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Old 16th February 2005, 05:12 AM   #1
exurbia is offline exurbia  Australia
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Question 12e1 sub for 807 ?

Hi chaps and chapettes,

Question , is there any way to sub a triode connected 12e1 for triode connected 807. I realise that the two are wildly different. Even the topcaps are different. They just look a lot nicer than 807 especially when lit.
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Old 16th February 2005, 06:17 AM   #2
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Yes, they are wildly different - one is basically for DC pass service while the other is commonly used for RF!

That being said, you may be able to modify the amp to use 12E1s provided you can meet the extra heater current (1.6A vs 0.9A). The 12E1 will probably be happier running at somewhat higher current, so you'll also have to be careful that it won't result in stressing your rectifiers and transformers (both power and output).

A schematic would help
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Old 16th February 2005, 06:30 AM   #3
qwad is offline qwad  Australia
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beats me why you want to move away from the 807 as they are extremely rugged and capable of taking plenty of punishment, also they are plentiful and cheap even for NOS ones as a matter of fact l have 4 of them sitting in my drawer just to the right of me as l type this cheers TC
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Old 16th February 2005, 06:32 AM   #4
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Ah, but I have six NOS 12E1s in the box of stuff behind me and they were even cheaper than 807s!
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Old 16th February 2005, 01:07 PM   #5
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AUN is correct about the increased heater requirements, and that they like to run lower (B+voltage) and hotter (Ia) than an 807 and into a lower load. Very good tube when you can get them to work optimally.

However, if you have an 807 amp you're not going to get a big power increase and/or any particular sonic benefits. Builts amps with both and may have even posted something here about them.
I have tons of 12E1 and 807, all good NOS and their wasn't much difference in the price. I'd advise keeping your amp as is, and building something specifically for the 12E1 should you decide to do so later.
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Old 16th February 2005, 01:25 PM   #6
exurbia is offline exurbia  Australia
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Talking 12e1 sub for 807

Thanks everyone,

I have two williamsons sitting here one has trafos and 5 pin sockets it is going to get 807's

#2 has no output trafos and no sockets it is going to be the proud owner of 12e1's. The circuit mods have been done already to bring it up to the wireless weekly article.

hopefully i will hear a difference between the two, with a 12e1 trioded what primary impedance would suit it best ? I will use B+ of 320 volts.
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Old 16th February 2005, 04:46 PM   #7
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Maximum screen grid volts for the 12E1 is 300v although nothing bad has happened when I have gone over that. Trouble is that things get less linear at the top of the voltage range ( if you have a look at the plate curves they start closing up when you get much past 200v.
I have had good results using this tube at around 200v and 130mA - this is not much good for single ended (transformers are expensive and power output is low) but works quite well in an SRPP parafeed arrangement with a B+ of about 440v
Will post my schematic later but this is the sort of circuit I am trying to describe.

I have seen the 12E1 described as a KT88 near equivalent, although this was by a tube supplier trying to sell them. In my opinion, it's an entirely different animal which is happiest at low voltages and high current - almost indestructable though and the maximum ratings appear to be conservative.

Click the image to open in full size.
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Old 17th February 2005, 10:09 AM   #8
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When triode connecting the 12E1, remember to put a 120R (approx) resistor between plate and screen grid. If you just wire them together directly it will oscillate fairly violently
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Old 17th February 2005, 10:37 AM   #9
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This is the circuit I'm using ( different version from the one in the picture)
Click the image to open in full size.
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Old 18th February 2005, 12:51 AM   #10
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Very nice looking amplifier. May I ask what the display is?
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