Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: Downhome Upstate on July 06, 2014, 07:14:03 AM
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I'm waiting on an Eros kit, and also the parts to assemble a SUT for my Denon 103R.
I have a small die-cast aluminum Hammond case for the SUT, but I'm thinking its too small (4.8 x 2.6 x 1.4) for adding a rotary switch and a pair of resistor networks to adjust the load.
Is there a good spot on the Eros top plate to put the rotary switch (an Elma 1-1264) and terminal lugs (for 2 sets of 5 or 6 resistors each) to hold the loading resistors? Or should I just get a bigger case for the SUT?
Thanks in advance. Hope you had a great holiday weekend.
Mike
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If you only are using one cartridge, there is no need to have an adjustable step-up. Resistor loading is something you want to avoid in a step-up setup because it can incite ringing in the transformer. Maybe a switch to change transformer taps, but even then, hardwiring is a better option with the low level signals you are dealing with. And, realistically, one tap on your transformer is going to be pretty ideal (assuming you're using something up to the task); a 103R wants to see ~100Ω reflected impedance (around 1:20 turns ratio). So you can set it and forget it...
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Got it, Josh. But doesn't the 1:20 tap (I'll be using Cinemag CM-1254's) give me a signal that's about double the the center of the design range for the Eros: 0.25 mv x 20 = 5 mv, rather than the 2.5 mv or less that the write-up on the product page suggests is optimal?
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Hmmmm, that sentence is written in a confusing way. What it's trying to say is that the Eros can work with lower output cartridges than the Seduction. S(r)eduction really can't run on less than 5mv. For the Eros, 5mv is golden, 2.5mv is a minimum guidline.
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Great! The 1:20 tap it is then. I'll find something else to do with my new Elma rotary switch.