(Image courtesy of the Tube Screamer Technology Page with red stuff added by me)
| TS7 Blindfold Tests /\ | ||
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Tube Screamer pedals all have this transistor circuit used as an output stage:
(Image courtesy of the
Tube Screamer Technology Page
with red stuff added by me)
The most common Tube Screamer mod is to change the values of the resistors higlighted in red.
The original TS-808 had:
Rb = 100 ohms
Rc = 10K ohms
Later versions of the Tube Screamer (including my TS7) have:
Rb =
470 ohms
Rc = 100K ohms
On the TS7, the resistors referred to above as Rb and Rc are designated R55 and R58, respectively:
The prevailing wisdom is that changing the resistors on a newer Tube Screamer to the values in the older TS808 (often referred to as an "808 mod") gives a better sound, especially when the pedal is being used to overdrive the input of a tube amplifier. When the Tube Screamer is being used like this, it usually is acting as a clean booster, i.e. it amplifies the signal without distorting it very much. To test the 808 mod in a similar situation, I created Test Rig 2, in which the Tube Screamer's output is sent through a Hughes & Kettner Tubeman pedal.
For the "non-808-modded" recordings, I had carbon film resistors in the output circuit with
these measured values:
Rb = R55 = 468 ohms
Rc = R58 = 99.2K ohms
I had done
some experimenting with these earlier, so they were not the actual resistors that came with the TS7. But they
were similar carbon film resistors with the values shown above.
For the "808-modded" portion of the test, I changed the two output resistors to carbon composition resistors
(as opposed to carbon film) with the 808's resistor values, since this is how it's usually done. The new resistors had
these measured values:
Rb = R55 = 102.1 ohms
Rc = R58 = 10.00K ohms.
In each section below, one of the recordings was done with the 808-modded TS7 and one was done with the non-808 modded TS7. They have been mixed randomly. Select the recording you think has the 808 modification.
| Section 1: Blues Riff | Recording A (1458K wav) | Recording B (2761K wav) |
| Section 2: Long Power Chord | Recording A (856K wav) | Recording B (1798K wav) |
| Section 3: Short Power Chord | Recording A (209K wav) | Recording B (103K wav) |
| Section 4: Lead with Dynamics | Recording A (2880K wav) | Recording B (1448K wav) |
| Section 5: Long Single Note | Recording A (479K wav) | Recording B (961K wav) |
| Section 6: Short Single Note | Recording A (85K wav) | Recording B (173K wav) |
| Section 7: Long Fourth | Recording A (1096K wav) | Recording B (521K wav) |
| Section 8: Short Fourth | Recording A (69K wav) | Recording B (144K wav) |
So far, everyone who has taken this test got them all correct. So this mod is apparently making a very audible difference.
