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45 amp build direct coupled
45 amp build direct coupled
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Old 21st March 2018, 05:37 AM   #1
faithintruth is offline faithintruth  Canada
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Default 45 amp build direct coupled

Well it's dead horse beating time. I have too many parts including over a dozen 45's. I was going to build one of several amps but could never decide. John Tucker's parafeed direct coupled 45 has always stuck in my mind.

I have attached some photos of schematics I'm playing with. Many missing values. I am thinking of Lundahl iron but am open to suggestions and changes. Maybe I'm barking up the wrong tree.

I'll leave it open for comments.
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File Type: jpg 20180321_141620.jpg (439.7 KB, 1001 views)
File Type: jpg 20180321_141706.jpg (474.0 KB, 985 views)
File Type: jpg 20180321_141727.jpg (354.0 KB, 921 views)

Last edited by faithintruth; 21st March 2018 at 06:12 AM. Reason: spelling
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Old 21st March 2018, 06:57 AM   #2
faithintruth is offline faithintruth  Canada
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Ok...that is a messed up power supply and completely the wrong attachment. I will upload the correct one next
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Old 21st March 2018, 07:03 AM   #3
juanitox is offline juanitox  France
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it will works fine i will make 3 change if it was mine , lundhal plate choke instead of CCS for the D3A , resistor and film cap for the D3A cathode bias ,
and film cap to ground for the 45 cathode.
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Old 21st March 2018, 12:54 PM   #4
faithintruth is offline faithintruth  Canada
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Any thoughts on this (Thomas Mayer) power supply for my amp

(Medwin LCLC + Mayer 6AX4)

This supply using the 5AR4 was drawn by a friend. There is always the original supply by Tucker (?)
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File Type: jpg 20180321_220024.jpg (539.7 KB, 811 views)
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Old 21st March 2018, 02:32 PM   #5
audiowize is offline audiowize  United States
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I would build the amp just about as you have it drawn. Since you need HLMP-6000 diodes for the C4S, just buy a few extras and settle for 1.57V of bias on the cathode of the D3A. I would not recommend a resistor and capacitor as a substitute for the LED, but it's certainly easy enough to try. It is worth mentioning that a plate choke on the driver can allow you to take driver B+ from the cathode of the 45.

I would absolutely go parallel feed if you possibly can. If you're using a 5K transformer, very few of them have sufficient inductance to give satisfying bass performance. I would look for at least 40H of primary inductance on your OT. With parallel feed, getting 100H isn't a problem.

The MJE5731A should replace the MJE350 in your C4S load. The metal tabs face in opposite directions, but otherwise the 5731A will handle more voltage and is much easier to heatsink.

The note about "1 or 2 of these windings for 45 filaments" is concerning. Each 45 needs its own filament winding!
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Old 21st March 2018, 05:09 PM   #6
6A3sUMMER is offline 6A3sUMMER  United States
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If you decide to do a Parafeed circuit, you will need a couple of things:

A very high quality air gapped plate load choke for the 45. It will need lots of Laminations, and lots of inductance.

A very high quality non-electrolytic high voltage capacitor to couple from the junction of the Plate and Plate Choke, to the Parafeed output transformer primary.

A 40H plate load choke(not nearly high enough inductance), and a 40H parafeed output transformer will have an effective load on the 45 of 20H. 20H is only 2,500 Ohms of inductive reactance.

A 100H plate choke and 40H parafeed output is 28.6H; it has 3,593 Ohms inductive reactance at 20Hz, that is a little better.

Of course depending on the capacitance of the Parafeed coupling cap, the Parafeed OT primary impedance, the music frequencies, and the loudspeaker load on the Parafeed output transformer, there will be large variations of impedance that the 45 is driving.
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Old 21st March 2018, 05:38 PM   #7
audiowize is offline audiowize  United States
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Sorry, I mixed up my recommendations a bit. With a 5K gapped transformer, inductance is a huge problem.

With parallel feed, a 40-50H plate choke is generally not hard to find for your application, and will work marvelously with a 4-5K output transformer.
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Old 21st March 2018, 06:14 PM   #8
6A3sUMMER is offline 6A3sUMMER  United States
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audiowize,

Yes, I forgot that the Parafeed transformer will probably have 100H to 300H or so.

That works with a 40H - 50H choke.

I keep putting off building a Parafeed amp, but you tempt me to order a pair of plate chokes.
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Old 21st March 2018, 06:17 PM   #9
audiowize is offline audiowize  United States
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Yeah, it's hard to go back to series feed...
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Old 22nd March 2018, 12:46 PM   #10
faithintruth is offline faithintruth  Canada
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Thanks for the suggestions to update the Tucker Simple 45.
I have tried to draw in the suggested changes. Made a few other changes. Still some values missing.
Looking at options for all the iron.

Getting warmer?
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