My 15 year old nephew built his own speakers so I figured it would be cool if we built an amp to power them with. I bought a L 20 amp kit from china and taught him how to solder it up. I picked up a broken amplifier off E-bay for the case and transformer and put the new L 20 amp boards inside. The broken amp was a Samson Servo 240 and was air cooled so there is a nice heat sink on the back to mount the new L 20 boards to. The transformer puts out 55 volts DC after the bridge rectifier which should match up nicely to the L 20 boards. I was also able to reuse two 10,000 uf 71 volt capacitors from the old amp.
The question is do we need a pre amp for this project? My nephew plans to run his I pod or a CD player threw this so they are at line level, but when I tested out the amp with my I pod I ran out of gain really fast and wasn't able to get the full volume out of the amp.
The amp sounds great with no hiss or hum, but I can't get enough volume out of it. I have it hooked up to a smaller PA monitor speaker which is good for 50 watts and can barely make it distort before running out of gain on the I pod volume. I hooked up a 100 watt sub woofer and easily maxed out the volume with out any distortion. The amp is no ware near clipping.
Please let me know if I need a pre amp for this amplifier and if ether one of these boards would be a good choice.
Thanks, Dale P.
[wiki=http://www.ebay.com/itm/320915557448?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649]%[/wiki]
[wiki=http://www.ebay.com/itm/220866124397?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649]%[/wiki]
The question is do we need a pre amp for this project? My nephew plans to run his I pod or a CD player threw this so they are at line level, but when I tested out the amp with my I pod I ran out of gain really fast and wasn't able to get the full volume out of the amp.
The amp sounds great with no hiss or hum, but I can't get enough volume out of it. I have it hooked up to a smaller PA monitor speaker which is good for 50 watts and can barely make it distort before running out of gain on the I pod volume. I hooked up a 100 watt sub woofer and easily maxed out the volume with out any distortion. The amp is no ware near clipping.
Please let me know if I need a pre amp for this amplifier and if ether one of these boards would be a good choice.
Thanks, Dale P.
[wiki=http://www.ebay.com/itm/320915557448?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649]%[/wiki]
[wiki=http://www.ebay.com/itm/220866124397?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649]%[/wiki]
That sounds like a fun project.
I want to try a pair of those boards at 95 volts.
I am using one of these as a headphone amp, and it works great as a pre amp.
Search "E5 headphone amp board weiliang"
I want to try a pair of those boards at 95 volts.
I am using one of these as a headphone amp, and it works great as a pre amp.
Search "E5 headphone amp board weiliang"
Last edited:
I have built several L20 amplifiers and run them without preamps using a CD player as a source and get huge amounts of volume. I use 50K potiemeters to attenuate the input which act as a volume control. I would try a regular CD player rather than an Ipod. I suspect there is some serious impedance imbalance for the Ipod. To use the Ipod you probably need to add some op amps to act as a buffer between Ipod and amp.
I tried running a CD player through it and still don't get enough gain. The CD player was run straight to the amp with out a pot switch for volume control, just wide open.
I'm putting 55 volts DC to each side of the amp for a total of 110volts DC to the board. The transformer and capacitors are from the Samson Servo 240 amp which put out 120 watts per channel at 8 ohms. Right now I'm just powering up one of the L 20 boards so the transformer should have plenty of power to put out more Watts. I don't have any type of pre amp here or I would give that a try. Perhaps I will run down to radio shack and pick up a cheap audio mixer to hook in line with the CD player and amp as they have a pre amp inside that should boost the line level.
Adding a pre amp isn't too big of a deal if I do need one, except for the fact that I'm running out of room inside the case. The original transformer only has high power taps so I would have to add a second transformer to power up the pre amp and then also find room for the pre amp it's self.
Dale P.
I'm putting 55 volts DC to each side of the amp for a total of 110volts DC to the board. The transformer and capacitors are from the Samson Servo 240 amp which put out 120 watts per channel at 8 ohms. Right now I'm just powering up one of the L 20 boards so the transformer should have plenty of power to put out more Watts. I don't have any type of pre amp here or I would give that a try. Perhaps I will run down to radio shack and pick up a cheap audio mixer to hook in line with the CD player and amp as they have a pre amp inside that should boost the line level.
Adding a pre amp isn't too big of a deal if I do need one, except for the fact that I'm running out of room inside the case. The original transformer only has high power taps so I would have to add a second transformer to power up the pre amp and then also find room for the pre amp it's self.
Dale P.
- Status
- Not open for further replies.