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

WAF direct coupled integrated Push Pull amplifier

203.163.97.36
Posted on February 17, 2014 at 16:07:52
fiacono@optusnet.com.au
Audiophile

Posts: 31
Location: Melbourne, Australia
Joined: May 21, 2003






Hi all
It’s been some time (years) after lots of A/B testing and this is what I finally (for now) came up with. The second photo is the WDF (Wife Disapproval Factor).
LL1676 input transformer (1:1) + volume controls + cascode 6H30pi (modified version of PP2C input) direct coupled to KT77 drivers + LL1660S + KT120 + LL1620AM. Power supply built on separate chassis using K&K Jensen 4 pole capacitors.
Gary Pimm’s CCS on all cathodes - had built a number of Gary’s BBCCS a few years back before Kevin released his IXYS CCS.
So far the best sounding amplifier I’ve built IMO.
regards
Frank

 

Hide full thread outline!
    ...
RE: WAF direct coupled integrated Push Pull amplifier, posted on February 19, 2014 at 03:44:47
D Mike
Audiophile

Posts: 128
Location: Michigan
Joined: October 24, 2005
 Remarkable! That's a great looking build. Love the pic of the proto board too.

Congrats on an outstanding effort. WAF is hard to achieve in this hobby.

 

RE: WAF direct coupled integrated Push Pull amplifier, posted on February 19, 2014 at 05:29:17
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 I can see why your wife would prefer the first one over the second. Not too unreasonable...

Seriously, I like very much the fact that the finished amp looks so good, but has the tubes mounted separately from the main top plate. That makes the amp somewhat future-proof, while retaining good looks. Well-executed and really good looking!

How much does this expanse of metal weigh?

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: WAF direct coupled integrated Push Pull amplifier, posted on February 19, 2014 at 21:24:22
Ejam
Audiophile

Posts: 17
Joined: March 15, 2001
 Frank

A few questions, if I may. First, can you detail your modifications to the PP2C cascode front end, and second relating to the PP2C cascode, doesn't this have enough gain to drive your kt120 output stage? Mine puts out 160V pp without breaking a sweat.

Regards

Anthony

 

RE: WAF direct coupled integrated Push Pull amplifier, posted on February 20, 2014 at 22:11:54
fiacono@optusnet.com.au
Audiophile

Posts: 31
Location: Melbourne, Australia
Joined: May 21, 2003
 Hi Anthony,

PP2C Changes were only minor.
I noticed a slight improvement using Gary’s BBCCS (must apply a higher –ve rail) cf the original CCS. I placed a variable resistor between the two cathodes and the wiper wired to the CCS for balancing purposes. I also discarded the coupling capacitors and wired the 6H30 plates directly to the KT77 grids. The KT77 were elevated to accommodate the higher Grid voltage similar to Kevin’s 6SN7 coupled directly to the 6BX7 drivers. This is how the current system is set up now.
I also noticed an improvement using the LL1676 input transformer, which is my preferred option, other than for isolation etc.

I did try driving the KT120 with just the PP2C but I required a preamplifier to get any decent volume. I was after a PP integrated amplifier with volume controls.
Driving the KT120s with lower source impedance (LL1660S as 2:25:2) sounded better than the PP2C high output impedance driving the KT120’s. To be fair I also tested this with the PP2C directly coupled to the KT120’s, that required much higher voltages on the KT120’s.

We all hear different things, sure other opinions will differ.

Will be try voltage regulation in the near future.

Hope I've answered your questions.

Regards
Frank

 

Page processed in 0.024 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 ]