I have an MB6582 with 4x8580 and 4x6581, and I got myself a stereo noise gate by building two MXR guitar pedal noise gate clones following the schematics on tagboardeffects (I built the stock version with the three changes mentioned in the very beginning) and boxing them up with a dual pot.
(UPDATE: If you build this, I advise to use 2N5485 instead of 2N5952 as transistor Q3, as it gives clearly better results. I built a second stereo unit of these today (24.7.2014), and went with the “stock version” schematic (see link above), using a 2N5952 as specified there and believing that that was what I had built before. However my earlier unit was gating the noise much more effectively, and after a while I noticed I had built it with a 2N5485, although it was otherwise like the “unmodded stock version” [bTW at some point I built the modded mono version as well and tried it on guitar, IMO the extra controls didn’t really do that much]. Changing to 2N5485 fixed the problem. I don’t know why this is though. Here are the datasheets, in case someone feels like researching.. 2N5952 and 2N5485.)
(UPDATE 2. March 5th, 2018. I had one more PCB for this lying around it, so I built it today and it worked without any problems. One thing I noticed was that in my screenshot below capacitors C5 and C13 are 100nF, but in the original tagboardeffects layout they’re 10nF. However, I’ve built all mine, including the one today, with 100nF caps and haven’t noticed any problems.)
The two switches can be used 1) to switch between battery and adapter power (= off for battery power), and 2) to switch off the stereo input jacks’ rings to use it in mono (for guitar etc). I’m not sure, but is the second switch actually redundant, as connecting a mono plug into the stereo jacks just connects the rings to ground? I put it there as a precautionary measure to avoid buzz and other problems, but then thought maybe it isn’t necessary.
Anyway, here’s a YouTube video on how it works on a pair of 6581s:
That’s funny 'cause I did exactly the same a few months ago, also using the MXR schematics. I have a single stereo input on one side, and on the other side 2 mono outputs (convenient to plug it to a mixing console) and a stereo pot to control the amount of noise gate reduction. It works really great and it is very simple to achieve, as jjonas said!
Of course, it is a bit tricky when dealing with sounds that have important gaps in volume…
Have just ordered some of the pcbs for your noise gate from osh park. I was wondering if there was a component list anywhere to save me having to trace the pcb and match it to the tag board and/or online schematic, which may or may not be the right one!
I’m sorry to say I don’t have the component list anymore. When I was making the gates, I printed the tagboard layout, counted each component and marked them out with a pencil on the schematic so that I knew which ones were already counted… and I threw away the paper when I was finished.
Anyway, here’s a screenshot of the Eagle pcb layout which will help you put the components in the right places. The component names don’t really refer to anything, I have no list of which component name equals to which value (“R17 = 1M” etc.), so you have to go by the values. Now that I think of it, I’ll include a screenshot with just the component values as well, it’s probably easier to read.
I’m also attaching the Eagle brd file so that you can open it in Eagle to check which value belongs to which component in case the screenshot is too vague. The layout was made in Eagle 6.5.0., in case that can make a difference.
A couple of things that come to mind:
The pcb has space for trimmers/pots for the modified version of the noise gate (for attack and release), but in the end I didn’t find they make much of a difference, so I just bridged them.
The noise gate takes regulated 9VDC, so for the regulator at the top I’ve used a 7809. The input voltage goes into “DC_IN” (upper left corner). The DC pin at the lower right corner (“9VDC”) is there for feeding the regulated 9VDC on to a second stereo noise gate that I have.
I soldered the resistors R17 and R37 on the “underside”.
The dual potentiometer goes to SENS1 and SENS2.
UPDATE 5.3.18: Capacitors C3 and C15 are 100nF in the screenshot, but they’re 10nF in the original tabgoardeffects layout. However, 100nF seems to work without problems (I’ve built all three I have with 100nF)
UPDATE 5.3.18: T1 & T2 and T4 & T5 are matched pairs of 2N3904’s, and T3 and T6 are 2N5485’s. The ICs are RC4558’s. The dual pot is 500k log.
I want to remind people that before someone verifies this, I cannot guarantee that this is a good product, worth people’s effort etc. I’m not a seasoned pcb designer! That said, everything’s worked for me, and I’ve been using this without problems ever since I first put it together 1–2 years ago or something like that. (UPDATE 5.3.18: I’ve built one more today, so let’s call it verified.)
