Excellent thread btw. I'm thinking of getting the L25D kit (2 boards naturally) myself.
What component changes are recommended to improve on the sonics other than what the kit comes with?
What component changes are recommended to improve on the sonics other than what the kit comes with?
I have tried several mods. Will you believe me it if I tell you that none made a measurable difference nor an audible difference ?
anyway, the power supply filtering caps are not large enough. I put 820u, the highest I could find that would fit the board.
Also, some resistors supplied as 2W were getting quite hot. I replaced them all by 3W.
L25D board I spent time with had multiple problems. It was using 20 ohm gate resistors and tripping .. the two boards also interfered with each other. So, good advice may be to switch the gate resistors to 10 ohm and keep them on separate power supplies with separate grounds ... it may work to put chokes in the ground lines, but too much choke could also be a problem.
Also ... next great suggestion for a mod is this: haven't done it yet, but have been thinking of it ..
the L25D doesn't seem to be able to genuinely power 4 ohm loads very well ... I think this may be reperable by doing the following:
switch the transistors to IRFB4227 and switch the gate resistors to 0 ohm resistors (wires)... next, to help the irs2092 power the 4227 transistors high gate charge, obtain a piece of aluminum just the right thickness and size to place between the irs2092 chip (on the under side of the board) and your underlying metal mounting plate. glue the aluminum to the chip with heat sink glue, and put heat sink grease on the other side of it. Mount the board so the heat sink connects solidly to the mounting plate. ... I'm going to try this one some time soon .. maybe I'll let you know how it goes. I also bolted some extra heat sink onto the heat sink and the output choke inductor. I the heat sink I placed on top of the transistor may have caused it to fail in a different way, causing the 2092 chip to take damage on failure ... If other components on the board take damage on failure, the board may instantly blow on power up with new transistors.
Also ... next great suggestion for a mod is this: haven't done it yet, but have been thinking of it ..
the L25D doesn't seem to be able to genuinely power 4 ohm loads very well ... I think this may be reperable by doing the following:
switch the transistors to IRFB4227 and switch the gate resistors to 0 ohm resistors (wires)... next, to help the irs2092 power the 4227 transistors high gate charge, obtain a piece of aluminum just the right thickness and size to place between the irs2092 chip (on the under side of the board) and your underlying metal mounting plate. glue the aluminum to the chip with heat sink glue, and put heat sink grease on the other side of it. Mount the board so the heat sink connects solidly to the mounting plate. ... I'm going to try this one some time soon .. maybe I'll let you know how it goes. I also bolted some extra heat sink onto the heat sink and the output choke inductor. I the heat sink I placed on top of the transistor may have caused it to fail in a different way, causing the 2092 chip to take damage on failure ... If other components on the board take damage on failure, the board may instantly blow on power up with new transistors.
quality of the l25d board
the l25d board was a pleasure to listen to for me.. it has a slightly different sound from an old hifi transistor amp.. seems just slightly zippier. Its ability to power a 4 ohm load is questionable. The choke inductor for the output gets pretty hot, even when the board is not driving power. The heat sink seems a little under sized. Some other components may be under sized. Mine kept tripping way too early while running a 4 ohm load so I had to play with them, and that got complicated. They misbehave if they are sharing ground lines. The misbehavior can include tripping or even blowing transistors. My opinion is that the irfb4020 transistors don't really quite have what it takes to drive a 4 ohm load. Getting past that is hard, and I don't know ho much risk there is of the output choke saturating if the current goes high. .. the board accepts +-80 ... wouldn't go over +- 70
the l25d board was a pleasure to listen to for me.. it has a slightly different sound from an old hifi transistor amp.. seems just slightly zippier. Its ability to power a 4 ohm load is questionable. The choke inductor for the output gets pretty hot, even when the board is not driving power. The heat sink seems a little under sized. Some other components may be under sized. Mine kept tripping way too early while running a 4 ohm load so I had to play with them, and that got complicated. They misbehave if they are sharing ground lines. The misbehavior can include tripping or even blowing transistors. My opinion is that the irfb4020 transistors don't really quite have what it takes to drive a 4 ohm load. Getting past that is hard, and I don't know ho much risk there is of the output choke saturating if the current goes high. .. the board accepts +-80 ... wouldn't go over +- 70
Here is my L25D
Upgraded heatsink
CP1 REMOVED and used Silver jumper cabel. Using Soniccap Gen 1 at the RCA input wire.
CP2 to 22uf/100v Elna Silmic II
CP4 to 22uf/100v Elna Silmic II
CP5 to 22uf/100v Elna Silmic II
CP6 to 22uf/100v Elna Silmic II
CP101 to 22uf/100v Elna Silmic II
CP3 to 10uf/50v Elna silmic II
CP7 to something between 300-1000 uf with 80-100v
CP8 to something between 300-1000 uf with 80-100v
C2 til 1n/400v Wima Mkp2
R114 to 2k2 3-5W
R117 to 5k1 3-5W
R118 to 5k1 3-5W
Upgraded heatsink
CP1 REMOVED and used Silver jumper cabel. Using Soniccap Gen 1 at the RCA input wire.
CP2 to 22uf/100v Elna Silmic II
CP4 to 22uf/100v Elna Silmic II
CP5 to 22uf/100v Elna Silmic II
CP6 to 22uf/100v Elna Silmic II
CP101 to 22uf/100v Elna Silmic II
CP3 to 10uf/50v Elna silmic II
CP7 to something between 300-1000 uf with 80-100v
CP8 to something between 300-1000 uf with 80-100v
C2 til 1n/400v Wima Mkp2
R114 to 2k2 3-5W
R117 to 5k1 3-5W
R118 to 5k1 3-5W
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To much !
It makes sense to change the input capacitors to a higher grade Elna Simic II the rest is waste of money , My amps sounded better after some hours with the input caps changed , more relaxed , less bright . The bigger 820 uF caps did improve the bass .
Make sure you have your stereo amps carrier frequency 25 kHz apart or as close as possible ! That's a very audible mod in stereo mode !
My L15D's are my favorite amps , very open and analytic sound after the 2cent mods .
Cheers ,
Rens
It makes sense to change the input capacitors to a higher grade Elna Simic II the rest is waste of money , My amps sounded better after some hours with the input caps changed , more relaxed , less bright . The bigger 820 uF caps did improve the bass .
Make sure you have your stereo amps carrier frequency 25 kHz apart or as close as possible ! That's a very audible mod in stereo mode !
My L15D's are my favorite amps , very open and analytic sound after the 2cent mods .
Cheers ,
Rens
Hi LJM
I see that the input capacitor in the L25D is 22uf E-cap. Will there be any problems changing this to a 4uf Film capacitor (soniccap Gen1)??
Regards
Jørgen Solvik
I see that the input capacitor in the L25D is 22uf E-cap. Will there be any problems changing this to a 4uf Film capacitor (soniccap Gen1)??
Regards
Jørgen Solvik
The input impedance of irs2092 is quite low. about 3.6k by memory.
With 22uF input cap, high-pass input filter is set at Fc= 2Hz
If you replace by 4u, it will set Fc=10Hz, ie impact low freq response.
I would not go lower than 10uF for the input caps of this amp. 10uF film capacitors tends to be big, which is not a good thing. They will act as antennas and capture the HF noise.
You can use non-polar electrolytic for best quality/size ratio.
D
Deleted member 148505
100uf 50V ordinary brand caps will perform better than 22uf/100v elna silmic II on CP2, CP4, CP5, CP101.
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My L25-D clicks in and out of protection when playing at a very low level or when idle. It otherwise functions normally.
It's input is an active crossover 60Hz - 2600Hz. It's driving an 8ohm load.
My power supply is a connexelectronic SMPS300re at +/-70v
Any ideas what the problem could be?
It's input is an active crossover 60Hz - 2600Hz. It's driving an 8ohm load.
My power supply is a connexelectronic SMPS300re at +/-70v
Any ideas what the problem could be?
Picture of my upgraded L25D boards With 1000uf buffer capacitors, had to place a couple of resistors and diodes under the board to fit the large capcitors.
I'm thinking about getting stereo set of 2x L15D boards. I have the following preamp/selector and was wondering if this could be used to drive the L15D's?
PGA2311 Preamplifier Remote Volume Assembled Premium Components Dale Resistors | eBay
PGA2311 Preamplifier Remote Volume Assembled Premium Components Dale Resistors | eBay
Member
Joined 2003
It benefits to have seperate well regulated low voltage supply rails. There are many better solutions than LM78XX nowadays.
I get away with the internal zeners and dropper resistors.
The op amp will have quite a good PSRR.
You have a little more overhead using internal zeners (<>7 volts).
The regulators would have to be 6 volts or less so the zeners don't fight the regulators.
Member
Joined 2003
Delete the zeners and 3.3k 1W resistors (ref. IRAUDAMP7S schematic) when injecting seperate regulated power supply. That should be obvious.