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EL503 interest

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Shrad

Mon Apr 20 2015, 07:24PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

hi all

I have got a nice 200W EL503 push pull amplifier with a fried EL503

given prices artificially high due to the tube hifi hype, I was wondering if anyone would have a spare EL503

please send me a PM if you have one

thanks all!

Ash Small

Wed Apr 22 2015, 02:39PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

If you can't find any EL503's, maybe this page (and the rest of the 'Champ' website will be useful, for converting to EL36/6CM5/EL360 tubes?

Shrad

Fri Apr 24 2015, 12:28PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

Hi Ash,

I had a look already and know of much designs which would suit my needs, but the problem of those EL503s is that their low impedance and the particular output transformer of that amplifier make that it is not practical without completely modifying the amplifier (replacing the complete push-pull)

while the champ example seems a simple solution, the guy is actually redoing all the power stage with nearly a custom power transformer for each tested tube and all things like that while keeping things simple in appearance as he writes things very well (that's the reason his site is such nice to read)

sadly I don't have that knowledge of tube designs myself, so I'm looking for something simple enough ;)

I think I'll remove the other one from the pair which poses problem and duplicate the bias circuit to be able to put in non paired tubes, and perhaps make another preamp based on tubes instead of transistors, but not a complete redesign

I still have 8 6080 which I plan to use as OTL amplifiers for stereo 30W amplifiers which will fit nicely with that 200W beast and a subwoofer, and optional guitar amp

I have a friend who has a spare EL503 but he is 1000km away, I'll have the opportunity to meet this summer when vacation in his area with the family and was looking for quick alternatives

sadly vacuumtubes.net is out of stock and others are 100â‚¬ (actually one is 36â‚¬ in germany but shipping included it is not interesting)

thanks anyway

Ash Small

Sat Apr 25 2015, 03:22AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I didn't realise you'd need to replace the OT.

I know someone who has thousands of tubes, I can ask him if he has a 503, or even a matched pair if you are interested.

I presume I'd need to post it/them to you?

Shrad

Sat Apr 25 2015, 01:01PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

yeah that's not an issue as shipping from UK is usually 2 days to Belgium

if you can find me a matched pair that would be really nice as I could restore it in its past glory, but as it's not an exceptional amplifier (that's a town hall sono amplifier rather than a hi-fi marvel) I wouldn't spend more than it cost me at start, or say less than 100â‚¬, because I could go for cheap and do a conversion with cheaper beam tubes

if you could ask your friend about a list of common higher wattage beam triodes, tetrodes and pentodes he would have it would also be interesting as I'm looking at a 2.1 tube setup for a long time now, and why not jump in now

Ash Small

Sat Apr 25 2015, 04:29PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'llprobably pay him a visit tomorrow. He designed the 'Mighty Atom' I posted details of a while back.

I've not come across bean triodes or pentodes before. I always thought thr Beam tetrode was just a way of getting around the pentode patent.

I'm building a single ended amp using a beam tetrode voltage regulator tube.

He said he doesn't think he has any EL503's, I'll ask him about the common higher wattage ones though. I'm pretty certain he'll have something suitable. Any idea what impedance you want?

Apparently there is a Russian equivalent, the 6P45S, but I've not looked into it. I just found it while googling.

[Moderator edit by Mads Barnkob: merged posts]

Shrad

Sat Apr 25 2015, 09:23PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

I've some 6P45S but the tube is approximately one third in size (or they are reserigraphied and I would be disappointed as they were in a kind of original 'CCCP' package)

the interesting thing about beam tubes is that a yoke is nearly the same as an OT and as they are cheap and designed for 1000's of hours of continuous use instead of the hundreds of classic audio tubes, they are gold for sturdy amplifiers provided a non conventional design

same for triodes used in regulated PSUs and voltage regulators, such as the 6080 (6AS7) which has low impedance and can drive a 8 ohm speaker with 8 tubes in a row without an OT, and is ultra cheap

for beam pentodes for example a matched pair is in the 30â‚¬ range, and even a 24LQ6 with 30W is less than 20â‚¬, so those can only be interesting

if you friend has a box of such tubes he wants to get rid of, that would be really nice for me to have a bunch of experimentation power tubes (I already have 100+ various small tubes for the rest, preamps etc...)

Ash Small

Sat Apr 25 2015, 11:01PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'll ask him about the above valves.

The beam tetrode I'm using in my single ended amp is from some old military equipment and high impedance (max 800V anode voltage, but I'll run it at ~500V. It's good for 35 watts or so. I think I have a suitable OT, I'm just waiting to find a suitable parafeed choke, or a core I can wind one on).

He knows a lot more about valves than I do.

I'll see what he has, what he wants to part with, and how much he wants.

Probably sometime in the afternoon/early evening. I'll try to post on here while I'm there.

Shrad

Sun Apr 26 2015, 07:57AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

that's very nice of you

in terms of choke, I would certainly not go myself for a conventional design for the B+... I want to try the PC controller route as it delivers the range needed for a triode with the suitable load characteristics

I really have to read my books but I feel this is a road to go for saving money and performance

a mosfet drive for the powere tubes could be nice too... but I'll stick with conventional first (

Mads Barnkob

Sun Apr 26 2015, 09:10AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

I have built a 100 Watt mono block amplifier using 6P45S tubes:

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Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob