Recommandation for 1:6 1:8 SUT under $5K?
I’m looking for some advice on a step-up transformer that pairs well with my Audio Research LS28SE, PH9, and Hana Umami Blue cartridge. I currently have both the Denon AU-S1 and AU-340. The AU-S1 sounds absolutely beautiful—very transparent and open—but at 1:13 the gain is too high, and I’m getting some clipping, especially on dynamic peaks. Even with the AU-340 at 1:10, I can still hear a bit of overload. I’ve tried playing with loading and parallel resistors, but the issue really comes down to gain. I think something in the 1:6 to 1:8 range would be perfect, enough to keep the clarity and tone I’m getting from the AU-S1 but with better headroom. My budget is around $5k, and I’m open to any recommendations for a high-quality SUT?
Eureka - found a pic - they use secondary loading. https://www.fidelity-magazine.com/audio-note-io-gold/
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A quick relatively inexpensive thing to try would be to get a pair of RCA spliiters, some screw terminal RCA plugs and a carbon film resistor kit. This will allow you to quickly and easily play with loading the primary of your S1. The goal here is to reduce the output of the S1 by about 50% (6dB ) and placing the RCA adapter into the S1 and the tonearm into one of the female sockets will allow the second socket to house The screw terminal jack with a desired load resistor. This will directly place the chosen resistor across the cartirge in parallel with the primary of the transformer. This is where the heresy begins.... I would suggest starting with 10Ω which will set the gain of the 1:13 transformer to something more like 1:6 or 1:7 to see if this solves your overload problem. I do want to be clear that is is not transformer overload that is causing your problem but feeding too high of a signal voltage into your MM stage. The primary loading, aside from reducing gain will have minimal impact on the sonics of the transformer and the heavy load has a reasonable chance of improving tracking ability. The resistance value can be played with and while 10Ω should net you 6dB more input overload while aggressively loading the cartridge and 27Ω will split the difference and net you around 3dB of overload headroom and load the cartridge at a small multiple of the 8Ω internal impedance. dave |
For what it's worth, and it isn't worth much, I was wrong when I posted at 8:56AM today that an 18 ohm resistor in parallel with the primary would result in the cartridge seeing a 27ohm load, assuming a 1:10 turns ratio and a 47K ohm phono input. Wrong, wrong, wrong. And I realized this while driving down a winding country road at sunset today. The correct answer is about 29 ohms, not 18 ohms. In my own defense, I came up with 18 ohms while lying in bed this morning and did the calculation in my head, too lazy to get up and write down the equations. |
