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Old 10th May 2005, 03:55 AM   #11
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Hi Audiophilenoob,

You may want to build your ribbons first and have your ears decide if this is true love, or just infatuation with a 150 lb Heavy Metal sculpture.

There are many amps that are stable into 2 ohms. You can buy or make a non-inductive 1 ohm resistor to put in series with your 1 ohm tweeter ribbon to trade-off 50% of the amp's power for transformer-free direct drive. A 100db/watt speaker only needs a few watts, but the first watt must have very low noise and distortion.

Many amplifier topologies can be adapted to drive a 1 ohm ribbon by dropping the output power supply to about 8 volts. There are high current 12V CT and 12.6V CT filiment transformers availble. The low driver stage voltages allow simple topologies with very low noise transistors to be used. The low output voltages make it simple to keep Class-A bipolar output transistors in the safe operating area.
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Old 10th May 2005, 06:31 AM   #12
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Default Re: Now we need a carrot

Quote:
Originally posted by mwmkravchenko


OK now what?

MArk

LOL well I can send you what you think it will cost... I can buy parts you need and send them to you and send you money when you're done... either way... let me know in an email or on here...
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Old 10th May 2005, 06:31 AM   #13
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Quote:
Originally posted by LineSource
Hi Audiophilenoob,

You may want to build your ribbons first and have your ears decide if this is true love, or just infatuation with a 150 lb Heavy Metal sculpture.

There are many amps that are stable into 2 ohms. You can buy or make a non-inductive 1 ohm resistor to put in series with your 1 ohm tweeter ribbon to trade-off 50% of the amp's power for transformer-free direct drive. A 100db/watt speaker only needs a few watts, but the first watt must have very low noise and distortion.

Many amplifier topologies can be adapted to drive a 1 ohm ribbon by dropping the output power supply to about 8 volts. There are high current 12V CT and 12.6V CT filiment transformers availble. The low driver stage voltages allow simple topologies with very low noise transistors to be used. The low output voltages make it simple to keep Class-A bipolar output transistors in the safe operating area.

true I should wait and make sure this is ideal for me...

I don't want to add a resistor.. it is not the ideal solution and since I will have to purchase SOME amp for these I figured it might as well be the best one possible
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Old 10th May 2005, 09:39 AM   #14
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Shame you are so keen on low THD numbers, there are plenty of nice tube amplifiers that make ribbons do nightingale stuff
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Old 10th May 2005, 11:07 AM   #15
Mark Kravchenko --- www.kravchenko-audio.com
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Default It's hard to argue when your right!

Quote:
There are many amps that are stable into 2 ohms. You can buy or make a non-inductive 1 ohm resistor to put in series with your 1 ohm tweeter ribbon to trade-off 50% of the amp's power for transformer-free direct drive. A 100db/watt speaker only needs a few watts, but the first watt must have very low noise and distortion
This is the simplest method and most likely the cheapest. A properly paralleled number of LM3886 could even do this!

Mark

Allways willing to add flies to the ointment
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Old 10th May 2005, 12:37 PM   #16
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Quote:
Originally posted by jacco vermeulen
Shame you are so keen on low THD numbers, there are plenty of nice tube amplifiers that make ribbons do nightingale stuff

well I'm not particularly keen on it... I just didn't think Tubes could be .7 ohm stable...

can they????? links or anything?
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Old 10th May 2005, 12:37 PM   #17
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Quote:
Originally posted by LineSource
Hi Audiophilenoob,

You may want to build your ribbons first and have your ears decide if this is true love, or just infatuation with a 150 lb Heavy Metal sculpture.

There are many amps that are stable into 2 ohms. You can buy or make a non-inductive 1 ohm resistor to put in series with your 1 ohm tweeter ribbon to trade-off 50% of the amp's power for transformer-free direct drive. A 100db/watt speaker only needs a few watts, but the first watt must have very low noise and distortion.

Many amplifier topologies can be adapted to drive a 1 ohm ribbon by dropping the output power supply to about 8 volts. There are high current 12V CT and 12.6V CT filiment transformers availble. The low driver stage voltages allow simple topologies with very low noise transistors to be used. The low output voltages make it simple to keep Class-A bipolar output transistors in the safe operating area.
ideally for a resistor a non-inductive 1 ohm with 1% tolerances?

any certain types that I should pick up for testing?
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Old 10th May 2005, 02:21 PM   #18
Mark Kravchenko --- www.kravchenko-audio.com
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Default Pick a peck of parts

You want either a metal oxide or a metal film. A power resistor in the metal film can be found in the Digi-Key catalog easily. See page 1079, 1081 in the catalog. This should work as an experiment. Get a decent wattage around 10 and up.

MArk
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Old 10th May 2005, 02:26 PM   #19
AndrewT is offline AndrewT  Scotland
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Hi,
I'm not a valve head so I'm talking out the top of my hat.
Most valve amps are transformer coupled to the load and they use a fixed turns ratio to determine the nominal load value.
It seems to me that you specify the turns ratio to suit 0r5, 0r7, 1r0 instead of the usual 4r & 8r.
When setting it up the designer will ensure it is stable.
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Old 10th May 2005, 06:24 PM   #20
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Can tubes be stable into .7 ohms?
Well if the output transformer is wound for a 1ohm output probably they can - but I thought you were trying to avoid a transformer...

Seems in the distant past I have seen a transformer coupled amp with 2 and maybe 1 ohm taps, but it might have been one of those McIntosh transistor amps with output transformers.

Bill

Edit: Andrew beat me to the cooment
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