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Old 12th October 2012, 10:28 AM   #51
xslavic is offline xslavic  Moldova
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I also added high pass on amp pcb, its RC,rised it to 20hz
but the volume is to low not more than 60w, i still didnt succeeded in using a preamp,its clipping the amplifier --but didnt get much amplification also
but still 60w from 1/2 kg of transistors is not good
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Old 14th October 2012, 04:06 PM   #52
xslavic is offline xslavic  Moldova
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Finally getting decent sound,used RC HP and LC low pass ,but still low
i can say sounds very good but not enough i have no preamp connected trying to match one
a-15 clone Mark levinson but no luck yet (same filters for preamp)
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Old 18th October 2012, 10:49 AM   #53
xslavic is offline xslavic  Moldova
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remove the 100k from line to gnd and in the HPF use hiher capacitance for hiher power out
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Old 21st October 2012, 02:10 PM   #54
xslavic is offline xslavic  Moldova
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Got more than 100w,apparently fuses after Thermistors limit the current to the amp
used 200k pot with pseudologarithmic 1k in parallel ,still no highs at low volume
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Old 12th December 2012, 03:03 PM   #55
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by xslavic View Post
Got more than 100w,apparently fuses after Thermistors limit the current to the amp
used 200k pot with pseudologarithmic 1k in parallel ,still no highs at low volume

You need a preamplifier.
With it, you can output the greater voltage.

Until close to your power supply voltage, + - 65 v is the ideal value of the output signal.

Premise is you need to input about 1.5 V signal, because the L20 magnification is about 34.
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Old 26th April 2013, 04:46 PM   #56
xslavic is offline xslavic  Moldova
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So i finished my amp,videos on youtube
cs4398 dac. So l20 input voltage 6v
sounds loud and clean no distortions or noise
help biasing to class A, 50w is enough
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Old 5th June 2013, 01:29 PM   #57
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Location: Melbourne, Australia.
I finally finished my L20 V9 monoblocks today. It's taken over 12 months. There's been a few smoke clouds along the way as per my previous posts. I have to say that they are the best solid state amps I have built so far and are very valve like in their sound. I normally listen through 300B 60W Audiospace monoblocks and the L20's are the closest I've come to bettering them. I still have the problem with high DC rails due to the wrong selection of toroids and high mains voltage and will have to do something about it eventually and that will probably mean buying new toroids.
David.
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Old 23rd July 2013, 07:58 AM   #58
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Default L20 Kit

Quote:
Originally Posted by xslavic View Post
So i finished my amp,videos on youtube
cs4398 dac. So l20 input voltage 6v
sounds loud and clean no distortions or noise
help biasing to class A, 50w is enough
Sir,
I also order this kit from ebay and would you please to summary what have you done from input C1 until output may be add a zobel, R feedback, and VDC etc?

Many thanks and regards,
Pamuji
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Old 30th July 2013, 11:55 AM   #59
Nicobis is offline Nicobis  France
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Default L20 V9 Power Amp

Hi, I am looking for the schematic diagram for the new LJM L20 V9 Power Amp ???????
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Old 15th August 2013, 02:55 AM   #60
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Default L20V9

I removed the supplied input capacitors on my monoblock builds and the sound is significantly better. But removing the capacitors is not a good idea if there is any DC on the input signal. Otherwise, the amps are stock standard and I have fitted speaker protection modules. I used new toroids which give +/-56V rails which for me are a lot safer than the +/-73V rails I had with the first toroids. Of course the power is lower but I never use more than about 20W on the loudest passages with my 92db speakers. The L20V9 really does sound very realistic, the bass end is well controlled and the overall sound is very smooth. It could be a little more detailed at the top end when I compare it to my 300B 60W monoblocks but they are a hard act to follow. I'm using 4x10,000uf on each power supply rail plus 10x22uf wound foil caps on each rail. I feel that this 220uf of foil caps on each rail cleans up the top end a little and have used the same idea on other builds. I am using massive heatsinks which are complete overkill and never seem to warm up. However, when the amps have been on for a few hours they do seem to sound a little more detailed and the layering is improved slightly.
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