Epifani UL-series Amp Tech - Jensen XFMR Install???

[lowfreqgeek]

I'm sure Epifani has closely guarded their IP for the UL-series amps, but I'm curious if anyone has installed a Jensen into their amp? The PCB with the DI has both a Jensen JT DB E footprint and a set of jumpers that I can only imagine go with that Jensen footprint. I've compared the DI on the Epifani to a number of others and it's good, but not great. A little too much mid-range with a "burnished" high-end. Kinda like a blanket on it. I prefer my JDI, Avalon, and even SRW Bass 350 DI. But things might be different with the Jensen installed (depending on what drives it).

I'd also love to see the schematic for the input sections of the active and passive inputs. There is a drastic difference in tone when using a passive instrument, and honestly, the "active" input sounds a bit anemic with a passive bass. I love having the 2 channels, but almost all my basses are passive, so it's almost a moot point - though I'll often set up each channel for a different bass and then use the "passive" input. I'm not sure if it's just a matter of swapping a resistor or pad to get a higher input impedance, or if it's different circuit altogether (kinda hidden...).

I can't believe I waited this long to open mine up, but I found a couple of cool features for channel 1: dip switches to set the treble shelf frequency (just like channel 2) and a pot to control the level of the cut on the mid-cut switch. I've NEVER used the mid-cut cause I always felt it was way too drastic for me. But now I know how to adjust it and it's very cool. There are other pots sprinkled throughout and I'd love to know what those do. Some may set bias currents for some of the discretes, so probably best to not poke around too much without knowing what each pot does.

Insight would be much appreciated. Otherwise I may have to resort to reverse engineering things, which means tearing it apart and not using it for a while. Not a good idea...

[MIJ-VI]

Irreversible reverse engineering can be interesting and even practical when safely performed on decommissioned gear of no further utility or market value, otherwise... *bump*

[KJung]

I know that a Jensen 'upgrade' to the DI was an option on these (at least when they first came out).... it was listed on the website in the UL specs. So, you are right there.

I know Nick also made a big deal about the DI design being unique, and that the annoying 'pop' you get when plugging or unplugging your instrument with these amps was related to the DI design (he said something about the input not being grounded to the chassis or something like that, in order to provide a more pure pass through to the DI... the DI was one of the few things I liked about that amp!).

I do believe in talking to Nick back in the day that the active input has a lower impedance input, but it is a bit fuzzy to me at this point. You might just be hearing the pad impact.

[lowfreqgeek]

The hooks are all there to add the Jensen, so it's definitely doable. BTW - the Aguilar AG500 has the same option. I never did it to mine as I moved on to the Epifani and sold the Aguilar before I got 'round to it, but I have the instructions from Dave @ Aguilar.

I haven't looked at the DI in a lot of detail, but I know it uses the same TL072 that my SWR Bass 350 uses. I also know that there are no DC-blocking caps in the DI path. I think Epifani changed this on the new models, but mine is an older one. The "internal" stuff like grounding and power schemes are harder to determine on visual inspection alone. I'm not sure that I'll change anything, though; I'm set for DIs with a JDI, DB900, GT Brick and a couple of amps...

Personally, I love the amp - at least with my UL112 stack. I've never had a problem being heard in a mix, and that goes from jazz to hard rock to country. It's a somewhat unique sound, to my ears, but I like it (and I rarely use the EQ for anything more than room compensation).