K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

Return to K&K Audio / Lundahl Transformers

Message Sort: Post Order or Asylum Reverse Threaded

IT transformer for 2-stage SE amp

110.22.9.84
Posted on May 15, 2014 at 15:06:46
RHone
Audiophile

Posts: 38
Location: Australia
Joined: November 28, 2002
 Hi Kevin,
I've built an amp that uses CCs loaded triode-wired pentodes as input with a 6CB5A SE output stage. The output stage tube is a triode wired TV pentode, brought to prominence by Thomas Mayer on his "Vinyl Savor" blog, thanks Thomas. It's a really cheap tube that has specs, when triode strapped, similar to a 300B.
For driver stage tubes I've been experimenting with 6688/E180F plus a bunch of Russian pentodes: 6j51P (similar to D3A), 6E6p and some others. They give an Rp of approx. 1-2.5 k and I've ben running the CCS at 10-15 ma.
I want to replace the CCS/cap coupling with an interstage transformer. I've searched here and poured over the specs and can't decide between 1660, 1692 and 1635. Some gain would be nice but not essential. I would really appreciate your advice!
Thanks,
Rod

 

Hide full thread outline!
    ...
RE: IT transformer for 2-stage SE amp, posted on May 15, 2014 at 16:48:03
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 I have had a lot of experience with the "D3a type" pentodes, triode-connected, as drivers, both SE and PP. That means D3a, 6J9P, 6J11P, 6J49P, and 6J52P. In most of the applications I've found that something like 175-200VDC on plates and 12-15mA makes very good sound in combination with the LL1692A. I typically use them without significant step-up, to ensure low impedance drive, but I don't quibble about the +0.6dB of 3.5:4! :=)) These are under appreciated tubes that deserve more use, especially the Russian ones that are so inexpensive and rarely microphonic (unlike the costly D3a).

I've not fared as well with the 6E6P sonically, although I didn't use it with fixed bias as Romy "the Cat" insists it must be used. He's right more often than most DIY posters, so that tube bears another trial sometime in the future.

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: IT transformer for 2-stage SE amp, posted on May 15, 2014 at 17:30:31
RHone
Audiophile

Posts: 38
Location: Australia
Joined: November 28, 2002
 Excellent, Kevin, and thanks for the prompt reply.
Rod

 

6E6P, posted on May 17, 2014 at 05:43:27
Maxamillion
Audiophile

Posts: 856
Location: New Jersey
Joined: May 26, 2006
 I use the 6E5P, which is very similar to the 6E6P with a different pinout, in my two stage Midlife Crisis amps, triode strapped with UF4007 plus 200R, and it sounds great at 190V and 26mA. It's direct-coupled to an 833C in a mu-follower configuration. Details here if interested:

 

PS: Cree SiC Schottky Diode Bias, posted on May 17, 2014 at 06:59:58
Maxamillion
Audiophile

Posts: 856
Location: New Jersey
Joined: May 26, 2006
 At 3.6V. So, essentially fixed bias. Lundahl grid choke on the 6E5P as well.

 

Page processed in 0.020 seconds.

[ Top 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 ]