[BUILD] 1176LN Rev D DIY

[markblasco]

What happens if your transistors for Q12 and Q13 aren't matched?  The hairball manual mentions using a multimeter with a tester to find two which match within 10%, but my multimeter doesn't have a tester on it.  If I just pick any 2, am I going to have problems, or do I need to go and buy a new meter which has those testing abilities?  There are 7 transistors with the same number, and there's no mention of matching any of the other ones, so I don't know if I can just put all of them in randomly, or if it's really important that they match.  Any help would be appreciated, thanks!

 

[mattvon]

What happens if your transistors for Q12 and Q13 aren't matched?  The hairball manual mentions using a multimeter with a tester to find two which match within 10%, but my multimeter doesn't have a tester on it.  If I just pick any 2, am I going to have problems, or do I need to go and buy a new meter which has those testing abilities?  There are 7 transistors with the same number, and there's no mention of matching any of the other ones, so I don't know if I can just put all of them in randomly, or if it's really important that they match.  Any help would be appreciated, thanks!

I'm far from an expert, but while I'm waiting for help with my issue I'll try to give you what I've gleaned.  In posts I've read, it is important that Q12 and Q13 need to be fairly closely matched, and the higher the hFE the better.  Do you know someone from whom you could borrow a meter which can test for hFE?  You'd need it for about 3 minutes, you could even call around to see if an electronic shop would let you measure your transistors to keep from having to buy one.

 

[JohnWatkins]

Just finished my second 1176 project.  The first was a pair of full kits from Mnats/Hairball.  This time I used mostly the same components, but I tried to branch out a little on my own too.  Both channels worked perfectly right out of the box, which was a big relief.  Thanks to Mike and Mnats for the great parts.

 

[mattvon]

Ok, thanks for helping me to understand the ground relationship.  When I referred to the ground near the L-pad, I meant the bare wire from pin 1 of the XLR.

I've checked and verified that I have .775VAC at the XLR by using one DMM lead on pin 2 and one DMM lead on pin 3.

I then checked and verified that I have .775VAC between the wire from pin 2 and pin 3 of the XLR before I soldered these wires to the L-pad. 

As soon as I connect the wire from pin 2 of the XLR to the "+" pad on the L-pad input and the wire from pin 3 of the XLR to the "-" pad on the input side of the L-pad, I get 0.00VAC at pins 2 and 3 of the XLR (as well as the "+" and "-" input pads of the L-pad).

I also get 0.00VAC when measuring between the "+" and "-"at the output pads of the L-pad. 

Rotating the L-pad fully CCW or CW has no effect on this reading. 

I checked and verified once again that I have .775VAC coming out of my signal generator.

Thanks for everyone's help and patience with this.

Pull the t-pad out of the case  if it's bolted to the front  and check your soldering there - if you can post a pic, it may help.

Ok, here are two pictures of the soldering on the L-pad, top and bottom.

I've checked continuity on the L-pad, no connection between the input and output "+" pads (regardless of position of rotation, CCW to CW), connectivity between the input and output "-" pads.  I also checked between each "+" to "-" pad for continuity, found none.

Bumping this up...I'm thinking I've got a faulty L-pad, as the voltage disappears as soon as I attach the "+" and "-" wires, but want to make sure I'm not missing anything else before I go about ordering another.  Appreciate any help that's given...

 

[Echo North]

Remove the wires and test the resistance between the - and + pads on the input side of the Tpad PCB.

Mike

 

[Echo North]

What happens if your transistors for Q12 and Q13 aren't matched?  The hairball manual mentions using a multimeter with a tester to find two which match within 10%, but my multimeter doesn't have a tester on it.  If I just pick any 2, am I going to have problems, or do I need to go and buy a new meter which has those testing abilities?  There are 7 transistors with the same number, and there's no mention of matching any of the other ones, so I don't know if I can just put all of them in randomly, or if it's really important that they match.  Any help would be appreciated, thanks!

You could have a hard time getting the NULL adjust to zero out.

Mike

 

[babaorum]

I have the same pb than Mattvon , nothing move on the meter when I test ratio 20 at 1K.

But I have maybe a big mistake in my wiring. I make a rotary version and I would to be sure :
The + and - from the meter pcb goes to output XLR or connectors of the VU-meter ? because I soudered the X and Y to the output XLR and +/- to the Vu-meter ... ? is it ok or wrong ?

Thanks for your help

 

[andyfromdenver]

What happens if your transistors for Q12 and Q13 aren't matched?  The hairball manual mentions using a multimeter with a tester to find two which match within 10%, but my multimeter doesn't have a tester on it.  If I just pick any 2, am I going to have problems, or do I need to go and buy a new meter which has those testing abilities?  There are 7 transistors with the same number, and there's no mention of matching any of the other ones, so I don't know if I can just put all of them in randomly, or if it's really important that they match.  Any help would be appreciated, thanks!

  Even the cheapest meter from super gross stores like Harbor Freight will give you a roughly accurate hfe reading.  $3 well spent.  I think you should absolutely measure them before you solder them in, you will be kicking yourself in the groin if you have to go back and desolder and put the correct ones in when/if there is a problem. 

  As an aside yet relevant, all 20 2n3708 in my bom were under 250 hfe (220-240), thankfully a friend is nearby who is building all this gear and he gave me some, he didn't believe me cause the 2n3708s are supposed to be much higher, but perhaps some batches get through that are "bad".

  Another aside, I personally feel like i'm cheating to build this gear when I don't understand how the circuit works (but I am actively learning), which is why I have languished in the tube guitar amp world for the last couple years (very understandable).  It's astoundingly awesome that this stuff has been broken down to a level that we can build it.
Imo, anyone else in that category should follow one simple mantra, "Do exactly as the instructions state".  Until you understand the reasons (thanks for the exp. Mike) it's the only way to guarantee your hard earned money will not go to waste.  And at the end of your "cheating" you will own a super amazing piece of studio gear!!

Best wishes with the build!
Andy

 

[andyfromdenver]

@Mattvon, have you checked for continuity from your 2 conductors to the sheild wire?  Perhaps in stripping them there is an exposed +/- that is grounding, or the insulator melted from heat??  I have to imagine the tpad is fine, and the problem is St. Elsewhere.  Also, did you rub off the grounds on the in-tran pcb and xlrs?  (i'm guessing so, just exploring possibilities)
Really hope you figure it out!
Andy

 

[markblasco]

Well, the only meter I could find near me with the HFE testing was $70, so I guess I'm going to have to do some searching online to find one cheaper if I do this build again.  I was able to get them tested this time, but I don't know if I'll be as lucky next time.  Mine all measured between 300-330.

 

[markblasco]

And now of course I do a quick amazon check and see some there for $8 which have the same tester.  I guess I'll end up just ordering one of those for future builds (assuming I get this one working correctly).

 

[mattvon]

Remove the wires and test the resistance between the - and + pads on the input side of the Tpad PCB.

Mike

Hi Mike,

Thanks for responding--I get 1.02kOhms between the + and - pads.

 

[mattvon]

Okay, with great happiness I report I had, of all things, an intermittent fault in the cable from my signal generator?!?  Oh well, I'm very glad to report I've successfully gotten my Q-bias calibration completed!

But...as with many things, the good news comes with some bad...I'm on to the next calibration step and I can't zero the VU meter with the gain reduction pot (accessed through the case on the front.  I've got the jumper set to the two pins furthest away from Q13, so I believe it's shorted.

The problem is, no matter which direction I turn the zero adjust pot, I don't get any movement on the VU meter at all.  I do get a range on my DMM of .12VDC in the extreme CCW position to 1.64VDC in the extreme CW position...but the VU meter never moves at all.

I'm confident the VU meter is working, as I was able to us it to set my Q-bias and it responded as expected.  Anyone have any experience with this?  All help appreciated!

 

[babaorum]

- I can do the first calibrating (GR -> 0dB with the bias trim and set '0' ).
- Nothing happens for the second (+4 and ratio 20:1 input and bias in all the range = nothing happens)

My meter potentiometer is like that :

Is it normal because the meter's pcb is right rear , should I change the position of the tab control of the meter ?

 

[andyfromdenver]

@matt, cool!  Hope you get it going soon

*edit* huge post about putting c7 e-lytic in backwards and having DC on my pot.
It's amazing how hearty the circuit is when it still sounds good, compromised!

Question, if C7 is a film, it's ok to be non polarized, but if using an e-lytic, it must be polarized? 

 

[Larsson]

So i´ve finally wrapped up my dual 1176 rev D and everything is working fine, except the Bourns T-attenuator on my right channel.
When i turn the pot a glitching sound is heard and at one point i get no signal in. This is if I really finetune the attenuator to a certain "sweet spot" where it dies. Otherwise it works. Its enough just turning the pot 1mm. Anyone who has experienced this? Is my attenuator broken?

Gotta say i love the fat sound from this unit!

 

[babaorum]

cool ! could you give a  detailled picture of the inside, maybe I could see why I'm wrong with my first channel of my stereo unit ?
Thanks
Regards
Baba

 

[mattvon]

Okay, I have a working compressor!!!  Well, almost fully working.

Even still, I'm very stoked.  All the ratio buttons work as expected, input and output work too, sounds amazing--hum free, smooth compression, etc.

Meter works in +4 and +8 modes (even though I haven't gotten past calibration step 2) but I still can get any movement at all with the zero pot on the VU when in GR mode.  I've tested the wires for continuity and the pot seems to be working as it should, but I'm open to suggestions.  I appreciate all who helped me make it this far!

 

[dmnieto]

Okay, I have a working compressor!!!  Well, almost fully working.

Even still, I'm very stoked.  All the ratio buttons work as expected, input and output work too, sounds amazing--hum free, smooth compression, etc.

Meter works in +4 and +8 modes (even though I haven't gotten past calibration step 2) but I still can get any movement at all with the zero pot on the VU when in GR mode.  I've tested the wires for continuity and the pot seems to be working as it should, but I'm open to suggestions.  I appreciate all who helped me make it this far!

Do you actually have any compression happening?
Set the meter at +4
Drive the input quite hot with the attack pot in "off", and then modify the output pot till you show 0dBu. When you switch it to on (by going to, for example 5). Do you see a drop in the meter?

 

[mattvon]

Okay, I have a working compressor!!!  Well, almost fully working.

Even still, I'm very stoked.  All the ratio buttons work as expected, input and output work too, sounds amazing--hum free, smooth compression, etc.

Meter works in +4 and +8 modes (even though I haven't gotten past calibration step 2) but I still can get any movement at all with the zero pot on the VU when in GR mode.  I've tested the wires for continuity and the pot seems to be working as it should, but I'm open to suggestions.  I appreciate all who helped me make it this far!

Do you actually have any compression happening?
Set the meter at +4
Drive the input quite hot with the attack pot in "off", and then modify the output pot till you show 0dBu. When you switch it to on (by going to, for example 5). Do you see a drop in the meter?

I do, I see a significant drop in the meter when following the conditions above.  The needle drops to about "-4.5" when I switch it on.  I also hear a significant drop in sound level.