Keep always one hand, left hand is better, close to your back.
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| ATTENTION: | this project is in designing phase so any part could be change in next weeks. |
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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 and targets should match these items:
The 700V is the voltage swing in class A2 operation (positive grid values on music peak)
The LL1620 + PCB_B give a turn ratio = sqrt(Rprim/Rsec) = sqrt(11500/8) = 38
so Vout(rms) = (DV / turn.ratio) / 1.41 = (700 /38) / 1.41 = 13Vrms on the seconday winding
and P = (V * V) / R = 13 * 13 / 8 = 21W in class A2
The 560V is the voltage swing in class A1 operation (always negative grid values)
so Vout(rms) = (DV / turn.ratio) / 1.41 = (560 / 38) / 1.41 = 10.45Vrms on the secondary winding
and P = (V * V) / R = 10.45 * 10.45 / 8 = 13.65W in pure class A1
The damping factor and so the output resistance is given by:
Rout = Rdc.sec.transf. + (Ra + Rdc.prim.transf) / (Rprim / Rsec) = 0.2 + (1900 + 308) / (11500 / 8) = 1.7ohm
where
0.2 is the LL1620 statis resistance of the secondary
1900ohm is the SV572-3 plate resistance
308ohm is the LL1620 static resistance of the primary
11500 is the primary load impedance
8 is the secondaries load impedance
The low frequenct cut-off is in the first stage is given by
ft(low) = (Ra + Rtransf.) / (2 * 3.14 * Ltransf.) = (2000 + 277) / ( 2 * 3.14 * 32.5) = 11.5Hz
where
2000ohm is the 5842 Raythoen plate resistance
277ohm is the LL1660 static resistance of primaries
in parallel connection (315+240)/2 = 277.5ohm
32.5H is the LL1660 inductance of the primaries
in parallel connection and with a gap for 10mA
NOTE: the LL1660 with the primaries in parallel
connection have a right gap for a double current.
as the previous the second stage will have a cut-off given by:
ft(low) = (Ra + Rtransf.) / (2 * 3.14 * Ltransf.) = (700 + 277) / (2 * 3.14 * 13) = 11.96Hz
where
700ohm is the SV300B plate resistance
13H is the LL1660 inductance of the primaries in
parallel connection and with a gap for 25mA
NOTE: the LL1660 with the primaries in parallel
connectin have a right gap for a double current.
the third will have a cut-off given by:
ft(low) = (Ra + Rtransf.) / (2 * 3.14 * Ltransf.) = (1900 + 308) / (2 * 3.14 * 40) = 8.8Hz
where
1900 is the SV572-3 plate resistance
40H is the LL1620 inductance with a gap for 90mA
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.
I am using a 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.
The driver tubes used are the Svetlana 300B.It is one of the lowest-distortion
tubes ever made, and is a close duplicate of the original Western Electric
300B.
The Svetlana 300B uses ultra-pure carbonized nickel plate material
and a proprietary oxide coating on the filament to give Western Electric-like
performance.
The filament is center-tapped to insure low hum. The Svetlana 300B
is manufactured in Russia at the
Svetlana factory in St. Petersburg.
The strict manufacturing and quality controls at the Svetlana plant
assure functionality and sound as good as Western Electric manufactured
products.
About input stage I have tested many combination starting from parallel
6SN7 to the 6H30 russian incredible tube but with
the 5842 Raytheon the sonic result is very more higher.
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 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
