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EL503 alternative


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4/7/2004 8:12 AM
Nyquist5
EL503 alternative
I have the opportunity to buy a relatively cheap 200Watt (so the seller says) EL503 amp (Faylon brand). The problem is that EL503's are very expensive valves and I would like to know if I can replace them with a more readily available valve.  
 
Looking at the plate to plate load specs, it seems that EL34 would be my best bet but I am not sure if the filament supply will hold up.  
 
Anybody has a solution for my problem?
 
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4/7/2004 1:44 PM
Chris ( CMW amps )

Hi  
 
Don't know about the filament-current from top of my head but I've rebuilded a couple of amps with EL503s to 6L6 or EL34 in the past . Remove the old sockets and install some octal ones , rewire the sockets and check the voltages to tweak the biasing before installing the output-tubes .  
 
Hope this foes help a bit ,  
 
Chris
 
4/7/2004 2:42 PM
Nyquist5

Thanks Chris,  
 
The amp uses 4 EL503, so am I right in assuming that the OPT primary impedance would be 1200Ohms? In this case, isn't it too low for 6L6s?  
 
Nyquist5
 
4/7/2004 2:50 PM
Chris ( CMW amps )

Hi Nyquist5  
 
( Terrible / busy day over here ) .  
I'll look for some datasheets . The amps I did rebuild all did have multi-tap-OTs so I was able to rewire them for a correct impedance .  
If it's 1200 into 8 ohms you could use it with 4xEL34 into 16 ohms .  
 
'nother customer within a few minutes .....  
 
Chris
 
4/7/2004 2:56 PM
Nyquist5

Thanks for your help Chris, it is much appreciated.  
 
Nyquist5
 
4/8/2004 9:04 AM
svokke

I agree with Chris.I have two faylon amps with EL503. They are still running with their original EL503's and I've got only one spare. I'm not worried though, a friend of mine used the transformers of a faylon for a 4*EL34 amp.  
200 is the normal price for a faylon amp. I bought mine for 200 (faylon universal) and 100 (faylon studio 2). I got the second one because it was so cheap.  
I'm not impressed by the sound of the amps, they have all have a solid state preamp that sounds bad. It is a good starting point for a diy amp though. Almost forgot to say that they were made here in Belgium.  
Greetz, Svokke
 
4/9/2004 1:55 PM
6 10

Hi guys.  
 
I have a couple of Italian FBT amps (500-R2) with one pair of EL503's.  
They are running at around 360 Volts, with a load of about 2,6k.  
 
I'm also thinking of rebuilding at least one of them for more common tubes. I guess the EL34 is the firts choice, but maybe 6550 would be even better?  
EL503's works with lower voltages and higher currents than EL34's, so I belive the power supply will handle 6550's too.  
Anyway, if one puts in normal 8-pin sockets and wire them for EL34's, it's easy to test with a number of different tubes, like 6L6/5881, EL34, 6550, KT66 and some more.  
 
EL503 takes 1,05A for the heaters, so both EL34 and 6550 will put some more stress to the supply.  
 
What are those Faylon amps? I've never heard of them!  
 
/Sixten
 

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