[BUILD] 1176 Rev F/G - new board, new transformer!

[Kingston]

more on the caps.. This unit seems really sensitive to changing them around. I tested a 1uF polyprop on C9 (was 47uF electrolytic), since it doesn't need a big 47uF dc removal cap in there apparently. The difference can be heard, and it makes sense to use a quality film cap here instead. Although it's fun to play around with these. The electrolytics don't sound worse actually, just a little different. I think I'll leave it in for the other channel.

And then further, I happened to have some unnecessarily large sized Solen 0,22uF film caps around. In they went to replace those small Panasonic SMF (under the board this time). They do sound better, further enhancing accuracy on transients.

I really need an oscilloscope now. I want to *see* what's happening.

 

[YLab]

Why have you changed C9 47uF to 1uF? and C10 1.0uF to 0,15uF?

C10 (.15uf) on the rev.F is identified as C8 on the rev. D ...   and C9 (1 uf) on the rev.F was identified C7 on rev.D.

Same values for the same positions on both revision   :

Hubert

 

[Kingston]

Same values for the same positions on both revision   :

Hubert

Not on the gyraf 1176 version, that the original mnats rev F is based on, they aren't!

http://www.gyraf.dk/gy_pd/1176/1176sch.gif

I don't know where jacob got those values vs. the JBL pro schematics...

 

[YLab]

Same values for the same positions on both revision   :

Hubert

Not on the gyraf 1176 version, that the original mnats rev F is based on, they aren't!

http://www.gyraf.dk/gy_pd/1176/1176sch.gif

I don't know where jacob got those values vs. the JBL pro schematics...

Oups, sorry for that,,  now i see!

Hubert

 

[danjpiscina]

Hi Guys. I'm wiring mnats rev F with Hairball i/p and o/p transformers. is there an official wiring guide around here? lots of wires on the output one and it's kind of freaking me out! Don't want to get something wrong and fry the board! Thanks for listening.

DP.

 

[danjpiscina]

anyone? anything?

 

[mnats]

Dan, I designed this new board to do two things - to remain true to the original Rev F as much as possible and to match the overall dimensions and layout of the Rev A and D. As with all my boards I believe that the best reference is the original schematic as far as wiring them is concerned.

But if you need a pictorial drawing you could probably refer to Skylar's Rev D drawing for most of the circuit as the wiring itself is very much the same. Watch out for the output pot wiring as I changed the pads around slightly from the D - the pads are numbered right on the board so just match the numbers to the pot in the drawing. The output transformer colors are printed right on the board as well. For the secondary of the output transformer, just refer to the schematic linked from the first post: tie violet and green together for point X then tie grey and blue together to get point Y. X and Y feed your meter switching and are your outputs that go to the XLR.

 

[danjpiscina]

Ok. Thanks Mako. So just to be sure, I need to put a 470Ω and a 0.022uf on the attack pot, a 270k on the release, and two 620Ω on the input? Forgive me, it's just it seems a lot has changed since the last time i tried to put one of these together! Also I can't seem to find any specs on the power transformer included in the kit. The color coding seems to change all the time! Any ideas? Thanks again,

Dan P.

 

[Echo North]

Ok. Thanks Mako. So just to be sure, I need to put a 470Ω and a 0.022uf on the attack pot, a 270k on the release, and two 620Ω on the input? Forgive me, it's just it seems a lot has changed since the last time i tried to put one of these together! Also I can't seem to find any specs on the power transformer included in the kit. The color coding seems to change all the time! Any ideas? Thanks again,

Dan P.

The attack and release pot resistors and caps should be the same.  The attenuator on the input does not require additional resistors like the original two deck model.

Wire it like so:
http://hairballaudio.com/web_images/attenuator.jpg

The power transformer shows the winding information on the side of it.  Follow the 120V primary (since you are in the USA) and the center tap (split) secondary here:
http://www.diyfactory.com/data/transformer_connections.gif

Mike

 

[simonrussell77]

I made a stereo mnats rev f with the Hairball kit (matched fets, transformers etc..) Sounds fantastic! Just thought you all might like to know of a mod I (and probably many others...) came up with to get a better signal to noise ratio. It's quite simple.. I added a switch that puts a 100k resistor in series with the link between (22) on the pcb and the 'GR off' switch. This makes the threshold higher and allows more input before gain reduction. In situations like vocal tracking this allows for subtle compression without having to turn the input down and the output up - which adds noise. 100k gives about 4db less gain reduction.

Thanks to Mako, Mike and Ed for all the great work. Unbelievable!

 

[danjpiscina]

Hi guys. I finished wiring my Ref F and powered it up. All seemed fine and I left it plugged in for a little while. The meter went to 0 like it should. I then unplugged it and brought it from the work bench to the studio. Plugged it in and hooked it up to an insert. I got a loud feedback that went away as soon as the output was cranked to the max. Then I heard it passed audio. It was distorted and I got no GR. After about a minute of playing with it (hearing the ratio switches produce strange oscillations) I started to smell smoke. I fried R36 (100 ohms). Quickly unplugged it. Does anyone have any ideas? Did I fry Q6 & 7 as well? Thanks for listening!

Dan.

 

[danjpiscina]

Anyone? I'm SOOOO close! Also, how is the VU lamp supposed to be wired on this board?

 

[danjpiscina]

Mike? Mako?

 

[Echo North]

The VU lamp can be wired from the secondary of the power transformer.  You'll want to use a voltage dropping resistor.

See here:
http://www.groupdiy.com/index.php?topic=20058.msg417594#msg417594

Not sure about your other issue.  Check your transformer wiring...check your resistor values...check your component placement....

Mike

 

[danjpiscina]

Thanks Mike. Got it up and running. It sounds pretty great! My other problem was a strange one. Once I replaced the 100 ohm and all transistors in the signal line amp, it worked fine. I'm thinking about building a pair of blue stripes now!

 

[regularjohn]

I recently built a Rev A using mnat's pcb, and I love it!  
Just curious if anyone's built the rev F pcb as a Rev G with the ic input?  I'm thinking of building a comp that's a bit cleaner (less coloration) than the Rev A.
I've got my la2a and Rev A that I've built that are really colored, and then my gssl that's ultra clean.  I'm looking for something in between those extremes.  Just curious if the Rev G might be it.
Thanks!

 

[regularjohn]

In the midst of building my dual Rev G!

I was looking up the resistance values for the ratio boards.  I noticed that the only difference is the 10M resistor parallel to S1A that is on the Rev D schem but not on the Rev F/G schem.  However, the 10M is on the ratio pcb for the Rev F/G.  What exactly does this resistor do?

 

[Echo North]

In the midst of building my dual Rev G!

I was looking up the resistance values for the ratio boards.  I noticed that the only difference is the 10M resistor parallel to S1A that is on the Rev D schem but not on the Rev F/G schem.  However, the 10M is on the ratio pcb for the Rev F/G.  What exactly does this resistor do?

It prevents "pops" that can happen when the circuit goes open between ratio selections.

I would try adding it and if it causes weirdness replace it with a jumper.
just remove it and put nothing there.

Mike

 

[regularjohn]

Cool, thanks Mike!

 

[Echo North]

Please see my edit.

I cannot imagine why having the 10M in there would cause any issues, but if you decided not to use it, DO NOT replace it with a jumper.  That would permanently close that part of the switch.

If you decided not to use just leave it out with no jumper.

Thanks,

Mike

ps: A kind thank you to the person who pointed out my misstep.