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Inductor Loaded De-Lite
Inductor Loaded De-Lite
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Old 23rd August 2019, 03:46 AM   #1
Jenghis is offline Jenghis
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Default Inductor Loaded De-Lite

Hi guys, quick question for you. Maybe I'm on to something, or maybe I'm way off base.

Could the 300 watt light bulb power resistor in the De-Lite circuit be replaced by a high current inductor, such as the Hammond 193V (150mH, 1 ohm, 3A max DC). Would such a change require a complete redesign of the circuit? Would it be easier to start from scratch? I'm assuming at the very least the power supply voltage would be lower, since the inductor can store so much energy. Can the inductance of the inductor make up for the loss of load resistance the light bulb supplied?

Since completing my ACA, I've been looking at solid state designs using some iron in the amplifier circuit, like the Nemesis, FAOW #2, and MoFo. For one reason or another, they don't quite satisfy my requirements. I like the De-Lite circuit, ruthlessly simple with no NFB. The added efficiency of an inductor makes the circuit more attractive. I tried doing a simulation of my circuit idea, but didn't get very far. I also don't know which version of the De-Lite would be best suited to this modification, I was thinking the De-Luxe circuit.

If this is a completely silly idea, please say so! If not, I'd love to to hear your guys' thoughts!
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Old 23rd August 2019, 08:40 AM   #2
El Reino is online now El Reino  Finland
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Inductor Loaded De-Lite
Go for it
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Old 23rd August 2019, 11:41 AM   #3
Dennis Hui is offline Dennis Hui  Canada
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Inductor Loaded De-Lite
You might want to have a look at Michael Rothacher's L'amp articles since
conceptually they are similar to what you are trying to do for the De-lite
(light bulb and then inductor, including a version with the 193V.):

http://blog.audiomaker.tech/pdf/lamp%20part%20one.pdf
http://blog.audiomaker.tech/pdf/lamp%20part%20deux.pdf
http://blog.audiomaker.tech/pdf/lamp%20193V.pdf

Cheers,
Dennis
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Old 23rd August 2019, 03:06 PM   #4
Jenghis is offline Jenghis
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Quote:
Originally Posted by Dennis Hui View Post
You might want to have a look at Michael Rothacher's L'amp articles since
conceptually they are similar to what you are trying to do for the De-lite
(light bulb and then inductor, including a version with the 193V.):

Cheers,
Dennis
Thanks Dennis! I'll take a look!
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Old 24th August 2019, 06:55 PM   #5
Jenghis is offline Jenghis
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Here's my quick and dirty schematic to get an idea of what I want to do:

Click the image to open in full size.

I'm assuming I want to keep the same bias current (2.2A), but half the supply voltage. A 36 VAC transformer should get me in the ballpark. Are there any glaring errors, or is this feasible?
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Old 24th August 2019, 07:52 PM   #6
res07njc is offline res07njc  United States
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I might be missing something but ~40Vdc at 2.2A is too much for that part? Best to think of that part as a 30W device. eg, 20Vds at 1.5A. Those light bulbs drop far more voltage than the Hammond.

Last edited by res07njc; 24th August 2019 at 08:18 PM.
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Old 24th August 2019, 07:52 PM   #7
Zen Mod is offline Zen Mod  Serbia
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Inductor Loaded De-Lite
anyone already using same part with 100W dissipation?

as res07njc sez - go with 24V rail
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Old 24th August 2019, 09:12 PM   #8
Ben Mah is online now Ben Mah  Canada
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Jenghis's schematic is a modification of Nelson's De-Lux De-Lite (fig. 10):

http://www.firstwatt.com/pdf/art_delite.pdf
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Old 24th August 2019, 09:29 PM   #9
Zen Mod is offline Zen Mod  Serbia
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Inductor Loaded De-Lite
yup and it's clearly written that there is 25V at mosfet drain

exactly what you need as PSU rail , using inductor instead of big voltage eaters
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Old 24th August 2019, 10:30 PM   #10
Jenghis is offline Jenghis
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Quote:
Originally Posted by Zen Mod View Post
yup and it's clearly written that there is 25V at mosfet drain

exactly what you need as PSU rail , using inductor instead of big voltage eaters
Whoops, I glossed over that very important bit of info. So if my rough calculations are correct, an 18 VAC transformer with the same 25,000 uf caps and 1 ohm resistor CRC filter should get me about a 24V rail. Pass mentions that the MOSFETS dissipate about 55W each. If they can actually dissipate that much power reliably, then I could stick to the 2.2 amp bias.
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