On 11 Jun 2004 08:40:35 -0700, the renowned Winfield Hill
wrote:

Albert wrote...

I wonder what the practical limits are for turns ratio for 8 ohm
input impedance? If I could get a 50 to 1 step up ratio, I would
have no problem generating enough voltage to turn my mosfet switch on!
I don't think transformers can be built with that much of a step up
ratio (and still be a relatively wide range audio frequency device).

Step-up and step-down transformers are basically the same, but
connected backwards. Up to 10,000-ohm CT to speaker (4-ohm) used
to be made for driving speakers from vacuum tubes. The impedance
ratio is the square of the turns ratio, so that'd be a 1:50 xfmr.

Radio Shack used to sell transformers similar to this. Now they
only offer the # 273-1380, rated at 1000:8 ohms or an 11:1 ratio.

Ocean State Electronics has many types of small audio transformers.
http://www.oselectronics.com/ose_p119.htm You could use two of
these, say a 1000:8 (p/n 45-714) plus a 100000 to 1000 (p/n 45-702)
to achieve an impressive overall 112:1 ratio.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

Mouser also carries (carried?) a wide range of "import" type small
audio transformers at very reasonable prices compared to Pico et al.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
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