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Warm Audio Discrete Compressor 76 WA76: DIY Stereo Link Mod.
If you are reading this, you must be as excited as I am about the new Warm Audio WA 76 Comp/Limiter. There is lot of information about the WA76 at the Warm Audio site (http://www.warmaudio.com) and sound clips and video of it in use.
The WA 76 is an awesome piece of gear, modelled after the original 1176. Of course then, the WA 76 is mono, but there is a way to modify two WA76s, so that they can pass a stereo signal: great for tracking stereo sources or for strapping across your mix buss.
This article demonstrates how to use the MNATS DIY kit from Hairball to link the FET circuitry of two WA76s to create a stereo signal from the two units. Hairball Audio (HbA) is a very respected company providing a variety of excellent DIY kits. They can be ordered directly from the Hairball Audio site ( here: http://www.hairballaudio.com/shop/product_info.php?cPath=39&products_id=50).
Here is an iphone pic from the HbA site of the completed board.
*Note: Phase I includes the build of the two stereo link boards. Phase II, to follow ASAP, but at a later date, will review the installation into the WA76s and power up.
Background:
Please go to the HbA site, to read about the design of the stereo link circuit, the following build guide (http://hairballaudio.com/guides/Stereo_Link_Wiring_Guide.pdf ) is from the HBA site and to find a reference to another thread for information about the DIY build. I followed the HbA information for my build.
Disclaimer: IMPORTANT NOTE: Phase 1 of this project; building the stereo boards, does not entail opening up the WA76 unit. However, Phase II of this DIY project involves working with circuits that carry LETHAL voltages. The processes and build procedures demonstrated in this thread are for educational purposes only. All work should only be performed by qualified technicians. While the part count in this project is low and build procedures outlined in this project straight-forward, information provided in this post and any subsequent ones should be studied to ensure a thorough knowledge of all connections and components is gained prior to attempting this build.
Before beginning this project, a few strong recommendations:
1. If you are new to DIY electronics and do not have confidence and the technical knowledge to trouble-shoot the circuit when problems arise, make sure you have a solid fall-back plan. Before purchasing parts, find someone (friend or professional), local to you who can assist in person, if you get stuck!
(If you decide DIY, is not for you, ZENN Audio is doing a stereo link mod for fee. I would certainly suggest you contact them directly to find out if that is your preferred route to Wa76 stereo compression nirvana and/or bliss: ohmmmmm :) !)
2. Get a temperature controlled soldering iron. Delicate electronic components can easily become damaged with even low-wattage, non-regulated soldering irons. (Weller, Hakko, and other name-brand tools are good.)
For example:
Or, a cheaper 45 watt regulated alternative.
3. Hakko 808 de-soldering tool. This expensive tool can save you from hours of frustration and damaging the traces on your PCB if you need to remove components after they have been soldered in.
Engaging the dilythium crystals:
OK, with a full understanding of the inherent risks involved in working with DIY electronics, the first step in this project is checking your materials against the build list.
After you order your kit, you will receive a well packaged container with the following parts, as described on the the HbA audio site:
Please note when you review the build guide, the kit does not include the 2 switches, 2 female TRS plugs, ( pic at end of thread), the internal wiring , (board to board and some shielded), nor a male to male TRS cable, and 4 small bolts to mount the red pcps, that you will need for to complete the build and for the two units to be fully functional in stereo mode.
You can check the HbA site for most of these parts. I ordered my switches and TRS plugs from Mouser.
To prepare myself for the build, I simply laid everything out on paper and grouped the like parts together.
To confirm and double check the resisters values, I went to the following interactive site (http://www.digikey.com/us/en/mkt/calculators/5-band-resistors.html), to enter the colour bands in sequence to confirm the resister value (isn't the internet great !)
I confirmed all the parts were received.
Then, I organized everything into two separate bags: l one for each build.
Note: Gold bars on black capacitors indicating polarity.
Final Prep: Ready, Set, Stop ! :)
Before you fire up your iron, please take some time to review the actual board and to note the position of the parts, in particular the polarity orientation of the capacitors, marked as round circles with a + label (9 o'clock) and the Op-amps A201 and A302, marked with a white circle, bottom left hand side. You will note that the capacitors are also marked clearly with a negative sign in relief against gold markings (see above and other pic later) and that their long leg aligns with the positive polarity. Getting this wrong, may give you the opportunity to hear the capacitors pop like firecrackers when you power up; fun , ya !!! (but not the intended purpose).
Notre devoirs/ Your Homework !
Please don't resist using use the following guide to confirm the colour code of your resisters, because otherwise your build just won't have the capacity to deal with this error.
Type Part Number PCB Position Colour code
Op-amp TLO72CP 2 A201 Black (white circle polarity)
Op-amp TLO71CP 2 A302 Black (white circle polarity)
Capacitor 22uf Pan. FM 10 C201-03, C301-02 Black and gold
Resisters 25K Xicon 1% MF 12 R201-02, R205-08 R,Gr,W,R,Br
Resisters 10K Xicon 1% MF 4 R316-17 Br,Bl,Bl,R,Br
Resisters 100K Xicon 1% MF 2 R203 Br, Bl,Bl,O,Br
Resisters 1K Xicon 1% MF 2 R204 Br,Bl,Bl,Br,Br
Resisters 22R 2 R209 Br,G,Bl,R,R
Board games: getting stuffed:
Please ensure you use sensible ventilation (small fan) when soldering and use good technique, clean the tip regularly, use good solder, heat the board/trace and let that draw the liquified solder. If you watch carefully, you will note that the trace takes on a different shimmering appearance, as it approaches the melting point of solder. If you touch the solder to the trace at this point, it should liquify, flow and draw. Resist the temptation to rush and touch the solder to the iron tip; (it will just make things worse; trust me :).
You will be stuffing the parts, meaning putting the legs through the boards and flipping the board over to solder from the bottom. It it is common practise to start with the shortest parts first and proceed to the tallest parts last (resisters, op amps, capacitors). I did one board starting with the resisters and one with the op amps, starting with the resisters seemed a little easier.
In placing the resisters, remember to follow the R values which are noted on the board and which you confirmed while doing your homework from the Digisite. Also, normally you gently bend the leg of the resisters around a small diameter screwdriver to achieve a right angle bend to ease their fit through the holes in the board. I also reviewed the photo from the HbA site and oriented my resisters identically, just check the colour sequence to see what I mean. Please note with the Op-amp polarity white dot, you will see a corresponding black circle etched into the top surface of the op-amp. Ensure that you align and/or overlap them when installing on board.
Its a good idea to raise the board above the height of the legs, which will protrude from its bottom ( Note: left picture above, pcb is raised).
An almost completed Board, no caps yet. (Note: the black circles indicating polarity on bottom left hand side of each Op-amp.)
It may have occurred to you that when you flip the board over for soldering, that the parts may fall out or shift. So, it is common practise to splay and or to bend the legs out away from each other underneath the board, 30 degrees or so should suffice. Remember to be gentle, the legs are very pliable, so will bend easily; easy does it !!
Once you turn the Board upside down, check that you have good clearance and access at each solder point. If not, complete the solders that are most accessible and then snip away, as close to the board as possible, the excess leg, beyond the solder point. This will allow access to the remaining solder points.
Bathtime:
Soldering will leave residue on your board and this is conductive, use some new, isopropyl, a toothbrush and a small dish, to clean off the board after your soldering and let it air dry.
Caps:
Now its time to install the caps. You will recall, I mentioned earlier the caps are polarity marked. Here you can clearly see the negative rectangle in relief against the gold vertical bar, running the length of the capacitor; top to bottom. Ensure that you align the polarity with the markings on the pcp itself. They are clearly marked in white against the red, but two are immediately adjacent (C201 and C202). Ensure you do one cap, (no ninja Black Lion audio) soldering guys or gals allowed !) at a time and double check before soldering. Remember to splay the legs, before turning it over and prior to soldering, tighten the bend up against the bottom of the pcp board, as the caps tend to lift away from the board. Placing them upside down, top of caps on a flat surface, should ensure they are uniformly seated, but best to check before you solder.
Completed Board:
All done ! Feels good, I assure you !
And when both are done, why it feels 100% better; would I lie to you ?!
Phase I to Phase II:
So, that is the end of the Phase I build. Congrats ! I will post the remainder of the build as Phase II, when I have completed it.
Essentially, we will end up with a linked arrangement that looks something like this, (diagram from HBA DIY thread):
p.s. Here are the two switches and the trs female jack that will be fitted into the WA76's !
From Mouser Electronics part numbers: Switch 611-t101stdcbe on/on and Chassis-jack 568-nj3fp6C.
The build in each WA 76 will be like this:
You will install a red pcb in each WA76 with the wires and trs cable doing the actual connection between the two units. Please note the black shielded cable from Stereo link (red) board to Output controller and to TRS female plug of the unit (Note: This is a picture of the hairball audio compressor, also from its DIY thread.)
Stay tuned: same bat time, same bat channel !!!
