fable

README.md

@@ -1,16 +1,17 @@
 # ambium
 
 Analog brown-noise generator. Single **+12 V** supply, breadboard-friendly.
-Deep filtered rumble to a **4 Ω speaker** via a TIP120 driver.
+Deep filtered rumble to a **4 Ω speaker** via a cool-running **Class-AB push-pull** output.
 
 Reference designators and model numbers are consistent across every diagram, the
 BOM, and the connection list — the connection list is the authoritative netlist.
 
 ## Parts
 
-- **U1** = LM358 (dual op-amp, DIP-8). U1B = amp + brown shaping. U1A unused (parked).
+- **U1** = LM358 (dual op-amp, DIP-8). U1B = amp + brown shaping. U1A = output driver.
 - **Q1** = 2N3904 (NPN). Avalanche noise source.
-- **Q3** = TIP120 (NPN Darlington, TO-220). Class-A speaker driver.
+- **Q2** = PN2222 (NPN). Push-pull top half (sources +).
+- **Q3** = PN2907 (PNP). Push-pull bottom half (sinks −).
 
 ## Nets
 
@@ -19,27 +20,9 @@ BOM, and the connection list — the connection list is the authoritative netlis
 ## Signal chain
 
 ```
- [noise]      [amp + brown]      [driver]
+ [noise]      [amp + brown]        [push-pull driver]
-Q1 2N3904  →  U1B LM358 −6dB/oct →  Q3 TIP120  →  4Ω speaker
+Q1 2N3904  →  U1B LM358 −6dB/oct →  U1A + Q2/Q3  →  4Ω speaker
- NOISE         AMP                   (class A)
+ NOISE         AMP                   OUT (Class AB, cool)
-```
-
-Legend:
-```
- [Rxx val]  resistor        ──┤├──   film / non-polar cap    ●  junction
-                            ──+┤├──  polarised cap (+ = + terminal)
-     │\                                                      ×  no-connect
- ────┤−\        op-amp:  IN− top, IN+ bottom, OUT right.     ►  net continues
-     │  >──     Powered from +12V / GND (LM358 pins 8 / 4).
- ────┤+ /
-     │/
-              E          transistor: E / B / C labels outside the box.
-              │
-           ┌──┴──┐
-      B ───┤ Qx  │   NPN
-           └──┬──┘
-              │
-              C
 ```
 
 ---
@@ -122,43 +105,73 @@ LM358 DIP-8, notch at top, pin 1 top-left. Amp = **unit B** (pins 5/6/7).
 DC handling: C1 blocks DC into Rin1, so the op-amp's own offset sees unity gain — output
 sits at VREF (6 V), no railing.
 
-Unit A unused → park as a follower so it can't oscillate: pin 3 → VREF, pin 2 → pin 1.
+Unit A (pins 1/2/3) = the push-pull output driver — see next section.
 Power/decoupling (whole chip, once): pin 8 → +12V, pin 4 → GND. 47µF bulk + 0.1µF at
 pin 8.
 
 ---
 
-## Output driver — TIP120 class-A follower (Q3), 4Ω speaker
+## Output driver — Class-AB push-pull (U1A + Q2/Q3), 4Ω speaker
 
-AMP is line level; the LM358 can't drive a speaker. Q3 emitter follower supplies the
+AMP is line level; the LM358 can't drive a speaker alone. Complementary emitter-
-current. Class A — needs a heatsink.
+followers **inside the U1A loop**: Q2 (NPN) pushes the positive half, Q3 (PNP) pulls
+the negative half. Both halves are actively driven, so there's **no idle resistor and
+near-zero quiescent current → it runs cool.** U1A drives both bases; global feedback
+from OUT hides crossover distortion (no bias diodes needed).
+
+Driver = LM358 **unit A** (pins 1/2/3), same chip as the amp.
 
 ```
-     +12V                              +12V
+                    ┌─────∪────┐
-      │                                 │
+ bases ─ OUT A   1 ─┤          ├ 8  V+     ──── +12V
-   [Rb1 10k]                            C (collector)
+   OUT ─ IN− A   2 ─┤  LM358   ├ 7  (OUT B → AMP, Stage 2)
-      │                              ┌──┴──┐
+   AMP ─ IN+ A   3 ─┤          ├ 6
-      ●───────●───────────────────B──┤ Q3  │  TIP120
+         V−      4 ─┤          ├ 5
-      │       │                      └──┬──┘
+                    └──────────┘
-   [Rb2 10k]  │                         │
-      │       │                         E
-     GND      │                         │
-              │                         ●──+┤├──► SPKR ─ GND
-   AMP ─+┤├───┘                         │   Cout2 470µF (+ → emitter)
-        Cc 10µF                     [Re 22Ω 3W]  4Ω
-                                        │
-        (base node ● = Rb1/Rb2/Cc)     GND
 ```
-The base node ● sits at ~6 V (Rb1/Rb2). Cc lands there and adds the AC — it never
-connects to +12V.
-- Rb1/Rb2 = 10k/10k → base ~6 V. Cc AC-couples AMP onto the base.
-- Emitter ~4.5 V (base − ~1.5 V Darlington drop). Iq = 4.5V/Re ≈ 200 mA.
-- Cout2 blocks DC; speaker sees AC only.
-- **Heatsink Q3** (~1.5 W idle). Re ≥3 W.
-- Cooler/quieter: Re = 47 Ω → Iq ~100 mA.
-- Bias sag (hum/distortion): stiffen divider to 4.7k/4.7k.
 
-TIP120 pinout (TO-220, face up, pins down): **1 Base · 2 Collector · 3 Emitter**.
+Push-pull output stage (totem pole):
+```
+                     +12V
+                      │
+                      C
+                  ┌───┴───┐
+   bases ──B──────┤  Q2   │   PN2222 (NPN — sources +half)
+                  └───┬───┘
+                      E
+                  [Re1 10Ω]
+                      │
+                      ●──────────► OUT ──+┤├──► SPKR ─ GND
+                      │                 Cout 470µF   4Ω
+                  [Re2 10Ω]            (+ → OUT)
+                      E
+                  ┌───┴───┐
+   bases ──B──────┤  Q3   │   PN2907 (PNP — sinks −half)
+                  └───┬───┘
+                      C
+                      │
+                     GND
+```
+
+Connections:
+```
+  input:      AMP ─────────────● pin 3 (IN+ A)
+  drive:      pin 1 (OUT A) ───● bases  → Q2.base + Q3.base
+  feedback:   OUT ─────────────● pin 2 (IN− A)
+  Q2:  C → +12V   B → bases   E → Re1 → OUT
+  Q3:  C → GND    B → bases   E → Re2 → OUT
+  OUT node = Re1 ● Re2 ● pin 2 (fb) ● Cout.+  ;  Cout.− → speaker → GND
+```
+- Idle ≈ 0 → **cool, no heatsink.** Re1/Re2 = **10 Ω ¼ W** (4.7–10 Ω ok; carry only AC — not hot).
+- OUT sits at ~6 V DC (follows AMP); **Cout 470 µF** blocks it, speaker sees AC only.
+
+TO-92 pinout (flat face toward you, leads down): **PN2222 = E-B-C**, **PN2907 = E-B-C**
+(confirm against your batch's datasheet).
+
+- PN2222/PN2907 cap ~600 mA → ~1 W into 4 Ω before current-limiting. Plenty for the
+  rumble, and cool. Want more power → TIP120+TIP125 pair, or an amp chip.
+- Crossover buzz at low level? Split the bases and add **2× 1N4148** between them for
+  bias. Usually unneeded — feedback handles it for a noise source.
 
 ---
 
@@ -166,39 +179,38 @@ TIP120 pinout (TO-220, face up, pins down): **1 Base · 2 Collector · 3 Emitter
 
 | Ref | Value | Part | Function |
 |-----|-------|------|----------|
-| U1 | — | LM358 (DIP-8) | U1B amp (U1A unused) |
+| U1 | — | LM358 (DIP-8) | U1B amp+brown, U1A output driver |
 | Q1 | — | 2N3904 | avalanche noise source |
-| Q3 | — | TIP120 | class-A speaker driver |
+| Q2 | — | PN2222 (NPN) | push-pull top (source) |
+| Q3 | — | PN2907 (PNP) | push-pull bottom (sink) |
 | R1 | 100k | resistor | avalanche current limit |
 | R2, R3 | 10k | resistor | VREF divider |
 | Rin1 | 1k | resistor | amp input |
 | Rf1 | 1M | resistor | amp feedback (low-freq gain ×1000) |
-| Rb1, Rb2 | 10k | resistor | Q3 base bias (~6 V) |
+| Re1, Re2 | 10Ω ¼W | resistor | push-pull emitter degeneration (4.7–10Ω ok) |
-| Re | 22Ω 3W | resistor | Q3 idle-current set |
 | C1 | 10µF | electrolytic | noise coupling |
 | Cref | 10µF | electrolytic | VREF bypass |
 | Cf1 | 8.2nF | film / ceramic | feedback / brown shaping (−6dB/oct, corner ~19 Hz) |
-| Cc | 10µF | electrolytic | AMP → base coupling |
+| Cout | 470µF ≥16V | electrolytic | speaker coupling (big, for lows) |
-| Cout2 | 470µF ≥16V | electrolytic | speaker coupling (big, for lows) |
 | — | 0.1µF | ceramic | LM358 decoupling |
 | — | 47µF | electrolytic | +12V bulk |
 
-Chip count: 1× LM358 + 1× 2N3904 + 1× TIP120. Q3 needs a heatsink.
+Chip count: 1× LM358 + 1× 2N3904 + PN2222/PN2907 pair. **No heatsink needed** (Class AB).
 
 ---
 
 ## Connection list (authoritative netlist)
 
 ```
-+12V   : R1.1, R2.1, U1.8, Rb1.1, Q3.collector, 47µF+
++12V   : R1.1, R2.1, U1.8, Q2.collector, 47µF+
-GND    : R3.2, Q1.base, Cref.−, U1.4, Rb2.2, Re.2, 47µF−, 0.1µF
+GND    : R3.2, Q1.base, Cref.−, U1.4, Q3.collector, 47µF−, 0.1µF
-VREF   : R2.2, R3.1, Cref.+, U1B.IN+(5), U1A.IN+(3)
+VREF   : R2.2, R3.1, Cref.+, U1B.IN+(5)
-         U1A.OUT(1) = U1A.IN−(2)                  (spare amp parked as follower)
 (src)  : R1.2, Q1.emitter, C1.+                 (internal raw-noise node)
 NOISE  : C1.−, Rin1.1                            (after C1)
-AMP    : U1B.OUT(7), Rf1, Cf1, Cc.1              (Rin1.2, Rf1, Cf1, U1B.IN−(6) = summing)
+AMP    : U1B.OUT(7), Rf1, Cf1, U1A.IN+(3)        (Rin1.2, Rf1, Cf1, U1B.IN−(6) = summing)
-base   : Cc.2, Rb1.2, Rb2.1, Q3.base             (~6 V bias)
+bases  : U1A.OUT(1), Q2.base, Q3.base            (driver output → both bases)
-SPKR   : Q3.emitter, Re.1, Cout2.+ ;  Cout2.− → speaker → GND
+OUT    : Q2.emitter→Re1 ; Q3.emitter→Re2 ; Re1.2 = Re2.2 = OUT node
+         OUT → U1A.IN−(2) (feedback) ; OUT → Cout.+ ; Cout.− → speaker → GND
 Q1     : collector = no-connect
 ```
 
@@ -209,7 +221,7 @@ Q1     : collector = no-connect
 1. **VREF** — confirm ~6.0 V.
 2. **Noise (R1, Q1)** — scope Q1 node → hiss (~mV). None? swap 2N3904 or raise supply to 12–15 V.
 3. **Amp (U1B)** — scope AMP → deep rumble (~volts), darker than the raw Q1 hiss (that's the brown slope).
-4. **Driver (Q3)** — feed AMP through Cc. Speaker hisses. Q3 warm, not hot; too hot → raise Re.
+4. **Driver (Q2/Q3)** — wire push-pull + feedback. Speaker rumbles. Transistors stay **cool** (near-zero idle). OUT DC ~6 V.
 
 ## Tuning
 
@@ -218,5 +230,5 @@ Q1     : collector = no-connect
 | Louder | ↑ Rf1 (raises low-freq gain; watch clipping) |
 | Darker / deeper | ↑ Cf1 (lowers corner, more brown) |
 | Brighter (toward white) | ↓ Cf1 (raises corner) |
-| Cooler driver | ↑ Re |
+| Kill crossover buzz | add 2× 1N4148 base-bias diodes |
-| More headroom | ↓ Re (hotter — bigger heatsink) |
+| More power | TIP120+TIP125 pair, or amp chip (PAM8403 / TDA2822) |

ambium.kicad_prl

@@ -0,0 +1,105 @@
+{
+  "board": {
+    "active_layer": 0,
+    "active_layer_preset": "",
+    "auto_track_width": true,
+    "hidden_netclasses": [],
+    "hidden_nets": [],
+    "high_contrast_mode": 0,
+    "net_color_mode": 1,
+    "opacity": {
+      "images": 0.6,
+      "pads": 1.0,
+      "shapes": 1.0,
+      "tracks": 1.0,
+      "vias": 1.0,
+      "zones": 0.6
+    },
+    "prototype_zone_fills": false,
+    "selection_filter": {
+      "dimensions": true,
+      "footprints": true,
+      "graphics": true,
+      "keepouts": true,
+      "lockedItems": false,
+      "otherItems": true,
+      "pads": true,
+      "text": true,
+      "tracks": true,
+      "vias": true,
+      "zones": true
+    },
+    "visible_items": [
+      "vias",
+      "footprint_text",
+      "footprint_anchors",
+      "ratsnest",
+      "grid",
+      "footprints_front",
+      "footprints_back",
+      "footprint_values",
+      "footprint_references",
+      "tracks",
+      "drc_errors",
+      "drawing_sheet",
+      "bitmaps",
+      "pads",
+      "zones",
+      "drc_warnings",
+      "drc_exclusions",
+      "locked_item_shadows",
+      "conflict_shadows",
+      "shapes",
+      "board_outline_area",
+      "ly_points"
+    ],
+    "visible_layers": "ffffffff_ffffffff_ffffffff_ffffffff",
+    "zone_display_mode": 0
+  },
+  "git": {
+    "integration_disabled": false,
+    "repo_type": "",
+    "repo_username": "",
+    "ssh_key": ""
+  },
+  "meta": {
+    "filename": "ambium.kicad_prl",
+    "version": 5
+  },
+  "net_inspector_panel": {
+    "col_hidden": [],
+    "col_order": [],
+    "col_widths": [],
+    "custom_group_rules": [],
+    "expanded_rows": [],
+    "filter_by_net_name": true,
+    "filter_by_netclass": true,
+    "filter_text": "",
+    "group_by_constraint": false,
+    "group_by_netclass": false,
+    "show_time_domain_details": false,
+    "show_unconnected_nets": false,
+    "show_zero_pad_nets": false,
+    "sort_ascending": true,
+    "sorting_column": -1
+  },
+  "open_jobsets": [],
+  "project": {
+    "files": []
+  },
+  "schematic": {
+    "hierarchy_collapsed": [],
+    "selection_filter": {
+      "graphics": true,
+      "images": true,
+      "labels": true,
+      "lockedItems": false,
+      "otherItems": true,
+      "pins": true,
+      "ruleAreas": true,
+      "symbols": true,
+      "text": true,
+      "wires": true
+    }
+  }
+}

kicad/ambium.spice.cir

@@ -1,25 +1,20 @@
 .title KiCad schematic
-U1 __U1
-Rf1 /VREF /AMP 1Meg
-Cf1 /VREF /AMP 8.2n
-Rin2 /AMP /VREF 10k
-U2 __U2
-Cout Net-_U2B--_ Net-_Cout-Pad2_ 10u
-Rin1 Net-_C1-Pad2_ /VREF 1k
 R2 +12V /VREF 10k
-Q1 __Q1
+C3 +12V GND 47u
-C1 Net-_Q1-E_ Net-_C1-Pad2_ 10u
 R3 /VREF GND 10k
-R1 +12V Net-_Q1-E_ 100k
 Cref /VREF GND 10u
-Ra /VREF Net-_U2A-+_ 100k
+C2 +12V GND 100n
-Ct /LFO_CV /VREF 10u
+R1 +12V /SRC 100k
-Rt /LFO_CV Net-_Rh-Pad2_ 1Meg
+C1 /SRC /NOISE 10u
-Rb2 /LFO_CV Net-_Q2-B_ 100k
+Rin1 /NOISE /SUM 1k
-Rs /BROWN Net-_Q2-C_ 47k
+Q1 __Q1
+Rf1 /SUM /AMP 1Meg
+Cf1 /SUM /AMP 8.2n
+U1 __U1
+Re2 Net-_Q3-E_ /OUT 10
+Q3 __Q3
+LS1 /SPKR GND Speaker
+Cout /OUT /SPKR 470u
+Re1 Net-_Q2-E_ /OUT 10
 Q2 __Q2
-Rh Net-_U2A-+_ Net-_Rh-Pad2_ 100k
-Cint /VREF /BROWN 100n
-Rf2 /VREF /BROWN 1Meg
-Rvol __Rvol
 .end