This
project will be update very soon !!!
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This
project will be update very soon !!!
The update is necessary to resolve
the problem of too many hot generated by LL1651 power supply transformer
and also to increase power output using a stronger driver stage for SV572-3.
| ATTENTION: | 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. |
The main results should match these items:
Note that the 560V is the voltage swing in class A1 operation (negative grid values)
The LL1620 + PCB_B give a turn ratio = sqrt(11500/8) = 38
so (560 / 38) / 1.41 = 10.45Vrms on the secondary winding
and 10.45 * 10.45 / 8 = 13.65W in pure class A1
This is also the max output power of the trasformer suggested by Lundahl in the datasheet.
In this design the driver is able to support peak in class A2.
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.
The total price of the transformers is about 928$.
The output tubes used are the Svetlana SV572-3.It is one of the lowest-distortion
tubes designed to work in Single Ended Amplifier operating in Class A1
with some peak escursion in Class A2.
About the input stage I have tested many tubes like 6SN7 Jan Philips, 6SN7 Raythoen, 6SN7 RCA (slim base), 6H8 (russian type) and for the driver stage 6BX7 RCA and 6BX7 GE.
The best sonic results are with 6H8 or 6SN7 Jan Philips and 6BX7 GE.
botton view
6BX7 ratings
The vacuum diode for the lower voltage should be the 5R4GY RCA and
the 5R4WGY Chaitam or 5R4GYA GE (show in the photos) for the high voltage.
About passive components types, I don't leave many choices:
Allen Bradley or Caddock resistances on anode, Holco or Caddock resistances
on cathode, ELNA Cerafine capacitors on cathode and power supply.
About wire forget the teflon ! use only stranded tinned copper wire with pvc isulator and for loudspeakers I am testing the elevator cables (paralleled wire with a good section).
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.The my custom transformer for the filaments has been make by F.I.A.T
s.r.l.
 |
via refrancore, 63
00166 Roma ITALY tel. 06 61561705 - 06 61567539 fax 06 61550871 |
If this amplifier is used after a CDplayer use the DACT 100K +100K stepper attenuator.
The interstage capacitor should be a 0.33uF 1000V Jensen Copper film paper in oil.
The 0.56 ohm resistors could be adjusted to have correct 5V on filaments of tubes and a value range from 0.47 ohm to 0.68 ohm should be good to test and match any rectifier.
The 8uF 630V (or 450Vac) could be metallized paper in oil or common motor start types.
About the 220K 2W use only no-inductive types as Resista.
Before to insert the SV572-3 tubes in the sockets switch on the amplifier
without the fuse and set the trimmers to get about -180V from the grids
of the SV572-3 and the ground.
After switch off, insert the fuse, insert the SV572-3 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
3 mm aluminum with external size 550 x 290 mm
3 mm aluminum with external size 550 x 140 mm
