Big upgrade of Neptune 820! Need some advice... - diyAudio
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Old 1st April 2009, 03:30 AM   #1
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Join Date: Mar 2009
Default Big upgrade of Neptune 820! Need some advice...

Hi all, first post here. I just bought a very inexpensive mixer on ebay - Neptune 820 from the late 70s. Its got built in spring reverb which is totally gnarly, and it works just fine. I thought it would be a fun project to try and soup it up - I've attached the schematic but left out the master section b/c of size restraints. The circuit is based on the RC4136 quad op amp, and my idea was to replace it with OP275s or OPA2406s using BrownDog adapters. I also thought about replacing the PSU caps and all the 10uf electrolytics. EQ caps as well?

My questions are:
1. What do you think the power supply will handle as far as the op-amp current consumption (the 4136 draws <2mA per amp)?
2. Is it worth buying the more expensive caps for this (Black Gates, etc.)?
3. Do you think this is a worthwhile project?
4. What are the "gotchas" I'm not thinking about?

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File Type: jpg neptune 820 channelps.jpg (85.8 KB, 105 views)
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Old 1st April 2009, 11:03 PM   #2
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Join Date: Mar 2009
Here is the rest of that circuit. Anybody want to offer their 2 cents?
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File Type: jpg neptune 820 master section2.jpg (49.6 KB, 73 views)
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Old 15th October 2012, 02:30 PM   #3
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Join Date: Sep 2007
If you're still around, did you ever do anything with this? How did it turn out?
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