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LJM L20 V9.0 Amplifier
LJM L20 V9.0 Amplifier
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Old 20th December 2016, 10:33 AM   #41
raffajaffa is offline raffajaffa  United Kingdom
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Join Date: Mar 2015
Location: Wirral Merseyside uk
Default Not Fluent on Scotch ? Aye

Lets Look at the evidence?.

Sadly cannot drink hard stuff or even Iron Brew. It is the only country in the world that does not have Cola as its number one soft drink. (from a quiz)
Also got the correct answer to the name of a Scottish Fish that begins and ends with a K,,

I do have Ecosse cables in and around the system, Mains in particular works well.

I did have Haggis for evening meal last saturday.

I met and Irishman Welshman and Scotsman in a Manchester pub and the aforesaid Mr McCracken unusually shouted " Drinks all round on me for the whole night."
The following morning I read that an Irish ventriloquist was found strangled ,

ps I had volunteered to do missionary work in Scotland once.
Well that was almost a year ago.,,,,,LOL.

Happy whatever it is to you and once again thanks for previous help.

PS I am going back to a two way speaker design so current amplifier may be starting to worry...LOL. again.
Dave CEO Dogsbody and all things superaudiosales4u...
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Old 19th April 2017, 05:52 PM   #42
Vortex is offline Vortex  Hungary
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Location: Budapest, Hungary, Europe
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Hi all, I just bought a pair of L20 V9.2 amps - question: what's the input voltage to feed these modules ? (I assume it's not 0dB / 775mV).

Thanks & cheers
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Old 16th July 2017, 06:46 PM   #43
David Church is offline David Church  United Kingdom
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I found that these amps work quite well on the 136kHz amateur band. The Zobel network on the output needs alteration, the 100nF should be changed to10nF (the one in series with the 10ohm resistor). By fitting the 2SA1930 & 2SC5200 output transistors I can get at least 200W out at this high frequency with 300W DC input.
I opted for a 1uF polypropylene capacitor in series with the output to avoid operator ****-ups and the nominal +/- 35 supply has a 1 second delay by shorting out a 220ohm resistor initially in series with the transformer primary.
The output transistors are directly fixed to seperate heatsinks so there's a little constructional conundrum isolating these from the chassis but it saves cooking them.
I've tried other LJM amps (they're not designed for this frequency!) and they are not up to this standard.
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Old 16th July 2017, 10:11 PM   #44
filthyone is offline filthyone
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Join Date: Oct 2015
Quote:
Originally Posted by Vortex View Post
Hi all, I just bought a pair of L20 V9.2 amps - question: what's the input voltage to feed these modules ? (I assume it's not 0dB / 775mV).

Thanks & cheers
I think it needs about up to 1.5V rms of input voltage for full output power on +-65 volt rails and 8ohms load
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Old 17th July 2017, 10:30 AM   #45
David Church is offline David Church  United Kingdom
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I tried it on +/- 50V unregulated and it gives no more output than +/- 35V unregulated, bear in mind this isn't audio though. Input is about 1V rms for +V to -V full output.
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Old 17th July 2017, 08:10 PM   #46
chalky is offline chalky
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I think there is no increase in output when going from +/-35V to +/-50V supplies because of the odd VAS loading arrangement. The VAS load is a constant current source in parallel with an unbootstrapped 33k resistor. Obviously this is going to limit the VAS voltage swing. Someday I'm going to mod one of my boards to do away with the 33k resistor, so that the only VAS loading is via the constant current source. This should lead to higher output with higher voltage supply rails and lower distortion.
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