Lets mod the Alesis Micro Limiter!

[Brett Siler]

I did add local psu .1 uf bypass caps and some feedback resistors had small mono ceramic caps added to reduce bandwidth

Would this reduce the amount of frequency bandwidth that gets compressed? Just out of curiosity why would you wanna do that? Does it change how the compressor reacts to certain frequencies (like not compressing lows, or highs well) or just too lower hissy noise?

I just bought another Micro Limiter for 32 bucks, and came up with a lot of neat ideas for this project.

[Jim Williams]

It's common for designers to omit feedback phase compensation caps when using low bandwidth opamps like the 07x series. They are tolerant of the stray capacitance that builds up across the feedback and input resistors due to their low 2 mhz bandwidth and fet inputs.

When you replace those with higher bandwidth parts the phase margin can be decreased leading to peaking on square waves or even oscillations using feedback resistors above 3k ohms. The small value feedback cap is chosen to roll off at above 200k hz. That avoids any phase shift in the 20~20k hz audio band and removes out of band noise. It's high enough to pass dog whistles and bat radar but it doesn't affect the sonics for humans.

[Brett Siler]

ah nice! Thanks for the info.

[Blue Jinn]

Came across this thread googline microlimter mods.... Anyway, wondering if any power supply upgrades were in order as well. 9vac in doesn't seem to give it much headroom, or am I off base here?

Seems like 12vac or even 15vac to get higher rails? (I'm assuming a lot here haven't even opened one yet) depending on the internals replaced/upgraded would be of benefit?

[The Scum]

From the schematic here:

http://www.diystompboxes.com/smfforum/i ... ic=93813.0

It's using a voltage doubler for +/- 12V rails.

I'd check what the rail limits are for the VCA before moving them any higher.

Jim's mods will give you more bang for your buck.

Followup edit:

The datasheet says "max supply allowed across the device is 25V." So there ya go.

[accordion squeezist]

I have a MicroEq (mono 3-band parametric)
Who wants it for free?

[The Scum]

Who wants it for free?

I'll PM you some postage stamps.

[bhmcc]

From the schematic here:

http://www.diystompboxes.com/smfforum/i ... ic=93813.0

It's using a voltage doubler for +/- 12V rails.

I'd check what the rail limits are for the VCA before moving them any higher.

Jim's mods will give you more bang for your buck.

Followup edit:

The datasheet says "max supply allowed across the device is 25V." So there ya go.

FYI - When Jim modded my Micro Limiter a few years ago, he changed the power supply too. It was apparently an important part of the upgrade as he made sure to remind me not to forget to send it with the ML.

[T-rex]

Alright, I am reviving this. I bought an RNLA and took one of my microlimiters out of the rack. It has some problems on the output pot but to my surprise when I opened it, I think it may have already been modded or at least had some power supply adjustments of some sort. I am going to pull another one (I have three - yeah I know, don't ask) and compare them then I will take some shots of both of them and post them up on the site.

Then I will try to see if I understand Jim's suggestions and then try to implement them. I love the damn things but the noise is a bit much. There are times I would love to use one but its not a garage rock tune so I can't deal with the noise. So all I want to do is lower the noise. If I can successfully do that, then maybe I will try something crazy.

[Brett Siler]

Maybe I got a lemon but I actually have one that isn't that noisy. I used it has one the Mix Buss Master for a hardcore album and it sounded awesome. That said I also have one that is noisy as shit. I would love to just lower the noise on it and keep the cool tone too.