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Old 9th December 2012, 12:27 AM   #1
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Default suggestions for a parallel feed 45 amp?

Hi from Quebec!

I have a set of parallel feed outputs and chokes (Magnequest) that I got from a friend in a trade. Most schematics I find on the net do use transistors in the first stage.

I am looking simple and neat, direct coupled, parallel feed, no transistors anywhere. Just because I'm not confortable working with them anyway.

So, if someone has a link to suggest, a schematic, or a great idea. I'm opened to persuasion.

My first thought was to build an adaptation of the Shishido 2A3 (wich I built and loved) but for 45. But since I do own these parallel feed trannies, I guess I should give it a try.

Thanks!
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Old 10th December 2012, 05:23 AM   #2
Seta45 is offline Seta45  Canada
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Default 45 direct coupled amp

http://www.bottlehead.com/VALVEarchi...7/va101997.pdf

Enjoy!
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Old 10th December 2012, 08:23 PM   #3
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Quote:
Originally Posted by Seta45 View Post
This was my first thought, but Seta45 doesn't want ransistors anywhere, and the Bottlehead design uses a CCS.
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Old 10th December 2012, 11:25 PM   #4
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Thanks for the suggestion, but that's exactly the design I had found.. and this one uses transistors.
Can Parallel Feed be built only with tubes ?

When it comes to building tube amps, I am a novice. Have built 3 of them.. they all worked, but I did follow the diagram, I admit. ;-) Then, I can do a few adjustments, but I'm no engineer. It's easier to tune pianos. ;-)
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Old 14th December 2012, 02:33 PM   #5
regal is offline regal  United States
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Quote:
Originally Posted by Sylver300B View Post
Thanks for the suggestion, but that's exactly the design I had found.. and this one uses transistors.
Can Parallel Feed be built only with tubes ?

When it comes to building tube amps, I am a novice. Have built 3 of them.. they all worked, but I did follow the diagram, I admit. ;-) Then, I can do a few adjustments, but I'm no engineer. It's easier to tune pianos. ;-)
It can you just need to use an inductor or resistor of the right value in place of the transistor shown in the link above.
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Old 14th December 2012, 03:43 PM   #6
smbrown is offline smbrown  United States
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You can't just sub in an inductor, the plate voltage on the driver will be messed up. A resistor will work, figure the current (I'm thinking it was 10ma, but didn't re-read the article, got stuck at the t-shirt ad). And the needed voltage drop (IIRC plate is 150v).
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Old 15th December 2012, 03:03 AM   #7
regal is offline regal  United States
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Originally Posted by smbrown View Post
You can't just sub in an inductor, the plate voltage on the driver will be messed up. A resistor will work, figure the current (I'm thinking it was 10ma, but didn't re-read the article, got stuck at the t-shirt ad). And the needed voltage drop (IIRC plate is 150v).
Obviously you would add a CRC filter to drop the voltage then sub the ccs with an appropriate inductor. A resistor would be OK depending on how sensitive the speakers are (hiss.)
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Old 15th December 2012, 10:23 AM   #8
mach1 is offline mach1  Australia
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Or even better just put a resistor in series with the plate choke to match voltages and get an even higher plate load.
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Old 15th December 2012, 05:44 PM   #9
Nick F is offline Nick F  United States
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Default Here's another one:

I don't remember for sure but I think Gordan Rankin shared this design.
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Old 17th December 2012, 01:35 AM   #10
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Default seems like a nice compromise

Quote:
Originally Posted by mach1 View Post
Or even better just put a resistor in series with the plate choke to match voltages and get an even higher plate load.
Nice compromise I think. Now, I must dust off some of my past knowledge and calculate how it should be built. I'll make a try and post it here.

Thanks friends.
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