Tube DIY Asylum

RE: Output transformer for triode connected 813 tube

172.59.56.188

DAK

In Reply to: RE: Output transformer for triode connected 813 tube posted by Palustris on March 14, 2025 at 15:52:06

Hi, Palustris and thank you for the link to the discussion on the 813 tube. This is very much what I need to develop my circuit. I shall endeavor to keep you all abreast of my progress. It seems like the Hammond OPT is a good starting point for my project. I am thinking about 30 watts of power per channel is plenty for Altec 19 speakers. cheers, dak

Follow Ups:

Output Power - Triode_Kingdom 08:58:40 03/15/25 (2)
FWIW, those transformers won't produce anything like 30W at the lowest octave. The Hammond frequency response graph (which is already down > 1dB at 20 Hz) was produced at an equivalent output power level on the order of a few mW. Based on their size, it's likely these transformers will saturate around 6W to 7W at the lowest frequency. That may or may not be sufficient for the Altecs. Just wanted to point this out as something to consider before you start your project.
- RE: Output Power - DAK 11:15:35 03/15/25 (1)
  Ok, so, if the B+ voltage is made lower to limit output power that could help ?
  - RE: Output Power - Triode_Kingdom 11:59:38 03/15/25 (0)
    Yes, lower B+ will reduce power across the entire spectrum. FWIW, the Magnequest FS-100 transformers in my 211 SETs behave the same way (also rated 30W). If the severe reduction in output power at 20Hz were used as the baseline, a 300B could do as well with OPTs this physical size.

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

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

Sonic Craft