EL2001 in META42 PS question
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wilsonjm

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I noticed that when I have a EL2001 in my meta42 PS as opposed to a jumper over it, my +/- voltages are offset by about 0.2V. Without the EL2001, the voltages are offset by about 0.002V (1/10 as much, within the spec for TLE2426).

What is the reason for this?
 
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ppl

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Wnen the EL-2001 is used as a virtual ground driver it is operated without the Aid of Negitive feedback ans thus DC offset will be High compaired to am opamp based Ground driver like the TLE-2426. I would not worry about an imbalance of 0.2 Mv of the supply rails as most regulators will not track that good. 0.2 MV for an EL-2001 as a VGD is great as i typicaly get 5-10 Mv and 60 Mv with the BUF-634. Absolute supply rail tracking is not as importent as maintaining that balance under load and if you aproack 10 Ma per channel with the TLE the Imbalance will be several hundred Mv, While under similar loading a EL-2001 will still be low.
 
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wilsonjm

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sorry ppl,

i didn't say 2mV with the EL2001. I have an offset of 2mV with the TLE2426. With the EL2001, it's 0.2V (not mV)
 
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ppl

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200 Mv Humm.... Somthing is not right Is the TLE driving the 2001? if so you should have less that 10 Mv or you might have instability try another 2001 check for solder Bridge.
 
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wilsonjm

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ppl,

i had connected a PS backwards a few days ago and my EL2001 was very hot. This is the one that gives me the 0.2V offset. I tried another EL2001 and got an offset of 0.14V, a bit better. maybe all my EL2001's are bad? i dunno..i don't hear anything bad in the audio.

is it possible it's the TLE that's bad? i was using a Elpac FW1824-760 that morsel said a while ago "almost fried my TLE2426 because the AC ground is tied to the negative rail". My TLE is splitting the +/- evenly (to 2mV) except when driving the EL2001, then it's 100-200mV.
 
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Humm at first one would think the TLE, However It in it self might be the unstable part, Try a 220 ohm resistor on the TLE's Out Pin Driving the 2001's input. Evean though these are Power supply circuits only cocerned with DC, Thay still have a bandwidth into the MHz. range. Try another TLE at first then givre the resistor a try
 
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Quote:

my +/- voltages are offset by about 0.2V.


In the META42 sitting on my bench at the moment, I'm getting 30-40mV of imbalance at all times. 200mV is indeed high.

Quote:

i had connected a PS backwards a few days ago and my EL2001 was very hot.


Sigh... That's what D1 is there for!


Chances are excellent that all chips on the board were damaged to some extent. You're lucky they're working at all.

Now promise me you'll at least go out to Radio Shack and get some 1N4001s, 'kay?
 
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wilsonjm

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tangent, my D1 is in place.

The EL2001 in the PS was the only chip taht got hot
 
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morsel

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Something else is probably wrong with your circuit. D1 should crowbar a reversed power supply to save the onboard components.
 
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wilsonjm

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morsel,

remember that FW1824-760 power supply you tried? the one you said the "AC ground is tied to the negative rail". before i read your post on that, i tried that PS.

now is the crowbar diode going to protect against that........
 
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morsel

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Like Tangent already said, you probably damaged or destroyed some components on your amp from what you did earlier. Try replacing the ICs and see if that helps.
 
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Quote:

remember that FW1824-760 power supply you tried? the one you said the "AC ground is tied to the negative rail". before i read your post on that, i tried that PS.

now is the crowbar diode going to protect against that........


That power supply won't always cause problems. If you used a battery-powered source, for example, you would never have a problem with it. If, instead, you used a wall-powered source, and that source ties its chassis and signal grounds together, and those grounds are also tied to your wall power's ground, then you'll have a problem. If that happens, then no, D1 won't help you. And, having the 2001G get hot would be exactly the symptom I'd expect.
 
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