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Post by paulrbarker on Oct 29, 2024 15:01:23 GMT
Ive probably confused people above. I’ll thinkof a simpler version.
So as we are going to try ultra linear push pull. Triode class AB = 16.5 watts Ultra Linear class AB is 37 watts. So we can expect ultra linear with the EL38 AB at least 37 watts.
Don’t forget the reason to consider ultra linear is because in class A triode we are limited by the g2 voltage tolerarance. We can only achieve ultra linear by also transitioning to push pull..
Back to EL38 Push Pull class A triode will give double the SE triode. So 13 Watt. When we alter to Ultra linear I can’t say what class A would deliver, but I know fromthe EL34 data that AB would deliver 37 watts.
I expect push pull triode will serve me enough power. But it may sound good in UL, so I’ll try it.
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Post by paulrbarker on Oct 29, 2024 15:14:02 GMT
Clive its worth building. You can get PL38’s from Langrex on ebay for £25 a piece four could share a 120v power supply, or individually 30v torroid shared parallel. I find they sound better than Mullard EL34’s and much cheaper.
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Post by Clive on Oct 29, 2024 19:36:50 GMT
They certainly look great value! I ought to get in there before prices rise…
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Post by paulrbarker on Oct 29, 2024 22:23:03 GMT
I think you’re safe, too many people building Mofo’s. Then puting a valve in front of it. I’m a dinasore.
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Post by paulrbarker on Oct 30, 2024 6:40:23 GMT
Clive you have a long list of good gear, especially the 301. Did you spot the Grease bearing on ebay lately. The guys photos were poor and I was hoping to pick it up for a sing. It still went cheap for what it is but way above my spending limit. Think it was £777. But the poor photos made me feel uncomfortable about the seller then his feedback was poor too often as a seller for my liking. Can’t take risks like that. The world is full of people who lie and aren’t honourable. Ref the EL38 (or PL38) they are magnificent. If you understand valve characteristics you will have seen some very clear clues. They have a bright oxide heater in a larger than usual anode. They are a true Pentode not a beam tube which is a pretender invented to avoid a patent. To wind the 3rd grid is a highly skilled operation, good to have it in the hands of Mullard in the day that was their specialty. People who have heard it all give a good report. Compare it to a modern production EL34 both in sound and in look oh dear. No wander so many folk are giving up on valves. They aren’t well made at all. The modern EL34’s sound shockingly awful. I’ve had a long relationship with certain valve dealers but their descriptions of the modern valves they are selling to the guitar boys all read as they did in the days when they were selling Mullards Siemens et all. But they are selling cow pats using the same old descriptions. You cant blame them. Its back to my statement about the grease bearing above. Be aware of liers. So what is marvelous about the EL38 characteristics? It is better made than todays valves. It is over strong made because of its intended roll. It has really good amount of transconductance, so it would do the job the EL84 does as a directly coupled cathode follower driver but better. Also Mullard EL84’s cost money. Though the Russian version are very good. All EL84 amps sound great. This valve is like a big brother to an EL84. I havent finished . The mu of the EL38 is such a useful thing to work with. OK its internal resistance is a little high. Theere are no free lunches. But many valves with slightly higher internal resistance sound special, such as the 211, 801a, 45 even. The mu of the EL38 gives the person who builds an amp like Picasso paints. My design here has so many elemnts of my lesson’s Ive learned by experience and knowing who to trust. Like Stephie especially. More charismatic peeople attract attention in the upper echelons where they are given a platform. But Stephie could kick them all into a cocked hat. But he understates things that sound far better, while they are preaching things that puff up their egos. I havent finished exploring and there are paintings of valve love on going. Ive been given what I need to build a MOFO but no, its not for me. Neither are solid state diodes or ccs’s for me. OK friends are doing marvelous things with solid state. But its not the only way and its not my way.
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Post by paulrbarker on Nov 8, 2024 15:40:21 GMT
I have decided not to change the Voltage Amplifier to diode bias, rather leave the resistive feedback single stage as it is. My next project is to get on with building the GM70. That will be enough of a challenge for someone with Cerebral Amyloid Angiopathy.
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