Search found 6 matches

by avcLover
Tue Jan 02, 2024 10:15 am
Forum: Attenuators
Topic: Bias output stage via AVC
Replies: 1
Views: 1850

Bias output stage via AVC

Hi All, I'm thinking of using fixed bias and kill two birds with one stone, volume and bias. Been experimenting with SIT transistors, a simple 2SK79/2SK60 SET. 2SK79 has 2K rp, loaded with 18K, the AVC at the output helps to lower the impedance. 2uf coupling capacitor for the equivalent 25K reactanc...
by avcLover
Tue Jan 02, 2024 10:00 am
Forum: Attenuators
Topic: How have the auoformers changed over the years
Replies: 4
Views: 5235

Re: How have the auoformers changed over the years

dave slagle wrote: Tue Nov 07, 2023 3:51 am no changes... Inductance is in the 200Hy range.

dave
Is this figure frequency dependent especially at the low end? So 200H at 20Hz etc?
by avcLover
Tue Feb 23, 2021 10:31 pm
Forum: Attenuators
Topic: Bal to SE and AVC
Replies: 5
Views: 4559

And because you've pointed me in the direction of a new 600:600 input transformer a crazy idea came about. A 600 1:1+1 input transformer capable of doubling the input voltage to 40Vpp max, apply a negative voltage for a fixed bias 3W PX4 amp without caps, standard 40H 5K gapped OTP. My DAC has a cla...
by avcLover
Tue Feb 23, 2021 10:15 pm
Forum: Attenuators
Topic: Bal to SE and AVC
Replies: 5
Views: 4559

The sketch is looks good and what I've been using, I guess if the DAC wasn't to BAL specs it wouldn't see the expected impedance and start humming. Also took your advice from a 2005 post on a bifilar choke setup and it works surprisingly well. Hooked up a Magnaquest cobalt 10K otp with headphones an...
by avcLover
Sun Feb 21, 2021 5:22 pm
Forum: Attenuators
Topic: Bal to SE and AVC
Replies: 5
Views: 4559

Small mistake in the schematic, pins 1 and 3 are reversed, I need to tattoo this on my arm, 1- Ground, 2 - Positive, 3 - Negative Didn't take long to make the changes as suggested with the floating AVC. Just for the hell of it I left the existing grid leak and gave it a try, a bass tilted signature,...
by avcLover
Sun Feb 21, 2021 9:20 am
Forum: Attenuators
Topic: Bal to SE and AVC
Replies: 5
Views: 4559

Bal to SE and AVC

Hi all, Been using a 28 step AVC with great success for a 10Y preamp/driver setup. However the input transformer placement is bugging me and thinking of redoing it. Current setup: 20Vpp balanced source into a 15K bridging transformer for SE conversion with a 15K load, AVC to the tube grid with a 100...