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Author Topic: TL071 preamp = super easy  (Read 18594 times)

joecool85

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TL071 preamp = super easy
« on: July 07, 2006, 07:18:00 PM »
Paul has been so kind as to do an easy layout for it too:

http://www.diyguitarist.com/PDF_Files/OpampGuitarPreamp.pdf

This would be PERFECT for any chipamp guitar amp.
« Last Edit: July 08, 2006, 09:42:04 AM by joecool85 »
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trevize

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Re: TL072 preamp = super easy
« Reply #1 on: July 08, 2006, 08:52:13 AM »
that's a single opamp like a tl071. The dual woud be ne5532 (which is one of the best dual opamps in audio applications).


joecool85

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Re: TL071 preamp = super easy
« Reply #2 on: July 08, 2006, 09:42:16 AM »
Sorry, typo.  I fixed it.
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SECONDandBOWERY

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Re: TL071 preamp = super easy
« Reply #3 on: July 27, 2006, 06:25:30 PM »
Could this bad boy be tweaked to work nicely with a bass?  You know: more emphasis on the lower frequencies?  Also, could you put a tonestack after/before it and still have enough of a signal to push a LM3886 poweramp?

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joecool85

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Re: TL071 preamp = super easy
« Reply #4 on: July 27, 2006, 06:33:20 PM »
Up the input cap to 10uF and it should be fine for bass.  As far as the tonestack goes, I'm not 100% sure, but I think you'd be fine.
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SECONDandBOWERY

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Re: TL071 preamp = super easy
« Reply #5 on: July 27, 2006, 06:37:09 PM »
Just th einput cap?  I thought alll of them would need to be changed...

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joecool85

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Re: TL071 preamp = super easy
« Reply #6 on: July 27, 2006, 07:43:26 PM »
The output caps are already 10uF which should be plenty large.
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ildar

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Re: TL071 preamp = super easy
« Reply #7 on: December 09, 2006, 04:35:55 PM »
Sorry for dredging up an old thread,but...
The preamp here is shown with a 9v supply, obviously intended for stompbox use. I have a schem for a similar circuit by Marshall, actually the preamp from the 3005 ss combo. The circuit is a dual opamp (lm 1458), has a tonestack, and most notably, takes a 24v supply.
As I'm using ROG "amp sims" as front ends, I'm increasingly using higher voltage-higher than 9v/12v, anyhow-and I think it's an important issue to bring up here.
That being said, has anyone tried this pre with higher than 9v?
« Last Edit: December 13, 2006, 04:57:47 PM by ildar »

joecool85

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Re: TL071 preamp = super easy
« Reply #8 on: December 09, 2006, 05:59:56 PM »
I don't know about this specific circuit, but I know that the TL071 itself can take substantially higher voltage.  Something like 30volts (normally used as +/-15v).
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ildar

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Re: TL071 preamp = super easy
« Reply #9 on: December 09, 2006, 10:31:43 PM »
Right, the LM1458 can take 40v iirc.
I'm struggling with getting these preamps up to line level. They do drive a power amp ok, as I've mentioned before, but there's still a little push lacking, if you know what I mean.

doug deeper

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Re: TL071 preamp = super easy
« Reply #10 on: December 13, 2006, 03:21:03 PM »
how would this preamp perform on a 12v unregulated supply?

teemuk

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Re: TL071 preamp = super easy
« Reply #11 on: December 13, 2006, 04:44:50 PM »
It's a very basic circuit designed to operate from battery. Should work nicely in most occasions. Few rules of thumb for opamp gain stages: Less current in the circuit means more noise. Lower supply voltage means earlier clipping and lower headroom. In other than battery powered circuits the lack of supply raild decoupling filters (located very near opamps) is a risk of instability. Good idea to isolate that gain set potentiometer from DC.

The half supply biasing arrangement of the opamp is a classic example of bad design. Input impedance is both resistors in parallel and there are also potential instability issues. A better idea is to connect a separate input resistor to that 1/2 supply point and to add some regulation to maintain the steady 1/2 Vcc.

Refer to this document for more refined ideas:
http://www.analog.com/library/analogDialogue/archives/35-02/avoiding/avoiding.pdf

The document also answer the question how the circuit performs with unregulated supplies.
« Last Edit: December 13, 2006, 04:48:20 PM by teemuk »