DVD-Software.info

[Fabio Berutti]

Dear RATs,

I just finished a 6S33 SE amp. It is as usual for me a very simple unit: a
6N30 "symmetric SRPP" drives a choke-loaded 6S19 which finally drives the
big one. No feedback is used anywhere. It requires some 12V pp for full
power provided by a dedicated preamp (ECC82 grounded cathode + DC coupled
ECC82 CF - dead flat from DC to 100KHz). The basic idea is:
- the SRPP is essentially "distortion free" in its required operating range
- the 6S19 has (more or less) the same characteristic curves of the 6S33
and is used @ a similar working point, hence 2nd harm. cancellation should
occur
- the 6S33 is used with a 900 ohms load to make it as linear as possible.
The thing gives out some 12-13 W into 8 ohms before distortion becomes
clearli visible on a scope.
I noticed that it has an extremely wide frequency response, maybe too much
on the highs, because the square wave @ 1 kHz, full power shows a clear
"peak" on the front side of the wave (the graph jumps clearly over the
"flat" line before making a dip and then stabilising on a nearly horizontal
line).
I suppose that the choke I used (150H) is too much for the 6S19 and gives
too much gain @ high frequencies.
I know it's too qualitative to have any clear idea, but... any suggestion?

Should I forget... merry Christmas and Happy new Year to all rodents

Fabio

[Fabio Berutti]

Sorry, I forgot to make one thing clear: I'm a CHEMICAL engineer, I do not
understand a %&£!! of electronics! I just weld pieces together, connect the
power cord and hope to survive. It's just for the fun of playing with
tubes, never thought I make anything better than anybody but on a personal
scale (it's mine, so it's the best for me).

FB

PS: I hope that there are no electronic engineers out there making toxic
chemicals or explosives just for the fun of it...

[Jon Yaeger]

Bon Giorno,

Sounds very interesting . . .

Is the 6S33 akin to the 6C33C? Have you got a schematic?

Jon

[Fabio Berutti]

6C33 is a common way to type the Cyrillic character for S like in
"CCCP"=SSSR.
Yes I have a schematic, I'll post to ABSE one of these days (hand draft, beg
Your pardon).
I'll include a pic of the 'scope if it is clear enough.
Ciao
FB

[Patrick Turner]

Fabio Berutti wrote:

[Ian Iveson]

Fabio,

Just got circuit and scope pix.

From 20kHz square it seems there is a little ringing at around
120kHz. I have seen much worse.

I am interested in why the square is not symmetrical. The downs have
a lump missing whereas the ups have the extra wiggle. Bits missing
make me think of current starvation...a valve cutting off or close,
so its impedance is very different at the +ve and -ve extremes.
Perhaps the top valve of the SRPP? Never tried one I dunno what goes
on there. Can't really tell which way up your trace should be, but
if it is the "right" way up then either that valve or the driver
could be near cut-off at that point.

Does the asymmetry diminish as the input is reduced? Do you then get
a bigger wiggle on the bottom than the top?

cheers, Ian

[Ian Iveson]

ps...could be grid current in output stage that contributes to the
current starvation.

cheers, Ian

[kosmin27]

hy everyone
i would like to see the schematic of the SE with 6C33C; please can someone post it here or on the internet and put the link here?

thank you all!