Following suggestions here, I got two 12V 5Ah SLAs and hooked them up to power my recently built Bugle. I did it mainly because I was quickly going through regular 9V batteries, but I also gathered from posts here that there may be some enhancement of performance. So I was disappointed to hear a distinct degradation. On an hour or so listening and comparing, the sound strikes me as tinnier, the bass is weaker; instruments lose some of the distinctiveness of their sound. It is as if a grainy jangly veil has been thrown over everything.
I first built the Bugle for 60dB gain and used a 39 ohm load resistance, as suggested by the cartridge manufacturer. I was hearing more hiss than I would like, so I modified the Bugle according to a suggestion here (Topic: Do I need shielded ICs from TT to Bugle @ 60db??; Reply #2 on: December 30, 2004). I lowered the 13k and 390 gain setting resistors in the first stage to 3.3k and 100 ohms, respectively. And I lowered the series 1k resistor in the first stage to 100 ohms. This indeed reduced the hiss to acceptable levels. (I modified one channel and then tested. There was an obvious difference.) As a bonus, the overall sound was noticeably better. The midrange had seemed kind of too strong, or boomy, to me. The change cleared this up. The Bugle was sounding great.
So, what might be going on, and what could I do to still use the SLAs (and charger) that I bought and have the better sound that I got with the standard 9Vs?