Bonsai,
R6 is 1k (and this is the value I used when I got I=634mA)
R20 is 2.2k (actually 2.19k)
R21 is 1k (actually 0.997k)
I checked Q11, it seems to be ok (without desoldering). 0.33 resistors are ok too (I saw in earlier posts they had to be checked, but that concerned Nx version)
I am now away for a week, so I won't be able to test during that time...
R6 is 1k (and this is the value I used when I got I=634mA)
R20 is 2.2k (actually 2.19k)
R21 is 1k (actually 0.997k)
I checked Q11, it seems to be ok (without desoldering). 0.33 resistors are ok too (I saw in earlier posts they had to be checked, but that concerned Nx version)
I am now away for a week, so I won't be able to test during that time...
nx amp scaling down
my fault...i saw this very well thought amp design just a couple of days ago.
My job is to build an amp that fits into the case see pic... which is very small and serves as the heatsink. My wife loves the design and so...
but due to heatsink size the original amp which gains really moon prices at ebay is rated 40 watts and they used to die on excess temp.
So how to scale the nx down to say +- 28 to 33 Volts does it make sense?
Further there is space for one pair of power BJTs i would use Thermal track NJL4281 / NJL4302 which i think have the same chip as your NJW3281 ....types
my fault...i saw this very well thought amp design just a couple of days ago.
My job is to build an amp that fits into the case see pic... which is very small and serves as the heatsink. My wife loves the design and so...
but due to heatsink size the original amp which gains really moon prices at ebay is rated 40 watts and they used to die on excess temp.
So how to scale the nx down to say +- 28 to 33 Volts does it make sense?
Further there is space for one pair of power BJTs i would use Thermal track NJL4281 / NJL4302 which i think have the same chip as your NJW3281 ....types
Attachments
yes thanks but the bias current of all stages must be the same as of the original
nx amp? That should be so because of the 10 volts clamp and resistors R30 R31?
so no re-calculation of resistor values required?
You are correct - you will need to make changes (From V2.10 document V2 PCB).
R18 and R19 - 2.2k (~8.5mA through the 10V zeners). These are 4.7k on the +-50V nx-Amp
re the NJW devices - I have not used these personally, so cannot offer a circuit to use the in built sense diode. My comment above was more to simply say that it is possible to use it.
There are not any other values that will need changing.
I assume you will just use a simple power supply and not the nx-Amp PSU +Protect board?
R18 and R19 - 2.2k (~8.5mA through the 10V zeners). These are 4.7k on the +-50V nx-Amp
re the NJW devices - I have not used these personally, so cannot offer a circuit to use the in built sense diode. My comment above was more to simply say that it is possible to use it.
There are not any other values that will need changing.
I assume you will just use a simple power supply and not the nx-Amp PSU +Protect board?
No, in fact there is no bug . I did not see D3 and D4 (zeners) were "crossed" between schematic and PCB. Again bad assumption from me...
sorry.
Here are my measurements (with R20 removed as advised), Vpos=Vneg=+/-25V,
I vpos=650mA :
Across R37 : 143mV
Across R36 : 143mV
Zeners 10.3 and -10.3V
Q9 emitter 129mV
Q11 emitter : -156mV
Across R33 : 1.22V
Across R32 : 1.2V
Across R25+R24 : 211mV
Between out and Gnd : 27mV (no way to go lower with R1 adjustment)
sorry.
Here are my measurements (with R20 removed as advised), Vpos=Vneg=+/-25V,
I vpos=650mA :
Across R37 : 143mV
Across R36 : 143mV
Zeners 10.3 and -10.3V
Q9 emitter 129mV
Q11 emitter : -156mV
Across R33 : 1.22V
Across R32 : 1.2V
Across R25+R24 : 211mV
Between out and Gnd : 27mV (no way to go lower with R1 adjustment)
