All things G1176 - the new "repost" thread.

[kenrinc]

guitarguy,

What are you using to input the test signal? Generator output should to to pins 2 and 3 on the input XLR. Makeup a test cable with one end male XLR and the other end with a jack for your audio generator. Test for signal at the XLR first. That is the pins on the back of the XLR. Then test for signal at the primary of the Lundahl followed by the secondary side. I didn't use Lundahl and the boards have a different layout for them but it doesn't mean anything other than you need to figure out which traces have that signal. Then you can go to the top of the input pot and check for signal there while adjusting input pot.

$.02

Ken-

 

[guitarguy12387]

Hey Ken,

Thanks for the input. I'm using an oscillator. 1khz sine wave.

I found a critical error: I was unaware that my input jacks (i'm using TRS jacks) are shorting when i put a cable in. So when i switched the wires to the opposite side, it works!!!

I also had two wires on the input knob backwards. That caused the input pot to be quite inconsistent. Thanks again for the help!

 

[Leffe111]

Hi everybody.
I´ve just finished a 2-1176 with the Mnats rev J pcb:s.
Connect a mic through my preamp, through the 1176 and into the recordingdevice.
There´s sound on both channels, and input resp output level works on both channels.
But, the sound is so, so thin, just like if you put two singlecoils out of fase with each others. The gain isn´t very hihg either. I have +30/-10V into the cards.
It´s not calibrated yet, except for the "gr meter zero"
The meters are not moving at any meter settings.
I´m using OEP input /output trafos.
Any suggestions where to start.
Best regartds
Leif

 

[Svart]

Hmm, I've been playing around with getting rid of the hum in my unit for a couple days now.  It's a dual unit, using Jakob's rev 7 PCBs.  When I increase the gain I have 120hz hum (around 50mv at full gain) coming from both boards.  Both boards have had BOTH of the ground trace cuts done with no real improvement with either.  I have redone the grounding a couple of times, trying full chassis grounding; running 10ga wires from the PCBs to the star point; running 10ga wire from only the input XLR/TRS to the star ground; running both input AND outputs to the star ground point, etc. 

I've even tried removing the power supplies from one of the boards and powering both boards with the rails from one board..  Still hums.

Last night I tried removing both power supplies and I built an external power supply and ran it into both PCBs.. still hums, just a little less.

The scope shows a 120hz saw-type waveform of around 100mv on both the 24 and -10v rails.  I have added around 2000uf to both rails and still have not seen this drop at all..  Which really puzzled me..

My toroid is 15VA but doesn't run hot and does not hum at all so without further troubleshooting I am fairly certain that it's not overloaded.

Any other things to try?

 

[Svart]

More strangeness..

I removed the raw DC source from the PCBs and looked at it by itself..  nice, clean DC.  Once I connect the DC source back onto either PCB I get a sawtooth waveform about 100mv in amplitude.  Very very strange.  I now have 3000uf on each rail with no change in the conditions.  It seems that the regulators might be oscillating??

 

[kenrinc]

Any suggestions where to start.
Best regartds
Leif

Start at post #1558 it's currently on page 78 I believe (they've changed things around so it's somewhere around there) Look for gswan's/kenrinc posts on diagnosing signal.  He helped me tremendously.

Ken-

 

[s2udio]

on both the 24 and -10v rails. 

should'nt that be +30 and -10 ?

My toroid is 15VA but doesn't run hot and does not hum at all so without further troubleshooting I am fairly certain that it's not overloaded

15va for a dual seems a little small ,check the ac voltage,i used a 25-0-25 @35va
check gswans site here
http://www.axtsystems.com/index.php?view=article&catid=34%3A1176ln&id=45%3A1176lncircuits&option=com_content&Itemid=62

 

[Leffe111]

Ok
When I connect a mic to the preamp, through the 1176, and in to the back of my EMU1820m breakoutbox(wich is tele balanced inputs) the sound gets thin, cind a out of phase. Going from the 1176 to the front(preamp input, xlr) of the 1820m, the sound seems normal. Seems like something with hot/cold/ground-signal connection.
Any suggestions anyone? Will calibrate next week.
Leif

 

[Svart]

should'nt that be +30 and -10 ?

yes, sorry I was thinking about the 24v regulator.

I'll try to find the source of the strange saw waveform tonight.

 

[Svart]

If I adjust Qbias around a bit I can make the hum go away.  I don't know how this affects audio performance yet though.  I still can't get the saw waveform killed yet and I don't know why..  It's a mystery.

 

[danjpiscina]

hi. i'm a total newbie. i want an 1176, so i built one (MNATS Rev. J with OEP i/p o/p transformers) but the most confusing part (for me at least) is the power transformer wiring. I have an "AMVECO toroid 22V, .682A :

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=TE62055-ND

it seems to be the transformer most people are using. has anyone successfully wired it with the 1176? can you walk me through it? any help would be MUCH appreciated.

Thanks for listening

dp.

 

[Echo North]

I think ideally you want a 24v transformer...but 22v should be fine.

I'm far from experienced myself, but I'll give this a try using your datasheet (from digikey) and Mark Burnley's page.

http://www.diyfactory.com/data/transformer_connections.gif

For the 120v primary (I see you're in the USA) I believe you want to go:
Violet/Black - Live
Red/Yellow - Neutral

For the center tap secondary:
Red/Brown - Center Pin (Center Tap=0v)
Blue - One of the side pins (22v)
Green - Other side pin (22v)

That should do it.

Mike

 

[gyraf]

I think (as mentioned earlier) that 22VAC is too little to give us the needed 30VDC (but it will depend on individual transformer manufacturing differences)

IMO, 2x24V is a bare minimum for the G1176

Jakob E.

 

[Leffe111]

Ok
So it was a hot/cold/ground issue that caused the "thin" signal. Gone now.
BUT!!
Have a software program, and i´ved sent -10dB into the 1176, output on max, input up till  +1dB is reached, down to 0VU with the q bias trimpot. So far so good.
But I can hear nothing or see on the meter, when i´m turning the attack or/and release pots. Both cards behaves the same!?!, (have built two monos in one case).
Gain is high.
Ratio seems to work(don´t know if it works as it should though)
Would really appreciate any input here.
tjoflöjt
Leif

 

[skal1]

at any how knows


I am about to bill a  mnat j version what is the current rating for a dual unit and is their a source in uk for this tx


regards

skal 1-2

 

[MartyMart]

at any how knows


I am about to bill a  mnat j version what is the current rating for a dual unit and is their a source in uk for this tx


regards

skal 1-2

I have not got to my "dual" just yet, but I bought the pwr traffo from Farnell, it's a 25-0-25 and 50VA - I think
it's a Clairtronic brand.
That will work fine and dandy for a dual.

Marty.

 

[gemini86]

I think (as mentioned earlier) that 22VAC is too little to give us the needed 30VDC (but it will depend on individual transformer manufacturing differences)

IMO, 2x24V is a bare minimum for the G1176

Jakob E.

I'm running a 2x22 @ 1.32A, with such a small load on it, I'm getting 30v no problem...

 

[Mylithra]

When you wire the Stereo interconnect, is one unit's controls suppose to control the others? If so, which unit is the control master?

 

[skal1]

nice 1
Marty


regards

skal1=2

 

[gswan]

Have a software program, and i´ved sent -10dB into the 1176, output on max, input up till  +1dB is reached, down to 0VU with the q bias trimpot. So far so good.
But I can hear nothing or see on the meter, when i´m turning the attack or/and release pots. Both cards behaves the same!?!, (have built two monos in one case).
Gain is high.
Ratio seems to work(don´t know if it works as it should though)
Would really appreciate any input here.
tjoflöjt
Leif

Leif,
The calibration procedure for the GR meter that uses the attack pot (on and off) is expecting the GR disable switch to be on the attack pot to enable/disable the GR amp. If you don't have this then leave the attack pot alone and meter the GR whilst enabling/disabling the GR amp using whatever method you have constructed to do this.

Geoff