diff --git a/amy/constants.py b/amy/constants.py
index e1be32b5..976537e2 100644
--- a/amy/constants.py
+++ b/amy/constants.py
@@ -19,6 +19,7 @@
 AMY_BUS_AUDIO_IN=2
 AMY_MAX_CORES=2
 AMY_MAX_CHANNELS=2
+AMY_NCHANS=1
 AMY_NCHANS=2
 AMY_CORES=2
 AMY_CORES=1
diff --git a/src/amy.h b/src/amy.h
index 071a280b..ab5bb81e 100644
--- a/src/amy.h
+++ b/src/amy.h
@@ -70,12 +70,14 @@ extern const uint32_t pcm_wavetable_len;
 #define BLOCK_SIZE_BITS 8 // log2 of BLOCK_SIZE
 #endif
 
+#ifndef AMY_SAMPLE_RATE
 #ifdef AMY_DAISY
 #define AMY_SAMPLE_RATE 48000
 #elif defined __EMSCRIPTEN__
 #define AMY_SAMPLE_RATE 48000
 #else
-#define AMY_SAMPLE_RATE 44100 
+#define AMY_SAMPLE_RATE 44100
+#endif
 #endif
 
 #define PCM_AMY_SAMPLE_RATE 22050
@@ -105,8 +107,16 @@ extern const uint32_t pcm_wavetable_len;
 #define AMY_MAX_CORES 2          
 #define AMY_MAX_CHANNELS 2
 
-// Always use 2 channels. Clients that want mono can deinterleave
+// Default to 2 channels. Constrained MCUs (e.g. ESP32-C3, single-core RISC-V)
+// default to mono; override with -DAMY_NCHANS=N.
+// Note: i2s.c picks the I2S slot mode based on this value.
+#ifndef AMY_NCHANS
+#if defined(CONFIG_IDF_TARGET_ESP32C3)
+#define AMY_NCHANS 1
+#else
 #define AMY_NCHANS 2
+#endif
+#endif
 
 
 // Use dual cores on supported platforms
diff --git a/src/i2s.c b/src/i2s.c
index ac5797f7..73c2b206 100644
--- a/src/i2s.c
+++ b/src/i2s.c
@@ -14,6 +14,13 @@
 #ifdef ESP_PLATFORM
 #include <esp_task.h>
 
+// I2S slot mode follows AMY_NCHANS so a mono build produces a mono I2S frame.
+#if AMY_NCHANS == 1
+#define AMY_I2S_SLOT_MODE I2S_SLOT_MODE_MONO
+#else
+#define AMY_I2S_SLOT_MODE I2S_SLOT_MODE_STEREO
+#endif
+
 ///////////////////////////////////////////////////////////////
 // ESP32, S3, P4 (maybe others)
 
@@ -79,7 +86,7 @@ amy_err_t esp32_setup_i2s(void) {
 #ifdef I2S_32BIT
     i2s_std_config_t std_cfg = {
         .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(AMY_SAMPLE_RATE),
-        .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, I2S_SLOT_MODE_STEREO),
+        .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, AMY_I2S_SLOT_MODE),
         .gpio_cfg = {
             .mclk = (amy_global.config.i2s_mclk == -1)? I2S_GPIO_UNUSED : amy_global.config.i2s_mclk,
             .bclk = amy_global.config.i2s_bclk,
@@ -96,7 +103,7 @@ amy_err_t esp32_setup_i2s(void) {
 #else // 16 bit I2S
     i2s_std_config_t std_cfg = {
         .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(AMY_SAMPLE_RATE),
-        .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_STEREO),
+        .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, AMY_I2S_SLOT_MODE),
         .gpio_cfg = {
             .mclk = (amy_global.config.i2s_mclk == -1)? I2S_GPIO_UNUSED : amy_global.config.i2s_mclk,
             .bclk = amy_global.config.i2s_bclk,
@@ -138,7 +145,7 @@ amy_err_t esp32_setup_i2s(void) {
         .slot_cfg = {
             .data_bit_width = I2S_DATA_BIT_WIDTH_32BIT,
             .slot_bit_width = I2S_SLOT_BIT_WIDTH_32BIT,
-            .slot_mode = I2S_SLOT_MODE_STEREO,
+            .slot_mode = AMY_I2S_SLOT_MODE,
             .slot_mask = I2S_STD_SLOT_BOTH,
             .ws_width = 32,
             .ws_pol = false, // false in STD_PHILIPS macro