frankenphono preamp update FWIW
mhardy6647
Posts: 33,804
was listening to some dump-find organ LPs :-) this morning on the living room hifi via an on-approval Silk SUT and JLTi MM/MC phono preamp combo sourced from one of the local gurus. Cosmetics of the installation leave a tad to be desired, so I thought youse guyses might be amused to see a photo of it.
The JLTi has two RCA jacks on it for the user to plug in loading resistors. A little empirical research with clip leads and a Radio Shack resistor assortment bag led to plugging in 27k loading resistors (I assume, but don't know, that the JLTi parallels the loading resistors with an internal - 47k?? - load). These are, audibly, pretty good choices (but entirely empirical and not terribly scientifically arrived at, at that). I just tried a variety of resistors across a few decades (or logs, as you prefer), picked a value that sounded good & soldered up two plugs.
Curiously, I have a little trouble with residual hum. I cannot imagine why! ;-)
Sounds great, though. Plenty of gain via this combination, too.
,
best,
mrh
The JLTi has two RCA jacks on it for the user to plug in loading resistors. A little empirical research with clip leads and a Radio Shack resistor assortment bag led to plugging in 27k loading resistors (I assume, but don't know, that the JLTi parallels the loading resistors with an internal - 47k?? - load). These are, audibly, pretty good choices (but entirely empirical and not terribly scientifically arrived at, at that). I just tried a variety of resistors across a few decades (or logs, as you prefer), picked a value that sounded good & soldered up two plugs.
Curiously, I have a little trouble with residual hum. I cannot imagine why! ;-)
Sounds great, though. Plenty of gain via this combination, too.
,
best,
mrh
Post edited by mhardy6647 on
Comments
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Now that's a funky phono pre. Is it battery powered or are those huge caps? Any plans to build a case?
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The active phono preamp is a JLTi and it runs off a wall wart. It has switch-selectable gain for moving magnet or low-output moving coil (LOMC) cartridges, but at the moment it's set for MM gain. The cans that are jury-rigged ahead of the JLTi -- and which occasioned my posting a photo of this monstrosity! -- are a pair of step up transformers (SUTs) from Silk (http://www.sacthailand.com/Transformer_MC.html). These are passive devices that raise the output voltage of an LOMC to MM signal levels to feed the active phono preamp. They'll be installed in a proper box after I formally acquire them (i.e., pay for them). The Silk SUTs are reasonably priced and sound very good.
At the moment, the LOMC in question is an entry-level Denon DL-103; nicest-sounding cheap LOMC out there as far as I am concerned. -
How much do those Silk SUTs cost per pair? Been thinking about getting something to step-up my Pearl phono. I've looked at Lundahl but their prices have gone skyhigh over the last few years (and haven't come down with the falling Euro value either...). Looking now at Cinemags now since they are more affordable. I'm using a MM now for economy reasons, but I'd like to move back a low output MC at some point.For rig details, see my profile. Nothing here anymore...
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Very interesting. That thing must be dead quiet with passive devices to raise the voltage. Sounds like you have a very unique set up there.
