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Old 28th October 2006, 12:09 AM   #1
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Default Junk Pile Linestage

Hey everyone, Thought I might start a thread on a little project I'm doing to try to learn about some of the pitfalls of preamp construction. When finished, I hope it will give me a place to try some different stuff. The PS is on a seperate chassis and consists of a CT TX, 6CA4, 10hy choke/25uf motor run cap, 5hychoke/motor run. It's putting out 211v into a 90ma test load. The filament supply is an old CDP PS which after a couple resistor changes is putting out ~ 25v of heavily filtered DC. I plan on running the 12B4 filaments in series, at least for now. The amplifier section will be a 12B4 per channel, with a 5k plate resistor. I'm thinking 100ohm resistor and 1000uf cap on the cathode? I have an assortment of output caps to try ranging from 3uf on up. Anyone ever use tantalium caps or motor run oilers for coupling? Anyhow, I hope to be able to design something someday, but for now I just have a lot of fun "slingin solder". If this gets to sounding like something I want to build for keeps, an RIAA stage will be the next project. Any comments, suggestions, or general poking fun is allways welcome and thanks in advance, Jay
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Old 28th October 2006, 12:17 AM   #2
bembel is offline bembel  Europe
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sound good Jaymanaa,
for your question have a search
----> motor run caps in the output? good or bad idea?

regards
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Old 28th October 2006, 02:11 AM   #3
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Default Re: Junk Pile Linestage

Quote:
Originally posted by jaymanaa
HAnyone ever use tantalium caps
No, these sound awful.

Quote:
Originally posted by jaymanaa
or motor run oilers for coupling?
Yes, these are generally good
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Old 29th October 2006, 12:00 AM   #4
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Default Re: Re: Junk Pile Linestage

Quote:
Originally posted by dsavitsk


No, these sound awful.



Yes, these are generally good

Thanks for the tip. I just happened to see them at the electronics store, and thought I may have made the next great discovery in tubes.


I'll give the motor oilers a try, Jay
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Old 29th October 2006, 01:48 AM   #5
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Default Re: Junk Pile Linestage

Quote:
Originally posted by jaymanaa
Anyone ever use tantalium caps or motor run oilers for coupling?
A must read:
http://members.aol.com/sbench102/caps.html
http://members.aol.com/sbench102/caps1.html
http://members.aol.com/sbench102/caps2.html
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Old 29th October 2006, 02:19 PM   #6
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Very good reading there Geek, thanks for the link. I checked out your sites as well............very cool. Most of the new motor runs that I'm finding on the cheap at AC supply houses (2 or 3 bux) are made in China. I think I'll cut one open and see what they are made of. Jay
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Old 5th November 2006, 11:43 PM   #7
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Just thought I'd post a follow up. I finished this thing today, and am quite impressed with the 12B4A. I used some Japanese IECs which are apparently a good variety (I've heard you have to find good 12B4s). The sound is very good from top to bottom after a couple hours "burn in". I ended up with 220v B+, which gave me ~60v on the plates via a 4.7K resistor. I had a bit of trouble on one channel at first (High pitched squeal) but after changing the grid stoppers to 500 ohm, and replacing a suspect interconnect, all is well. I've allways been an octal fan, but this little 9pin has made a beleiver out of me. It has plenty of gain to make my 2A3s happy. I think I will build it for real, and add a RIAA circuit. I've never done an RIAA before, does anyone have a favorite? Oh yeh, I ended up using a .50uf output cap, and 1000uf cap with 100ohm R on the cathode. Jay
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