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In the Forum: Melquiades Amplifier
In the Thread: Bias help
Post Subject: The crash-guidance about the transformer ordering.Posted by Romy the Cat on: 6/18/2009
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Dominik, I think you took it a bit wrong and delivered to Tribute a message with a wrong accent.

As I understated that was the reply from the Tribute guy. No one accuses him in cutting down core size but based upon the available inductance you will be available to choose what currant you would like your transformer to be gaped at.

The higher currant you drive the lower plate impedance and it might be useful in some cases. You chose 8:1 load that is in the middle of the road and you shall be OK with 200-300mA or with gap of 230-330mA.  Now how the “core size” play in all of it? Amount of lowers cut off frequency (at full power) is a subject of inductance. Inductance is a subject of 3 derivatives - core size, gap size, amount of wire. The amount of wire is fixed by the turns ration. The core size is fixed by the selection of the Tribute’s laminations. The only variable you have is to moderate the gap size (or the max DC currant the transformer will be handling). The higher currant the lower inductance. So, asking Tribute to make it 200mA, 250mA, 300mA or 350mA you will be changing your LF cut off. The in here is to know if it will be from 12Hz to 25 Hz or from 20Hz to 40Hz. To answers this question you need to know what is the core size Tribute uses. The “total weight for one transformer” is not accurate and in mostly irrelevant number, the size of the enclosure it will fill is also very abstract number. He needs to give you the inductance numbers at let sat 200mA and at 300mA and it will instantly show you very objectively the core size. Some manufacturer do not like use inductance numbers and they more accustom to talk about lower cut off at full power. That is inductance too.

I kind of supplied a lot of thing but it shell give you a basic idea what you need to look for. If you would like “your friend … to order a pair too” then he needs to give to the friend the inductance number at 250mA – that will let the friend to know what he will be requesting. Do not forget that Tribute guy knows very much what he does and he do not need your or mine help. However, knowing the objective capacity of Tribute core from a perspective of LF is something that will help you estimate what to order.

The Cat

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