Other Chips For a RAT Circuit?

[sevenisthenumber]

I just wanna get opinions on some other options for the RAT ic other than the run of the mill LMN308. Let me know your thoughts!

[petemoore]

  I've heard of people using an LM741 [as in Dist+], but the chip in the Rats is a compensated type. There's a HF compensation point in the chip and you choose the HF rolloff point with cap value across the relevant pins [IIRC,...pins 1 and 8].
  There might be one or two other chips [LM358 ?] you could check on to determine if they're compensated.
   The 308 is really the 'RAT's choice though.

[DougH]

TL070, different pinout than LM308

[Gus]

People have tried other singles be aware of the comp pins as noted above and changes you might have to make

[petemoore]

   Let me know your thoughts!
  Have you tried a Distortion Plus lately ?
  I like the 'raggedy ol' 741 circuit, [DOD250 ?], the diagram is pretty straightforeward considering there is plenty of talk around the gain knob and relevant cap/resistors involved with the gain/voicing of the circuit [the rest of it is pretty simple...make this value bigger and X goes up].
   But tweeking it in...HF taming control [you really don't need it if you're always using it through the same amp / same room /same volume], simply adding a pot and cap to ground...very useful item for me...I spent forever re-working the circuit before figureing out to put a tone knob on where the cap across the diodes was.
 

[WGTP]

NE5534 is popular.  Jack Orman at AMZ uses it.  I thought the TL070 had the same pin out.  I have used both and the NE5532 seems a little sweeter...   

[sevenisthenumber]

How can that cap be adjusted to compensate? I never knew what it did!?

[aron]

You need to lift that cap to use other op amps. The info is all over the web.

[sevenisthenumber]

You need to lift that cap to use other op amps. The info is all over the web.

thanks Aaron. I hate to bug but I cant seem to find that info....?

Is this why with certain chips i get oscillation and motor boating after the gain knob is over 80%?

[Mark Hammer]

LM748 is a possibility.  It is a chip similar to the LM308 in a number of characteristics.

[slacker]

It's not a chip but Joe Davisson's discrete opamp sounds great in a RAT type circuit.

[aron]

>There's a HF compensation point in the chip and you choose the HF rolloff point with cap value across the relevant pins [IIRC,...pins 1 and 8].

30pf cap.

[aron]

I made this last night for the discrete op amp. Untested maybe someone can find mistakes in it. I want to try it on some pedals I have.

http://www.diystompboxes.com/smfforum/index.php?topic=76066.0

[slacker]

Looks good to me Aron.

[frank_p]

I made this last night for the discrete op amp. Untested maybe someone can find mistakes in it. I want to try it on some pedals I have.

http://www.diystompboxes.com/smfforum/index.php?topic=76066.0

Oh ! I wondered what your post was about...  Now it's more clear.  Perhaps you should put a note in the topic because some who will stumble on it will not understand what it is about.

What did Joe Davidson used it for ?

[StephenGiles]

TL070, different pinout than LM308

No, it's the same pin out.

[aron]

Frank, it's cool. It gives your pedal a different sound entirely. You use it to sub for a single op amp. Like in my Shaka Pedals.

Read about it here:

http://www.diystompboxes.com/analogalchemy/sch/diodeopamp.html

[aron]

Thank you Ian!

[frank_p]

Thanks Aron !

[WGTP]

I'm no expert, but it looks like the LM308, NE5534 and TL070 all have the same pin out with the compensation cap at pins 1 and 8.