In Reply to: RE: Poor Design for a Preamp posted by Tre' on February 16, 2025 at 12:57:28:
Tre made the suggestion to use 68k+22k resistors to give me a dropping output level but not to limit upper frequency. Tried this ides with a 6N7 preamp I also had noise issues with and it worked well.Even with my DIY shieldless lead (175pF) into 100K upper 3db was 37KhZ. 6N7 are power tubes and Im not sure of they have a very high frequency range or not. Regardless I'm happy with 37K.
Applying the same 68k+20k idea to the 01a preamp gave me noise level outputs of 1.9mV and 0.9mV a big improvement over the ~4.0mV with the 300k+100k setup. At good volume only by putting my ear to my 93db sensitive 12" woofers do I hear the slightest hum then only in the left channel.
Good result for two preamps so far and two to go. Lucky I have a good collection of Rs to mod the others.
| retro-thermionic |
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: Poor Design for a Preamp - mwhouston 17:55:07 02/26/25 (5)
- RE: Poor Design for a Preamp - FlaCharlie 10:19:33 02/27/25 (2)
- RE: Poor Design for a Preamp - mwhouston 14:13:55 02/27/25 (1)
- Metal Tubes / Tube Sources - FlaCharlie 10:43:52 02/28/25 (0)
- Confusion - FlaCharlie 09:50:01 02/27/25 (1)
- RE: Confusion - mwhouston 14:08:29 02/27/25 (0)