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Martin Griffith said:
What are you using for the input transistors? LM394's are quite obsolete. A quick search shows the Mat03 is on Last Time Buy at Digikey
EBay seems to have a sufficient supply.
 
dustbro said:
EBay seems to have a sufficient supply.

There is an older thread regarding replacing the LM394 and someone used 2 OPA2604's in its place with great results supposedly. However, I didn't see any data posted to support this. But dustbro is right, there are plenty LM394s on eBay.

Thanks!

Paul
 
Potato Cakes said:
There is an older thread regarding replacing the LM394 and someone used 2 OPA2604's in its place with great results supposedly.
Supposedly is the word. I don't see how a BiFET opamp with 10nV/sqrtHz noise voltage can replace an LM394 with 10 times less.


  But dustbro is right, there are plenty LM394s on eBay.
I would be very cautious about possible counterfeits, though.
 
abbey road d enfer said:
Supposedly is the word. I don't see how a BiFET opamp with 10nV/sqrtHz noise voltage can replace an LM394 with 10 times less.

I would be very cautious about possible counterfeits, though.

Indeed, caution is necessary with buying NOS transistors/ICs on the eBay.

When the prototype boards show I will try the dual 2604 option after it's working with LM394s.

Thanks!

Paul
 
You can use MAT02EH instead of the LM394,  it has better specs actually.

I buy MAT02EH from this source, fast shipping and never had a problem:

mary
Aosiwei Electronics Co.,Ltd

Tel:  +86 -27-82848366                        Fax:    +86-27-82848466

E-mail: [email protected]
MSN: [email protected]     
Website:    www.aosiwei.com
 
Analog have a few matched pairs http://www.analog.com/en/products/linear-products/matched-transistors.html and I might get some ssm2212 which are not too expensive ( for RS!). I was thinking of the AMEK 2500  with npns maybe the 2n5088. I'm always wary of buying NOS. The Aosiwei Electronics site wouldn't let me search anyway.
 
abbey road d enfer said:
I would be very cautious about possible counterfeits, though.

Very true... I just bought a boatload of LF351 from china, and they exploded in my circuit. TL081 worked fine
 
dustbro said:
Very true... I just bought a boatload of LF351 from china, and they exploded in my circuit. TL081 worked fine

I think nobody wants such a situation on the first power up..

But i have a question regarding C3 on the phantom power. Is the cap not a bit overrated with 100VDC? I have to admit i just know from some articles that electrolytic caps likes to run at 75% of its max rating. After some basic math (yes i dont have much to do at work...) i ended up with a 63VDC max rating.
Hope i didnt get that wrong ::)
 
Pusch3l said:
I have to admit i just know from some articles that electrolytic caps likes to run at 75% of its max rating.
  Who sez? Capacitor ratings are for continuous operation, and tolerate about +15% surges. Useful life of el caps is more dependant on temperature than voltage (as long as it's < than the rated voltage).


  After some basic math (yes i dont have much to do at work...) i ended up with a 63VDC max rating.
Hope i didnt get that wrong ::)
You're right, 63V is adequate for phantom isolation.
If I had to choose between 63V/105°C and 100V/85°C, I would choose the former.
 
Whoops said:
You can use MAT02EH instead of the LM394,  it has better specs actually.

I buy MAT02EH from this source, fast shipping and never had a problem:

mary
Aosiwei Electronics Co.,Ltd

Tel:  +86 -27-82848366                        Fax:    +86-27-82848466

E-mail: [email protected]
MSN: [email protected]     
Website:    www.aosiwei.com

Did a business once with that company, and for 5 years she and her colleagues wouldn't stop spamming my inbox.
 
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