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NOStalgia - the all-FET JLH/PLH Class A amplifier
NOStalgia - the all-FET JLH/PLH Class A amplifier
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Old 20th August 2012, 05:54 PM   #21
knutn is offline knutn  Norway
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Join Date: Mar 2006
Location: Oslo
Originally Posted by gusto142 View Post
Hej Knut,

Can you inform us about the current status of this project?

Time is a precious resource, I am afraid. However, I have had time to initial listening tests, which resulted in a change in layout of the power supply, because of a quite load hum coming from the speakers.

After the modification, I still have some hum, but it is not that annoying during listening. And yes, the initial listening is promising.

However I hate to have sounds from my amplifiers that should not be there, so I am also planning to modify the amplifier PCB.

I also have to inquire whether my unregulated CRC power supply is sufficient for this amplifier.
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Old 20th August 2012, 08:35 PM   #22
Dzius is offline Dzius  Poland
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Location: Warsaw
You can use regulated power supply from Nelson Zen v5 I guess.
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Old 8th October 2012, 06:33 PM   #23
knutn is offline knutn  Norway
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Join Date: Mar 2006
Location: Oslo
I have used the weekend to further RC-filter the negative supply. This has reduced the hum to nearly inaudible level. I have used a 1 ohm resistor and a 22mF capacitor. I assume a doubling of the capacitor will remove the hum completely.

I have considered the use of a capacitance multiplier instead of the RC-filter, but the result has convinced me to go on with the RC-filter, and the additional voltage drop is less than 2 volts (on the negative leg).

I also have had time to listening test, and I must say I am satisfied with the sound. And as for my other earlier class A amplifiers, there is more than enough power - loud and clean is it.
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