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PostPosted: 16 Feb 2020, 20:00 
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Joined: 08 Oct 2013, 21:32
Posts: 12
Location: Florida
http://www.s5electronics.com/gstereo.html

Please, would you please teach me how to modify the [[12G Stereo Integrated Tube Amplifier Kit]] so that the output impedance is 23-ohms. I know it will probably still work with my headphones even if I don't modify the output impedance. However, I would still like to change the output impedance to 23-ohms. If you would explain how I can do that, I would be hugely grateful.

http://www.s5electronics.com/gstereo.html


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PostPosted: 18 Feb 2020, 03:00 
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Joined: 23 Feb 2017, 02:02
Posts: 677
You get less output power when you use 23 ohms.

The output volume becomess less, and you cannot modify the output impedance unless you change the output transformer design.


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PostPosted: 18 Feb 2020, 21:34 
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Joined: 08 Oct 2013, 21:32
Posts: 12
Location: Florida
so are you saying if I change ONLY the output transformers such that the ideal load changes to 23 ohms, then the amp will definitely have a lower watt output? Sorry for the newbie question...but i'm definitely newb


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PostPosted: 20 Feb 2020, 07:21 
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Joined: 23 Feb 2017, 02:02
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Currently with 8ohms output impedance, use any phone other than 8 ohms you get less power output, the volume becomes lower.
Match the transformer so is 23Ohms output impedance you get higher output power, the headphone can become louder.

Nothing wrong with running higher impedance like 23ohm on 8ohms impedance system.

But run 4 ohms on 8ohms system then you can blow up the system at high output powers.


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PostPosted: 20 Feb 2020, 12:46 
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Joined: 19 May 2011, 05:38
Posts: 48
Using that amp with headphones and worrying about power is like worrying if the sun was burning out tomorrow. You are only going to use 10% of the available power if you value your hearing.


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PostPosted: 21 Feb 2020, 00:30 
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Joined: 23 Feb 2017, 02:02
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Hes quite right


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PostPosted: 23 Feb 2020, 15:28 
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA
Hi, Likely way less than 10%. The S-5 is not a particularly noise and hum free amp. Actually it is quite the opposite. However all is not lost. I believe since it can easily deliver 1-2 watts clean I would add a resistor network at the output. I would probably use a 10ohm 5 watt resistor from the output to ground and tap off the hot side of it with another 10ohm one to feed the phones. It would cut the output down in size that gets to the phones and by a like amount cut down the hum and noise. You can experiment with the value of the second resistor to improve the quality of the output (less hum and noise) a bit up to the point the amp starts to distort. Alternatively an 8ohm "L" pad on the output feeding the phones would be a good solution. It would cost more than the resistors though.

IMO you will likely find that regardless of what you do the H+N will be unsuitable for phones. The amps were never designed to be that clean sounding and it can get really costly to fix it. I tried, it was my first tube amp experience. But that is ancient history.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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