Updated: 20-Aug-01 16:23
Doede's Audio Tweaks...


Item 2 New Power Supply for the TUBE Stage:

As you can read from my design philosophy, I design power supplies in such a way, that the regulator part (transissstors, yek) are kept far away behind a string of RC networks. No doubt, this sounds much better than to present the Regulator or MOSFET straight to the Tube Ra….. And I was happy with it, till I got emails again !!! thanks guys, for keeping me awake. The salvation here was called: Rectifier Tube and PI filter ! I already heard from audible differences between the different rectifiers, so I used (yes !) EBAY gain and bought some different types to test. I decided to build a experimental first version.

Click for large Image
The Tube power supply test

If you look close at the picture you will see 3 sockets for 3 different Tubes and different filaments. This enables real A – B comparison. I am able to switch on the DDDAC between TUBE and built in RCRCRC power supply. The first version I built, was a double PI with 2 Chokes of 5H first C of 1uF to bring the Voltage at the same level as the internal supply (no plops at switching…) in the middle a 270uF Elco and the third 20uF Solen. Why this crazy alignment? I thought it would be good to have lots of uF to have no hummmmmm. Late more about this. So I started listening and I was not impressed, not even converted!!! The TUBE power supply was may be a bit smoother, but I needed to listen very carefully. Funny enough, I could here clearly the "relative" difference when I changed Tubes. AZ types nice and smooth, 5U4G dark, warm, flat. GZ34, dynamic attack but bit sharp. Overall not convincing uh? I start to ask around, and asked for some experience. Dick and Frank were great help here. At the end the conclusion was: the more uF you build in, the slower and less dynamic the sound becomes.

So I waited till the Angela MKP in OIL C’s arrived and replaced the Elco and Solen with the Angela’s (both 20uF) and used a 10H choke. No problem, no hummmm, but at the edge, so I cannot go lower. I couldn’t wait, Sorry, I sat down after 1 hour of burn in and , wowwwwwwwww this is finally makes a difference. Not the same step as going from, for example, from 300B Chinese to AVVT or so, but very nice improvement in the more emotion in the music. The music becomes more fluid, natural and very dynamic. No breaks as Dick always states…. This is the cream on the cake, the sugar in the coffee! And what about the Tubes?????? Mhhhhhh, funny, but with the Angela C’s the differences became smaller !!! Still possible to recognize the character, but less, they ALL sound unstressed and quite nice. Still I prefer the AZ11 and AZ41, but it s close finish. There are no loser’s here. I keep on hammering on that, because I read too often, that every little teak makes the old situation look like crap. MAJOR improvements are NOT possible, we tweak our way through and little step by step we get more music……… Dick will test these C’s as well, so keep an eye on his site as well.

(update Aug 20)
In the meantime, Dick and I have been using these (actually ACS branded) MKP in Oil C's and came to the conclusion, that these capacitors are almost as good as the vintage paper in oil types, with the difference, that they are available as new production ! I am using this C as well as decoupling C from Cathode to ground in the KR300BXLS stage. Again another tweak possibility to obtain the right combination of C's to fine-tune the tonal balance of the amplifier !!!


IMPORTANT: The information provided on this page is intended as guide for DIY activities and therefore free to copy and or publish. If any one wishes to use any of the information from my WEB site, please make sure to refer and footnote to my URL Link as source! Doede Douma