diff --git a/src/amy.c b/src/amy.c
index 9c5f6bb..f9ef426 100644
--- a/src/amy.c
+++ b/src/amy.c
@@ -1764,7 +1764,7 @@ int16_t * amy_fill_buffer() {
 
             // TODO -- the esp stuff here could sit outside of AMY
             // For some reason, have to drop a bit to stop hard wrapping on esp?
-#if defined(ESP_PLATFORM) || defined(__IMXRT1062__)
+            #if defined(ESP_PLATFORM) || defined(__IMXRT1062__) || defined(AMY_ISSUE_425)
                 uintval >>= 1;
             #endif
             if (positive) {
diff --git a/src/amy.h b/src/amy.h
index 232d75d..02cc0d5 100644
--- a/src/amy.h
+++ b/src/amy.h
@@ -43,6 +43,7 @@ extern const uint16_t pcm_samples;
 
 
 // Set block size and SR. We try for 256/44100, but some platforms don't let us:
+#ifndef AMY_BLOCK_SIZE
 #ifdef AMY_DAISY
 #define AMY_BLOCK_SIZE 128
 #define BLOCK_SIZE_BITS 7 // log2 of BLOCK_SIZE
@@ -50,7 +51,9 @@ extern const uint16_t pcm_samples;
 #define AMY_BLOCK_SIZE 256
 #define BLOCK_SIZE_BITS 8 // log2 of BLOCK_SIZE
 #endif
+#endif
 
+#ifndef AMY_SAMPLE_RATE
 #ifdef AMY_DAISY
 #define AMY_SAMPLE_RATE 48000
 #elif defined __EMSCRIPTEN__
@@ -58,8 +61,11 @@ extern const uint16_t pcm_samples;
 #else
 #define AMY_SAMPLE_RATE 44100 
 #endif
+#endif
 
+#ifndef PCM_AMY_SAMPLE_RATE
 #define PCM_AMY_SAMPLE_RATE 22050
+#endif
 
 // Transfer types.
 #define AMY_TRANSFER_TYPE_NONE 0