Over the years I've accumulated several preamps and amplifiers. I've always been surprised that all this gear sounds pretty much alike in various combinations. Lately I've been using a Transcendent Sound Grounded Grid preamp with 12AU7 tubes I built from a kit with a Latino VTA ST120 also kit built and running KT120 power tubes and 6SN7 drivers. I like the Grounded Grid but the kit came with some near bottom-of-the barrel components. In particular, the output capacitors looked like the cost $5 per 100. I quickly replaced these about three years ago with Russian PIO caps but I used 0.22 uF caps instead of the original 1 uF values. In response to a question regarding output cap values and frequency response, AKer Gadget explained cap value and frequency rolloff. It appeared the 0.22 uF value might be restricting low frequency response. I decided to get some Mundorf EVO oil and aluminum caps in the specified 1 uF value and swap out the PIO's. I was immediately surprised by the improved low bass response. This simple and quite inexpensive mod I can really hear! Maybe I don't have lead ears after all.