OTL Asylum OTL, Output Transformerless Amplifier User Group.

---

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

---

[ Alert Moderator ]

---

Re: Impedance of MP-1 phono section?

Posted by Lew (A) on February 9, 2007 at 13:00:23

In Reply to: Impedance of MP-1 phono section? posted by Dave Garretson on February 8, 2007 at 09:58:23:

The output impedance will be equal to the value of the plate resistor (50K ohms) in parallel with the plate resistance of the 12AT7 that serves as a voltage amplifier at the output of the phono stage. rp for the 12AT7 is 10K to 12K ohms. Therefore the output Z is roughly 10K ohms. Thus the volume control needs to be at least 100K ohms (or 10X the output Z of the stage) for an adequate treble response. Like you, I heretofore thought that the input impedance of the stock series stepped attenuator in the MP1 was indeed 100K ohms.

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

Signature Sound

[ Signature Sound Lounge ]

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

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

---