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Old 18th January 2010, 10:57 PM   #6681
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by AndrewT View Post
If the light bulb is still in place when trying to bias an amp then as the bias adjuster is turned up, the bulb reduces the voltage fed to the transformer.
"reduces voltage fed to transformer"
Oh, I thought the lightbulb(s) should be mounted in series with each rail, between supply and amp
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Old 19th January 2010, 03:04 PM   #6682
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Quote:
Originally Posted by Zen Mod View Post
in this case - you can't , because of need to implement inverting topology .

that's SUSY bridged F5
As i understand it, the susy topology needs inverting amps. Which is not the case here.
Susy topology doesn't crosses the feedback loops neither.
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Old 19th January 2010, 05:01 PM   #6683
wensan is offline wensan  United States
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Quote:
Originally Posted by bobodioulasso View Post
As i understand it, the susy topology needs inverting amps. Which is not the case here.
Susy topology doesn't crosses the feedback loops neither.
So I make the input stages of "two" F5 become "one" differential pair stage,
Then, the other side's output will become invert output.
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Old 19th January 2010, 05:02 PM   #6684
tinitus is offline tinitus  Europe
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Well, searched a lot, but only a search on "poor mans variac" or "dim bulb tester" gave any result

Seems most common to connect it between complete finished amp and wall socket
Only found one single different version (decibel dungeon)
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Old 19th January 2010, 10:10 PM   #6685
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Quote:
Originally Posted by wensan View Post
So I make the input stages of "two" F5 become "one" differential pair stage,
Then, the other side's output will become invert output.
Imho, once you put a diff pair in the circuit, it's a different amp.
The harmonics change.
You can probably see that using a simple sim with no trouble.

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Old 19th January 2010, 10:15 PM   #6686
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by bear View Post
Imho, once you put a diff pair in the circuit, it's a different amp.
The harmonics change.
You can probably see that using a simple sim with no trouble.

_-_-bear
anyway - if SUSY is a goal - it's all about differentiation .
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Old 20th January 2010, 05:35 PM   #6687
tinitus is offline tinitus  Europe
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Hi,
Please, I need input on how to choose between these transformers
I will buy two trafos to build seperate monos
I dont know much about R-core trafos, quality etc

SELECTRONIC ::: L'univers électronique :::

230V / 2x 18V 300VA

230V / 2x 18V 500VA
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Old 20th January 2010, 05:52 PM   #6688
massimo is online now massimo  Italy
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Quite good, but shipment outside France colud be expensive chez Seletronic....
Widely used by our French friends
Made in India
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Old 20th January 2010, 06:36 PM   #6689
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Ask yourself the following questions:

- what is the maximum current draw possible from each amp, peak?
- at what voltage will the rail run?
- multiply the two numbers.

That is the maximum watts drawn from this amp.

Now, this is roughly identical to "VA".
A 300VA transfomer will deliver maximum 300 watts of power.
BUT, it depends on how it was rated!
There are three rating classes in the USA: CCS, ICAS, and ummm... I forget the proper nomenclature, but "consumer" is close enough.

CCS = "Continuous Commercial Service".
ICAS = "Intermittant Commercial <something> Service" (brain dead today...)
And consumer is less than that.

The rating is based upon % drop under load.

CCS = 10% drop under full load.

So your rails will drop 10% under full load with a CCS rated transformer run at whatever full load for it is. In this case you could draw 300watts from the iron and see a 10% drop.

Greater drop as you go down the chain...

I like to design for better than CCS when feasable.

I think you have to look at the numbers and decide how much Vdrop in the rails you can live with given the likely current draw, and then find out how the manufacturer rates the iron to begin with.

Bottom line, if cost is no object, weight and size not important, larger is better in power iron (with a few less important issues still playing a role), imho.

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Old 20th January 2010, 07:06 PM   #6690
brianco is offline brianco  Ireland
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Quote:
Originally Posted by tinitus View Post
Hi,
Please, I need input on how to choose between these transformers
I will buy two trafos to build seperate monos
I dont know much about R-core trafos, quality etc

SELECTRONIC ::: L'univers électronique :::

230V / 2x 18V 300VA

230V / 2x 18V 500VA
SELECTRONIC ::: L'univers électronique :::
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