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Old 13th April 2011, 12:24 AM   #11
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This is a guitar distortion pedal, and an especially nasty one at that (that's a good thing .

There's no chance in hell you'll here the difference between different types of caps on C7 & C11. Don't swap out the opamps either, if you want The opamp Big Muff sound, you want the stated opamps.
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Old 13th April 2011, 12:49 AM   #12
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Quote:
Originally Posted by jean-paul View Post
But boy, a ua741 and a 4558 for audio......
The 4558 is probably a JRC NJM4558. A guitarist friend told me this has the best sound for distortion pedals.
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Old 13th April 2011, 01:01 AM   #13
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The JRC 4558 from the 80's have mythical "mojo" due to being used in the early Ibanez Tubescreamers, produced for Ibanez by Maxon. It's all hype and $3000 IEC cords. Just stick in a 4558 and it'll sound great.
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Old 13th April 2011, 06:17 AM   #14
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I always throw them in the bin but I will keep them from now on, maybe they will have TDA1541A-like status in some years

Seriously, the thing may be OK for this purpose but otherwise a NE5532 is much better than it ( in normal audio gear that is).
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Last edited by jean-paul; 13th April 2011 at 06:19 AM.
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Old 13th April 2011, 03:46 PM   #15
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No, 5532 is not better.

4558 has output stage that with 6.8K - 7.5K from output to + rail can can be biased in audiophile quality opamp. However, noises could be lower, speed could be faster, input currents lower, but anyway when I see 4558 in an old pro gear I bias it's output instead of replacing by something new.
5532 is what come to the fashion after 4558 in pro audio. It is like AKMS-74 after AK-47, the same Kalashnikov of pro audio. But the older one still sounds better... However, if you have OPA1612 in DIP case you can replace both in consoles, preamps, equaluzers, compressors, stc..., with great success, but if you don't... Don't rush.

Speaking of original questions, both caps can be electrolytic, and it changes nothing sound-wise. Also, which opamp you use here also almost does not matter: results are different levels of noises and output shifts, that would be good if any newer opamp than 4558 is used.

4558 in this type of pedal does not give any difference. This pedal uses diodes in negative feedback; they distort. If you want some other effect from this pedal, you may add one more switch that shorts out some diodes in feedback, so clipping starts asymmetrically. It would add some musicality to distortions, blues-like clipping of SE amp.

Also, long time ago I made and used a pedal similar to this one, with gain pot before the limiter controlled by pedal. It was easy and convenient, to use a pedal to control overdrive by foot.
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Old 13th April 2011, 05:08 PM   #16
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Wavebourn, your findings do not correlate with my findings on 4558. When I was a child I learnt that replacing them for the (then best) audio opamp NE5532 was a step forward....

Wouldn't use NE5532 nowadays ( input current, speed, offset etc. ) although it is a very good measuring device. I would use one of the newer National types instead when I would smell a 4558 in a device for HiFi. In fact I recently found some and replaced them for LME49860 which was more than a big step forward.

Back to the subject, we're going off-topic.
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Old 13th April 2011, 05:18 PM   #17
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Quote:
Originally Posted by jean-paul View Post
OK let me put it this way: in normal consumer audio gear replacing of a 4558 for a NE5532 (or preferably one of the newer National opamps) is a step forward. In fact it was one of the first swaps I did long ago as a child and discovered that some opamps could sound/measure better than others.
If instead of replacing them you would bias them as I described above, you could be surprised. Especially, when it is a console with several of them in each channel strip. Replacing by 5532 you get like "better SS sound". Biasing them you are getting like tube sound from SS console.

Here is an example:

http://wavebourn.com/female_sample.mp3
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