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PostPosted: 19 Jun 2010, 16:22 
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This will be my Uniamp build log.

Uniamp Links

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PostPosted: 19 Jun 2010, 16:42 
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Hi guys,
The Hammond chassis and Hammond 193J chokes arrived. The chassis is a Hammond 1444-32CWW which measures about 17" x 10" x 3", is aluminum and has wooden side panels.

So now I am looking for opinions and suggestions for the layout. WAF is not an issue, the two potential layouts shown in the photos below have been chosen to minimize potential noise.

Layout 1
Attachment:
Uniamp-Layout-1.jpg


Layout 2 (below)
Attachment:
Uniamp-Layout-2.jpg

Basically the two are the same. I chose the layout to keep the power transformer and heater wiring as far away as possible from the signal. Power input will be the back left corner and power switch will be at the front left below the power transformer. The speaker outputs will be below the OPT. The signal input will be on the right end of the chassis.

On the PCB, the HV AC and 5V heaters are on the left end, the 6.3V heaters for the driver tubes are at the bottom middle, the B+ and choke connections are on the top left corner, the power tube connections are at the top middle, the signal input and phase splitting transformer are at the top right corner.

Please let me know which of the two layout you think is better for minimizing unwanted noise. Or let me know if you have any suggestions.

Cheers


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PostPosted: 19 Jun 2010, 20:30 
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Just subbed in to this on Gio,

The chassis looks great can wait to see what you think of these !

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PostPosted: 19 Jun 2010, 20:37 
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Gio I like layout one better however you can improve on it again,

the laminations of the transfomer and choke cores need to be at 90 degrees to each outher - specifically with respect to the power tranny and the output tranny, the magnetic fields will interact other wise the choke will also play a part here, i would perhaps turn the power tranny 90 deg so its laminations are not pointed at the input tubes - although it might be best to check on this to see if the field is strongest at the laminations the end bell probably i am going a bit to far but i want to save you from hum before you drill the chassis

it may not even be a problem though

-Dan

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PostPosted: 19 Jun 2010, 22:54 
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The uniamp is excellent for tube rolling but does not squeeze the most out of any one tube. After increasing current flow through my SE UL KT88 amp and HEARING the different I would recomend setting the amp for a particular tube and getting the most out of it. Or a few switches to adjust idle current to suit a few different tubes.

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PostPosted: 20 Jun 2010, 22:20 
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Thanks Dan - just the feedback I was looking for.
Dan wrote:
although it might be best to check on this to see if the field is strongest

Is there a general rule of thumb with EI transformers where the magnetic field is the strongest?

Also, does anyone see any issues with having the OPT that close to the rca input?

Cheers

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PostPosted: 20 Jun 2010, 23:08 
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I have some information on this from Morgan Jones book, Building Valve amplifiers

i will see if i can dig it up for you - It has an excellent section on construction techniques more specifically tube amp layout.

ie:

1.5 envelope widths minimum between power tubes
Xfrmr orientation
AC Heater wiring in the corners of the chassis, twisted, or DC etc etc

-Dan

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PostPosted: 21 Jun 2010, 10:51 
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I agree with Dan on layout one :up: The placement of the transformers is quite important, the inductor also performs best when furthest away from the power transformer I have heard. ;)

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PostPosted: 21 Jun 2010, 17:56 
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What I have also found is keep the driver tube from the power tranni.

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PostPosted: 22 Jun 2010, 12:20 
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Hi guys, I have both the Morgan Jones tube books, but there are no comments about where the magnetic field is strongest. However, based on the few photos in the books, it seems that the core is generally not pointed at the tubes.

I will shoot Edcor an email and see if they have any comments about where the magnetic field is the strongest.

Cheers

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