Quick question about bias..quite urgent!

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chamelious

www.thesunexplodes.com
Amp: ashdown fallen angel 60w all tube. I'm replacing the power tubes, 2xEL34' fixed bias, with some EL34's reccomended to me by doug from dougs tubes. Do i just stick them in or must they be biased?
 
chamelious said:
Amp: ashdown fallen angel 60w all tube. I'm replacing the power tubes, 2xEL34' fixed bias, with some EL34's reccomended to me by doug from dougs tubes. Do i just stick them in or must they be biased?
Click to expand...

They should be biased. Fixed bias doesnt mean it is non adjustable.
VP
 
Excellent thanks thats what i was beggining to suspect from what i've read, now i've just got to find somewhere to do it, nowhere local does :(
 
if you can find a schemo perhaps we can help you DIY...
 
What happens if i dont do it? The nearest place that can even do it is like an hour and a halfs drive away and he's gonna charge me £25-30 for it, which is almost as much as i paid for the bastardsin the first place.
 
worst case... tubes dont last... sounds like shit... best case??? they just happen to need aprox what the old ones did and all is copaecetic...
 
dementedchord said:
worst case... tubes dont last... sounds like shit... best case??? they just happen to need aprox what the old ones did and all is copaecetic...
Click to expand...

No so fast. If he is buying Electro-Harmonix tubes, a worst case scenario is the amplifier puts on a little light show and possible causes some damage on the circuit board. Right of the hop, I'll say I know SFA about the innards of any Ashdown. But with a Marshall JCM2000, I have seen the board burnt real bad, and a resistor or two taken along for the ride.
How is this possible? Well, EH EL34's have a horrible quality control. I am not kidding. I will go to my local store and buy twenty EL34's at one time. I take 'em home, and with a home-made Bias Probe I check the idle Plate current with the bias as high as it will go (the most negative voltage). From those twenty tubes, the current will range anywhere from say 18mA all the way up to 60mA :eek:. Obviously, putting these two tubes together in a 50-watt amplifier isn't too healthy for the amplifier. But that's life, and I try and match them as best as I can. The piss-off is I'll end up with those two tubes left over at the end of the day, while all the others are matched up and earmarked for various amplifiers. The next trip, I buy just twelve or so, and keep going.
The point is, if you don't buy matched tubes already, you may get a real mismatched pair. Especially if they are Sovtek. Or EH.
 
This is what i got, 2 of these: What would i need to do it myself?


Click to Enlarge
Ruby EL34BSTR

This new high gain EL34 from the Shuguang factory has dynamic tone, a thicker glass envelope and gold plated grid.
 
chamelious said:
This is what i got, 2 of these: What would i need to do it myself?


Click to Enlarge
Ruby EL34BSTR

This new high gain EL34 from the Shuguang factory has dynamic tone, a thicker glass envelope and gold plated grid.
Click to expand...
What is "dynamic tone"?
 
ranjam said:
No so fast. If he is buying Electro-Harmonix tubes, a worst case scenario is the amplifier puts on a little light show and possible causes some damage on the circuit board.
Click to expand...

agreed... i was just trying to down play it... although the likelyhood of this happening is minimal... assuming the amp is working at present... if the tubes roached as opposed to just getting old and sounding bad then there may be something else wrong and the likelyhood of them going cherry is greater...
 
chamelious said:
This is what i got, 2 of these: What would i need to do it myself?

Ruby EL34BSTR

This new high gain EL34 from the Shuguang factory has dynamic tone, a thicker glass envelope and gold plated grid.
Click to expand...

Ruby are pretty good since the Chinese seem to being trying harder lately. These are really only a few extra dollars, but people like Parts Express say they are premium matched. Maybe dougstubes.com has them a little cheaper? And Doug is a cool guy to boot. But from memory, they were more consistent than EH, had more output, and seemed matched better. I know I've purchased new Groove Tubes, and taken them home to find 4mA or even 5mA difference in the idle Plate current :confused:.
JJ had even more output, but buying unmatched can be hit-and-miss (although nowhere near as bad as EH). And they did have an issue with the pins being a little small, and they would lose contact with the socket :eek:. I haven't tried JJ lately, but I hear they have this problem solved. Anyway, if your asking about the Ruby Tubes, I will only confirm and add to the online gossip that they are really nice.
DIY bias? Whay not?
http://cgi.ebay.com/AMP-HEAD-Bias-Tester-6L6-6V6-EL34-6550-Tube-Probe_W0QQitemZ300348250246QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item45ee269886&_trksid=p3286.c0.m14
 
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