On Jul 16, 8:17*am, flipper wrote:
On Tue, 15 Jul 2008 13:09:14 -0700 (PDT), bigwig
wrote:
On Jul 14, 4:32*am, flipper wrote:
On Sun, 13 Jul 2008 14:37:05 -0700 (PDT), bigwig
wrote:
On Jul 13, 3:51*pm, flipper wrote:
On Sun, 13 Jul 2008 06:14:42 -0700 (PDT), bigwig
wrote:
On Jul 12, 11:28*pm, flipper wrote:
On Sat, 12 Jul 2008 07:02:27 -0700 (PDT), bigwig
wrote:
Hello,
*Im new to the group. Has anyone built an amp. with or played with 5B
255M?. I have a load of these valves and would like to put them to
use. The curves seem the same as the 807/6L6 types. I would like to
know if anyone has had any experience with them before I go and build
something. I was thinking PPP class AB1 ultralinear.
*Thanks Matt.
Well, Brimar said it's electrically similar to the 807.
http://www.mif.pg.gda.pl/homepages/f.../5/5B-254M.pdf
The STC data sheet is more comprehensive
http://www.mif.pg.gda.pl/homepages/f...0/5/5B254G.pdf
*(612k)
RCA 807 for comparison.
http://www.mif.pg.gda.pl/homepages/f.../084/8/807.pdf
(1.7Meg)
Ok great thanks guys,
*I have a few 7N7s so I think I will build something along the lines
of a Williamson. Should look nice with all Loktal valves. PPP output
stage, 3.3K output transformer.
Thanks for your help with the datasheets.
* * * * * * * * Matt.
You're welcome.
I'm building a 'midget' Williamson (6 Watts from 13FD7s) and Patrick
Turner had an excellent suggestion. Long tail pair the post phase
splitter triodes.
If you use spice to simulate it won't look like that does much, unless
you simulate tube mismatch where it makes a world of difference.- Hide quoted text -
- Show quoted text -
Sounds good,
* I need to wind my transformers next weekend(if the wire turns up).
These will be the first OPTs I have wound and my first large valve
project.
Ah, in that case you might want to talk with Patrick Turner because
he's the OPT expert in here.
I built a small EL84 based amp a few years ago. It sounded
very good to my tone deaf ears.
My PP 6GK6 (EL84 clone) amp is my favorite. So far anyway 
I have built numerous MOSFET amps,
some with stupidly good specs. but they all sound a bit harsh to me.
So I need a reasonably sized valve amp, hence this project. Perhaps we
could trade notes as we go.
Be glad to. Not sure there'd be much correlation with my little pip
squeak but I suppose you never know. Ironically, I was thinking about
a 6BG6 '807 variant' amp when I switched gears and decided to build
this small 13FD7 feller for my sister.
The 'idea' grew from my 'PC Speaker' amp but that one is 6AW8s, using
the same basic topology as the 6GK6 amp, and I took a completely
different approach with this one.
Got pictures of the 'PC Speaker' amp (and others) on my homebrew web
server at *http://flipperhome.dyndns.org/*but the 13FD7 isn't there
yet because it isn't done yet There's a picture of the first
component fit on alt.binaries.schematics.electronic, though.
* * * * * * * * Matt.- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
Hi,
*Sorry Im so late replying. You have some interesting stuff on your
pages.
Thanks.
I have printed all of Patricks transformer and matching pages,
this is what I have based my plans on. I also have RDH4 and some other
transformer related books although these are mainly aimed at
industrial uses. Im hoping to wind somewhere near 6K or so. This will
let me configure it for half that for push pull parallel and also play
about with pure triode, pure tetrode and ultra linear. Im in two minds
at the moment I might even add cathode feedback windings but this
limits my options somewhat.
I see. So you're looking at the 400V plate, 300V screen mode and the
UL taps for PPP half impedance.
* What transformers do you use on your amps?
Well, the 12AX7/6GK6 amp can use any 8K PP OPT, of course, and I
originally had a pair of HKs I got off ebay on it but lately I've
become interested in using line transformers (and the cathode bias
current mirror).
First reason is obviously cost and I've been doing 'PC Speaker' type
amps where you're not running a grand or two worth of speakers so, as
the theory went, you're not going to get 20Hz even if the amp does.
As it turns out they do better than you'd think, judging from the raw
specs, because average program power is much less than peak so you
don't really 'need' full power at the extreme low end for most
material (that I listen to anyway). Best performance should be with
triodes, because of the low plate impedance (and plate feedback),
which is why I'm trying the 13FD7s in this latest amp.
I would like to build a
smallish amp for a friend to play with. He seems happy with the 8-10W
class A transistor amp he built so I think he will like valves more.
Only trouble is he has really ineficient Mission bookshelves so push
pull is the only way (for a reasonable outlay). Im not a fan of single
ended anyway.
Well, that 6GK6 PP amp is a classic design for around 15 Watts,
depending on where B+ comes out, and Edcor makes some reasonably
priced OPTs in 3 different bandwidths but I imagine you'd wind your
own.
The 13FD7 amp I'm working on would do 8 Watts, *maybe a tad more, if
it had a larger B+ transformer but I wanted to keep the thing small
and that limited me to 50VA at around 230V B+. I also thought about
using the Edcors too they wouldn't fit either.
I know what you mean about speaker efficiency, and it makes a
difference what the listening expanse is. Those 'PC Speakers' I built
aren't very efficient either but, then, they're not intended to be
'room' speakers since, in theory, you'd be sitting rather close to
them. Still, I was rather surprised at how much volume they do with
just 3-4 watts and I routinely use them, with the 'PC Speaker' amp,
for background music (got Pirates of the Caribbean playing right now).
But ya know what the 'problem' is? It sounds so good you want to turn
the volume up. It's almost like a teaser for "man, I need to get a
bigger one of these things." hehe
Which is not necessarily a 'bad thing' because you can build the small
ones for not terribly much and then decide of you want a 'biggie'.
* Matt.- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
Hello,
Your site is great!. I like the trick with a 7805. Years ago I used
to work in a TV repair shop owned by an ex RAF RADAR guy. He taught me
that little trick, you must be careful not to push it too far though
otherwise you end up with quite a good saw tooth oscillator. I saw a
design from an Indonesian guy that used this to make a linear supply
at low inputs that switched to a switcher at higher inputs. It was
quite ingenious.
I checked out Edcors site, they have an extensive range!. I think I
will wind these trannys and then for my friends buy some. By the time
I purchased c-cores, wire insulation etc. plus the laour intensive
task of winding them it will work out about twice the price of a pre-
wound set. Mind you I will probably get the bug of winding them and
after the initial outlay I guess it gets cheaper. Also at least I will
get exactly what I want (providing my maths are OK).
Your use of TV tubes is good, they are plentifull and cheap. I have
seen a lot of people put these type of tubes down but they must be
using them wrong. The reason I chose 5B255M (apart from the fact I had
some) is because they are very cheap, plentifull and as far as I can
tell a later ruggedised version of the 807.
Have you thought about using mains trannys? I know it sounds crap,
but they are cheap and could be worth playing with. Steve Bench used a
couple on an amp he built, check out his web site
http://members,aol.com/sbench101/.
As for my power supply Im going to use an industrial control
transformer in reverse (415-230V). I experimented with this with a SS
bridge and I was getting almost 600V! plus a massive switch on surge.
If I was to use this I would be mad, I would have to go for AB2 I
guess. What I plan is to play with a half solid state half vacuum
rectifier bridge and a regulator. Any suggestions? perhaps a full
vacuum bridge with damper diodes would drop it a bit.
Matt.