On Wed, 14 Nov 2007 09:47:11 -0800, Andre Jute wrote:
On Nov 14, 12:32 pm, Patrick Turner wrote:
Andre Jute wrote:
By the way, Andre, thanks yet again for the 417As. They are now
about to move from potato amp status to SET drivers. I think would
like a little more power. I've just got a pair of FE127es to play
with and have been in mad box-building mode. :-)
--
Mick (Working in a M$-free zone!)
Web:http://www.nascom.infohttp://mixpix.batcave.net
My pleasure, Mick. Did I somehow miss the thread in which you told us
the design of your potato amp? And, of even more interest, the
speakers you used them with.
And what the devil are FE127es? You're getting weirder and weirder
Mick; soon you'll be insisting tube rectification sounds better than
than those square black thingies lying dead with their legs in the
air.
Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/ "wonderfully
well written and reasoned information for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review
Its strange you should mention potatoes in relation to tubes.
I used to use boiled potatoes as my secret weapon in bike races over
100km.
They did seem to work better than a Mars bar.
Mars bars are rubbish. The lift doesn't last very long. What works is
carbs. I carry a packet of fig rolls on my bike; highly recommended by
the coach of the British mudbikers. When I was a rugby player, the team
diet was fillet steak and all the potatoes you could eat.
Inevitably, I collected the name, Potato Pat, and I didn't mind. I had
the full license to use potatoes winningly as I wanted. Why now, I was
tree quarters Irish, because of me Irish mum, and because of me dad,
two turds English.
Well now, Padraig...
And now, yeah, what is an FE127?
Are they not Foster five inch drivers?
Yeah, I shoulda seen the clue in Mick's "mad box building" but I took
that to mean he was drilling a chassis for these weird FE127es tubes...
Fostex, eh? I heard about them: Japanese-style Lowther type point source
speaks with whizzer cones. Said to be very nice indeed in tapered
quarter wave pipes. Indeed, I once published a design that could be used
interchangeably with 8in Lowthers and the equivalent Fostex drivers,
with someone reporting on the single driver conference that the Fostex
went a bit deeper in my design than the Lowther. Personally, I hated the
design, because with the Lowther it was very sensitive to just how you
stuffed the area behind the driver, otherwise you got a screechy treble
overwhelming everything, which had to be fixed with stupid little tufts
of wool between the whizzer and the main cone; I hate that sort of
kludging, and don't care overly much for those who try to promote it as
"tweaking". In my Fidelio type horns the Lowthers work without that sort
of messing around; of course, my smallest Lowther horn has four times
the footprint of a TQWP, so there is a certain wife acceptance factor
involved for the young at heart.
What sorta boxes did you build for the Fostex, Mick?
Well... they are a bit like this:
http://www.diyaudio.com/forums/showt...hreadid=109208
but I've resized them for the bigger drivers and added bracing. The top
box is a reflex enclosure, the port being the full width slot across the
back. This fires downwards onto a reflector (I don't think this is a
"real" horn in that I don't think the horn section is either tuned or big
enough to make a huge difference). The basic idea is that frequencies
around Fs are reinforced, helping the bottom end a bit.
I'll have a better idea in a couple of days when I've had a first
listen. :-) Hopefully I'll be able to resist gluing them together long
enough to get some photos!
Unfortunately, the FE126e speakers, which I originally ordered, appear to
be unavailable at the moment so I've used their shielded cousins. That
has probably cost me some sensitivity. The 126s are supposed to be 94dBW
and the 127s 91dBW at 1m, but the bass on the 126s is uneven and benefits
from some series resistance. That loses some power and must surely make
the damping worse, so perhaps I've not lost much.
In answer to your earlier query, Andre, no, I didn't post anything about
the spud amp. It was pretty basic and I just re-used my old OPTs -
nothing special. It was actually built on the stripped chassis of my
ECC82 paralleled PP amp so it looked extremely horrid too! The speakers
aren't too bad, but are getting a bit old now. One of my brothers built
them originally from a Wilmslow driver kit. I just wish he hadn't brush-
painted them blue... :-(
The new monoblock amps will be 417A and 6P3C (triode-strapped) to start
with. I have plans to change the output bottle to 6C4C or 6B4G dht (much
like 6.3v 2A3) later and to put a slightly more meatier OPT on them. That
may have to wait until I've got Christmas over with though. So I start
with about 1.4W and upgrade to nearly 3W! :-)
--
Mick (Working in a M$-free zone!)
Web:
http://www.nascom.info http://mixpix.batcave.net