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DIY Stompboxes => Building your own stompbox => Topic started by: lightningfingers on September 07, 2004, 12:20:02 PM

Title: 386 input impedance
Post by: lightningfingers on September 07, 2004, 12:20:02 PM
Is 20Kohms too big too drive an LM386?
Title: 386 input impedance
Post by: Hal on September 07, 2004, 03:09:18 PM
why is this in the lounge?  This is an on topic post, if i've ever seen one....

and i dont know the answer to your question :-D
Title: 386 input impedance
Post by: niftydog on September 07, 2004, 08:15:44 PM
QuoteIs 20Kohms too big too drive an LM386?
huh?

Are you saying that you have a source output impedance of 20kohms, and you want to drive an LM386 with that source?

Well, it depends on your circuit design, but given that the datasheet gives a typical input impedance of 50kohms it's probably not that good. best case scenario;

loaded voltage = unloaded voltage from source x [50k/(20k+50k)]

loaded voltage = 0.71 x unloaded voltage.

How have you calculated the output impedance? It seems very high.
Title: 386 input impedance
Post by: lightningfingers on September 08, 2004, 05:08:21 AM
I didnt calculate, I asked the person who had worked on it before me, Its for that old tube radio that tried to kill me. It works now, but I want more volume, hence the 386 question.

QuoteWell, it depends on your circuit design, but given that the datasheet gives a typical input impedance of 50kohms it's probably not that good. best case scenario;

Does this mean I should use an interstage transformer?

EDIT: I don't know why it was in the lounge, coulda sworn I was in this forum :?  :)  :?
Title: 386 input impedance
Post by: niftydog on September 08, 2004, 07:50:51 PM
QuoteIt works now, but I want more volume, hence the 386 question.

what are you proposing to do?
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