AW: question about audio OP amp

Scott Bernardi scott.bernardi at fritz.com
Fri Jul 10 18:15:28 CEST 1998


I've seen the same discussion about the opamps used in distortion devices;
specifically, the opamps used in the Ibanez Tube Screamer. Apparently when
originally designed, they used 4558 dual opamps because they were cheap. In
later years, the 4558 became obsolete and the newer units with 1448's
sounded "trashy" - hence an increased market for vintage Tube Screamers.
The Tube Screamer, and in fact many distortion boxes, uses diodes in the
feedback loop of the opamp to clip the signal and cause distortion. There
is some speculation that it is the way an opamp recovers from severe
clipping that has an effect on the sound.
I built a Tube Screamer clone using TL072's, and it sounds pretty good to
me. 'Course i haven't done an A-B comparison.


At 12:24 AM 7/11/98 +1000, you wrote:
>At 01:04 PM 10/07/98 +0200, JH wrote:
>
>>Never heard of anyone who did a real A/B comparison and said
>>he liked the 741 better, so this is most probably just a myth.
>>
>There is endless discussion on the ampage guitar fx diy bulletin board
>about different sounding chips in fuzz units (these are the same # chip, 
>different manufacturers and dates). I don't doubt there ARE differences 
>when chips are used 'out of design range'.
>And I've seen ckts that depended on the relatively slow slew rate of 741s 
>to work.. but I don't think this is one of them.
>
>paul perry melbourne australia
>
>
>
--------------------------------------
Scott Bernardi
voice: 415-538-0439 
fax:   415-904-8375
scott.bernardi at fritz.com



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