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SV572-3 Single Ended Amplifier

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.



This project born to create a single tube high power single eneded amplifier using the new SV572-3 Svetlana.

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.


All the audio transformers used in this project are Lundahlproducts:

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$.

I am using a DACT stepper attenuator instead of the normal ALPS or NOBLE solution, because the the sound is clearer. A good review of these components can be found on the article published in Hi-Fi World.

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.


5R4 connections get from

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.
For all my new projects, I am using the very good ELNA Cerafine capacitors that I love and which can be find at good price by
The ELNA Cerafine capacitors contain super fine ceramic particles which, through chemical reaction, improve the discharging speed between the anode and electrolyte with very low distortion.
Any other electrolytic or polypropylene capacitor give very lower sonic performances introducing some alteration. Only the Blackgate WKZ could give better sound, but I have not tested it and I know of some problems during startup phase.

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
tel. 06 61561705 - 06 61567539   fax 06 61550871

The main schematic


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.

Power supply


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.

Digital Input stage

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.

Sonic results

Layout views

click on the images to get real scale

external size 56cm x 42cm

Layout size

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