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Overdrive1979· Ibanez / Maxon (Japan)

Ibanez TS808 Tube Screamer

The mid-humped op-amp overdrive that defined modern blues-rock.

Schematic previewDraft · not yet verified

Ibanez TS808 Tube Screamer
Power & VREF biasInput buffer (Q1, common-collector)Non-inverting op-amp clipper (IC1A)Tone stage (IC1B, active baxandall-style)Level pot + output buffer (Q2)V19G0C12100uR1510kR1610kC1147uVIN1SINE(0 0.1 1k)C120nR11kR2510kQ12SC1815R310kC21uR510kIC1AJRC4558C347nR44.7kR751kRV1500kD11N4148D21N4148C451pR81kC50.22uR1010kIC1BJRC4558RV220kR11220C90.22uC71uRV3100kC60.1uR12510kQ22SC1815R1410kR17100C1010uR1810kVOUT1VCC00VCC0VCCVREFVREF0VREF0ININQ1B_INQ1B_INQ1BQ1BVREFQ1BVCCQ1EQ1E0Q1ECLIP_INCLIP_INVREFCLIP_INCLIP_FBCLIP_OUTVCC0CLIP_FBZI_MIDZI_MIDVREFCLIP_OUTDRIVE_WDRIVE_WCLIP_FBCLIP_FBCLIP_OUTCLIP_FBCLIP_FBCLIP_OUTCLIP_OUTCLIP_FBCLIP_OUTLP_OUTLP_OUT0LP_OUTVREFLP_OUTTONE_FBTONE_OUTVCC0TONE_FBTONE_WLP_OUTTONE_WTONE_W2TONE_W20TONE_OUTLEVEL_INLEVEL_INLEVEL_W0LEVEL_WQ2BQ2BVREFQ2BVCCQ2EQ2E0Q2EOUT_CAPOUT_CAPOUTOUT0OUT
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Connectivity passes validation, but reference-topology and visual-schematic review are still in progress. Loading into the editor preserves explicit pinNets (logical connectivity is the source of truth — wires are cosmetic).

About

A symmetric soft-clipping overdrive built around a JRC4558 op-amp in a non-inverting gain stage. Two anti-parallel 1N914 diodes inside the feedback loop create smooth, compressed clipping while the surrounding R/C network sculpts the famous mid-hump.

Signal chain preview

5 stages
Input
Input buffer (2N5088 emitter follower)
Non-inverting op-amp gain stage (JRC4558, gain set by 500k Drive pot)
Soft-clipping diodes (1N914 anti-parallel in feedback loop)
Tone control (single tilt-style around op-amp half)
Output level pot + buffer
Output

Quick facts

  • Soft clipping with diodes in the feedback loop = compressed, dynamic feel.
  • Frequency response has a ~720 Hz mid peak that cuts through a band mix.
  • Stevie Ray Vaughan used a TS808 to push his Fender amps into singing sustain.
  • JRC4558D op-amp is widely considered 'the' chip, though many alternatives sound nearly identical.

Controls

  • Drive (500k log)
  • Tone (20k linear)
  • Level (100k log)

Mod recipes Pro

4 mods
  • Keeley Mod Plus

    Wider frequency response and less mid-hump — closer to a transparent boost.

    How: Replace C3 (input cap) 0.047 µF with 1 µF film, replace C5 (output cap) 0.22 µF with 1 µF film, swap clipping diodes D1/D2 with 1N4001 for higher clipping threshold and more headroom.

  • TS9 to TS808 conversion

    Restore the original 1979 lower-noise output topology.

    How: Change R10 (output) from 100Ω to 470Ω and R11 (pulldown) from 10kΩ to 100kΩ.

  • LED clipping

    Brighter, more open distortion with higher output volume.

    How: Replace D1/D2 (1N914) with 2× red LEDs back-to-back. Expect ~+6 dB output.

  • True bypass

    Eliminate buffered-bypass tone-suck when off.

    How: Rewire the input/output jacks through a 3PDT footswitch; cut the JFET bypass switching trace.

References

Community-sourced (ElectroSmash, FreeStompboxes wiki). Verify part numbers before ordering.