TS 9 operation

From mhjel–(at)–ki.fi Wed Nov 13 09:40:26 CST 1996
From: “Mathias C. Hjelt”
Newsgroups: rec.music.makers.guitar,alt.guitar.amps
Subject: TS-9 (Re: Placement of satur. tube amp in fx chain)
Date: Wed, 13 Nov 1996 11:30:19 +0200
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Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:115712 alt.guitar.amps:27337

Cybermonk wrote:

>>I don’t know about the Tube King, but the Ibanez TS-9 was nothing
>>but two op-amps (definitely solid state), and one of them had diodes
>>in the feedback to produce distortion (also definitely solid state).

>I believe that the Tube Screamer, however, simply mixes
>run-of-the-mill distortion with clean guitar signal. I hypothesize
>that all true guitar “overdrives” do the same.
>
>Would someone please verify that the Tube Screamer lets some clean
>signal through, mixed with some distortion?

As far as I can tell, the TS-9 doesn’t mix clean and distorted sound.
First, the signal is buffered by a transistor, in order to avoid
impedance problems. Then it goes into an op-amp with two clipping
diodes (one in each direction) and the Drive pot in the feedback.
There’s also some RC stuff for static tone shaping in the feedback.
The first op-amp is followed by a simple RC low-pass filter, and
then another op-amp which is configured in an interesting way,
providing you with the Tone control. The Level control is nothing
but a passive volume control pot right before the output jack.

In any case, *everything* goes through the diode stage. There’s no
mixing of post-clip and pre-clip signals going on in the device
(unless all the schematics I’ve seen are completely wrong). The only
thing which may make it sound like part of the sound is clean, is
the simple EQ:ing it does. Diodes clip in a really rude way, but
only if the signal goes above a certain level, so everything that’s
EQ:d down low enough will pass through without clipping.

For those of you who are into electronics and would like to build
a TS9 clone, check out http://members.aol.com/jorman/ts9.gif

A whole lot the good ol’ fuzz boxes and overdrive boxes do it the
same way – simple frequency response tweaking and solid-state
clipping. In the old days, people used germanium transistors rather
than op-amps and signal diodes, but basically they all did the same
kind of harsh clipping. There are some exceptions – some devices
use FETs to obtain a transfer curve more similar to that of an
overdriven tube. If I recall, the well-known Tech21 Sans-Amp GT2
is mainly FET-based. Craig Anderton’s Tube Sound fuzz uses CMOS
hex inverters (yeah, that’s right), which include FET-related
stages, giving that soft clipping.

Anyhow, many years ago I once tried putting in a clean/clip balance
pot into a terribly sounding transistor fuzz design of mine, but
it sounded even more weird, so I scrapped it. Haven’t heard about
any commerical devices doing this, but then, I haven’t looked into
any fancier overdrive boxes.

Cheers,

Mathias C. Hjelt
Audio Dream
mhjel–(at)–ki.fi