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Ohm Sweet Ohm [message #31949]

Wed, 06 September 2006 06:02

Damir
Messages: 1005
Registered: May 2009

Illuminati (2nd Degree)

Radioactivity, Antenna, Home Computer...and other nice songs for all of us DIY/Electronic people...

P.S. apart from music listening, is anyone actually working on something?

http://www.evilmusic.com/reviews/kraftwerk/311.html

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Re: Ohm Sweet Ohm [message #31950 is a reply to message #31949]

Wed, 06 September 2006 11:52

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

I'm converting my EL 84 to tube rec at the moment. And trying to re-design the PS on my Eico amp. The can caps are no longer made in those values so I got to replace them with new values. I thought maybe to just toss the cans and build outboard cap strips. Whats the rule for the first cap in an input cap PS? If the cap is 20uf can we go to 47uf? I would model this in PSUD but many of the values are impossible to find.

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Re: Ohm Sweet Ohm [message #31951 is a reply to message #31950]

Wed, 06 September 2006 23:43

Forty2wo
Messages: 163
Registered: May 2009

Master

Hi M,
The input cap is limited by the rectifier tube. It is usually listed in the tube manual. 20uf is about right for most. A few like the 5U4 go to 40uf .
You can push the spec a little, but I don’t recommend it.

What you can do, is increases the capacitance on the second and third stages. For an old Eico, without looking at the schematic X2 or more is not unreasonable. If you are going to build a cap bank. Buy a few extra. Lets say your can cap was 20-20-20uf , try 20-40-40uf . What I would do, is buy a handful of 10-20uf caps, decent ones are less than 2 bucks, each , less on E-bay. Start small, then add till you get the sound you like. Look to the after market ST70 setups for inspiration.

If you need to stick with the can cap format AES is making new ones…John

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Re: Ohm Sweet Ohm [message #31952 is a reply to message #31951]

Thu, 07 September 2006 12:54

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Hey John; that is excellent. The Eike uses a GZ 34/ 5ar4 rec tube and yes you are correct the input cap is 20uf. Very simple but good rule of thumb that; easy to remmember. Aes makes I think a 40uf input followed by 20uf. Is That right?

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Re: Ohm Sweet Ohm [message #31953 is a reply to message #31952]

Thu, 07 September 2006 18:14

Forty2wo
Messages: 163
Registered: May 2009

Master

AES has a bunch of them, a bit pricy though. Look under multi section, FP.
BTW you can use the sections in any order or parallel two or more sections to suit your needs.

One tube manual I have (Sylvania) says the 5AR4 max is 60uf. But 5AR4’s didn’t cost then what they do now. 30uf is probably OK…John

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Re: Ohm Sweet Ohm [message #31954 is a reply to message #31949]

Fri, 08 September 2006 11:39

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

I've got a copy of Radioactivity on Vinyl. Loved that album in the 70's.

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Re: Ohm Sweet Ohm [message #31955 is a reply to message #31953]

Sat, 09 September 2006 18:53

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

So John; you can use whatever terminals have the available value on the can? IE; if the can is valued at 40/20/20 and the PS calls for 20/20; then you could just wire in the two 20uf sections and leave the 40uf out of the circuit completely right?

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Re: Ohm Sweet Ohm [message #31956 is a reply to message #31955]

Sun, 10 September 2006 18:59

Forty2wo
Messages: 163
Registered: May 2009

Master

Yep, or connect the 40 to one of the 20s for a 20/60…John

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Re: Ohm Sweet Ohm [message #31957 is a reply to message #31956]

Mon, 11 September 2006 08:34

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Thats what I needed John; thanks now I can order.
What are you building or listening too John if I may ask?
Now with the completion of the Eico and the tube rec EL 84 I need to start thinking about an amp.
1 I believe that you use less expensive passive parts; matched carbon comp resistors and decent caps; Orange drop 716's etc.
2 A reasonable homebuilt chassis and instead spend the money on tubes and transformers.
What do you think?
Good connectors also.
The one thing I need to study is good grounding and safety practice. I know lot of the safety wiring issues compromise sound but I want it safe.
Bus ground or star ground?

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Re: Steve Brown and I are working on this amp [message #31958 is a reply to message #31949]

Wed, 13 September 2006 05:08

Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA

Illuminati (2nd Degree)

The last of the parts showed up yesterday.

Simple 45:

So far have a mock-up built to avoid drilling the wrong holes in the 1/8" thick, 12x17 aluminum top late. And position so many components.

The PT is a Hammond 373BX. The psu chokes and filament transformer are Hammond as well.
The parafeed OPT's are Magnequest as are the plate chokes.
Then there are Audio Note Tantalum and Kwame resistors, Obbligato oil caps and so forth.

Should have the plate drilled out and over to the powder coat guy by Monday. Then I finally get to listen to Steve explain where the wires go and more importantly, why!

Can't wait to listen and show off!

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