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Old 17th October 2014, 06:23 PM   #1
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Default Clipping - Saturation or Mismatching Impedance?

I hope this will help others as well as educate me.

I am experimenting with using power transformer as output transformers in a 1-2 watt single end home brew amp.

I have tried EI, R-core and toroidal expecting saturation. However, the only difference between them seems to be clarity, Bass response and clipping. R-core and Toroidal excell in highs...Is this due to saturation? or impedance mismatch? I'm sure both but which has more effect?

I have used the following with 6L6GC at 75mA- 250V at plate
115v to 15v r-core = 504 impedance, incredible mids and highs little base- early clipping - Weighs nearly 2lbs.
115v- 6.3v EI = 2.6k impedance, balanced and good frequency response...full volume, no clipping weighs over 1lb

6V6 or 6L6gc at 30mA - 280V at plate
115 - 3.15v EI= 10.7k impedance, good bass, balance and clarity...early clipping..weighs 1lb+
115- 4.25v Toroidal= 5.8k impedance incredible clarity...little bass...early clipping. Only weighs 15 ounces

I understand I am breaking some HI FI rules... I just want to recognize and understand the results more than "it doesn't work".

Thanks
Roger

Last edited by rcollege; 17th October 2014 at 06:29 PM.
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Old 17th October 2014, 06:42 PM   #2
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Toroidal has low leakage inductance, but can't tolerate any DC current. Hence the lack of bass, it's saturated and the inductance is gone. They're only good for PP and parafeed.

Any transformer without an air gap in the core will struggle in SE, but cheap EI cored ones kind of work.
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Old 17th October 2014, 07:24 PM   #3
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The power transformer is not suitable for use in SE.
Very low inductance, large leakage inductance, saturation of the core (no non-magnetic gap).
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Old 17th October 2014, 09:06 PM   #4
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You will have better results in this experiment if you use a smaller power tube that runs on low current. Maybe 1/2 of a 6sn7?
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Old 18th October 2014, 05:12 PM   #5
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Quote:
You will have better results in this experiment if you use a smaller power tube that runs on low current. Maybe 1/2 of a 6sn7?
Will be very bad, these tubes have a low current and a large Ri.
Parasitic parameters of the transformer will kill the sound.
Take the normal audio transformer.
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Old 18th October 2014, 05:29 PM   #6
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Of course it will be bad. The experiment here is how to be more bad than horrible.
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Old 19th October 2014, 12:14 AM   #7
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Default not as bad as yu might think

Quote:
Originally Posted by costis_n View Post
Of course it will be bad. The experiment here is how to be more bad than horrible.
Well the 6J5GT sounded great with the EI 10.7 k inductance with only 10ma.
loud enough...but i'm sure it made the tube beg for mercy.
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Old 19th October 2014, 02:17 AM   #8
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This poor vacuum valve is now complaining in the forum for tubes... Whats wrong with this guy!?!??!?!?!
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Old 21st October 2014, 09:07 PM   #9
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[QUOTE=Whats wrong with this guy!?!??!?!?! [/QUOTE]

Would you like me to provide you with a list?

I'm sorry...I had to try the 6J5GT...10mA, 287V and a solid sound
Its a small room so the pea power (probably milliwatts) it was pushing out filled more than just the room. (and yes...it is in a room much larger than a porta potty)
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