We released TontaubeV1, a character-level TTS model for long-form generation [P]

Hey everyone, My brother and I just released TontaubeV1, a 2.9B-parameter open-weight TTS model focused on expressive speech, long-form generation/narration, and low-latency local inference. It is primarily aimed at English and German and supports zero-shot voice cloning from up to one minute of reference audio. It builds on DualCodec, a multi-codebook discrete audio codec. It was trained on 7 languages and ~200k hours of audio (mostly tested in English and German). I wanted to make a post to highlight two choices that worked well for us and seem less common in current TTS models: 1. Character-level tokenization We start from a Qwen3-1.7B checkpoint for our semantic codebook model. Many modern, and especially LLM-based, TTS models use the tokenizer from the backbone model, add special/audio tokens, and train the model on predicting the next token. We experimented early on with character-level tokenization and found that it generally worked better than using the original BPE tokenizer from Qwen. We still use the tokens emitted by the Qwen tokenizer, but force it to tokenize spoken text as a sequence of individual characters. When experimenting with forcing Qwen to predict text in this mode, we found that it was still able to answer questions correctly, which suggested to us that language understanding was retained even with this unusual representation. We did this because a) context length usually is not as much of an issue for TTS as it is for regular LLMs, since we do not require huge reasoning budgets and use chunking, and b) it makes the character-to-sound mapping much simpler internally. Speech is a lot about syllables and short character sequences. When using the regular BPE tokenizer, we found that the model went out of distribution more often and was more likely to encounter a sequence of tokens that was rare or absent from the TTS training data. Complex sequences of special characters can be particularly confusing because they may tokenize into combinations