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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  Substitutes for LM308? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Substitutes for LM308?  (Read 3812 times)
Steben
Posts: 1491


Steven Burvenich


Substitutes for LM308?
« on: May 24, 2005, 07:21:04 AM »

I was thinking of some Rat or Dist+ experiments, but I don't I want to use the LM741 nor the rare LM308.
Anyone knows a less noise, but low slew rate OpAmp?
I thought I saw some hints, but can't remember where.
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MartyMart
Posts: 6064


Martin L / Berlin for a while


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Substitutes for LM308?
« Reply #1 on: May 24, 2005, 09:13:19 AM »

A TL070 should be fine, in fact my "re-issue" Rat has one inside !!
sounds great, and I used one in the "Mongoose" too - very similar circuit

Marty.
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"Success is the ability to go from one failure to another with no loss of enthusiasm"
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spudulike
Posts: 698

Hugh Jardon, Newcastle


Substitutes for LM308?
« Reply #2 on: May 24, 2005, 09:37:41 AM »

TL070s are just as hard to find IME - I had better luck finding LM301's.
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The Tone God
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Posts: 5299


Maggie


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Substitutes for LM308?
« Reply #3 on: May 24, 2005, 12:02:40 PM »

Quote from: spudulike
TL070s are just as hard to find IME - I had better luck finding LM301's.


Digikey has TL080s in DIP form which should be sufficant. Digikey is availible in the UK.

Andrew
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Paul Marossy
Posts: 12527


Just Another Guitarhead


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Substitutes for LM308?
« Reply #4 on: May 24, 2005, 03:54:28 PM »

I used a CA3130 in mine. I don't know how available those are - I had them given to me. Chances are they are out of production...
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"Tone is in the fingers."
jdjonsson
Posts: 18


NTE?
« Reply #5 on: May 24, 2005, 04:04:41 PM »

I've had ok luck with NTE replacements, even though they're expensive. I used an NTE1641 in place of an MN3007 in my Tonepad Small Clone, and didn't notice any difference when I finally ordered the MN3007 from Smallbear.

The NTE938M is listed at mouser as a replacement for the LM308, and they're $10 each.

Might work.
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spudulike
Posts: 698

Hugh Jardon, Newcastle


Substitutes for LM308?
« Reply #6 on: May 24, 2005, 04:19:09 PM »

:shock:  $10  :shock:
Thats £5.47. RSH sell LM301A at 45 pence each ...
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littlegreiger
Posts: 319


Substitutes for LM308?
« Reply #7 on: May 24, 2005, 06:27:10 PM »

You could use any single opamp, like a TL071, as long as it has the same pinout or you adjust your build to fit the new pinout.
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nelson
Posts: 2275



Substitutes for LM308?
« Reply #8 on: May 24, 2005, 11:44:50 PM »

These guys have the LM308 for 80p.

http://www.elclondon.co.uk/acatalog/ELC_Online_Catalogue_LM_SERIES_49.html

minimum order of 5 pounds though.
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Steben
Posts: 1491


Steven Burvenich


Substitutes for LM308?
« Reply #9 on: May 25, 2005, 01:04:24 AM »

But what about the slew rate (seem to guarantee softer clip and smoother pick attack)? Should this be taken serious? the TL... series seem to have faster slew rate. Maybe they sound ok, but different. I don't know.
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WGTP
Posts: 2458


Substitutes for LM308?
« Reply #10 on: May 25, 2005, 08:01:04 AM »

IIRC the slew rate of the TL070 can be adjusted with the extra cap it has that the TL071 doesn't.  Same as the LM308.   Cool
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Paul Marossy
Posts: 12527


Just Another Guitarhead


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Substitutes for LM308?
« Reply #11 on: May 25, 2005, 08:26:17 AM »

Quote
You could use any single opamp, like a TL071, as long as it has the same pinout


If you do use a TL071, omit that 30pF cap between Pin 1 & 8. The TL071 is internally compensated, and that cap on that the LM308 requires isn't required with the TL071. And, IIRC, the cap that is internal to the TL071 is around 30pF as well. I think it was 27pF.

The thing that's kind of cool about the LM308 type opamps is that you can mess with different value caps. I don't know that there is any benefit in doing that, but the option is there.  Cool
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MR COFFEE
Posts: 365

Bart M


Substitutes for LM308?
« Reply #12 on: May 25, 2005, 01:49:31 PM »

What WGTP said - ditto.

The TL070 with a larger compensation cap sounds the same EXCEPT it doesn't HISS so damn much.

By overcompensating the '070, it drops the slew rate to match the '308 which slews at an anemic 0.1v/us. Which just happens to sound good in this applcation for just the reasons you stated.

The noise of the TL070 is an order of magnitude better. You CAN hear that. And you'll like the quiet.

Steve Daniels at Small Bear stocks TL070s - go there.  Smiley
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Bart
Khas Evets
Posts: 500


Substitutes for LM308?
« Reply #13 on: May 25, 2005, 03:54:07 PM »

Mr Coffee, what value cap did you use on the TL070?
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Prive
Posts: 179


Substitutes for LM308?
« Reply #14 on: May 31, 2005, 06:15:36 PM »

I have some LM208, anyone use it?

Saludos, Marcelo.
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MR COFFEE
Posts: 365

Bart M


Substitutes for LM308?
« Reply #15 on: May 31, 2005, 08:42:43 PM »

To drop the slew rate of the TL070 from 13v/us down to the 0.1v/us of the LM308 requires overcompensation.

There is nothing sacred about 0.1v/us, BTW.

If 18pf yields 13v/us in a TL070, then 180pf slows you down to ~ 1v/us, assuming the charging current mirror doesn't saturate (which it probably will if you go for 0.1v/us)

Start there and work down to what sounds good to your ears.

This is about LISTENING and using your own artistic skills.

FWIW... and oh, YMMV.  Smiley
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Bart
Doug_H
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Substitutes for LM308?
« Reply #16 on: June 01, 2005, 07:17:47 AM »

Yes, from what I remember (long time ago I played with this stuff) 180p sounded about right with the TL070. The LM308 is a real p.o.s.. Don't waste your $$ or time with it, IMO. Nothing magic about it - just noisy and harsh. The TL070 sounds real good in this kind of ckt.

Doug
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grolschie
Posts: 459


Re: Substitutes for LM308?
« Reply #17 on: June 05, 2009, 11:38:41 PM »

I used a CA3130 in mine. I don't know how available those are - I had them given to me. Chances are they are out of production...

I tried a CA3130EZ in my Rat today. Really nice.   Smiley
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WGTP
Posts: 2458


Re: Substitutes for LM308?
« Reply #18 on: June 07, 2009, 10:44:19 AM »

There is also the NE5534 that has a little nicer sound with the stock cap.

http://focus.ti.com/lit/ds/symlink/sa5534a.pdf
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Stomping Out Sparks & Flames
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