Author Topic: Intersound IVP layout  (Read 1930 times)

jimladladlooklike

Re: Intersound IVP layout
« Reply #40 on: March 12, 2021, 04:08:38 PM »
So I just breadboarded a version of the schematic I posted, except I didn't have an LM741 handy, so opted for an LM386 instead.

It's powered with +9v DC. (The LM386 doesn't can't handle more than 18V, so will have to use a suitable replacement eventually.)

I used two 560r resistors for the voltage divider, hooked up to the two outer pins of a trim pot, the centre pin of which is connected to the non-inverting input of the op amp.

I replaced the transistors with a 2N5088 and a 2N5087.

After measuring, the reading I get are: C1 + terminal = +9v, "ground" terminal = +4.5v and C2 - terminal = 0V. So basically what I have is a voltage divider... I then disconnected the two above capacitor legs and measured there, having noticed that they were connected to +9V and ground, but I don't know what that achieved as the voltages were all over the place. Is there something I'm missing? are the parts I used not the right kind?

EDIT: I was measuring wrong. I was taking the ground reading from the bottom left point of the schematic, not the junction of the two caps.

It works fine! Now I just need to test with an LM741 when I can get some. Thanks for all of your help on this guys, I feel like I'm learning a lot and it's much appreciated.
« Last Edit: March 12, 2021, 04:23:46 PM by jimladladlooklike »

iainpunk

Re: Intersound IVP layout
« Reply #41 on: March 12, 2021, 05:04:34 PM »
The LM386 isn't a (normal) opamp, its a power amp, with some odd quirks when it comes to biasing, to make it work with less external parts. try any other real opamp, that would probably work better.
if you want to simplify and use the 386, you can leave out the transistors, and put both inputs to ground, this provides a strong, stable Vbias

cheers
« Last Edit: March 12, 2021, 05:07:36 PM by iainpunk »
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
『snailpilled』

jimladladlooklike

Re: Intersound IVP layout
« Reply #42 on: March 13, 2021, 08:12:40 AM »
Oh okay, thanks for the pointer. I was planning on using an LM741 because of it's max input voltage anyway, just wanted to make something similar with what I had to hand. Note to self, always read the datasheet.

iainpunk

Re: Intersound IVP layout
« Reply #43 on: March 13, 2021, 04:51:58 PM »
Quote
Note to self, always read the datasheet.
that shouldn't be just a note, that should be your RULE #4, the other rules will come to you along the way.

cheers
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
『snailpilled』