Trident CB9054 B-Range Limiter - Schematics?

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earthsled

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Dec 1, 2009
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Asheville, NC USA
Hi all! I have been working with kpearsall over the last few days. He has a prototype PCB design worked up along with some rough schematics in Eagle format.

Unfortunately, kpearsall is too busy to work on tidying up the schematics at this time. I would do it, but I don't have the Eagle software.

So, we'd like to get some help with the schematic re-draw.
Anyone out there want to help?
 

Rob Flinn

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Jun 3, 2004
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Sussex, UK
Did you not get the circuit diagram & board layout that forthmonkey (I think) made available for free the other year ?  I haven't tested it myself so can't verify it works, but if you want a copy PM me your email addy.
 

earthsled

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Did you not get the circuit diagram & board layout that forthmonkey (I think) made available for free the other year ?  I haven't tested it myself so can't verify it works, but if you want a copy PM me your email addy.

Nope. I didn't know about that. I've PM'd you...
 

Kid Squid

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Port Toilet, South Wales
Hi Earthsled,

These limiters weren't made by AD&R, that was the earlier version - the generic F700 type that was licensed by AD&R and used by Helios etc

These were made by Triad developments ( the design part) of Trident.

I done quite a bit of digging on these a few years back, back when time was a luxury ! but never got that far.
I got four of them myself, and I still havent racked up the buggers  :-[

Best,
Steve
 

earthsled

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Kid Squid -
You are correct. These modules were made by Trident / Triad for the B-Range console.

The schematics and documents Rob Flinn has are for the 9146 model NOT the 9054. The circuit is similar, but the 9054 has a completely discrete audio path (rather than op-amp).
 

pucho812

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third stone from the sun
I have been told the daking stuff is based off the discrete trident designs, the a range mic pre eq and the discrete compressor.  Wonder if that is true.
 

kpearsall

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Boards are in production for a small team of prototypers. Boards will be available for anyone who wants to build these after we work out the bugs and create a calibration routine. Metalwork will also be available for anyone wanting to build these in original style chassis. I figure 8 of these will rack up nicely in a 4u rack. Note the sidechain was setup for Quad, so the couple switch links 4 units, with trimming for precision. If one were feeling inclined, a simple mod would allow for linked surround sound compression.

It's been a very fun time learning all about a compressor that no one has documentation on. One based on such an amazing line amp is a huge bonus. Feel free to ask questions, we're starting to figure this all out.
 

kpearsall

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New things to read!

Thanks to Earthsled, (thank you!) I actually took in a pair for repair. The ones that were in the Nashville flood. There was quite a bit wrong with them, but I was able to get it all done rather quickly, and now I've got them for a week or two while I wait for new pots from the UK. I was pretty happy with the sound of these except I noticed an bass guitar and vocals that there was an odd attack artifact I didn't like. Turns out one of the chips in the dual precision rectifier was bad, and when replaced it got very smooth. I'm extremely happy with these little guys.

They also had two additional trimmers installed on the bottom board for trimming meter GR zero, and output metering. I'm currently trying to figure out the best way to adjust the distortion trimmer, and FET bias.

If anyone has anything they would like me to measure or test now would be the time!
 

kpearsall

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So, there is no FET bias. The trimmer i had thought was it, is actually a Threshold control. The only biasing to be done, is in the sidechain to make sure the two halves of the waveform are rectified evenly. The "distortion" trimmer, and a trimmer right before the 3 chips Dual precision rectifier circuit are used to balance this out. This circuit may also be a problem area, as both units had trouble here. One with the bad chip, the other with a bad chip and a blown transistor (yes the unobtanium RCA 40361) right after it.

With the sidechain dialed in, you can set the threshold to taste, i guess, but I'm setting them with a -10dBm signal at the input, input knob centered and getting just one dB of GR. This seems to be the best I've come up with. Still gives you room to slam drums, while bass and program material need the input turned down a bit so they aren't slamming. I'm going to do further tests at a studio I work at tomorrow to fine tune that and come up with a best case scenario for various input signals. These units have Neve 31267's on input and output wired for 6dB of gain. This is not really ideal, and some issues may go away without them there. If transformers are really needed I suggest just using 1:1. I think these are creating more problems than they are solving.

Last things are just setting the meter trimmer for accurate gain reduction from 0-10dB, and setting the trimmers for external sidechain input to be approx. the same volume as the internal signal if you are going to stereo or quad link them. Add two additional trimmers for surround sound if you wish. I've had pretty good results using them on program material.

Two attack setting doesn't seem to be a big drawback actually. Sometimes I wish there were more release settings, but I think the same thing about the 33609 and that never stops me from using it.
 

njm

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Oct 16, 2010
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113
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London
New things to read!

Thanks to Earthsled, (thank you!) I actually took in a pair for repair. The ones that were in the Nashville flood. There was quite a bit wrong with them, but I was able to get it all done rather quickly, and now I've got them for a week or two while I wait for new pots from the UK. I was pretty happy with the sound of these except I noticed an bass guitar and vocals that there was an odd attack artifact I didn't like. Turns out one of the chips in the dual precision rectifier was bad, and when replaced it got very smooth. I'm extremely happy with these little guys.

They also had two additional trimmers installed on the bottom board for trimming meter GR zero, and output metering. I'm currently trying to figure out the best way to adjust the distortion trimmer, and FET bias.

If anyone has anything they would like me to measure or test now would be the time!
I've got four of these in the workshop at the moment for racking, if you need any further measurements or anything checking. I did start trying to work out the circuit but pffff that takes ages!

I noticed some differences, on two of the units C32 is not fitted and on the other two it is a 10uf tant. Slight differences to the 2s release time

I service an A-range and a B-range so pretty familiar with those, i can see the discrete signal path is the same amplifier circuit
 

kpearsall

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Joined
Aug 12, 2010
Messages
250
Location
Los Angeles
Still got a pair here, but thank you. Shoot me a PM if you want a schematic to help you out. Trying to get back to building these but I'm rebuilding a console from the ground up. Spent 40 years or so in a shed. I've forgotten what "free time" is...
 

aaquilato

Active member
Joined
Feb 3, 2012
Messages
42
New things to read!

Thanks to Earthsled, (thank you!) I actually took in a pair for repair. The ones that were in the Nashville flood. There was quite a bit wrong with them, but I was able to get it all done rather quickly, and now I've got them for a week or two while I wait for new pots from the UK. I was pretty happy with the sound of these except I noticed an bass guitar and vocals that there was an odd attack artifact I didn't like. Turns out one of the chips in the dual precision rectifier was bad, and when replaced it got very smooth. I'm extremely happy with these little guys.

They also had two additional trimmers installed on the bottom board for trimming meter GR zero, and output metering. I'm currently trying to figure out the best way to adjust the distortion trimmer, and FET bias.

If anyone has anything they would like me to measure or test now would be the time!
Yes!

Ruud.
I was looking for a tech. Kpearsall was suggested. Those units he’s talking about are mine. Waiting on their return now to put them back into use. Thanks kpearsall!
 

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