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LJM Audio

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Erlend Sæterdal

Member
Joined 2007
ekremy18 said:
most people in this title say that 2x28VA is the safe voltage limit to L7 amp and you can see the some burned boards (report or photos) due to voltage above 29V limit

you claim that L7 can use, e.g 2x40VA but in practice, it is not true as you see

what is the safe voltage limit and what is the output power in this voltage?
Click to expand...

And your post is nonsens. What do you mean by VA?
 
E

Erlend Sæterdal

Member
Joined 2007
ekremy18 said:
Sorry i mean AC, i guess you can understand this, there is a "voltage" word in the text
Click to expand...

I have built one with 6 L7 2x 33 vac. As I remember

Billede 052.jpg
 
Last edited:
L

ljm_ljm

Member
Joined 2006
L20.5 by LJM Low THD Amp

L20.5 sound accurate, low distortion, it is suit HIEND representative products.
Whether level before use, all can be very good.
Designed by suit the L series 200 w power amplifier, the use of special CFP output, as well as COSCODE input stage.
Each channel 4 on imported from KEC KTB817 KTD1047 power tube.
Ultra-low distortion circuit, HIEND design standards.
8 r output power 200 w, 200 w + 4 r - 63 - v power supply.
8 r 125 w, 125 w 4 r + - 50 v power supply.
4 r 250 w, 250 w 2 r + - 50 v power supply
Maximum output current 15 a and maximum voltage sine wave output v. + - 63 (+ - 65 v power supply)
The static current 20 ma per channel
Static power * 0.02 = the power supply voltage (2 w + - 50 v)
Power Supply Voltage range Power Supply Voltage: 24 v to 65 v + - + -
Recommendation: the power supply voltage and the radiator

+ - 35 to + -50 v, radiator 0.5 KG per channel
+ 40-60 v, radiator per channel 1 kg
GAIN GAIN = 31 times
Frequency response = 20 to 25 k HZ to 0.15 DB. 10 HZ = 0.7 DB HZ 20 k = 0.05 DB

THD+N FREQUENCY（+ -35V DC POWER）
THD =0.0015%

IMD intermodulation distortion test = 0.002 (50 w output power 8 R)

THD+N 失真图
THD+N= 0.001-0.002% 20HZ-20KHZ The output power of 10 w 8 ohm load

THD+N=0.001% A weighting
 

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pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
Last edited:
2

2ramiro

Member
Joined 2017
Hello
I have 2 l15d Modules they were working fine but then i accidentally pulled the input cable from the computer out while the amp was working.
After that one amp makes loud noise , and after some seconds r29 starts smocking , it already burned the c9 one time.
I can't find any broken part and it also sounds nearly normal if you turn the Volume above the noise level.
Any idea where to find the issue ?
Thanks
Ramiro
 
E

ekremy18

Member
Joined 2016
Uncle Fedor said:
Hi

I have finished my amp based on this kit.

The parts I used:
- kit containing 2 pcbs and all parts soldered by myself
- 2 of large aluminium heatsinks
- 200W transformer 220/4*25V
- 4 of capacitors 10000u*50V
- 2 of rectifiers KBPC1010
- speaker protection board kit soldered by myself
- ALPS 27 potentiometer (not fake I hope)
- large 44mm knob
- input and speaker terminals
- some speaker wire
- some microphone wire
- power socket and switch
- 2 little leds with resistors
- plywood cabinet, handmade

Finally, it was worth it. The sound is so clear and so nice that I decided to send to retire my Sony reciever that served to me for 10 years. Goodbye, Sony )

PS: while writing it, I realized my error: I shoud use 2*50AC power. Although, then I should buy other filter capasitors for 80V or 100V (50V ones was on hand). Yet, I like the result. Maybe, one time I make another amp, using right transformer, right cabinet, and add some new features. Likely, it will be another L7.

528051d1454091515-l7-mosfet-amp-img_20160129_202737-jpg
Click to expand...

Hi, do you need a seperate preamp with L7 amp? or gain of L7 is already enough for home use, such as lm3886 gain clone?
 
Hugh Jazz

Hugh Jazz

Banned
Joined 2013
Hi guys - I've been enjoying an L7 for years. Good job! Unfortunately, I turned it on again today and it seems to have lost gain. It still drives 8 ohm cleanly but has lost maybe 20dB or so. Any idea what might have died? Input transistors? The speakers test fine and the source is fine but my investigation hasn't got any further than isolating the issue to the amp. Any ideas?
 
D

daveayerst

Member
Joined 2012
Have you measured your power supply voltage/current ?

Nanoloop said:
Hi guys - I've been enjoying an L7 for years. Good job! Unfortunately, I turned it on again today and it seems to have lost gain. It still drives 8 ohm cleanly but has lost maybe 20dB or so. Any idea what might have died? Input transistors? The speakers test fine and the source is fine but my investigation hasn't got any further than isolating the issue to the amp. Any ideas?
Click to expand...
 
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