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Old 16th February 2014, 12:38 AM   #1
billbo is offline billbo  Australia
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Smile 12E1 SE amp suggestions.

Hello every one. I have a few sets of Ediswan 12E1's. Any suggestions about a single ended setup with these tubes? Application notes etc
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Old 16th February 2014, 03:09 AM   #2
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I would start by building up some loadlines first off....I'll move this over to "paint" & start some loadlines & bias.

It doesn't show it here but this is triode strapped


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Old 16th February 2014, 11:48 AM   #3
12E1 is offline 12E1  United Kingdom
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I am getting together parts for a parallel-single-ended design using 12E1. I am taking the K5881 PSE design from World Audio Designs as my start point. It was published in the HiFi World DIY Supplement in February 1995. But the 12E1 requires substantially different biasing from the 5881, so I am considering a mixed bias approach for the output stage with some cathode resistance but also some negative bias voltage, adjustable for each output valve individually. I will probably allow 5881s to be used with some minimal wiring changes since I have quite a few of them as well. I will also switch to valve rectification with CLCLC filtering - I have a bunch of EY500's that need a good home. Output transformers will be Hammond 1640SEA. It's a work in progress - some months from conclusion I think.
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Old 16th February 2014, 05:04 PM   #4
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I'm assuming you want to bias each valve independently trying to avoid "current hogging" by any one valve. Thinking aloud here,....There must be a way to bias each valve independently, "automatically" to compensate for current draw....some type of feedback to re-bias valve to valve, ensuring an equal split between the two.
More than likely this has been "thought up" before....thinking aloud...

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Old 16th February 2014, 09:29 PM   #5
billbo is offline billbo  Australia
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I found some data on this tube.
http://www.mif.pg.gda.pl/homepages/f...025/1/12E1.pdf
I will draw up some load lines and see what I get. I am trying to work around with what I have got in my parts box. (power tarnnys opt's etc.)
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Old 17th February 2014, 08:43 AM   #6
12E1 is offline 12E1  United Kingdom
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Quote:
Originally Posted by Richard Ellis View Post
I'm assuming you want to bias each valve independently trying to avoid "current hogging" by any one valve. Thinking aloud here,....There must be a way to bias each valve independently, "automatically" to compensate for current draw....some type of feedback to re-bias valve to valve, ensuring an equal split between the two.
More than likely this has been "thought up" before....thinking aloud...

__________________________________________________ _Rick.........
The "normal" method for a PSE is to simply use equal cathode resistors for each valve and to keep the cathodes separate. That way there will indeed be a degree of self-regulation, as with any cathode resistor loaded valve circuit.

However, the 12E1 requires rather more grid bias (negatively) than, say, an EL34 or the 5881 that I am also looking at. The impact is that for the 12E1 a larger cathode resistor is needed to drop sufficient voltage. That not only wastes power, but it also detracts from the output swing available at the anode, since more of the total supply voltage is taken by the cathode circuit. That is why I am looking at a mixed bias scheme. I can gain headroom for the anode by not relying solely on the cathode resistor for bias, heat dissipated from the cathode resistor is lower, and the degenerative feedback from the cathode resistor helps to keep the quiescent current stable. And it's just as easy to fit adjustment pots for four output valves as it is for two. (I have some nice locking pots that I plan to use.) The complication is that a negative bias supply is needed, but that's not a big deal in my case.
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Old 17th February 2014, 09:17 AM   #7
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This is one of those situations where a CCS for each cathode seems the logical answer. Could be used in conjunction with partial fixed bias as well.
In fact one solution would be to use fixed bias but then put your CCS on a negative rail such that the anticipated ideal bias sits the cathode right on zero volts, but with room to move either way. A negative rail of -10V would work for most CCS.

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Old 17th February 2014, 12:49 PM   #8
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just a quick note - you'll need more than 40V of bias - I tried running a 12E1 in my (apparently not so) Universal single-ended amplifier and I couldn't adjust the bias enough to get the current below 100mA per tube. I haven't made the mods yet to run this tube... someday.
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Old 17th February 2014, 01:35 PM   #9
12E1 is offline 12E1  United Kingdom
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Quote:
Originally Posted by kstagger View Post
just a quick note - you'll need more than 40V of bias - I tried running a 12E1 in my (apparently not so) Universal single-ended amplifier and I couldn't adjust the bias enough to get the current below 100mA per tube. I haven't made the mods yet to run this tube... someday.
Yes - I saw your earlier thread about the bias requirements recently. I am currently planning to have about +15v to +20v on the cathode, and the grid adjustable from around -20v to -60v, but could go further if needed.

@Shoog: I'll consider loading the cathodes with a CCS, but it's not in the current plan for my PSE build. For PSE I'd need one CCS per tube I guess.

@billbo: Let us know what you come up with. Would be good to compare notes.
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Old 20th February 2014, 09:13 PM   #10
billbo is offline billbo  Australia
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Default 12E1 bias supply

Lets say you -20 votls cathode bias and another -30 volts fixed bias, total is -50 volts grid to cathode. This still means you need a 50 volt swing about the zero axis to get full output. Is this true?
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