CBS AudiMAX II in the sick bay

audiokid

Chris
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Joined
Mar 20, 2000
Location
Nanaimo BC, Canada

Link555

Well-Known Member
Joined
Mar 31, 2007
Location
North Vancouver
Nice, thanks for posting!

Re: acoustic guitar.

I think I prefer the last example the best as it sounds a bit more even to the strum and picking but of course this might change based on other instruments in a song.
That intresting as I purposely pushed number 3 that into heavy saturation.
 

audiokid

Chris
Moderator
Joined
Mar 20, 2000
Location
Nanaimo BC, Canada
Lastly here is vocal with the bleed from a nylon string guitar, here is the source:
View attachment 20276
Vocal 1
Input 10
Attack 50
Threshold 50
Release 30
Output 100
View attachment 20273
Vocal 2
Input 50
Attack 20
Threshold 50
Release 70
Output 100
View attachment 20274
Vocal 3
Input 15
Attack 50
Threshold 30
Release 30
Output 100
View attachment 20275
Vocals:
I prefer example 3 the best.
I like this processor on vocals. Thanks for the examples, Link and Bob.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
Yes, interesting to hear those clips - thanks for doing them.

Did you keep any notes about what the meter was showing in the different settings in the various tracks?

I heard some distortion in the acoustic guitar track that wasn't in the original. It's not an output overload, since the samples are a long way below FS. It was most noticeable about 2 sec into the first strum; this would be before the Audimax had time to settle into an average level for the track.

I carried out one of the checks I have devised for judging compressor operation, which is to play the uncompressed and compressed tracks simultaneously into L and R headphones, and listen to when and by how much the image jumps around. It's interesting that the guitar moves the most of all the sample tracks, even the drum kit. I think this says something about the crest factor of acoustic guitar waveforms, and how the Audimax II compressor responds to that.
 

Link555

Well-Known Member
Joined
Mar 31, 2007
Location
North Vancouver
I doubled check the cathode voltages on the v3 .... pretty close with the tweaked resistors. About 4-8 mV difference.

7DE2B6E7-3494-41EE-B1A5-D657C24A11D2.jpeg


5798B3C0-2429-4F94-977D-E681DF462FBA.jpeg

The 12AU7 is matched with the pot to about +/-2mv.

Here is random video, the sound is just the iPad mic in a noisy room, but you can see how the meter behaves.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
That's really good matching of the current through the dual triode. It's running at quite a bit lower standing current than I thought it would do.

One of the things that surprised be with the compression clips and again on the meter video is the subtlety of the effect from the Audimax II, showing what a gross adjustment in settings you have to make to get any substantial movement in the meter. It really is a long-term leveller, both up and down, though I've not seen much evidence of it doing any expansion. It could be that the JLM mods took that part of the operation away.

For usage other than levelling in an AM transmitter station, I would be tempted to try reducing the 1uF control cap to 100nF and see if the box was a bit more lively when presented with the sort of material that the owner might be putting through it. Maybe even a selecter switch on the rear to give a choice.
 
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