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Old 11th June 2004, 02:07 PM   #1
Sherman is offline Sherman  United States
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Question Tube buffered NIGC trafo thoughs?

I'm putting together my list of "goodies" to try a pair of tube buffered NIGCs. My plan it to build two monoblocks so I guess I'll be wasting half a tube but that's OK.

Does anyone have any thoughts on this for a filament transformer- http://www.jameco.com/cgi-bin/ncomme...s=503;528;781;

(Part no- 102162 in case the link doesn't work.)

And this for the higher voltage (+-35VDC)
http://www.jameco.com/cgi-bin/ncomme...s=503;528;781;

(Part no- 102103).

They seem to meet the voltage and current requirements and I would be using one of each for each channel.

Also I'm looking at this one to supply the LM3875TF-
http://www.allelectronics.com part number TX-245
(I can't ge the link to copy correctly.)

Any thoughts before I plunk down my cash... er, plastic?
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Old 11th June 2004, 10:26 PM   #2
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Default Re: Tube buffered NIGC trafo thoughs?

Quote:
Originally posted by Sherman
I'm putting together my list of "goodies" to try a pair of tube buffered NIGCs. My plan it to build two monoblocks so I guess I'll be wasting half a tube but that's OK.
Just wire then to use different halves of the tubes... when one half wears out (ie probably when you are old & grey) you can swap the tubes across mono-blocks and use the other half.

Quote:
Does anyone have any thoughts on this for a filament transformer-
Should be more then enuff

Quote:
And this for the higher voltage (+-35VDC)
Beefier than what i was planning on using... i was going to run them at a higher voltage thou.

Quote:
Also I'm looking at this one to supply the LM3875TF
with +/- 12V you are going to be down around 15-16V rails... something closer to +/- 18V would give you more power.

dave
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Old 11th June 2004, 10:52 PM   #3
Sherman is offline Sherman  United States
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Default Re: Re: Tube buffered NIGC trafo thoughs?

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Originally posted by planet10


...with +/- 12V you are going to be down around 15-16V rails... something closer to +/- 18V would give you more power...

dave
Dave,
Thanks for the feedback!

I actually thought about using a three pole two position rotary switch to change tube halves! Probably won't though!

For the GC power trafo I was planning on using the CT as 0 volts and wiring the outside to the bridge and getting 30VDC or so after rectification. Using one trafo for each channel of course.

So in the finished amps I would have three trafos mounted, probably on top of the case with the tube front and center! I'm looking at those surplus A/B switches at allelectronics.com as cases. I bought a few and the size seems plenty for a monoblock. I'll probably paint them black and attach a piece of Paduak wood to each side to dress them up!
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Old 11th June 2004, 10:59 PM   #4
Sherman is offline Sherman  United States
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Dave,
One other thing, I remember in another thread you also mentioned you would run your tube at a higher voltage (70V ?). What benefit is there to running the tube at a higher voltage in this configuration?

I thought I would stick to Joe's "plan" but if there is a big benefit from the higher voltage I might go ahead and do it.
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Old 11th June 2004, 11:36 PM   #5
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Hi,

Quote:
For the GC power trafo I was planning on using the CT as 0 volts and wiring the outside to the bridge and getting 30VDC or so after rectification. Using one trafo for each channel of course.
That's actually the way it should be done for dual rails IMO.

Cheers,
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Old 12th June 2004, 02:43 AM   #6
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Default Re: Re: Re: Tube buffered NIGC trafo thoughs?

Quote:
Originally posted by Sherman
For the GC power trafo I was planning on using the CT as 0 volts and wiring the outside to the bridge and getting 30VDC or so after rectification. Using one trafo for each channel of course.
24V CT means it is a 12-0-12 trafo... unless you stack 2 in series you are limited to 12x1.414-diode drop for the rails.


Quote:
Originally posted by Sherman
One other thing, I remember in another thread you also mentioned you would run your tube at a higher voltage (70V ?). What benefit is there to running the tube at a higher voltage in this configuration?
Joe used 35-0-35 (ie 70 V anode to cathode) to keep the voltage in the usual SS range . I beleive these are happiest with 200-250 V total.

dave
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Old 13th June 2004, 11:09 PM   #7
Sherman is offline Sherman  United States
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Default Re: Re: Re: Re: Tube buffered NIGC trafo thoughs?

Quote:
Originally posted by planet10


24V CT means it is a 12-0-12 trafo... unless you stack 2 in series you are limited to 12x1.414-diode drop for the rails.

Joe used 35-0-35 (ie 70 V anode to cathode) to keep the voltage in the usual SS range . I beleive these are happiest with 200-250 V total.

dave

The voltage between the two outside leads on the trafo is 24 volts. I can connect those leads to the bridge and use the CT as zero volts. At least that's how I did it with on of my GCs. (That one was only a single bridge but it worked.)

I looked up the specs on the tube and found there are a few different ones with slightly different specs but I did notice the higher voltage. Hmmm. I'll have to give the voltage some more thought, though I have to admit liking only having to come up with 35VDC!
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