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Opamp replacement for Trident 24
Old 16th May 2018
  #1
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firby's Avatar
 

Opamp replacement for Trident 24

Hello.

A year ago I pulled out the Opamps for the line inputs and the fader buffers on my Trident 24 desk. In the Line Input there was a TLO71 and in the fader buffer there was a 5532. I put burr brown opa134 chips in. I just put them in the channels that were going 'to tape' thru the direct outs on the channels.

The difference in the mixes was positive. The tracks heading to tape did not suffer as much destruction as before. There is more useable high freq and there are some other nice changes that are harder to articulate.

Now I want to try the newer TL071 chip which I think might be a TLE072 maybe ? I want to get the right chip because I once bought some OPA2134 opamps by mistake and they did not work for anything. They had a dual configuration instead of a single configuration if I remember correctly.

Also, if there is another chip that may work in there without further modification then I would like to get a couple of those too.

This desk has been recapped by me with your help in the past (thanks!) and I had an aftermarket 10 amp power supply built. So, It should have the juice to run a few of whatever.

Regards
Old 16th May 2018
  #2
If you try to replace a TL071 with a TLE2072 you'd definitely be in for the same trouble you got into with the OPA2134. Try a TLE2071. Single channel just like your TL071.
Old 16th May 2018
  #3
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these sound really good in my desks mixing busses:
https://www.bursonaudio.com/products...ound-opamp-v5/
they should be a drop in replacement and are discrete. but pretty costy - and maybe overkill.....
Old 16th May 2018
  #4
Trident 65/24 modules require local phase compensation feedback caps as some are missing. They also require local .1 uf psu bypass caps if any wideband opamps are used. A scope is required to check the work or they risk becoming hf oscillators.
Old 16th May 2018
  #5
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Right now, I'm just looking for opamps for input channels. When I get ready to do the master, I'll send it out. Jim Williams did a group for me and it's pretty fabulous. It is the cleanest board in the whole desk.

But, I'm looking for opamps to affect just a little bit of change in the input channels at the moment. Those channels are recapped and working the best. I am leaving the mix channels alone for the meantime as the desk sounds really good for an old noisy desk. It's got vibe or whatever. It was modified before back in the old days.

However, less crud is good for digital recording.

So, from my scrawled notes. What I did was swap an OPA134 for IC1 which is the line in, and also swapped a OPA134 into IC11 which is for the fader. I don't know if fader buffer is the right term but that's what I marked down.

So have I changed every opamp in the signal path if I have a line signal going to the direct out with the above configuration ? This is assuming no eq engaged, no aux active, not monitoring on mix or groups. I am wondering if I also need to swap IC9? which is the EQ buffer (my schematics are hard to read). I thought if the eq is not engaged perhaps this chip is out of the circuit.

The chips that I changed are on the first 8 channels which are not mix channels. I have no real illusions of bettering the last engineer's/designer's work. But, the signals getting to tape are more intact. The problem with mixing and tracking on an old noisy desk is that the signal gets wacked on the way into the ADC and then again at mix. If I send the signal through the Burr Browns to tape, then the mix stage is much more coherent. This desk is like an acidic process. It sounds pretty good but you only want to hit all of that once!

I don't know that I love the sound of the Burr Browns enough to mix with them as is, the channels seem kind of weird in the top end. I think that could be good for aux sends though, where ever stuff needs to be bright.

Can you help me decide which TLE2071s to get:
Mouser has TLE2071CP, TLE2071ACP, TLE2071ACPE4 -- These all look like they would fit in the sockets. What is the distinction between CP ACP ACPE4 ?

THANK YOU for the help!
Old 17th May 2018
  #6
The OPA1641 is a better choice than the old-in-the-tooth OPA134. It draws less current than the 071 with a fast slew rate and 5 nv noise. It also has a large phase margin so it may not turn into an oscillator. For a fet opamp the ADA4625-1 is excellent and only 3 nv noise. TLE opamps are 25+ years old as many better chips are now available.
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