CL-oneB research topic
« on: June 07, 2018, 02:19:12 PM »
Hi folks!
Wonna open one more CL-oneB opto compressor thread.
Who used this device know how good it is.

Original schematic can be found  in tech docs page.

Main audio path looks pretty typical:
input transformer > threshold/ratio/gain pots >  gain reduction element (aka GRE) > tube output amp (pretty typical for all tubetech gear)

The most interesting part of all compressors is a side-chain/detector schematic.
I redraw this schematic in a more visual and understandable way.  Check it out.
 In the future I'm planning to emulate it in LTspice.

The most "magic" element is a GRE which is a complex opto element (black box in the real device).
as I read in the previous threads:
GRE contain LED/LDR combination and "gain-change-linealizing" circuitry.

Any ideas how to test/create/emulate a such GRE for getting correct compression curve from a such side-chain/detector schematic?)

« Last Edit: June 08, 2018, 09:14:21 AM by dirty1_1garry »


Re: CL-oneB research topic
« Reply #1 on: June 19, 2018, 12:34:02 PM »
it seems not so much interest in the topic;)
Well, no matter))

I've emulated schematic in LTspice and it works (but only manual mode, hmm). Instead of original opto element I've used VTL5C2 model that was found in the web. Operation of sidechain schematic hardy depends on opto properties and thats still a question.
« Last Edit: June 19, 2018, 12:45:48 PM by dirty1_1garry »

Re: CL-oneB research topic
« Reply #2 on: June 19, 2018, 12:45:11 PM »
Here is a .asc pack for those who wona experiment with
Enjoy

PS: download and change file .img > .zip

weiss

Re: CL-oneB research topic
« Reply #3 on: March 14, 2019, 12:52:26 PM »
interested in this..
did you ever try this further?

ruffrecords

Re: CL-oneB research topic
« Reply #4 on: March 14, 2019, 01:15:22 PM »
The ratio control is interesting and seems to be very similar to the conclusion I came to from studying the LA2A and experimenting with Vactrols. With the ratio pot at zero ohms it is a straightforward feedback compressor and the ratio depends on the opto characteristics. In my tests with a VTL5C3 I found the input output characteristic was log/log. So a 1dB change in control voltage caused a 1dB change is attenuation. In a simple feedback compressor, where the side channel is fed from the 5C3 output, this means if the output increases by 1dB then the gain reduction increases by 1dB so the input must have increased by 2dB. This gives a 2:1 ratio.

As you operate the threshold pot a proportion of the input is fed to the side chain along with a proportion of the output of the 5C3 is fed to the side chain. This means it is part feedback and part feed forward compression and it is the feed forward element that increases the ratio. With a 1dB/1dB input output relationship a 100% feed forward compressor reduces the gain by 1dB for every 1dB increase in input so the ratio is infinite. The10K pot ensures this point is never reached. In practice I have found it is relatively straightforward to obtain ration up to 10:1.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: CL-oneB research topic
« Reply #5 on: March 14, 2019, 05:27:31 PM »
interested in this..
did you ever try this further?

No new movements... unfortunately I have no any additional input information

pucho812

Re: CL-oneB research topic
« Reply #6 on: March 14, 2019, 05:47:35 PM »
there is a service manual in the tech documents have you seen it?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

Re: CL-oneB research topic
« Reply #7 on: March 14, 2019, 05:51:14 PM »
there is a service manual in the tech documents have you seen it?

Of course, I got all this information from service manual mainly

Re: CL-oneB research topic
« Reply #8 on: March 14, 2019, 05:54:49 PM »
The ratio control is interesting and seems to be very similar to the conclusion I came to from studying the LA2A and experimenting with Vactrols. With the ratio pot at zero ohms it is a straightforward feedback compressor and the ratio depends on the opto characteristics. In my tests with a VTL5C3 I found the input output characteristic was log/log. So a 1dB change in control voltage caused a 1dB change is attenuation. In a simple feedback compressor, where the side channel is fed from the 5C3 output, this means if the output increases by 1dB then the gain reduction increases by 1dB so the input must have increased by 2dB. This gives a 2:1 ratio.

As you operate the threshold pot a proportion of the input is fed to the side chain along with a proportion of the output of the 5C3 is fed to the side chain. This means it is part feedback and part feed forward compression and it is the feed forward element that increases the ratio. With a 1dB/1dB input output relationship a 100% feed forward compressor reduces the gain by 1dB for every 1dB increase in input so the ratio is infinite. The10K pot ensures this point is never reached. In practice I have found it is relatively straightforward to obtain ration up to 10:1.

Cheers

Ian

Deep thoughts, I have to think it over


 

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