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Topic: Tube Screamer OD mod question.....Asymmetrical diodes |
ajm
From:
Los Angeles
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Posted 12 Sep 2022 9:02 am |
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This is today's circuit design/mod question.
A generic Tube Screamer circuit has two diodes in an op amp feedback loop, pointing in opposite directions.
This is Symmetrical clipping.
A common mod is to replace one of the diodes with two, both pointing the same direction. This is Asymmetrical clipping and will clip the signal more on the top (or bottom).
So when this mod is done, in the feedback loop, you'll have three diodes:
- One diode pointing one way, and
- Two diodes pointing the other way.
So here's the question, most applicable to those who have actually done this mod:
Does it make any difference sound wise which of the original diodes is replaced with two?
I hope I asked/described this clearly.
Thanks in advance for the replies. |
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Mike Auman
From:
North Texas, USA
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Posted 12 Sep 2022 10:53 am
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Short answer - no. You can see it on a scope, but you won't hear the difference between positive and negative cycle clipping. We can't hear phase (polarity.) What you will hear is the difference in overtones and harmonics that asymmetrical clipping gives you compared to symmetrical, and the difference in amplitude due to the added diode. There's more about distortion at http://www.geofex.com/effxfaq/distn101.htm and more about the Tube Screamer and mods at http://www.geofex.com/article_folders/tstech/tsxtech.htm
_________________
Long-time guitar player, now wrestling with lap steel. |
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Bill A. Moore
From:
Silver City, New Mexico, USA
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Posted 12 Sep 2022 2:10 pm
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I modded a Boss SD-1 several years ago with Monte Allums GT mod. The mods made the pedal quieter of course, but also more versatile, the ability to add just a little edge or go wild. One of the mods was a switchable (Boss) asymmetric to (Ibanez) symmetric clipping.
No one I've asked to play with it, has been able to hear a difference, although all prefer one or the other! |
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Michael Brebes
From:
Northridge CA
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Posted 13 Sep 2022 9:16 am
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Another option has been to have one as a silicon diode and the other a germanium diode. The each clip at different voltages so it makes it non-symmetrical.
_________________
Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 13 Sep 2022 3:59 pm
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| ajm wrote: |
| A common mod is to replace one of the diodes with two, both pointing the same direction. |
Or three, or four, or even five. The more series diodes on one side, the more asymmetrical the clipping.  |
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