OTL Asylum OTL, Output Transformerless Amplifier User Group.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ OTL Asylum ]

---

[ Alert Moderator ]

---

RE: You can use the JT-347 with the Ruby no worries.

Posted by MP (A) on May 23, 2022 at 18:15:21

In Reply to: You can use the JT-347 with the Ruby no worries. posted by Ralph on May 23, 2022 at 13:22:56:

Thank you, Ralph. That is wonderful.

I was concerned when I saw JT-347 specs on Jensen website, supporting up to 72 ohm cartridge.

The Benz Ruby H internal impedance is 95 ohms. Assuming MP-3 phono loading is 47K. The 1:8 ratio JT-347 will present a loading impedance of 734 ohms [47000/(8x8)]. The cartridge-SUT loading ratio will be 7.7 (734/95).

Interestingly, I have an unused Ruby H, bought the same time, that has output 0.8 mv (instead of 0.6 mv) and the same 95 ohms internal impedance, according to the accompanied measurement.

Thinking ahead, my eventual goal will be getting MP1, MP 1 has overall 8db more gain than MP3. I would assume MP1 could handle Ruby H without SUT. what ratio SUT would be needed for the 0.2mV Spectral cartridge?

The rest system is M60 MK3.3 and Quad 989 with Zero-former, The only potential future change would be getting MA1 or another pair of M60 for mono-strap.

Lastly, would Grado Reference 1 cartridge 5mV overload MP1 phono? the Grado has worked very well over the years with MP3 with volume setting between 8-10 am.

Thank you so much for your generous support.

This post is made possible by the generous support of people like you and our sponsors:

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---