Dinosaural OTC-201 Opticompressor  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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aionios
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Post by aionios »

Schematic attached! This is an original optical compressor design from Dan Coggins (Lovetone). Not very many were made, but it has nonetheless made it into the rigs of Ed O'Brien and Steven Wilson.

Full tracing log here, including photos of the process:
https://aionelectronics.com/blog/tracin ... ompressor/

There is also a PCB available here:
https://aionelectronics.com/project/con ... r-otc-201/
Attachments
OTC-201 schematic
OTC-201 schematic
Aion Electronics - DIY PCB projects for classic and obscure circuits

atalas
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Post by atalas »

Awesome work as always. Love the articles and pics.
Excited to see which other traces you're working on!

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bajaman
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Post by bajaman »

great work - but the bipolar transistors are incorrectly marked on the schematic ?
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aionios
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Post by aionios »

bajaman wrote:great work - but the bipolar transistors are incorrectly marked on the schematic ?
Right you are, I got the original trace and the DIY version mixed up. I attached the corrected one.
Attachments
OTC-201 Opticompressor v1.1
OTC-201 Opticompressor v1.1
Aion Electronics - DIY PCB projects for classic and obscure circuits

atalas
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Post by atalas »

aionios wrote:
bajaman wrote:great work - but the bipolar transistors are incorrectly marked on the schematic ?
Right you are, I got the original trace and the DIY version mixed up. I attached the corrected one.
How crucial is the specific vactrol used? I think I have some VTL5C1 laying around, would the substitution for the VTL5C4 work?

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Post by LaceSensor »

Looks like its time to sell my original (!)

Great work, this is a really amazing compressor.

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Post by LaceSensor »

Ive had a Dinosural OTC-201 for a long while now - really an amazing compressor. Felt I had to build this.
Suffice to say I can cop all the sounds of the original. I am somewhat partially convinced that the pot tapers arent the same
My clone gets louder more quickly, in a comparative fashion turning up the level and sustain knobs. However, the levels match up at the extremes, so I beleive the pot values are accurate.

Overall, great project. I'd have loved to have availed of Aions fixing and enclusure kit, but alas out of stock. It did mean that I could use a really nice silver hammered paint enclosure I have been stashing for oooh 7 years...!

Enjoy pics.

Image

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Post by pedalgrinder »

I have one of these boards made it and i have never found a compressor i have been more happy with on bass this one is amazing hands down. My only complaint is this. I would like an led to pulse brighter on and low level pulsing in regards to how much it is compressing it doesn't have to spot on accurate but to give me some form of indication of its compression level via a led mainly on stage thats where thats handy can anyone lead me to a circuit or know of one i could add for this purpose. Thanks in advance. :?
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