Ampeg Portaflex B-15N
Ampeg · 1960
What It Is
The Ampeg Portaflex B-15N is a 30-watt combo bass amplifier with a distinctive flip-top design — the speaker cabinet inverts and locks around the amp head for transport. Introduced in 1960, the B-15N became the default bass amplifier in professional recording studios through the 1960s. It is the amp heard on the vast majority of Motown, Stax, and Atlantic soul and R&B recordings of that era. James Jamerson recorded virtually every Motown classic through a B-15N. Unlike the SVT, the B-15N is a studio amp — not made for volume, but for tone. Warm, defined, and immediate.
Tonal Character
Warm and round with a natural midrange presence that makes bass lines immediately audible in a mix without needing to push volume. The 15-inch speaker adds depth. Pushed past clean, the B-15N produces a soft, organic breakup that is musically compelling. Less headroom than the SVT, but more character at lower volumes. Ideal for recording and small-venue performance.
Tube Complement
Not sure what these mean? See the Tube Reference →
Found In
| Platform | Model Names |
|---|---|
| HeadRush | 66 FLIP BASS |
Videos
Manual
View ManualFamous Uses
- →James Jamerson — Motown (virtually every 1960s Motown track)
- →Bob Babbitt — Motown
- →Countless Stax and Atlantic sessions
Best For
Controls Explained
Descriptions reflect the real-world gear these models are inspired by. Your modeler's implementation may vary. Use as a starting point — always trust your ears.
Volume
The single volume control governs both preamp gain and overall output level. At low settings (1–4), the B-15N is clean and warm — this is the Motown studio tone that James Jamerson used on virtually every classic recording. As volume increases past 5–6, the amp begins to gently saturate in a musically pleasing way — not crunchy or aggressive, but adding a subtle harmonic richness that makes bass lines feel more alive. At high settings (8+), the breakup becomes more pronounced and the low end starts to compress. On a modeler, set volume to where you want the simulation to feel naturally compressed, typically 5–7.
Bass
Controls low-end weight. The B-15N's closed-back 1×15 design produces tight, focused bass — different from the open, airy quality of the Bassman's 4×10. Setting bass higher (6–8) produces the deep, round thump associated with soul and R&B recordings. Lower settings (3–5) produce a tighter, more defined low end that suits funk bass where note clarity matters. Unlike the SVT, the B-15N doesn't have enormous sub-bass headroom — it's a warm rather than a huge amp.
Treble
Adds definition and upper-harmonic presence. At low settings, the B-15N has a somewhat dark character that can be warm and beautiful on upright bass or finger-style electric. At moderate treble settings (5–7), bass lines gain definition and note separation without becoming aggressive. The classic Jamerson tone uses relatively low treble — the definition came from playing style rather than EQ. For more modern funk or rock applications, bringing treble up to 6–8 adds the presence needed to cut through.
Sample Configurations
Starting points for common tones — dial in from here.
| Name | Volume | Bass | Treble | Notes |
|---|---|---|---|---|
| Motown Studio | 4 | 6 | 3 | The James Jamerson reference tone. Warm, round, immediate. |
| Warm R&B | 5 | 5 | 5 | Slightly more treble for note separation on melodic bass lines. |
| Pushed Saturation | 7 | 5 | 4 | Volume past clean threshold. Soft, organic breakup. |
Suggested Pairings
- →Ampeg 1×15 (Eminence) — Stock pairing — warm and full
- →Fender 2×12 (Jensen P12R) — Brighter, good for recording