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PostPosted: 28 Dec 2010, 10:17 
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Location: Las Vegas Nevada USA
mwhouston wrote:
Its really is hard to find a winder cheaper than Edcor. I paid big bucks for my locally wound unit but Edcor didn't have a model which suited.

I don't know how they price them so low. On top of that, I live in a state adjacent to Arizona where Edcor is located and UPS shipping is only about 10-15% of the cost of the transformers. :D :P :smoking:

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PostPosted: 04 Jan 2011, 19:39 
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Thought I am still waiting a filament tranni I thought I would try a few layouts. Though in a number of these images you can see the a filament tranni it will probably be mounted in the base rather than on it.

The amp is seperate from the PS. The amp top plate dimensions are: 360mm wide and 300mm deep. The PS top plate is: 200mm wide and 430 deep. I would have liked both the amp and PS bases to have been the same depth so they would look matching when sitting side-by-side but I could not make this happen without the amp base being far too deep. The layout I like is the 6sn7 between the OPTS and 300B infront of them.

Any comments:
Attachment:
300blayout.jpg
Attachment:
300blayout2.jpg
Attachment:
300blayout3.jpg
Attachment:
300bPSlayout.jpg
Attachment:
300bPSlayout2.jpg
Attachment:
300blayout4.jpg


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PostPosted: 06 Jan 2011, 06:11 
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Good news. The RIGHT filament tranni is dew for pick-up.

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PostPosted: 06 Jan 2011, 20:48 
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sampleaccurate wrote:
I read a website (can't find it right now) that made big claims about the impedance of the filament supply for directly heated cathodes. Basically this guy was saying that the ends of the heater (cathode) filament in DHTs should NOT be AC bypassed with a normal DC voltage supply or capacitors. In other words, even for grounded cathodes, the heater supply should provide power (in this case DC) to the filament while at the same time looking as close to an open circuit as possilbe on BOTH sides of the filament supply to any AC signal.

A CCS as a heater supply would do no good (in his opinion) since only the end of the heater with the CCS would "look" like a high impedance to the signal. The other end would offer a low impedance to ground. He came up with a circuit using a CCS on one side and some circuitry on the other side that effectively allowed DC to pass and blocked AC, without chokes and very inexpensively. He gave some reasons why this was desireable but I can't remember what they were. It was something to do with the signal potential that develops across the cathode and that shorting it (so the cathode has no AC voltage across it whatsoever - a "unipotential cathode" DHT?) causes a decline in sound quality for some reason, AGAIN that I can't remember.

If his "theory" is correct it would indicate the best place for chokes would be on the heater side of the caps with no caps directly across the heater to short the AC. I wish I could find the article - I'm only giving sketchy details. He may be full of it but I found it interesting.

Thinking about it, it makes some sense. If the cathode is powered by DC, one end will hog a little more signal current than the other. NEGLECTING the DC completely, it seems to me there would be a slight imbalance in the signal voltage that is seen at each end of the cathode. A cap or low impedance DC supply across this will create a small circulating current composed of the signal being amplified, would it not? How this translates into the sound of the amp I have NO IDEA. I just found it interesting.

I believe you are talking about Rod Colemans CCS-Gyrator filament supplies, I agree that the caps across the heater supply should be avoided, but that is probably a topic for another thread.


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PostPosted: 11 Jan 2011, 18:01 
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A little progress report:

All electronic parts for this amp have been purchased and delivered - finally. Today I ordered the top and bottom plates for both the PS and amp. I ordered 2mm Al plate, standard grade. I'm told I can pick them up tomorrow.

From here the plate will be taken to my base builder. These may take a few weeks to come through. And then construction can start.

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PostPosted: 19 Jan 2011, 17:05 
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Update: The top and bottom Al sheets have been cut for the assembly of the amp and PS base. Speaking of bases the base maker has the plate and hopefully they will be ready in the next few weeks.

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PostPosted: 04 Feb 2011, 23:02 
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I just received the two bases for the amp and PS. As yet they are roughly knocked together and require sanding and finishing. Not sure if I'll polyester, beeswax or oil stain the timber yet. The top plates will porbably be black.
Attachment:
BasesSS.jpg


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PostPosted: 05 Feb 2011, 23:13 
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Location: Northern VA
You'll be playing tunes in no time!
:trumpet:


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PostPosted: 06 Feb 2011, 02:11 
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rock4016 wrote:
You'll be playing tunes in no time!
:trumpet:

Mate donkeys to go!

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PostPosted: 06 Feb 2011, 16:17 
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mwhouston wrote:
rock4016 wrote:
You'll be playing tunes in no time!
:trumpet:

Mate donkeys to go!


Ok. Now I'm confused. :?

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