Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

My suggestion...

Posted by Triode_Kingdom (A) on March 12, 2007 at 20:56:10

In Reply to: How do I lower the gain of a 6SN7-based SET? Is there a family tube with lower gain... posted by jeffreybehr on March 11, 2007 at 20:23:11:

Jeffrey, after reviewing the schematic, I see that the front end isn't exactly what you think. True SRPP stages have roughly half the gain compared to the same tube type configured in common cathode. SRPP also does not have a bypass on Rk (the lower cathode resistor). To derive some approximate numbers, I Spice modeled the front end of your amplifier. Here are the results:

Factory Configuration:
1st Stage VB1 Gain = +23 dB (voltage gain 14)
2nd Stage VB2 Gain = +22 dB (voltage gain 12.5)
Total Front End Gain: +45 dB

True SRPP:
1st Stage VB1 Gain with C2 Removed: +17.5 dB
2nd Stage VB2 Gain with C4 Removed: +17.5 dB
Total Front End Gain: +35 dB

In other words, if you remove C2 and C4, amplifier gain will decrease by approximately 10 dB. Spice shows frequency response relatively unaffected by this, but of course, there may be "atmospheric" changes that only you can judge. I personally don't configure SRPP stages with bypass caps, so speaking for myself, this would be a simple decision. I sugest you remove those two caps, listen for a few days, and report back. :)

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 © 2024, Audio Asylum, all rights reserved ]

---

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

---