Rev 4 of the schematic ...

Attached files CBS AUDIMAX II MODS R4.pdf (49.3 KB) 

audiokid does the PDF link above work you? It does not work on my iPhone or iPad...it asks if you want to download then immediately quits.

i tried it and it worked.

It's OK for me on a W7 PC running Firefox - a single click on your icon brings up Adobe Reader with the schematic. With W10 running Edge on both a different PC and on a Microsoft Surface Go II tablet, clicking the icon downloads the .pdf, then puts an invitation to click a confirmation at the bottom of the browser screen (half off the screen on the Go). Clicking that opens the .pdf schematic directly in Edge on both devices.

Apple set up issue on my end then, thanks

Ready for testing...
  

Attached files

That front panel looks really smart, Link! Not instantly recognisable from a distance as an Audimax II, though.

Mind you, I'd read about them but never seen even a picture of one until you posted photos of this unit in the state it was when it came in.

I hope the owner is duly appreciative of all the work you have put in.

Stellar work Link ..... (pun intended).

Thanks guys, and extra special thanks to Boswell! It’s amazing to have your input, it’s hard to express just how much it is appreciated. Thank you!

Just listening now... it’s a really cool piece... lots of attitude, but not over the top. Maybe I can convince the owner to post some sample clips. :)

Link555, post: 467578, member: 31690 wrote:
Thanks guys, and extra special thanks to Boswell! It’s amazing to have your input, it’s hard to express just how much it is appreciated. Thank you!

Just listening now... it’s a really cool piece... lots of attitude, but not over the top. Maybe I can convince the owner to post some sample clips. :)

Post away Link ... thanks !

Link555, post: 467567, member: 31690 wrote:
audiokid does the PDF link above work you? It does not work on my iPhone or iPad...it asks if you want to download then immediately quits.

. I have to download it however but works on iphone as well.

Thats a beauty!

Thanks Bob for your permission to post some clips, Here are some very random sound samples. I did not match levels or do any extra tweaking. I took a small snippet from a mono source and ran it through the CBS audimax rIIz three times with different settings. I tried to push the settings on the compressor to see what it could do. Normal cautionary notes, these clips are real musicians doing their thing. These aren't perfect performances, or even mixed. Its raw. The idea is to hear a bit of the compressor, not the performance. The Acu gtr, drums and bass come from a band called Signal and Sound, the vocal comes from Kola Collective.

The first sample is an acoustic guitar. Below is the source file:
 
Now Running that through the compressor with the settings as follows:
ACU GTR 1
Input 10
Attack 90
Threshold 0
Release 20
Output 100
 
ACU GTR 2
Input 100
Attack 100
Threshold 50
Release 10
Output 10
 
ACU GTR 3
Input 100
Attack 50
Threshold 30
Release 60
Output 30
 

Attached files CBS Audimax rIIz ACU GTR 1.wav (6.9 MB)  CBS Audimax rIIz ACU GTR 2.wav (6.9 MB)  CBS Audimax rIIz ACU GTR 3.wav (6.9 MB)  Source ACU GTR.wav (6.9 MB) 

Ok next let's try some bass, below is the source:
 
Bass 1
Input 10
Attack 90
Threshold 50
Release 50
Output 100
 
Bass 2
Input 20
Attack 90
Threshold 10
Release 10
Output 100
 
Bass 3
Input 20
Attack 20
Threshold 10
Release 10
Output 100
 

Attached files CBS Audimax rIIz Bass 1.wav (6.4 MB)  CBS Audimax rIIz Bass 2.wav (6.4 MB)  CBS Audimax rIIz Bass 3.wav (6.4 MB)  Source Bass.wav (6.4 MB) 

Now some single OverHead mic on a drum kit, here is the source:
 
OH 1
Input 10
Attack 20
Threshold 30
Release 15
Output 100
 
OH 2
Input 20
Attack 50
Threshold 0
Release 50
Output 100
 
OH 3
Input 100
Attack 50
Threshold 30
Release 60
Output 30
 

Attached files CBS Audimax rIIz Drum kit OH 2.wav (6.9 MB)  CBS Audimax rIIz Drum kit OH 3.wav (6.9 MB)  CBS Audimax rIIz Drum kit OH-1.wav (6.9 MB)  Source Drum kit OH.wav (6.9 MB) 

Lastly here is vocal with the bleed from a nylon string guitar, here is the source:
 
Vocal 1
Input 10
Attack 50
Threshold 50
Release 30
Output 100
 
Vocal 2
Input 50
Attack 20
Threshold 50
Release 70
Output 100
 
Vocal 3
Input 15
Attack 50
Threshold 30
Release 30
Output 100
 

Attached files CBS Audimax rIIz Vocal 1.wav (8.6 MB)  CBS Audimax rIIz Vocal 2.wav (8.6 MB)  CBS Audimax rIIz Vocal 3.wav (8.6 MB)  Source Vocal.wav (8.6 MB) 

Link555, post: 467677, member: 31690 wrote:
Thanks Bob for your permission to post some clips, Here are some very random sound samples. I did not match levels or do any extra tweaking. I took a small snippet from a mono source and ran it through the CBS audimax rIIz three times with different settings. I tried to push the settings on the compressor to see what it could do. Normal cautionary notes, these clips are real musicians doing their thing. These aren't perfect performances, or even mixed. Its raw. The idea is to hear a bit of the compressor, not the performance. The Acu gtr, drums and bass come from a band called Signal and Sound, the vocal comes from Kola Collective.

The first sample is an acoustic guitar. Below is the source file:
Source ACU GTR.wav
Now Running that through the compressor with the settings as follows:
ACU GTR 1
Input 10
Attack 90
Threshold 0
Release 20
Output 100
CBS Audimax rIIz ACU GTR 1.wav
ACU GTR 2
Input 100
Attack 100
Threshold 50
Release 10
Output 10
CBS Audimax rIIz ACU GTR 2.wav
ACU GTR 3
Input 100
Attack 50
Threshold 30
Release 60
Output 30
CBS Audimax rIIz ACU GTR 3.wav

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.

Link555, post: 467678, member: 31690 wrote:
Ok next let's try some bass, below is the source:
Source Bass.wav
Bass 1
Input 10
Attack 90
Threshold 50
Release 50
Output 100
CBS Audimax rIIz Bass 1.wav
Bass 2
Input 20
Attack 90
Threshold 10
Release 10
Output 100
CBS Audimax rIIz Bass 2.wav
Bass 3
Input 20
Attack 20
Threshold 10
Release 10
Output 100
CBS Audimax rIIz Bass 3.wav

Re Bass:
Much prefer the last one again as it have a better attack to my ears.

its a pretty useful compressor, a bit of a Swiss Army knife...it has a lot of range.

Link555, post: 467679, member: 31690 wrote:
Now some single OverHead mic on a drum kit, here is the source:
 
OH 1
Input 10
Attack 20
Threshold 30
Release 15
Output 100
 
OH 2
Input 20
Attack 50
Threshold 0
Release 50
Output 100
 
OH 3
Input 100
Attack 50
Threshold 30
Release 60
Output 30
 

Interesting, again I much prefer the last example as it sounds more dynamic and alive.

audiokid, post: 467681, member: 1 wrote:
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.

Link555, post: 467680, member: 31690 wrote:
Lastly here is vocal with the bleed from a nylon string guitar, here is the source:
Source Vocal.wav
Vocal 1
Input 10
Attack 50
Threshold 50
Release 30
Output 100
CBS Audimax rIIz Vocal 1.wav
Vocal 2
Input 50
Attack 20
Threshold 50
Release 70
Output 100
CBS Audimax rIIz Vocal 2.wav
Vocal 3
Input 15
Attack 50
Threshold 30
Release 30
Output 100
CBS Audimax rIIz Vocal 3.wav

Vocals:
I prefer example 3 the best.
I like this processor on vocals. Thanks for the examples, Link and Bob.

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.

I doubled check the cathode voltages on the v3 .... pretty close with the tweaked resistors. About 4-8 mV difference.

 
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.

Attached files

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.

Thanks Boswell, good suggestion. Bob is going to give it a test spin now so we will see what kind Of response he’s looking for soon.