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 Forum index » DIY Hardware and Software
Somebody who knows op amps.
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Uncle Krunkus
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PostPosted: Sat Sep 16, 2006 4:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well,
It seems like the EQ effect has dropped off a bit.
And it actually seems more susceptable to the oscillations/overdrive.
It's definately a combination of having the gain up and the freq down.
From what I could see on the specanal the lower end of the frequency pot would put it at or below DC!
I haven't got the second channel connected yet. Would the lack of the second 10K pot make the difference? i.e. there's 10K across the inputs instead of 5K. I'll chuck a 10K across it and get back to ya.

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Uncle Krunkus
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PostPosted: Sat Sep 16, 2006 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Adding the 10K had no effect at all. Changing to a new battery did though! Embarassed
I really need to build a nice benchtop PSU.
It sounds really good now. Still self oscillates with gain up and freq down, but it's a more "musical" oscillation, and is easier to get rid of.
It's drawing 12.5mA which seems okay. Could I get it any lower?
Is there anything I can do to better match the inputs? i.e. improve S/N ratio etc.
It's definately come a long way since you got back!
Thanks Jan.

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blue hell
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PostPosted: Sat Sep 16, 2006 5:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:

It's definately come a long way since you got back!
Thanks Jan.


You're welcome Andrew, but you really did it yourself, I didn't even ask the right questions, well one, maybe Very Happy Glad though it goes forwards.

A poor battery BTW does have a high internal resistance, which does give trouble over the supply rails. the 100 uF cap you added was supposed to prevent that, but apparently it is not big enough, unless the battery was really in bad shape.

Next time I'll try to ask about the battery first.

Meanwhile, yes I think it would be useful for every DIYer to have a simple dual power supply with lets say 1 Amp of current (with a limiter preferably) and a regulatable voltage up to about +/-25 or +/-30 Volts or so.

But even a fixed one with +/-9V would be very useful I guess, the current limiter is quite handy for avoiding blowups sometimes, really nice to have. It's not too hard to build your own, you could even make it voltage controlled Very Happy

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Jan
also .. could someone please turn down the thermostat a bit.
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Uncle Krunkus
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PostPosted: Sat Sep 16, 2006 5:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, I know how easy it would be to make. I've got a nice 1.5Amp 18/0/18 transformer too. The problem is more one of available time, priorities, and laziness. Laughing

Maybe we should do a thread on how to put one together so everybody could follow along. Then again, I wonder about promoting the idea of people doing mains voltage projects, when we don't know the level of experience individuals may have. What do you think?

Last edited by Uncle Krunkus on Sat Sep 16, 2006 5:24 pm; edited 1 time in total
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blue hell
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PostPosted: Sat Sep 16, 2006 5:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wasn't laziness just the common word for prioritizing .. ?
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Jan
also .. could someone please turn down the thermostat a bit.
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Uncle Krunkus
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PostPosted: Sat Sep 16, 2006 5:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm not sure,
My laziness is when I stop doing anything and go and have a sleep at 2pm. Prioritizing means I'm deciding what I will do next.
But I suppose I do sometimes do that in my sleep. Laughing

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