Stereo 1176 support - Mnats/Hairball

[velo-hobo]

Thanks for the ratio switch and filter info dmnieto!  man, I learn some new stuff every time I check updates to this thread.

I may still try the ratio switch configuration I described above.  It doesn't use the extra pads on the ratio PCB,  but I think it will place the 2:1 position next to the 4:1.  OCD a bit I guess.

Any thoughts on passive RC filters vs. active Sallen-Key?  What made you choose the active approach?

I was thinking it'd be cool to add another rotary switch to enable different frequencies for the HPF, but that seems like it would easier to do with a simple RC filter.

 

[Bobby Baird]

Check it out heres how mako does 2:1 on his new 500 series 1176. http://mnats.net/files/FET-D500.pdf

Looks like a series of 22k & 27K to get close to the 47K and 68r & 82r to get the 150r for the 2:1 ratio

 

[velo-hobo]

Awesome, yeah hairball just dropped their 500-series FETs today (developed by mnats and the same thing you link to)

Thanks for posting the pdf link, I was hoping to check out the schematic when the hairball build guide was released in two weeks but now I don't have to wait.  Good to confirm multiple circuit designers are using the same component values to achieve 2:1.

 

[Bobby Baird]

I am searching for the alpha 6 position 2 pole 2 deck switch to add a 2:1 ratio to my build Manufacturer Part #: SR2921F-0206-19R0B-E9-S-W. Seems mouser has stopped carrying this piece. Does any one know where an alternative place to buy a couple of these, are someone that has a few laying around they want to move?

 

[velo-hobo]

That's a bummer! Weird that they don't have a lead time listed, usually when something is out of stock they do (the 5-position version of that switch was backordered til just a few weeks ago)

Also I'm not seeing that Alpha switch anywhere else on first glance (not at digikey or newark or in a web search)

Maybe look at this one from Electroswitch, also on Mouser: C4D0406N-A

Kinda expensive but it looks like it has the same important bits - 6 position, 2 decks, 2 poles per deck, 30° index angle

There is a Grayhill available from Mouser too but it appears to be the PCB-mount rather than panel-mount version.

 

[Bobby Baird]

Yep, I think they must have discontinued the 6-way, but I will contact mouser anyway to see if they can order 2. I ordered all the other bits for my build along with the the 5-way switches if the 6-ways don't pan out. Time to fire up the solder. The power switch is dpdt right? Here's the one I ordered it's 20 amp, but I don't think that's a problem. Mouser Part #: 506-AWTN1504. I'm just confused about the switch function thing where you can choose on off on, on none on, on on ect, ect.

 

[velo-hobo]

Actually, looks like Stew-Mac still has 'em, but with a knurled shaft as opposed to smooth.  No big deal I suppose.  I bet other guitar parts retailers might have them too, look for 6-position 4-pole rotary switches, I think Alpha is a common supplier for these types of places.

http://www.stewmac.com/Pickups_and_Electronics/Components_and_Parts/Switches/Rotary_Switches.html

It's the 6-position 4-pole, and looks like it is the Alpha.

EDIT: Allparts seems to have the smooth-shaft version, with a pointer knob included:

http://www.allparts.com/EP-0920-000-6-position-Rotary-Switch_p_1345.html

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Power switch is DPDT, the one you reference should work fine, 20-amp is sufficiently over-spec! Just check the physical dimensions to make sure it won't crowd or interfere with anything else on your faceplate.  The power switches I bought are a little big and I barely got them to fit to my liking next to the stereo link and bypass mini-switches (in dan's cases)

You wanna switch both hot and neutral just in case the wall circuit you are plugging into has them reversed.  Check the mnats 1176 wiring guide for info on how to do it up right:

http://mnats.net/1176_reva-d_hairball_wiring_power.html

(As he shows, the transformer leads go on the center/switching terminals - if you put the supply voltage on the switching terminals instead, you'd have live power on the unused terminals in the off position, which would constitute a shock hazard. )

 

[Bobby Baird]

With that ratio switch you suggested I guess it doesn't matter that it has 4-poles you could just solder the poles together to make a 2-pole 6 position switch with 2 decks for wiring the slam function. The pcb is set up for 2-pole on the ratio, so you would have to accommodate with a 4-pole switch. I assume you could solder the lugs together on a multi-pole switch to make a 2-pole. I going to get a quote from mouser first on the alpha. Thanks for the help.

 

[velo-hobo]

The Alpha switch from Mouser could be considered a 4-pole - 2 decks, 2 poles per deck.  The Allparts one looks like pretty much the same exact thing, so it should be fine to wire up as shown in Mako's rotary switch wiring guide.

 

[Bobby Baird]

Bought the Allparts 6-position alpha switches. They are just like the 5-way that mako recommends with the extra position. Should work out great for the extra ratio. Thanks velo-hobo for helping me find the parts. I had to order a couple more things from mouser, but I believe I have every part to build my 2-1176 with various mods. I do want to hear from other members about stepped pots for input and output for better stereo tracking. I have been looking at the elma's. I would need to make a bridged t-pad attenuator for input, but I think 1db steps might be to much for input. Outputs could be more like 2db steps. It my be eaiser to just do stepped outputs and try to match input as best as possible with the variable t-pad's.

 

[Bobby Baird]

Here is a diagram of the 2:1 ratio mod I came up with for the 6-position Alpha switch. If you are looking at the back of the pcb and pot it should be noted that to have the 2:1 next to the 4:1 instead of placing it after the slam position. The pot will have to be rotated one position clockwise relative to the pcb board to mimic Mako's Slam pictorial, as well as his jumper positions being soldered one position over clockwise http://mnats.net/1176_slam_mode_rotary.html. By shifting the pot one position relative to the ratio pcb board you effectively give you the 2:1 switch position full ccw next to the 4:1. As long as you make sure the wiper on the pot lines up with the position in the picture you should be fine.

 

[Bobby Baird]

Completed build! Features 2:1 ratio, 130 hpf, capi bypass relay, link boards, and slo-mode ala 1176 ae, but with one exception instead of the 10 mS slow attack of the ae version, I used a cap for a 30 mS attack time. This will be comparable to the slowest attack setting of an ssl buss compressor.

 

[velo-hobo]

Slick, what are those CAPI relays zip-tied to?  I got them and realized they're meant to plug into another PCB (custom or otherwise intended for those) - doh, no provision for mounting to standoffs included.  I might 3D print some little brackets to hold them (have a makerbot at my work and would be a cool excuse to use it for something functional!)

Also, would love to see a close-up photos of your ratio switch assembly, but that might be hard now that they're in place!

I have a slightly different idea for the ratio scheme, will post photos once I get it put together.  Been very busy with work and other stuff so not making much progress on my builds at the moment.

 

[Bobby Baird]

I bought these for the relays http://www.mouser.com/Search/ProductDetail.aspx?R=PP1S-S10-Xvirtualkey64400000virtualkey644-PP1S-S10-X. Buy 4 and screw 2 together for each set of relays to make a relay holder, and then bolt to case. Remember when you bypass input to output on the first relay the second one is to take the output transformer out of circuit so you don't have loading when in bypass on the output. First relay as follows: input xlr goes to "O" pins. "A" pins goes to t-pad, and "B" pin goes to output xlr. For the second relay take the red and blue wire from the output transformer and wire to "O" pins.  "A" pins will go to output xlr, and the B pins will be empty, so in bypass the transformer will be out of circuit. Here's some photos of ratio switch. It's IMPORTANT you slide the M.Nat's slam wiring scheme down one position are else you will be left with 2:1 clockwise after slam. Check out my picture above of the ratio layout and you will see what positions goes with which ratio as you turn the rotary switch. It took me a night to wrap my head around it, but it works great. What I did was turn the rotary switch to the furthest clockwise position which will be your slam position you will need to bridge those decks as in M.Nat's pictorial and the 4:1 decks. Leaving 2:1 out of loop like I did or you could wire the 2:1 in the slam loop there's no rules, but it sounds like slam to me how I set it up. Here's some photos.

 

[Bobby Baird]

See how you have to turn the whole switch over one position to address the new 2:1 position relative to the pcb.  Instead of straight up and down as in M.Nat's rotary wiring guide. I have both 5-way and 6-way switches an the extra position on the 6-way is clockwise instead of counterclockwise relative to the 5-way switch. So to compensate you must turn the whole 6-way switch relative to the pcb board to achieve 2:1 @ the counterclockwise position. Here's a photo of the slo-mode switch. With caps on the attack switch you will have to bridge the c27 .022uF position on rotary pcb.

 

[velo-hobo]

Thanks for that - didn't realize I needed a pair of relays for each channel, but makes sense to take the OT out of circuit too.  I'll need to buy some more from Jeff.

Still might make some 3D printed brackets but we'll see.  I haven't gotten to thinking about layout yet, just been stuffing all my boards and gathering parts for my mods.  I'm building 3 stereo units so probably a good idea to move slowly.

 

[Bobby Baird]

I had a better idea of how you could use the capi relays with the headers mounted on some vector board and just solder some flying leads or connect the header underneath the vector board to some barrier strip terminals to connect your shielded balanced wire to. This approach might be more elegant than brackets.

 

[Janalex]

Hi all,

My first post on the forum. I'm going to build one of these units and am about to order the parts. Has anyone compiled a complete bom for this project?  I was going to start by ordering the stereo bundle kit from hairball,  case from collective cases, 2 mouser rev d carts, a pair of meter and ratio boards, and pair of mnats rev d boards. We were going to build the power supply on each board instead of the dual supply. I think this only leaves the rotary  switches and all the pots to add to the mouser kart... Can you please confirm the part numbers for all the pots and rotary switched as well as the knobs?

 

[Bobby Baird]

Hi, Janalex

Welcome to the forum, first off there are a few things on the mono bom provided by hairball that are not added for a stereo build, such as switches and rotary knobs, power indicator lamp, lamp bulbs, transistor socket's, shrink wrap, wire if you don't have it, and lamp and led resistors. First, I would like to ask you, do you intend to run the 2-1176 stock or do you intend to hot rod-it. This will determine the parts one will need. I strongly recommend reading through this thread to get a grasp of options available. Do you intend to link them, or run them dual mono? Why not have one power supply? Have you used mouser before? Is this your fist diy project? Do you have this http://mnats.net/files/1176LN_REVD_V2.2_DOC.pdf?
Any how you are going to need a power switch which is pretty important that's not listed on the mono bom. Dan's case is pretty narrow between 2: link, and bypass dpdt switches that leaves a bit of room for the power switch. I had to go into the c&k datasheets to figure out the one that would fit. You will need to learn how to decipher component datasheets and the parts # schemes. Are else you will end up buying a part that won't fit. It's is very important to double check yourself. Don't assume someone's bom will cover your build or fit your front panel. It's better to be safe than sorry.

Mouser's site is down for maintenance right now, but you will need 2- Alpha 4-pole 3-position rotary switch for meters. 2- Alpha 2-pole 5-position double deck rotary switch for ratio. 2- Output control pot's 250k audio taper. 2- 25k attack pots. 2- 5m release pots.

 

[Potato Cakes]

One thing I think that made the biggest difference with my build was to remove the stereo link boards and replace it with a 600r output termination switch.  I was able to get my 2 channels close enough that the few times I would use link will be fine without the link boards.  The matching was pretty close!  But the added benefit of being able to switch the 600r in and out was huge (both channels on a stereo switch).  That is one a number of you guys may want to try or heck its DIY just add a few holes and have both link and the 600r's on the outputs.

Dan, do you have the model number for the termination switch and the stereo switch you used?

Thanks!

Paul