Topic: Inexpensive "NADY" Preamp and Phantom adapters

[afri-cola-man]

I don't know if it's true 48 volts. But it did definitely power my mics. The instruction manual doesn't give any hints about the actual voltage supplied. I try to post some pics tomorrow or on Sunday.

[Church-Audio]

I don't know if it's true 48 volts. But it did definitely power my mics. The instruction manual doesn't give any hints about the actual voltage supplied. I try to post some pics tomorrow or on Sunday.

We need realy sharp pictures of the circuit board PLEASE thanks

[Ryan Sims]

FWIW, I own a Nady mixer for home use and the phantom power on this thing is a joke.  It will power my LDC but it is extremely noisy.

[Church-Audio]

FWIW, I own a Nady mixer for home use and the phantom power on this thing is a joke.  It will power my LDC but it is extremely noisy.

It might not be noisey for the little preamp so we have to take a look at it.

[poorlyconditioned]

FWIW, I own a Nady mixer for home use and the phantom power on this thing is a joke.  It will power my LDC but it is extremely noisy.

It might not be noisey for the little preamp so we have to take a look at it.

Yep.  The two questions I have are;
- what chip(s) generate phantom power from 9V
- do the opamps run on something better than 9V only (like +/- 12V or something)

If the power supply and build is reasonable it is easy to change opamps/caps/etc to get great sound.

  Richard

[Church-Audio]

FWIW, I own a Nady mixer for home use and the phantom power on this thing is a joke.  It will power my LDC but it is extremely noisy.

It might not be noisey for the little preamp so we have to take a look at it.

Yep.  The two questions I have are;
- what chip(s) generate phantom power from 9V
- do the opamps run on something better than 9V only (like +/- 12V or something)

If the power supply and build is reasonable it is easy to change opamps/caps/etc to get great sound.

  Richard

I think there is only two ways to get that kind of voltage one is an inverter and switch the dc from the battery to ac. Then once its ac you can send it into a step up transformer with a center tap then use a pump charge IC to ram up the voltage or simply use a series of pump charge ic chips to get you there by cascading them does that make sense? its a dc to dc converter of some kind that for sure but as we increase voltage current must be reduced.. so I would say a supply like this might be good for 40mA max before it cacks out.. So if most mics need about 10mA to run properly that only leaves 20mA for the preamp that's not much... But most surface mount ic chips will work at 20mA...

[afri-cola-man]

I don't know if it's true 48 volts. But it did definitely power my mics. The instruction manual doesn't give any hints about the actual voltage supplied. I try to post some pics tomorrow or on Sunday.

We need realy sharp pictures of the circuit board PLEASE thanks

You can find the pictures here.
http://www.mp-acm.de/hitec_audio/hitec_audio_pre_mobile_2.html
That's the best I could manage with my digital camera. I hope they're of any help.
Ulrich

I had to remove the pictures [2007-03-25] due to urgent need of the webspace they blocked. If anybody does still need them, please don't hesitate to pm me.

[Church-Audio]

I don't know if it's true 48 volts. But it did definitely power my mics. The instruction manual doesn't give any hints about the actual voltage supplied. I try to post some pics tomorrow or on Sunday.

We need realy sharp pictures of the circuit board PLEASE thanks

Dude HUGE +T thanks alot!!!


You can find the pictures here.
http://www.mp-acm.de/hitec_audio/hitec_audio_pre_mobile_2.html
That's the best I could manage with my digital camera. I hope they're of any help.
Ulrich

[Church-Audio]

Well from what I have seen if the Nady is the same on the inside it could benefit from changing all the resistors to metal film and all 1% values because 5% does not cut it for me... This will help balance out the left and right sides and bring the noise floor down. The Tantalum coupling caps have to go... and get replaced with Mylar then I would take a good look at the electrolytics and see if they can be changed out for a better quality cap.. After that I would take a look at the opamps for a burr brown substitute that could be used current draw would obviously be a huge factor here. I would then take a huge look at the cheesy 1$ pots they are using and maybe replace them with a rotary 12 position pot with precision resistors on it. Then I would rip out that diode limiter peace of turd and use the switch for a high pass filter... that might be tricky you would probably have to put in a small sub board with the HPF caps on it. and swap them out for the coupling caps ether in the input ( preferred method ) or somewhere close the the first stage. But again in order to figure the cap out you need to figure out the source impedance of the circuit ( that's not something I can figure out ) or anyone with out a schematic.. So trial and error with a MLS analyzer could show what the cap is doing..

Then after that you might have a pretty good preamp or at least as good as it could be... They are using a SIX hex inverter hex chip to get the 48v or so voltage but I think max current is only going to be 12mA I suspected they were cascading inverters some how. So that's a pretty good chip they may be better ones that will drop in The chip is a TC4069UBP its a Toshiba chip here is the data sheet for it. I think that they must "split" of the supply and then use a virtual ground and create a + and - supply for the opamps.
http://www.datasheetcatalog.com/datasheets_pdf/T/C/4/0/TC4069UBP.shtml

[poorlyconditioned]

Well from what I have seen if the Nady is the same on the inside it could benefit from changing all the resistors to metal film and all 1% values because 5% does not cut it for me... This will help balance out the left and right sides and bring the noise floor down. The Tantalum coupling caps have to go... and get replaced with Mylar then I would take a good look at the electrolytics and see if they can be changed out for a better quality cap.. After that I would take a look at the opamps for a burr brown substitute that could be used current draw would obviously be a huge factor here. I would then take a huge look at the cheesy 1$ pots they are using and maybe replace them with a rotary 12 position pot with precision resistors on it. Then I would rip out that diode limiter peace of turd and use the switch for a high pass filter... that might be tricky you would probably have to put in a small sub board with the HPF caps on it. and swap them out for the coupling caps ether in the input ( preferred method ) or somewhere close the the first stage. But again in order to figure the cap out you need to figure out the source impedance of the circuit ( that's not something I can figure out ) or anyone with out a schematic.. So trial and error with a MLS analyzer could show what the cap is doing..

Then after that you might have a pretty good preamp or at least as good as it could be... They are using a SIX hex inverter hex chip to get the 48v or so voltage but I think max current is only going to be 12mA I suspected they were cascading inverters some how. So that's a pretty good chip they may be better ones that will drop in The chip is a TC4069UBP its a Toshiba chip here is the data sheet for it. I think that they must "split" of the supply and then use a virtual ground and create a + and - supply for the opamps.
http://www.datasheetcatalog.com/datasheets_pdf/T/C/4/0/TC4069UBP.shtml

Great diagnosis, Chris.

So what are those four transistors used for?  Is that part of the limiter circuit?

OK, it looks like they are using the TL074 chip for a preamp.  That is easily replaceable with any (FET input) opamp, right?

  Richard

[poorlyconditioned]

I don't know if it's true 48 volts. But it did definitely power my mics. The instruction manual doesn't give any hints about the actual voltage supplied. I try to post some pics tomorrow or on Sunday.

We need realy sharp pictures of the circuit board PLEASE thanks

You can find the pictures here.
http://www.mp-acm.de/hitec_audio/hitec_audio_pre_mobile_2.html
That's the best I could manage with my digital camera. I hope they're of any help.
Ulrich

++++thanks for the Photos!!!

  Richard

[Church-Audio]

Well from what I have seen if the Nady is the same on the inside it could benefit from changing all the resistors to metal film and all 1% values because 5% does not cut it for me... This will help balance out the left and right sides and bring the noise floor down. The Tantalum coupling caps have to go... and get replaced with Mylar then I would take a good look at the electrolytics and see if they can be changed out for a better quality cap.. After that I would take a look at the opamps for a burr brown substitute that could be used current draw would obviously be a huge factor here. I would then take a huge look at the cheesy 1$ pots they are using and maybe replace them with a rotary 12 position pot with precision resistors on it. Then I would rip out that diode limiter peace of turd and use the switch for a high pass filter... that might be tricky you would probably have to put in a small sub board with the HPF caps on it. and swap them out for the coupling caps ether in the input ( preferred method ) or somewhere close the the first stage. But again in order to figure the cap out you need to figure out the source impedance of the circuit ( that's not something I can figure out ) or anyone with out a schematic.. So trial and error with a MLS analyzer could show what the cap is doing..

Then after that you might have a pretty good preamp or at least as good as it could be... They are using a SIX hex inverter hex chip to get the 48v or so voltage but I think max current is only going to be 12mA I suspected they were cascading inverters some how. So that's a pretty good chip they may be better ones that will drop in The chip is a TC4069UBP its a Toshiba chip here is the data sheet for it. I think that they must "split" of the supply and then use a virtual ground and create a + and - supply for the opamps.
http://www.datasheetcatalog.com/datasheets_pdf/T/C/4/0/TC4069UBP.shtml

Great diagnosis, Chris.

So what are those four transistors used for?  Is that part of the limiter circuit?

OK, it looks like they are using the TL074 chip for a preamp.  That is easily replaceable with any (FET input) opamp, right?

  Richard

Yes the transistors are for the limiter. Its a way of ramping up the signal to drive the diodes hard enough to get them to clamp down lol its pretty lame. We are not talking state of the art here more state of the FART...
I would get rid of the tl074 that's a real dinosaur of an opamp anything by  burr brown would smoke it. I will check out substitutions based on chip size ect.. And see what we can come up with THAT corporation also makes really good opamps I am going to be designing a full sized stereo preamp based on the THAT chip the 1503 or something I forget the name but its a very good chip very easy to make a good preamp out of.

I wonder if the limiter is hard bypassed? I hope so.. This thing can be modified there is very little surface mount stuff going on, to be honest I really did think it was going to be all surface mount. I wondered how they could build it so cheap with out using surface mount. I really wonder if Nady did any changes to this unit? I think it would be a good thing to take a peek inside the Nady as well.. I have an email out the the company that makes this preamp to see if they will supply me with a schematic that will make it so much easier to see what they are doing in with this design..

[Chuck]

The phantom power circuit looks like basically the same one in the Rolls 224. Oh well...

[Church-Audio]

The phantom power circuit looks like basically the same one in the Rolls 224. Oh well...

Hey Chuck do they use the same chip? to get the voltage up? and I can assume from your reaction that the Rolls does not work very well??

[poorlyconditioned]

Well from what I have seen if the Nady is the same on the inside it could benefit from changing all the resistors to metal film and all 1% values because 5% does not cut it for me... This will help balance out the left and right sides and bring the noise floor down. The Tantalum coupling caps have to go... and get replaced with Mylar then I would take a good look at the electrolytics and see if they can be changed out for a better quality cap.. After that I would take a look at the opamps for a burr brown substitute that could be used current draw would obviously be a huge factor here. I would then take a huge look at the cheesy 1$ pots they are using and maybe replace them with a rotary 12 position pot with precision resistors on it. Then I would rip out that diode limiter peace of turd and use the switch for a high pass filter... that might be tricky you would probably have to put in a small sub board with the HPF caps on it. and swap them out for the coupling caps ether in the input ( preferred method ) or somewhere close the the first stage. But again in order to figure the cap out you need to figure out the source impedance of the circuit ( that's not something I can figure out ) or anyone with out a schematic.. So trial and error with a MLS analyzer could show what the cap is doing..

Then after that you might have a pretty good preamp or at least as good as it could be... They are using a SIX hex inverter hex chip to get the 48v or so voltage but I think max current is only going to be 12mA I suspected they were cascading inverters some how. So that's a pretty good chip they may be better ones that will drop in The chip is a TC4069UBP its a Toshiba chip here is the data sheet for it. I think that they must "split" of the supply and then use a virtual ground and create a + and - supply for the opamps.
http://www.datasheetcatalog.com/datasheets_pdf/T/C/4/0/TC4069UBP.shtml

Great diagnosis, Chris.

So what are those four transistors used for?  Is that part of the limiter circuit?

OK, it looks like they are using the TL074 chip for a preamp.  That is easily replaceable with any (FET input) opamp, right?

  Richard

Yes the transistors are for the limiter. Its a way of ramping up the signal to drive the diodes hard enough to get them to clamp down lol its pretty lame. We are not talking state of the art here more state of the FART...
I would get rid of the tl074 that's a real dinosaur of an opamp anything by  burr brown would smoke it. I will check out substitutions based on chip size ect.. And see what we can come up with THAT corporation also makes really good opamps I am going to be designing a full sized stereo preamp based on the THAT chip the 1503 or something I forget the name but its a very good chip very easy to make a good preamp out of.

Nice plan.  You're talking about the THAT 1510/1512.  Those are replacement for TI INA217, which are replacements for AD SSM2017/19.  All nice chips, that's for sure.  They are what is inside the DMIC-20.  They use a boost circuit to get from +6V to +/-12V.  Theirs is an inductor-based one (Maxim 743), but you can also use "charge pumps" (LT1054) to do it too.  I actually started breadboarding this before I started buying (and hacking) so much gear.  And now I've just bought an Edirol R09  .  When will it end.  Someone save me from myself!

  Richard