back
to www.audiodesignguide.com |
To get more information contact me at: webmaster@audiodesignguide.com |
by Andrea Ciuffoli - 2001
contact me for any problem or question:
webmaster @ audiodesignguide.com
This is a expert
only project because the high power supply voltage, about 900V, it can kill!
Keep always one hand, left hand is better,
close to your back.
25 Apr. 2007 - NEWS:
1 jan 2002 - NEWS:
The main results and targets should match these items:
The following photos are refered to the prevous test version with only 2 x 100uF capacitors.
Here the output characteristic of the tube 845 with the specific
operation point (click to enlarge)
You can calculate the output power with:
600Vp / sqrt(11500ohm / 8ohm) = 600V / 38 (turn ratio) = 15.8Vp => 11.2Vrms
=> 15.6W on 8ohm in pure class A1 operation
but the driver stage implemented in this design with a 300B is able
to control the 845 in class A2 operation to get a sure power of 20W
All the audio transformers used in this project are
Lundahl products and the distributor list is available here.Primary Windings:-
0-115V @ 50/60Hz
0-115V @ 50/60Hz
For series/parallel operation
Secondary Windings:-
0-1000-1050-1100V @ 0.4A rms
One tap used at a time
0-380V @ 0.2A rms
0-380V @ 0.2A rms
0-200V @ 0.2A rms
Primary Windings:-
0-115V @ 50/60Hz
0-115V @ 50/60Hz
For series/parallel operation
Secondary Windings:-
6 x 0-6.3V @ 3A rms
2 x 0-10V @ 4A rms
1 x 0-6.3V @ 4A rms
2 x 0-5V @ 4A rms
Lundahl is one of the world´s
leading manufacturer of audio transformers used in many professional studio
recording and radio stations so He have a very big experince and all these
products use a custom audio C-core.
I am using a The output tubes used are the Golden Dragon 845.
About passive components types, I don't leave many choices:
Caddock resistances on cathode, ELNA Cerafine capacitors on cathode.
In all my previous projects I have used in the power supply the ELNA
Cerafine capacitors with a very high sonic performances and compact size.
If we skip any economic aspect and no size problem the first components
is a paper in oil capacitor.
In comparation test the paper in oil are best of the ELNA Cerafine
or other electrolityc type.
Searching a paper in oil capacitor is very important buy new product
as the Jensen and not an old stock.
About wire forget the teflon ! use only stranded tinned copper wire with pvc isulator and for loudspeakers the same.
A very good quality stranded tinned copper wire could be buy directly from
E-Z-HOOK that carries an extensive line of fine stranded and extra flexible wire.
Before to insert the 845 tubes in the sockets switch on the amplifier
without the fuse and set the trimmers to get about -180V from the grids
of the 845 and the ground.
After switch off, insert the fuse, insert the 845 and switch on the
ampl.
This project give a first class sonic performance but this can be easily
compromised by a bad input signal so I suggest you to don't use preampl.
and use one of my DAC projects.
Using one of my top DAC projects all the DIYer's will reach the same
sonic result.
The DAC normally included into commercial CDPlayer (even these of significant
price) have a rather low performance because the common usage of high NFB
operational amplifiers "destroy" the sound given compression effects and
poor soundstage stability.
Layout views
click on the images to get real scale
external size 56cm x 42cm
click on the images to get real scale