hot for my modulator,
so I mostly ignore the meters and use my ears. The vactrol seems to be a light-coupled variable resistance device used
to create a control voltage for variable gain in a 12AX7 triode amp stage.
Very musical, NO pumping action on difficult tracks, and some of the harshest songs have been tamed to sound much better.
Listening at low levels on multiple radios in the house and car revealed silky smooth highs and high density, and a natural sounding compression at any listening level.
Made the sound way better on even my Sangean 803A.
Bass is not swamping out the control signal, and I am sounding close enough to Big MusicRadio sound for $300 that
I'm very happy. Now if only there were a magic way to get decent radiation for a pt 15 on a tiny city lot.
Oh, yes. Out in the car, and driving around the block, it's a real radio station finally.
The higher density sounds like it costs a lot more.
Maybe I should do a recording somehow off the line-out from the car radio detector of the 1972 Motorola.
Designed in USA, no longer built here, which cost another couple hundred dollars, I guess, when they were.
Now built in China, I am still satisfied with the value, but think maybe it should still cost more and pay the Chinese better,
because it seems worth far more than 300 dollars.
Maybe today I will post another AM 1620 aircheck on Pod-O-Matic today. I have some issues with switching-mode pwr supply
noise within the server leaking into the audio. Actually the pwr supply is radiating and intermodulating at RF, not really in the audio.
Big toroid lossers on many leads have so far not killed the little warblies.
The server computer has built-in UPS, gel-cell pack w/charger. It's the dang charger control circuit, I've figured out. Grrrr.