Everything powers up fine........I just got done with my A12 and J99... my A12 has a low dirty signal... and J99 has a low clean signal... with input and output all the way up!?!?!?!? My A12 is the first pre in the chain.... if that's faulty, would that affect the J99?
Help!
LOW LEVEL SIGNAL ON MY J99!!!!!!!!!!!
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LOW LEVEL SIGNAL ON MY J99!!!!!!!!!!!
by agno » Sat Nov 26, 2005 9:40 am
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by tele_player » Sat Nov 26, 2005 12:07 pm
Why not unplug the A12 and see if it changes?
Are the voltages on the J99 opamps correct?
Are the voltages on the J99 opamps correct?
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by agno » Sat Nov 26, 2005 1:15 pm
tele_player \$m[1]:Why not unplug the A12 and see if it changes?
Are the voltages on the J99 opamps correct?
everything looks fine but U3, pin 4 and 8 are reading at about +/-4.5V. If I'm using my common sense right... I'm reading the board accordingly... starting from the upper left pin on U3 which is to be pin#1... so the bottom 2 parralell from each other should 4 and 8 right? If so... that's waht I got... I checked U6 and U7.... they're fine.. I don't know what else to check...
Oh on my A12..I had a reversed diode.... all the tests on that are fine now.... to be honest that's what I forgot to do... was to test the damn thing... Let me know what you think.....
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by tele_player » Sat Nov 26, 2005 5:25 pm
U3 should be running at +/- 12V. The following diagram will help you:
http://www.analog.com/en/prod/0,2877,AD712,00.html
(I found this by google search for 'ad712 pinout')
Remember - voltages are referenced to ground, so you'd put one of your meter leads on ground somewhere on the board, and use the other to measure the voltages at pins 4 and 8. Pin 4 should be -12, and pin 8 should be +12, and they should be correct within +/- 5%.
http://www.analog.com/en/prod/0,2877,AD712,00.html
(I found this by google search for 'ad712 pinout')
Remember - voltages are referenced to ground, so you'd put one of your meter leads on ground somewhere on the board, and use the other to measure the voltages at pins 4 and 8. Pin 4 should be -12, and pin 8 should be +12, and they should be correct within +/- 5%.
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by agno » Sat Nov 26, 2005 8:10 pm
Thanx Tele...now that we have that all sorted out... I'm having another problem...
Everything is works but the signal is HOT! Way too hot... I'll have both Input gain and output trim all the way down, and still get a pretty good level. The funny thing is that no matter how hot the signal I'm not distorting??? They sound awesome but both the J99 and A12 are about 3-4 notches louder than my MP2NV and TG2. I'm also getting sound pressure...(airy noise) that I would get if I cranked up my other pres full blast at about 11-12 O'clock.... WTF is going on? Someone help me please....!
-Agno
Everything is works but the signal is HOT! Way too hot... I'll have both Input gain and output trim all the way down, and still get a pretty good level. The funny thing is that no matter how hot the signal I'm not distorting??? They sound awesome but both the J99 and A12 are about 3-4 notches louder than my MP2NV and TG2. I'm also getting sound pressure...(airy noise) that I would get if I cranked up my other pres full blast at about 11-12 O'clock.... WTF is going on? Someone help me please....!
-Agno
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by tele_player » Sat Nov 26, 2005 9:59 pm
What did you change? You wrote above that you were getting a 'low clean' signal?
From here, it's hard to tell what's going on. Have you tested that the trim pot works? Have you tested that the gain switch works? Have you double-checked the wiring and jumpers of your input transformer?
From here, it's hard to tell what's going on. Have you tested that the trim pot works? Have you tested that the gain switch works? Have you double-checked the wiring and jumpers of your input transformer?
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by agno » Sat Nov 26, 2005 10:33 pm
tele_player \$m[1]:What did you change? You wrote above that you were getting a 'low clean' signal?
From here, it's hard to tell what's going on. Have you tested that the trim pot works? Have you tested that the gain switch works? Have you double-checked the wiring and jumpers of your input transformer?
Well the first time.... I forgot to test both pres.... A12 and J99.... I forgot to adjust the voltage regs... and I had a reversed diode on the A12.
Now I've done every single step.... I am a little confused on the jumpers.... J1 and J2.. are you supposed to jumper across them with one jumper - what I did was a put one jumper over the top pins... one on J1 and one on J2... to it's parallel to the input tranny. The wiring is fine also....
The trim pots seem to be working fine.... the stop is also in the correct spot.
but mind you ...... I'm having the same problem with my A12.........Does it have to do with the voltage? Everything is up to spec...... I was thinking maybe it has something to do with the jumpers, on my DMM it registers zero ohms.... is this right?
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by agno » Sun Nov 27, 2005 2:21 am
Okay......I went back, U3 pin 4 & 8 are reading at +/-24.1V... really wierd... because at first it said +/-12V like it should, then I tried it again.. it said +/-24.1V and it stays that way now... I wasn't sure if I did it right the first time... that's why I went back... and it's definitely +/-24.1V ........ (mind you I put the negative of my DMM on pin 4 and Positive on pin8) is that the way I'm supposed to do it.... or could this be the problem? If so, why would get the same hot signal with my A12??? Could it be the PS03? Maybe my power harness?
I'm an amatuer taking a shot in the dark here fellas, thanx ahead for your input......
-AGNO
I'm an amatuer taking a shot in the dark here fellas, thanx ahead for your input......
-AGNO
- agno
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by tele_player » Mon Nov 28, 2005 9:02 am
You measured incorrectly. The negative lead goes on ground somewhere on the board, use the other to measure the voltages. 24v between pins 4 and 8 is correct, so I'd bet there's nothing wrong there.
Your PS03 is probably fine, otherwise the above voltages would probably be wrong.
What are you plugging these preamps into? They should go into a +4 line input. If they're going into a -10 device, they'll both seem real hot.
Your PS03 is probably fine, otherwise the above voltages would probably be wrong.
What are you plugging these preamps into? They should go into a +4 line input. If they're going into a -10 device, they'll both seem real hot.
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by agno » Mon Nov 28, 2005 4:03 pm
tele_player \$m[1]:What are you plugging these preamps into? They should go into a +4 line input. If they're going into a -10 device, they'll both seem real hot.
I'm plugging them into my balanced patchbay to my rosetta which is calibrated at -10dB. That makes sense but... why are my other pres (MP2NV and TG2) substantially lower than the A12 and J99? Even with an inline pad my SCA's are hotter than them.
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by agno » Mon Nov 28, 2005 4:03 pm
tele_player \$m[1]:What are you plugging these preamps into? They should go into a +4 line input. If they're going into a -10 device, they'll both seem real hot.
I'm plugging them into my balanced patchbay to my rosetta 800 which is calibrated at -10dB. That makes sense but... why are my other pres (MP2NV and TG2) substantially lower than the A12 and J99? Even with an inline pad my SCA's are hotter than them.
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by tele_player » Mon Nov 28, 2005 6:59 pm
Why would the Rosetta be calibrated for -10 with pro preamps?
-10 = consumer or 'prosumer'
+4 = pro, like the Great River, Chandler and Seventh Circle
I've built and used A12's and J99's. Working correctly, they're no hotter than they should be.
On the J99, re-read the instructions for how to jumper J1 and J2. You'll use a single jumper there.
-10 = consumer or 'prosumer'
+4 = pro, like the Great River, Chandler and Seventh Circle
I've built and used A12's and J99's. Working correctly, they're no hotter than they should be.
On the J99, re-read the instructions for how to jumper J1 and J2. You'll use a single jumper there.
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by agno » Mon Nov 28, 2005 7:42 pm
tele_player \$m[1]:Why would the Rosetta be calibrated for -10 with pro preamps?
-10 = consumer or 'prosumer'
+4 = pro, like the Great River, Chandler and Seventh Circle
I've built and used A12's and J99's. Working correctly, they're no hotter than they should be.
On the J99, re-read the instructions for how to jumper J1 and J2. You'll use a single jumper there.
That's the way the Rosetta comes by default... you have to order a calibration card to adjust it... (I may be wrong... lol to be honest I think I am)
and yes I used one jumper (on the J99) parallel of the input transformer across J1 and J2... and it's still hotter than my Great River and Chandler... my question is why? Out of all the info I've given in this thread... why?
Everything seems to be right but it's still substantially louder... about 5 notches.... My TG2 and MP2NV are neck and neck...
Oh by the way, thanx again for the input Tele.. I really appreciate...
-AGNO
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by tele_player » Mon Nov 28, 2005 8:14 pm
Well, you haven't given much info above. The correct thing to do would be to measure the gain, but you're not equipped to do that - scope, signal generator and know-how. But since you're saying the A12 and J99 are both doing it, I suspect nothing's wrong.
Forget notches. The A12 and J99's gain range is 9db to 70db. Maybe the others you're using let you set the gain below 9db?
Forget notches. The A12 and J99's gain range is 9db to 70db. Maybe the others you're using let you set the gain below 9db?
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by agno » Mon Nov 28, 2005 9:52 pm
tele_player \$m[1]:Well, you haven't given much info above. The correct thing to do would be to measure the gain, but you're not equipped to do that - scope, signal generator and know-how. But since you're saying the A12 and J99 are both doing it, I suspect nothing's wrong.
Forget notches. The A12 and J99's gain range is 9db to 70db. Maybe the others you're using let you set the gain below 9db?
Well as I stated I'm getting noise @ 12 o'clock on my sca's that I would get on my other pres all the way up... Does that sound "normal"?
And the J99 is way louder than the A12... louder than described... I even adjusted the jumpers on the J99 for the 250ohm input impedance just to poke around... and I heard no audible difference... it was still just as loud...
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